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Commit 29687512c0b084957112cc2c0743ce34cd0d5055

Authored by James Bottomley
1 parent 8816624222
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

[SCSI] fix up documentation for change in ->queuecommand to lockless calling 

The current doc still says we call it with the host lock held, which is
going to cause confusion.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>

Showing 1 changed file with 31 additions and 28 deletions Inline Diff

Documentation/scsi/scsi_mid_low_api.txt
Diff comments   View file @ 2968751
1 Linux Kernel 2.6 series 1 Linux Kernel 2.6 series
2 SCSI mid_level - lower_level driver interface 2 SCSI mid_level - lower_level driver interface
3 ============================================= 3 =============================================
4 4
5 Introduction 5 Introduction
6 ============ 6 ============
7 This document outlines the interface between the Linux SCSI mid level and 7 This document outlines the interface between the Linux SCSI mid level and
8 SCSI lower level drivers. Lower level drivers (LLDs) are variously called 8 SCSI lower level drivers. Lower level drivers (LLDs) are variously called
9 host bus adapter (HBA) drivers and host drivers (HD). A "host" in this 9 host bus adapter (HBA) drivers and host drivers (HD). A "host" in this
10 context is a bridge between a computer IO bus (e.g. PCI or ISA) and a 10 context is a bridge between a computer IO bus (e.g. PCI or ISA) and a
11 single SCSI initiator port on a SCSI transport. An "initiator" port 11 single SCSI initiator port on a SCSI transport. An "initiator" port
12 (SCSI terminology, see SAM-3 at http://www.t10.org) sends SCSI commands 12 (SCSI terminology, see SAM-3 at http://www.t10.org) sends SCSI commands
13 to "target" SCSI ports (e.g. disks). There can be many LLDs in a running 13 to "target" SCSI ports (e.g. disks). There can be many LLDs in a running
14 system, but only one per hardware type. Most LLDs can control one or more 14 system, but only one per hardware type. Most LLDs can control one or more
15 SCSI HBAs. Some HBAs contain multiple hosts. 15 SCSI HBAs. Some HBAs contain multiple hosts.
16 16
17 In some cases the SCSI transport is an external bus that already has 17 In some cases the SCSI transport is an external bus that already has
18 its own subsystem in Linux (e.g. USB and ieee1394). In such cases the 18 its own subsystem in Linux (e.g. USB and ieee1394). In such cases the
19 SCSI subsystem LLD is a software bridge to the other driver subsystem. 19 SCSI subsystem LLD is a software bridge to the other driver subsystem.
20 Examples are the usb-storage driver (found in the drivers/usb/storage 20 Examples are the usb-storage driver (found in the drivers/usb/storage
21 directory) and the ieee1394/sbp2 driver (found in the drivers/ieee1394 21 directory) and the ieee1394/sbp2 driver (found in the drivers/ieee1394
22 directory). 22 directory).
23 23
24 For example, the aic7xxx LLD controls Adaptec SCSI parallel interface 24 For example, the aic7xxx LLD controls Adaptec SCSI parallel interface
25 (SPI) controllers based on that company's 7xxx chip series. The aic7xxx 25 (SPI) controllers based on that company's 7xxx chip series. The aic7xxx
26 LLD can be built into the kernel or loaded as a module. There can only be 26 LLD can be built into the kernel or loaded as a module. There can only be
27 one aic7xxx LLD running in a Linux system but it may be controlling many 27 one aic7xxx LLD running in a Linux system but it may be controlling many
28 HBAs. These HBAs might be either on PCI daughter-boards or built into 28 HBAs. These HBAs might be either on PCI daughter-boards or built into
29 the motherboard (or both). Some aic7xxx based HBAs are dual controllers 29 the motherboard (or both). Some aic7xxx based HBAs are dual controllers
30 and thus represent two hosts. Like most modern HBAs, each aic7xxx host 30 and thus represent two hosts. Like most modern HBAs, each aic7xxx host
31 has its own PCI device address. [The one-to-one correspondence between 31 has its own PCI device address. [The one-to-one correspondence between
32 a SCSI host and a PCI device is common but not required (e.g. with 32 a SCSI host and a PCI device is common but not required (e.g. with
33 ISA or MCA adapters).] 33 ISA or MCA adapters).]
34 34
35 The SCSI mid level isolates an LLD from other layers such as the SCSI 35 The SCSI mid level isolates an LLD from other layers such as the SCSI
36 upper layer drivers and the block layer. 36 upper layer drivers and the block layer.
37 37
38 This version of the document roughly matches linux kernel version 2.6.8 . 38 This version of the document roughly matches linux kernel version 2.6.8 .
39 39
40 Documentation 40 Documentation
41 ============= 41 =============
42 There is a SCSI documentation directory within the kernel source tree, 42 There is a SCSI documentation directory within the kernel source tree,
43 typically Documentation/scsi . Most documents are in plain 43 typically Documentation/scsi . Most documents are in plain
44 (i.e. ASCII) text. This file is named scsi_mid_low_api.txt and can be 44 (i.e. ASCII) text. This file is named scsi_mid_low_api.txt and can be
45 found in that directory. A more recent copy of this document may be found 45 found in that directory. A more recent copy of this document may be found
46 at http://web.archive.org/web/20070107183357rn_1/sg.torque.net/scsi/. 46 at http://web.archive.org/web/20070107183357rn_1/sg.torque.net/scsi/.
47 Many LLDs are documented there (e.g. aic7xxx.txt). The SCSI mid-level is 47 Many LLDs are documented there (e.g. aic7xxx.txt). The SCSI mid-level is
48 briefly described in scsi.txt which contains a url to a document 48 briefly described in scsi.txt which contains a url to a document
49 describing the SCSI subsystem in the lk 2.4 series. Two upper level 49 describing the SCSI subsystem in the lk 2.4 series. Two upper level
50 drivers have documents in that directory: st.txt (SCSI tape driver) and 50 drivers have documents in that directory: st.txt (SCSI tape driver) and
51 scsi-generic.txt (for the sg driver). 51 scsi-generic.txt (for the sg driver).
52 52
53 Some documentation (or urls) for LLDs may be found in the C source code 53 Some documentation (or urls) for LLDs may be found in the C source code
54 or in the same directory as the C source code. For example to find a url 54 or in the same directory as the C source code. For example to find a url
55 about the USB mass storage driver see the 55 about the USB mass storage driver see the
56 /usr/src/linux/drivers/usb/storage directory. 56 /usr/src/linux/drivers/usb/storage directory.
57 57
58 The Linux kernel source Documentation/DocBook/scsidrivers.tmpl file 58 The Linux kernel source Documentation/DocBook/scsidrivers.tmpl file
59 refers to this file. With the appropriate DocBook tool-set, this permits 59 refers to this file. With the appropriate DocBook tool-set, this permits
60 users to generate html, ps and pdf renderings of information within this 60 users to generate html, ps and pdf renderings of information within this
61 file (e.g. the interface functions). 61 file (e.g. the interface functions).
62 62
63 Driver structure 63 Driver structure
64 ================ 64 ================
65 Traditionally an LLD for the SCSI subsystem has been at least two files in 65 Traditionally an LLD for the SCSI subsystem has been at least two files in
66 the drivers/scsi directory. For example, a driver called "xyz" has a header 66 the drivers/scsi directory. For example, a driver called "xyz" has a header
67 file "xyz.h" and a source file "xyz.c". [Actually there is no good reason 67 file "xyz.h" and a source file "xyz.c". [Actually there is no good reason
68 why this couldn't all be in one file; the header file is superfluous.] Some 68 why this couldn't all be in one file; the header file is superfluous.] Some
69 drivers that have been ported to several operating systems have more than 69 drivers that have been ported to several operating systems have more than
70 two files. For example the aic7xxx driver has separate files for generic 70 two files. For example the aic7xxx driver has separate files for generic
71 and OS-specific code (e.g. FreeBSD and Linux). Such drivers tend to have 71 and OS-specific code (e.g. FreeBSD and Linux). Such drivers tend to have
72 their own directory under the drivers/scsi directory. 72 their own directory under the drivers/scsi directory.
73 73
74 When a new LLD is being added to Linux, the following files (found in the 74 When a new LLD is being added to Linux, the following files (found in the
75 drivers/scsi directory) will need some attention: Makefile and Kconfig . 75 drivers/scsi directory) will need some attention: Makefile and Kconfig .
76 It is probably best to study how existing LLDs are organized. 76 It is probably best to study how existing LLDs are organized.
77 77
78 As the 2.5 series development kernels evolve into the 2.6 series 78 As the 2.5 series development kernels evolve into the 2.6 series
79 production series, changes are being introduced into this interface. An 79 production series, changes are being introduced into this interface. An
80 example of this is driver initialization code where there are now 2 models 80 example of this is driver initialization code where there are now 2 models
81 available. The older one, similar to what was found in the lk 2.4 series, 81 available. The older one, similar to what was found in the lk 2.4 series,
82 is based on hosts that are detected at HBA driver load time. This will be 82 is based on hosts that are detected at HBA driver load time. This will be
83 referred to the "passive" initialization model. The newer model allows HBAs 83 referred to the "passive" initialization model. The newer model allows HBAs
84 to be hot plugged (and unplugged) during the lifetime of the LLD and will 84 to be hot plugged (and unplugged) during the lifetime of the LLD and will
85 be referred to as the "hotplug" initialization model. The newer model is 85 be referred to as the "hotplug" initialization model. The newer model is
86 preferred as it can handle both traditional SCSI equipment that is 86 preferred as it can handle both traditional SCSI equipment that is
87 permanently connected as well as modern "SCSI" devices (e.g. USB or 87 permanently connected as well as modern "SCSI" devices (e.g. USB or
88 IEEE 1394 connected digital cameras) that are hotplugged. Both 88 IEEE 1394 connected digital cameras) that are hotplugged. Both
89 initialization models are discussed in the following sections. 89 initialization models are discussed in the following sections.
90 90
91 An LLD interfaces to the SCSI subsystem several ways: 91 An LLD interfaces to the SCSI subsystem several ways:
92 a) directly invoking functions supplied by the mid level 92 a) directly invoking functions supplied by the mid level
93 b) passing a set of function pointers to a registration function 93 b) passing a set of function pointers to a registration function
94 supplied by the mid level. The mid level will then invoke these 94 supplied by the mid level. The mid level will then invoke these
95 functions at some point in the future. The LLD will supply 95 functions at some point in the future. The LLD will supply
96 implementations of these functions. 96 implementations of these functions.
97 c) direct access to instances of well known data structures maintained 97 c) direct access to instances of well known data structures maintained
98 by the mid level 98 by the mid level
99 99
100 Those functions in group a) are listed in a section entitled "Mid level 100 Those functions in group a) are listed in a section entitled "Mid level
101 supplied functions" below. 101 supplied functions" below.
102 102
103 Those functions in group b) are listed in a section entitled "Interface 103 Those functions in group b) are listed in a section entitled "Interface
104 functions" below. Their function pointers are placed in the members of 104 functions" below. Their function pointers are placed in the members of
105 "struct scsi_host_template", an instance of which is passed to 105 "struct scsi_host_template", an instance of which is passed to
106 scsi_host_alloc() ** . Those interface functions that the LLD does not 106 scsi_host_alloc() ** . Those interface functions that the LLD does not
107 wish to supply should have NULL placed in the corresponding member of 107 wish to supply should have NULL placed in the corresponding member of
108 struct scsi_host_template. Defining an instance of struct 108 struct scsi_host_template. Defining an instance of struct
109 scsi_host_template at file scope will cause NULL to be placed in function 109 scsi_host_template at file scope will cause NULL to be placed in function
110 pointer members not explicitly initialized. 110 pointer members not explicitly initialized.
111 111
112 Those usages in group c) should be handled with care, especially in a 112 Those usages in group c) should be handled with care, especially in a
113 "hotplug" environment. LLDs should be aware of the lifetime of instances 113 "hotplug" environment. LLDs should be aware of the lifetime of instances
114 that are shared with the mid level and other layers. 114 that are shared with the mid level and other layers.
115 115
116 All functions defined within an LLD and all data defined at file scope 116 All functions defined within an LLD and all data defined at file scope
117 should be static. For example the slave_alloc() function in an LLD 117 should be static. For example the slave_alloc() function in an LLD
118 called "xxx" could be defined as 118 called "xxx" could be defined as
119 "static int xxx_slave_alloc(struct scsi_device * sdev) { /* code */ }" 119 "static int xxx_slave_alloc(struct scsi_device * sdev) { /* code */ }"
120 120
121 ** the scsi_host_alloc() function is a replacement for the rather vaguely 121 ** the scsi_host_alloc() function is a replacement for the rather vaguely
122 named scsi_register() function in most situations. The scsi_register() 122 named scsi_register() function in most situations. The scsi_register()
123 and scsi_unregister() functions remain to support legacy LLDs that use 123 and scsi_unregister() functions remain to support legacy LLDs that use
124 the passive initialization model. 124 the passive initialization model.
125 125
126 126
127 Hotplug initialization model 127 Hotplug initialization model
128 ============================ 128 ============================
129 In this model an LLD controls when SCSI hosts are introduced and removed 129 In this model an LLD controls when SCSI hosts are introduced and removed
130 from the SCSI subsystem. Hosts can be introduced as early as driver 130 from the SCSI subsystem. Hosts can be introduced as early as driver
131 initialization and removed as late as driver shutdown. Typically a driver 131 initialization and removed as late as driver shutdown. Typically a driver
132 will respond to a sysfs probe() callback that indicates an HBA has been 132 will respond to a sysfs probe() callback that indicates an HBA has been
133 detected. After confirming that the new device is one that the LLD wants 133 detected. After confirming that the new device is one that the LLD wants
134 to control, the LLD will initialize the HBA and then register a new host 134 to control, the LLD will initialize the HBA and then register a new host
135 with the SCSI mid level. 135 with the SCSI mid level.
136 136
137 During LLD initialization the driver should register itself with the 137 During LLD initialization the driver should register itself with the
138 appropriate IO bus on which it expects to find HBA(s) (e.g. the PCI bus). 138 appropriate IO bus on which it expects to find HBA(s) (e.g. the PCI bus).
139 This can probably be done via sysfs. Any driver parameters (especially 139 This can probably be done via sysfs. Any driver parameters (especially
140 those that are writable after the driver is loaded) could also be 140 those that are writable after the driver is loaded) could also be
141 registered with sysfs at this point. The SCSI mid level first becomes 141 registered with sysfs at this point. The SCSI mid level first becomes
142 aware of an LLD when that LLD registers its first HBA. 142 aware of an LLD when that LLD registers its first HBA.
143 143
144 At some later time, the LLD becomes aware of an HBA and what follows 144 At some later time, the LLD becomes aware of an HBA and what follows
145 is a typical sequence of calls between the LLD and the mid level. 145 is a typical sequence of calls between the LLD and the mid level.
146 This example shows the mid level scanning the newly introduced HBA for 3 146 This example shows the mid level scanning the newly introduced HBA for 3
147 scsi devices of which only the first 2 respond: 147 scsi devices of which only the first 2 respond:
148 148
149 HBA PROBE: assume 2 SCSI devices found in scan 149 HBA PROBE: assume 2 SCSI devices found in scan
150 LLD mid level LLD 150 LLD mid level LLD
151 ===-------------------=========--------------------===------ 151 ===-------------------=========--------------------===------
152 scsi_host_alloc() --> 152 scsi_host_alloc() -->
153 scsi_add_host() ----> 153 scsi_add_host() ---->
154 scsi_scan_host() -------+ 154 scsi_scan_host() -------+
155 | 155 |
156 slave_alloc() 156 slave_alloc()
157 slave_configure() --> scsi_adjust_queue_depth() 157 slave_configure() --> scsi_adjust_queue_depth()
158 | 158 |
159 slave_alloc() 159 slave_alloc()
160 slave_configure() 160 slave_configure()
161 | 161 |
162 slave_alloc() *** 162 slave_alloc() ***
163 slave_destroy() *** 163 slave_destroy() ***
164 ------------------------------------------------------------ 164 ------------------------------------------------------------
165 165
166 If the LLD wants to adjust the default queue settings, it can invoke 166 If the LLD wants to adjust the default queue settings, it can invoke
167 scsi_adjust_queue_depth() in its slave_configure() routine. 167 scsi_adjust_queue_depth() in its slave_configure() routine.
168 168
169 *** For scsi devices that the mid level tries to scan but do not 169 *** For scsi devices that the mid level tries to scan but do not
170 respond, a slave_alloc(), slave_destroy() pair is called. 170 respond, a slave_alloc(), slave_destroy() pair is called.
171 171
172 When an HBA is being removed it could be as part of an orderly shutdown 172 When an HBA is being removed it could be as part of an orderly shutdown
173 associated with the LLD module being unloaded (e.g. with the "rmmod" 173 associated with the LLD module being unloaded (e.g. with the "rmmod"
174 command) or in response to a "hot unplug" indicated by sysfs()'s 174 command) or in response to a "hot unplug" indicated by sysfs()'s
175 remove() callback being invoked. In either case, the sequence is the 175 remove() callback being invoked. In either case, the sequence is the
176 same: 176 same:
177 177
178 HBA REMOVE: assume 2 SCSI devices attached 178 HBA REMOVE: assume 2 SCSI devices attached
179 LLD mid level LLD 179 LLD mid level LLD
180 ===----------------------=========-----------------===------ 180 ===----------------------=========-----------------===------
181 scsi_remove_host() ---------+ 181 scsi_remove_host() ---------+
182 | 182 |
183 slave_destroy() 183 slave_destroy()
184 slave_destroy() 184 slave_destroy()
185 scsi_host_put() 185 scsi_host_put()
186 ------------------------------------------------------------ 186 ------------------------------------------------------------
187 187
188 It may be useful for a LLD to keep track of struct Scsi_Host instances 188 It may be useful for a LLD to keep track of struct Scsi_Host instances
189 (a pointer is returned by scsi_host_alloc()). Such instances are "owned" 189 (a pointer is returned by scsi_host_alloc()). Such instances are "owned"
190 by the mid-level. struct Scsi_Host instances are freed from 190 by the mid-level. struct Scsi_Host instances are freed from
191 scsi_host_put() when the reference count hits zero. 191 scsi_host_put() when the reference count hits zero.
192 192
193 Hot unplugging an HBA that controls a disk which is processing SCSI 193 Hot unplugging an HBA that controls a disk which is processing SCSI
194 commands on a mounted file system is an interesting situation. Reference 194 commands on a mounted file system is an interesting situation. Reference
195 counting logic is being introduced into the mid level to cope with many 195 counting logic is being introduced into the mid level to cope with many
196 of the issues involved. See the section on reference counting below. 196 of the issues involved. See the section on reference counting below.
197 197
198 198
199 The hotplug concept may be extended to SCSI devices. Currently, when an 199 The hotplug concept may be extended to SCSI devices. Currently, when an
200 HBA is added, the scsi_scan_host() function causes a scan for SCSI devices 200 HBA is added, the scsi_scan_host() function causes a scan for SCSI devices
201 attached to the HBA's SCSI transport. On newer SCSI transports the HBA 201 attached to the HBA's SCSI transport. On newer SCSI transports the HBA
202 may become aware of a new SCSI device _after_ the scan has completed. 202 may become aware of a new SCSI device _after_ the scan has completed.
203 An LLD can use this sequence to make the mid level aware of a SCSI device: 203 An LLD can use this sequence to make the mid level aware of a SCSI device:
204 204
205 SCSI DEVICE hotplug 205 SCSI DEVICE hotplug
206 LLD mid level LLD 206 LLD mid level LLD
207 ===-------------------=========--------------------===------ 207 ===-------------------=========--------------------===------
208 scsi_add_device() ------+ 208 scsi_add_device() ------+
209 | 209 |
210 slave_alloc() 210 slave_alloc()
211 slave_configure() [--> scsi_adjust_queue_depth()] 211 slave_configure() [--> scsi_adjust_queue_depth()]
212 ------------------------------------------------------------ 212 ------------------------------------------------------------
213 213
214 In a similar fashion, an LLD may become aware that a SCSI device has been 214 In a similar fashion, an LLD may become aware that a SCSI device has been
215 removed (unplugged) or the connection to it has been interrupted. Some 215 removed (unplugged) or the connection to it has been interrupted. Some
216 existing SCSI transports (e.g. SPI) may not become aware that a SCSI 216 existing SCSI transports (e.g. SPI) may not become aware that a SCSI
217 device has been removed until a subsequent SCSI command fails which will 217 device has been removed until a subsequent SCSI command fails which will
218 probably cause that device to be set offline by the mid level. An LLD that 218 probably cause that device to be set offline by the mid level. An LLD that
219 detects the removal of a SCSI device can instigate its removal from 219 detects the removal of a SCSI device can instigate its removal from
220 upper layers with this sequence: 220 upper layers with this sequence:
221 221
222 SCSI DEVICE hot unplug 222 SCSI DEVICE hot unplug
223 LLD mid level LLD 223 LLD mid level LLD
224 ===----------------------=========-----------------===------ 224 ===----------------------=========-----------------===------
225 scsi_remove_device() -------+ 225 scsi_remove_device() -------+
226 | 226 |
227 slave_destroy() 227 slave_destroy()
228 ------------------------------------------------------------ 228 ------------------------------------------------------------
229 229
230 It may be useful for an LLD to keep track of struct scsi_device instances 230 It may be useful for an LLD to keep track of struct scsi_device instances
231 (a pointer is passed as the parameter to slave_alloc() and 231 (a pointer is passed as the parameter to slave_alloc() and
232 slave_configure() callbacks). Such instances are "owned" by the mid-level. 232 slave_configure() callbacks). Such instances are "owned" by the mid-level.
233 struct scsi_device instances are freed after slave_destroy(). 233 struct scsi_device instances are freed after slave_destroy().
234 234
235 235
236 Passive initialization model 236 Passive initialization model
237 ============================ 237 ============================
238 These older LLDs include a file called "scsi_module.c" [yes the ".c" is a 238 These older LLDs include a file called "scsi_module.c" [yes the ".c" is a
239 little surprising] in their source code. For that file to work an 239 little surprising] in their source code. For that file to work an
240 instance of struct scsi_host_template with the name "driver_template" 240 instance of struct scsi_host_template with the name "driver_template"
241 needs to be defined. Here is a typical code sequence used in this model: 241 needs to be defined. Here is a typical code sequence used in this model:
242 static struct scsi_host_template driver_template = { 242 static struct scsi_host_template driver_template = {
243 ... 243 ...
244 }; 244 };
245 #include "scsi_module.c" 245 #include "scsi_module.c"
246 246
247 The scsi_module.c file contains two functions: 247 The scsi_module.c file contains two functions:
248 - init_this_scsi_driver() which is executed when the LLD is 248 - init_this_scsi_driver() which is executed when the LLD is
249 initialized (i.e. boot time or module load time) 249 initialized (i.e. boot time or module load time)
250 - exit_this_scsi_driver() which is executed when the LLD is shut 250 - exit_this_scsi_driver() which is executed when the LLD is shut
251 down (i.e. module unload time) 251 down (i.e. module unload time)
252 Note: since these functions are tagged with __init and __exit qualifiers 252 Note: since these functions are tagged with __init and __exit qualifiers
253 an LLD should not call them explicitly (since the kernel does that). 253 an LLD should not call them explicitly (since the kernel does that).
254 254
255 Here is an example of an initialization sequence when two hosts are 255 Here is an example of an initialization sequence when two hosts are
256 detected (so detect() returns 2) and the SCSI bus scan on each host 256 detected (so detect() returns 2) and the SCSI bus scan on each host
257 finds 1 SCSI device (and a second device does not respond). 257 finds 1 SCSI device (and a second device does not respond).
258 258
259 LLD mid level LLD 259 LLD mid level LLD
260 ===----------------------=========-----------------===------ 260 ===----------------------=========-----------------===------
261 init_this_scsi_driver() ----+ 261 init_this_scsi_driver() ----+
262 | 262 |
263 detect() -----------------+ 263 detect() -----------------+
264 | | 264 | |
265 | scsi_register() 265 | scsi_register()
266 | scsi_register() 266 | scsi_register()
267 | 267 |
268 slave_alloc() 268 slave_alloc()
269 slave_configure() --> scsi_adjust_queue_depth() 269 slave_configure() --> scsi_adjust_queue_depth()
270 slave_alloc() *** 270 slave_alloc() ***
271 slave_destroy() *** 271 slave_destroy() ***
272 | 272 |
273 slave_alloc() 273 slave_alloc()
274 slave_configure() 274 slave_configure()
275 slave_alloc() *** 275 slave_alloc() ***
276 slave_destroy() *** 276 slave_destroy() ***
277 ------------------------------------------------------------ 277 ------------------------------------------------------------
278 278
279 The mid level invokes scsi_adjust_queue_depth() with tagged queuing off and 279 The mid level invokes scsi_adjust_queue_depth() with tagged queuing off and
280 "cmd_per_lun" for that host as the queue length. These settings can be 280 "cmd_per_lun" for that host as the queue length. These settings can be
281 overridden by a slave_configure() supplied by the LLD. 281 overridden by a slave_configure() supplied by the LLD.
282 282
283 *** For scsi devices that the mid level tries to scan but do not 283 *** For scsi devices that the mid level tries to scan but do not
284 respond, a slave_alloc(), slave_destroy() pair is called. 284 respond, a slave_alloc(), slave_destroy() pair is called.
285 285
286 Here is an LLD shutdown sequence: 286 Here is an LLD shutdown sequence:
287 287
288 LLD mid level LLD 288 LLD mid level LLD
289 ===----------------------=========-----------------===------ 289 ===----------------------=========-----------------===------
290 exit_this_scsi_driver() ----+ 290 exit_this_scsi_driver() ----+
291 | 291 |
292 slave_destroy() 292 slave_destroy()
293 release() --> scsi_unregister() 293 release() --> scsi_unregister()
294 | 294 |
295 slave_destroy() 295 slave_destroy()
296 release() --> scsi_unregister() 296 release() --> scsi_unregister()
297 ------------------------------------------------------------ 297 ------------------------------------------------------------
298 298
299 An LLD need not define slave_destroy() (i.e. it is optional). 299 An LLD need not define slave_destroy() (i.e. it is optional).
300 300
301 The shortcoming of the "passive initialization model" is that host 301 The shortcoming of the "passive initialization model" is that host
302 registration and de-registration are (typically) tied to LLD initialization 302 registration and de-registration are (typically) tied to LLD initialization
303 and shutdown. Once the LLD is initialized then a new host that appears 303 and shutdown. Once the LLD is initialized then a new host that appears
304 (e.g. via hotplugging) cannot easily be added without a redundant 304 (e.g. via hotplugging) cannot easily be added without a redundant
305 driver shutdown and re-initialization. It may be possible to write an LLD 305 driver shutdown and re-initialization. It may be possible to write an LLD
306 that uses both initialization models. 306 that uses both initialization models.
307 307
308 308
309 Reference Counting 309 Reference Counting
310 ================== 310 ==================
311 The Scsi_Host structure has had reference counting infrastructure added. 311 The Scsi_Host structure has had reference counting infrastructure added.
312 This effectively spreads the ownership of struct Scsi_Host instances 312 This effectively spreads the ownership of struct Scsi_Host instances
313 across the various SCSI layers which use them. Previously such instances 313 across the various SCSI layers which use them. Previously such instances
314 were exclusively owned by the mid level. LLDs would not usually need to 314 were exclusively owned by the mid level. LLDs would not usually need to
315 directly manipulate these reference counts but there may be some cases 315 directly manipulate these reference counts but there may be some cases
316 where they do. 316 where they do.
317 317
318 There are 3 reference counting functions of interest associated with 318 There are 3 reference counting functions of interest associated with
319 struct Scsi_Host: 319 struct Scsi_Host:
320 - scsi_host_alloc(): returns a pointer to new instance of struct 320 - scsi_host_alloc(): returns a pointer to new instance of struct
321 Scsi_Host which has its reference count ^^ set to 1 321 Scsi_Host which has its reference count ^^ set to 1
322 - scsi_host_get(): adds 1 to the reference count of the given instance 322 - scsi_host_get(): adds 1 to the reference count of the given instance
323 - scsi_host_put(): decrements 1 from the reference count of the given 323 - scsi_host_put(): decrements 1 from the reference count of the given
324 instance. If the reference count reaches 0 then the given instance 324 instance. If the reference count reaches 0 then the given instance
325 is freed 325 is freed
326 326
327 The Scsi_device structure has had reference counting infrastructure added. 327 The Scsi_device structure has had reference counting infrastructure added.
328 This effectively spreads the ownership of struct Scsi_device instances 328 This effectively spreads the ownership of struct Scsi_device instances
329 across the various SCSI layers which use them. Previously such instances 329 across the various SCSI layers which use them. Previously such instances
330 were exclusively owned by the mid level. See the access functions declared 330 were exclusively owned by the mid level. See the access functions declared
331 towards the end of include/scsi/scsi_device.h . If an LLD wants to keep 331 towards the end of include/scsi/scsi_device.h . If an LLD wants to keep
332 a copy of a pointer to a Scsi_device instance it should use scsi_device_get() 332 a copy of a pointer to a Scsi_device instance it should use scsi_device_get()
333 to bump its reference count. When it is finished with the pointer it can 333 to bump its reference count. When it is finished with the pointer it can
334 use scsi_device_put() to decrement its reference count (and potentially 334 use scsi_device_put() to decrement its reference count (and potentially
335 delete it). 335 delete it).
336 336
337 ^^ struct Scsi_Host actually has 2 reference counts which are manipulated 337 ^^ struct Scsi_Host actually has 2 reference counts which are manipulated
338 in parallel by these functions. 338 in parallel by these functions.
339 339
340 340
341 Conventions 341 Conventions
342 =========== 342 ===========
343 First, Linus Torvalds's thoughts on C coding style can be found in the 343 First, Linus Torvalds's thoughts on C coding style can be found in the
344 Documentation/CodingStyle file. 344 Documentation/CodingStyle file.
345 345
346 Next, there is a movement to "outlaw" typedefs introducing synonyms for 346 Next, there is a movement to "outlaw" typedefs introducing synonyms for
347 struct tags. Both can be still found in the SCSI subsystem, but 347 struct tags. Both can be still found in the SCSI subsystem, but
348 the typedefs have been moved to a single file, scsi_typedefs.h to 348 the typedefs have been moved to a single file, scsi_typedefs.h to
349 make their future removal easier, for example: 349 make their future removal easier, for example:
350 "typedef struct scsi_cmnd Scsi_Cmnd;" 350 "typedef struct scsi_cmnd Scsi_Cmnd;"
351 351
352 Also, most C99 enhancements are encouraged to the extent they are supported 352 Also, most C99 enhancements are encouraged to the extent they are supported
353 by the relevant gcc compilers. So C99 style structure and array 353 by the relevant gcc compilers. So C99 style structure and array
354 initializers are encouraged where appropriate. Don't go too far, 354 initializers are encouraged where appropriate. Don't go too far,
355 VLAs are not properly supported yet. An exception to this is the use of 355 VLAs are not properly supported yet. An exception to this is the use of
356 "//" style comments; /*...*/ comments are still preferred in Linux. 356 "//" style comments; /*...*/ comments are still preferred in Linux.
357 357
358 Well written, tested and documented code, need not be re-formatted to 358 Well written, tested and documented code, need not be re-formatted to
359 comply with the above conventions. For example, the aic7xxx driver 359 comply with the above conventions. For example, the aic7xxx driver
360 comes to Linux from FreeBSD and Adaptec's own labs. No doubt FreeBSD 360 comes to Linux from FreeBSD and Adaptec's own labs. No doubt FreeBSD
361 and Adaptec have their own coding conventions. 361 and Adaptec have their own coding conventions.
362 362
363 363
364 Mid level supplied functions 364 Mid level supplied functions
365 ============================ 365 ============================
366 These functions are supplied by the SCSI mid level for use by LLDs. 366 These functions are supplied by the SCSI mid level for use by LLDs.
367 The names (i.e. entry points) of these functions are exported 367 The names (i.e. entry points) of these functions are exported
368 so an LLD that is a module can access them. The kernel will 368 so an LLD that is a module can access them. The kernel will
369 arrange for the SCSI mid level to be loaded and initialized before any LLD 369 arrange for the SCSI mid level to be loaded and initialized before any LLD
370 is initialized. The functions below are listed alphabetically and their 370 is initialized. The functions below are listed alphabetically and their
371 names all start with "scsi_". 371 names all start with "scsi_".
372 372
373 Summary: 373 Summary:
374 scsi_activate_tcq - turn on tag command queueing 374 scsi_activate_tcq - turn on tag command queueing
375 scsi_add_device - creates new scsi device (lu) instance 375 scsi_add_device - creates new scsi device (lu) instance
376 scsi_add_host - perform sysfs registration and set up transport class 376 scsi_add_host - perform sysfs registration and set up transport class
377 scsi_adjust_queue_depth - change the queue depth on a SCSI device 377 scsi_adjust_queue_depth - change the queue depth on a SCSI device
378 scsi_bios_ptable - return copy of block device's partition table 378 scsi_bios_ptable - return copy of block device's partition table
379 scsi_block_requests - prevent further commands being queued to given host 379 scsi_block_requests - prevent further commands being queued to given host
380 scsi_deactivate_tcq - turn off tag command queueing 380 scsi_deactivate_tcq - turn off tag command queueing
381 scsi_host_alloc - return a new scsi_host instance whose refcount==1 381 scsi_host_alloc - return a new scsi_host instance whose refcount==1
382 scsi_host_get - increments Scsi_Host instance's refcount 382 scsi_host_get - increments Scsi_Host instance's refcount
383 scsi_host_put - decrements Scsi_Host instance's refcount (free if 0) 383 scsi_host_put - decrements Scsi_Host instance's refcount (free if 0)
384 scsi_partsize - parse partition table into cylinders, heads + sectors 384 scsi_partsize - parse partition table into cylinders, heads + sectors
385 scsi_register - create and register a scsi host adapter instance. 385 scsi_register - create and register a scsi host adapter instance.
386 scsi_remove_device - detach and remove a SCSI device 386 scsi_remove_device - detach and remove a SCSI device
387 scsi_remove_host - detach and remove all SCSI devices owned by host 387 scsi_remove_host - detach and remove all SCSI devices owned by host
388 scsi_report_bus_reset - report scsi _bus_ reset observed 388 scsi_report_bus_reset - report scsi _bus_ reset observed
389 scsi_scan_host - scan SCSI bus 389 scsi_scan_host - scan SCSI bus
390 scsi_track_queue_full - track successive QUEUE_FULL events 390 scsi_track_queue_full - track successive QUEUE_FULL events
391 scsi_unblock_requests - allow further commands to be queued to given host 391 scsi_unblock_requests - allow further commands to be queued to given host
392 scsi_unregister - [calls scsi_host_put()] 392 scsi_unregister - [calls scsi_host_put()]
393 393
394 394
395 Details: 395 Details:
396 396
397 /** 397 /**
398 * scsi_activate_tcq - turn on tag command queueing ("ordered" task attribute) 398 * scsi_activate_tcq - turn on tag command queueing ("ordered" task attribute)
399 * @sdev: device to turn on TCQ for 399 * @sdev: device to turn on TCQ for
400 * @depth: queue depth 400 * @depth: queue depth
401 * 401 *
402 * Returns nothing 402 * Returns nothing
403 * 403 *
404 * Might block: no 404 * Might block: no
405 * 405 *
406 * Notes: Eventually, it is hoped depth would be the maximum depth 406 * Notes: Eventually, it is hoped depth would be the maximum depth
407 * the device could cope with and the real queue depth 407 * the device could cope with and the real queue depth
408 * would be adjustable from 0 to depth. 408 * would be adjustable from 0 to depth.
409 * 409 *
410 * Defined (inline) in: include/scsi/scsi_tcq.h 410 * Defined (inline) in: include/scsi/scsi_tcq.h
411 **/ 411 **/
412 void scsi_activate_tcq(struct scsi_device *sdev, int depth) 412 void scsi_activate_tcq(struct scsi_device *sdev, int depth)
413 413
414 414
415 /** 415 /**
416 * scsi_add_device - creates new scsi device (lu) instance 416 * scsi_add_device - creates new scsi device (lu) instance
417 * @shost: pointer to scsi host instance 417 * @shost: pointer to scsi host instance
418 * @channel: channel number (rarely other than 0) 418 * @channel: channel number (rarely other than 0)
419 * @id: target id number 419 * @id: target id number
420 * @lun: logical unit number 420 * @lun: logical unit number
421 * 421 *
422 * Returns pointer to new struct scsi_device instance or 422 * Returns pointer to new struct scsi_device instance or
423 * ERR_PTR(-ENODEV) (or some other bent pointer) if something is 423 * ERR_PTR(-ENODEV) (or some other bent pointer) if something is
424 * wrong (e.g. no lu responds at given address) 424 * wrong (e.g. no lu responds at given address)
425 * 425 *
426 * Might block: yes 426 * Might block: yes
427 * 427 *
428 * Notes: This call is usually performed internally during a scsi 428 * Notes: This call is usually performed internally during a scsi
429 * bus scan when an HBA is added (i.e. scsi_scan_host()). So it 429 * bus scan when an HBA is added (i.e. scsi_scan_host()). So it
430 * should only be called if the HBA becomes aware of a new scsi 430 * should only be called if the HBA becomes aware of a new scsi
431 * device (lu) after scsi_scan_host() has completed. If successful 431 * device (lu) after scsi_scan_host() has completed. If successful
432 * this call can lead to slave_alloc() and slave_configure() callbacks 432 * this call can lead to slave_alloc() and slave_configure() callbacks
433 * into the LLD. 433 * into the LLD.
434 * 434 *
435 * Defined in: drivers/scsi/scsi_scan.c 435 * Defined in: drivers/scsi/scsi_scan.c
436 **/ 436 **/
437 struct scsi_device * scsi_add_device(struct Scsi_Host *shost, 437 struct scsi_device * scsi_add_device(struct Scsi_Host *shost,
438 unsigned int channel, 438 unsigned int channel,
439 unsigned int id, unsigned int lun) 439 unsigned int id, unsigned int lun)
440 440
441 441
442 /** 442 /**
443 * scsi_add_host - perform sysfs registration and set up transport class 443 * scsi_add_host - perform sysfs registration and set up transport class
444 * @shost: pointer to scsi host instance 444 * @shost: pointer to scsi host instance
445 * @dev: pointer to struct device of type scsi class 445 * @dev: pointer to struct device of type scsi class
446 * 446 *
447 * Returns 0 on success, negative errno of failure (e.g. -ENOMEM) 447 * Returns 0 on success, negative errno of failure (e.g. -ENOMEM)
448 * 448 *
449 * Might block: no 449 * Might block: no
450 * 450 *
451 * Notes: Only required in "hotplug initialization model" after a 451 * Notes: Only required in "hotplug initialization model" after a
452 * successful call to scsi_host_alloc(). This function does not 452 * successful call to scsi_host_alloc(). This function does not
453 * scan the bus; this can be done by calling scsi_scan_host() or 453 * scan the bus; this can be done by calling scsi_scan_host() or
454 * in some other transport-specific way. The LLD must set up 454 * in some other transport-specific way. The LLD must set up
455 * the transport template before calling this function and may only 455 * the transport template before calling this function and may only
456 * access the transport class data after this function has been called. 456 * access the transport class data after this function has been called.
457 * 457 *
458 * Defined in: drivers/scsi/hosts.c 458 * Defined in: drivers/scsi/hosts.c
459 **/ 459 **/
460 int scsi_add_host(struct Scsi_Host *shost, struct device * dev) 460 int scsi_add_host(struct Scsi_Host *shost, struct device * dev)
461 461
462 462
463 /** 463 /**
464 * scsi_adjust_queue_depth - allow LLD to change queue depth on a SCSI device 464 * scsi_adjust_queue_depth - allow LLD to change queue depth on a SCSI device
465 * @sdev: pointer to SCSI device to change queue depth on 465 * @sdev: pointer to SCSI device to change queue depth on
466 * @tagged: 0 - no tagged queuing 466 * @tagged: 0 - no tagged queuing
467 * MSG_SIMPLE_TAG - simple tagged queuing 467 * MSG_SIMPLE_TAG - simple tagged queuing
468 * MSG_ORDERED_TAG - ordered tagged queuing 468 * MSG_ORDERED_TAG - ordered tagged queuing
469 * @tags Number of tags allowed if tagged queuing enabled, 469 * @tags Number of tags allowed if tagged queuing enabled,
470 * or number of commands the LLD can queue up 470 * or number of commands the LLD can queue up
471 * in non-tagged mode (as per cmd_per_lun). 471 * in non-tagged mode (as per cmd_per_lun).
472 * 472 *
473 * Returns nothing 473 * Returns nothing
474 * 474 *
475 * Might block: no 475 * Might block: no
476 * 476 *
477 * Notes: Can be invoked any time on a SCSI device controlled by this 477 * Notes: Can be invoked any time on a SCSI device controlled by this
478 * LLD. [Specifically during and after slave_configure() and prior to 478 * LLD. [Specifically during and after slave_configure() and prior to
479 * slave_destroy().] Can safely be invoked from interrupt code. Actual 479 * slave_destroy().] Can safely be invoked from interrupt code. Actual
480 * queue depth change may be delayed until the next command is being 480 * queue depth change may be delayed until the next command is being
481 * processed. See also scsi_activate_tcq() and scsi_deactivate_tcq(). 481 * processed. See also scsi_activate_tcq() and scsi_deactivate_tcq().
482 * 482 *
483 * Defined in: drivers/scsi/scsi.c [see source code for more notes] 483 * Defined in: drivers/scsi/scsi.c [see source code for more notes]
484 * 484 *
485 **/ 485 **/
486 void scsi_adjust_queue_depth(struct scsi_device * sdev, int tagged, 486 void scsi_adjust_queue_depth(struct scsi_device * sdev, int tagged,
487 int tags) 487 int tags)
488 488
489 489
490 /** 490 /**
491 * scsi_bios_ptable - return copy of block device's partition table 491 * scsi_bios_ptable - return copy of block device's partition table
492 * @dev: pointer to block device 492 * @dev: pointer to block device
493 * 493 *
494 * Returns pointer to partition table, or NULL for failure 494 * Returns pointer to partition table, or NULL for failure
495 * 495 *
496 * Might block: yes 496 * Might block: yes
497 * 497 *
498 * Notes: Caller owns memory returned (free with kfree() ) 498 * Notes: Caller owns memory returned (free with kfree() )
499 * 499 *
500 * Defined in: drivers/scsi/scsicam.c 500 * Defined in: drivers/scsi/scsicam.c
501 **/ 501 **/
502 unsigned char *scsi_bios_ptable(struct block_device *dev) 502 unsigned char *scsi_bios_ptable(struct block_device *dev)
503 503
504 504
505 /** 505 /**
506 * scsi_block_requests - prevent further commands being queued to given host 506 * scsi_block_requests - prevent further commands being queued to given host
507 * 507 *
508 * @shost: pointer to host to block commands on 508 * @shost: pointer to host to block commands on
509 * 509 *
510 * Returns nothing 510 * Returns nothing
511 * 511 *
512 * Might block: no 512 * Might block: no
513 * 513 *
514 * Notes: There is no timer nor any other means by which the requests 514 * Notes: There is no timer nor any other means by which the requests
515 * get unblocked other than the LLD calling scsi_unblock_requests(). 515 * get unblocked other than the LLD calling scsi_unblock_requests().
516 * 516 *
517 * Defined in: drivers/scsi/scsi_lib.c 517 * Defined in: drivers/scsi/scsi_lib.c
518 **/ 518 **/
519 void scsi_block_requests(struct Scsi_Host * shost) 519 void scsi_block_requests(struct Scsi_Host * shost)
520 520
521 521
522 /** 522 /**
523 * scsi_deactivate_tcq - turn off tag command queueing 523 * scsi_deactivate_tcq - turn off tag command queueing
524 * @sdev: device to turn off TCQ for 524 * @sdev: device to turn off TCQ for
525 * @depth: queue depth (stored in sdev) 525 * @depth: queue depth (stored in sdev)
526 * 526 *
527 * Returns nothing 527 * Returns nothing
528 * 528 *
529 * Might block: no 529 * Might block: no
530 * 530 *
531 * Defined (inline) in: include/scsi/scsi_tcq.h 531 * Defined (inline) in: include/scsi/scsi_tcq.h
532 **/ 532 **/
533 void scsi_deactivate_tcq(struct scsi_device *sdev, int depth) 533 void scsi_deactivate_tcq(struct scsi_device *sdev, int depth)
534 534
535 535
536 /** 536 /**
537 * scsi_host_alloc - create a scsi host adapter instance and perform basic 537 * scsi_host_alloc - create a scsi host adapter instance and perform basic
538 * initialization. 538 * initialization.
539 * @sht: pointer to scsi host template 539 * @sht: pointer to scsi host template
540 * @privsize: extra bytes to allocate in hostdata array (which is the 540 * @privsize: extra bytes to allocate in hostdata array (which is the
541 * last member of the returned Scsi_Host instance) 541 * last member of the returned Scsi_Host instance)
542 * 542 *
543 * Returns pointer to new Scsi_Host instance or NULL on failure 543 * Returns pointer to new Scsi_Host instance or NULL on failure
544 * 544 *
545 * Might block: yes 545 * Might block: yes
546 * 546 *
547 * Notes: When this call returns to the LLD, the SCSI bus scan on 547 * Notes: When this call returns to the LLD, the SCSI bus scan on
548 * this host has _not_ yet been done. 548 * this host has _not_ yet been done.
549 * The hostdata array (by default zero length) is a per host scratch 549 * The hostdata array (by default zero length) is a per host scratch
550 * area for the LLD's exclusive use. 550 * area for the LLD's exclusive use.
551 * Both associated refcounting objects have their refcount set to 1. 551 * Both associated refcounting objects have their refcount set to 1.
552 * Full registration (in sysfs) and a bus scan are performed later when 552 * Full registration (in sysfs) and a bus scan are performed later when
553 * scsi_add_host() and scsi_scan_host() are called. 553 * scsi_add_host() and scsi_scan_host() are called.
554 * 554 *
555 * Defined in: drivers/scsi/hosts.c . 555 * Defined in: drivers/scsi/hosts.c .
556 **/ 556 **/
557 struct Scsi_Host * scsi_host_alloc(struct scsi_host_template * sht, 557 struct Scsi_Host * scsi_host_alloc(struct scsi_host_template * sht,
558 int privsize) 558 int privsize)
559 559
560 560
561 /** 561 /**
562 * scsi_host_get - increment Scsi_Host instance refcount 562 * scsi_host_get - increment Scsi_Host instance refcount
563 * @shost: pointer to struct Scsi_Host instance 563 * @shost: pointer to struct Scsi_Host instance
564 * 564 *
565 * Returns nothing 565 * Returns nothing
566 * 566 *
567 * Might block: currently may block but may be changed to not block 567 * Might block: currently may block but may be changed to not block
568 * 568 *
569 * Notes: Actually increments the counts in two sub-objects 569 * Notes: Actually increments the counts in two sub-objects
570 * 570 *
571 * Defined in: drivers/scsi/hosts.c 571 * Defined in: drivers/scsi/hosts.c
572 **/ 572 **/
573 void scsi_host_get(struct Scsi_Host *shost) 573 void scsi_host_get(struct Scsi_Host *shost)
574 574
575 575
576 /** 576 /**
577 * scsi_host_put - decrement Scsi_Host instance refcount, free if 0 577 * scsi_host_put - decrement Scsi_Host instance refcount, free if 0
578 * @shost: pointer to struct Scsi_Host instance 578 * @shost: pointer to struct Scsi_Host instance
579 * 579 *
580 * Returns nothing 580 * Returns nothing
581 * 581 *
582 * Might block: currently may block but may be changed to not block 582 * Might block: currently may block but may be changed to not block
583 * 583 *
584 * Notes: Actually decrements the counts in two sub-objects. If the 584 * Notes: Actually decrements the counts in two sub-objects. If the
585 * latter refcount reaches 0, the Scsi_Host instance is freed. 585 * latter refcount reaches 0, the Scsi_Host instance is freed.
586 * The LLD need not worry exactly when the Scsi_Host instance is 586 * The LLD need not worry exactly when the Scsi_Host instance is
587 * freed, it just shouldn't access the instance after it has balanced 587 * freed, it just shouldn't access the instance after it has balanced
588 * out its refcount usage. 588 * out its refcount usage.
589 * 589 *
590 * Defined in: drivers/scsi/hosts.c 590 * Defined in: drivers/scsi/hosts.c
591 **/ 591 **/
592 void scsi_host_put(struct Scsi_Host *shost) 592 void scsi_host_put(struct Scsi_Host *shost)
593 593
594 594
595 /** 595 /**
596 * scsi_partsize - parse partition table into cylinders, heads + sectors 596 * scsi_partsize - parse partition table into cylinders, heads + sectors
597 * @buf: pointer to partition table 597 * @buf: pointer to partition table
598 * @capacity: size of (total) disk in 512 byte sectors 598 * @capacity: size of (total) disk in 512 byte sectors
599 * @cyls: outputs number of cylinders calculated via this pointer 599 * @cyls: outputs number of cylinders calculated via this pointer
600 * @hds: outputs number of heads calculated via this pointer 600 * @hds: outputs number of heads calculated via this pointer
601 * @secs: outputs number of sectors calculated via this pointer 601 * @secs: outputs number of sectors calculated via this pointer
602 * 602 *
603 * Returns 0 on success, -1 on failure 603 * Returns 0 on success, -1 on failure
604 * 604 *
605 * Might block: no 605 * Might block: no
606 * 606 *
607 * Notes: Caller owns memory returned (free with kfree() ) 607 * Notes: Caller owns memory returned (free with kfree() )
608 * 608 *
609 * Defined in: drivers/scsi/scsicam.c 609 * Defined in: drivers/scsi/scsicam.c
610 **/ 610 **/
611 int scsi_partsize(unsigned char *buf, unsigned long capacity, 611 int scsi_partsize(unsigned char *buf, unsigned long capacity,
612 unsigned int *cyls, unsigned int *hds, unsigned int *secs) 612 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
613 613
614 614
615 /** 615 /**
616 * scsi_register - create and register a scsi host adapter instance. 616 * scsi_register - create and register a scsi host adapter instance.
617 * @sht: pointer to scsi host template 617 * @sht: pointer to scsi host template
618 * @privsize: extra bytes to allocate in hostdata array (which is the 618 * @privsize: extra bytes to allocate in hostdata array (which is the
619 * last member of the returned Scsi_Host instance) 619 * last member of the returned Scsi_Host instance)
620 * 620 *
621 * Returns pointer to new Scsi_Host instance or NULL on failure 621 * Returns pointer to new Scsi_Host instance or NULL on failure
622 * 622 *
623 * Might block: yes 623 * Might block: yes
624 * 624 *
625 * Notes: When this call returns to the LLD, the SCSI bus scan on 625 * Notes: When this call returns to the LLD, the SCSI bus scan on
626 * this host has _not_ yet been done. 626 * this host has _not_ yet been done.
627 * The hostdata array (by default zero length) is a per host scratch 627 * The hostdata array (by default zero length) is a per host scratch
628 * area for the LLD. 628 * area for the LLD.
629 * 629 *
630 * Defined in: drivers/scsi/hosts.c . 630 * Defined in: drivers/scsi/hosts.c .
631 **/ 631 **/
632 struct Scsi_Host * scsi_register(struct scsi_host_template * sht, 632 struct Scsi_Host * scsi_register(struct scsi_host_template * sht,
633 int privsize) 633 int privsize)
634 634
635 635
636 /** 636 /**
637 * scsi_remove_device - detach and remove a SCSI device 637 * scsi_remove_device - detach and remove a SCSI device
638 * @sdev: a pointer to a scsi device instance 638 * @sdev: a pointer to a scsi device instance
639 * 639 *
640 * Returns value: 0 on success, -EINVAL if device not attached 640 * Returns value: 0 on success, -EINVAL if device not attached
641 * 641 *
642 * Might block: yes 642 * Might block: yes
643 * 643 *
644 * Notes: If an LLD becomes aware that a scsi device (lu) has 644 * Notes: If an LLD becomes aware that a scsi device (lu) has
645 * been removed but its host is still present then it can request 645 * been removed but its host is still present then it can request
646 * the removal of that scsi device. If successful this call will 646 * the removal of that scsi device. If successful this call will
647 * lead to the slave_destroy() callback being invoked. sdev is an 647 * lead to the slave_destroy() callback being invoked. sdev is an
648 * invalid pointer after this call. 648 * invalid pointer after this call.
649 * 649 *
650 * Defined in: drivers/scsi/scsi_sysfs.c . 650 * Defined in: drivers/scsi/scsi_sysfs.c .
651 **/ 651 **/
652 int scsi_remove_device(struct scsi_device *sdev) 652 int scsi_remove_device(struct scsi_device *sdev)
653 653
654 654
655 /** 655 /**
656 * scsi_remove_host - detach and remove all SCSI devices owned by host 656 * scsi_remove_host - detach and remove all SCSI devices owned by host
657 * @shost: a pointer to a scsi host instance 657 * @shost: a pointer to a scsi host instance
658 * 658 *
659 * Returns value: 0 on success, 1 on failure (e.g. LLD busy ??) 659 * Returns value: 0 on success, 1 on failure (e.g. LLD busy ??)
660 * 660 *
661 * Might block: yes 661 * Might block: yes
662 * 662 *
663 * Notes: Should only be invoked if the "hotplug initialization 663 * Notes: Should only be invoked if the "hotplug initialization
664 * model" is being used. It should be called _prior_ to 664 * model" is being used. It should be called _prior_ to
665 * scsi_unregister(). 665 * scsi_unregister().
666 * 666 *
667 * Defined in: drivers/scsi/hosts.c . 667 * Defined in: drivers/scsi/hosts.c .
668 **/ 668 **/
669 int scsi_remove_host(struct Scsi_Host *shost) 669 int scsi_remove_host(struct Scsi_Host *shost)
670 670
671 671
672 /** 672 /**
673 * scsi_report_bus_reset - report scsi _bus_ reset observed 673 * scsi_report_bus_reset - report scsi _bus_ reset observed
674 * @shost: a pointer to a scsi host involved 674 * @shost: a pointer to a scsi host involved
675 * @channel: channel (within) host on which scsi bus reset occurred 675 * @channel: channel (within) host on which scsi bus reset occurred
676 * 676 *
677 * Returns nothing 677 * Returns nothing
678 * 678 *
679 * Might block: no 679 * Might block: no
680 * 680 *
681 * Notes: This only needs to be called if the reset is one which 681 * Notes: This only needs to be called if the reset is one which
682 * originates from an unknown location. Resets originated by the 682 * originates from an unknown location. Resets originated by the
683 * mid level itself don't need to call this, but there should be 683 * mid level itself don't need to call this, but there should be
684 * no harm. The main purpose of this is to make sure that a 684 * no harm. The main purpose of this is to make sure that a
685 * CHECK_CONDITION is properly treated. 685 * CHECK_CONDITION is properly treated.
686 * 686 *
687 * Defined in: drivers/scsi/scsi_error.c . 687 * Defined in: drivers/scsi/scsi_error.c .
688 **/ 688 **/
689 void scsi_report_bus_reset(struct Scsi_Host * shost, int channel) 689 void scsi_report_bus_reset(struct Scsi_Host * shost, int channel)
690 690
691 691
692 /** 692 /**
693 * scsi_scan_host - scan SCSI bus 693 * scsi_scan_host - scan SCSI bus
694 * @shost: a pointer to a scsi host instance 694 * @shost: a pointer to a scsi host instance
695 * 695 *
696 * Might block: yes 696 * Might block: yes
697 * 697 *
698 * Notes: Should be called after scsi_add_host() 698 * Notes: Should be called after scsi_add_host()
699 * 699 *
700 * Defined in: drivers/scsi/scsi_scan.c 700 * Defined in: drivers/scsi/scsi_scan.c
701 **/ 701 **/
702 void scsi_scan_host(struct Scsi_Host *shost) 702 void scsi_scan_host(struct Scsi_Host *shost)
703 703
704 704
705 /** 705 /**
706 * scsi_track_queue_full - track successive QUEUE_FULL events on given 706 * scsi_track_queue_full - track successive QUEUE_FULL events on given
707 * device to determine if and when there is a need 707 * device to determine if and when there is a need
708 * to adjust the queue depth on the device. 708 * to adjust the queue depth on the device.
709 * @sdev: pointer to SCSI device instance 709 * @sdev: pointer to SCSI device instance
710 * @depth: Current number of outstanding SCSI commands on this device, 710 * @depth: Current number of outstanding SCSI commands on this device,
711 * not counting the one returned as QUEUE_FULL. 711 * not counting the one returned as QUEUE_FULL.
712 * 712 *
713 * Returns 0 - no change needed 713 * Returns 0 - no change needed
714 * >0 - adjust queue depth to this new depth 714 * >0 - adjust queue depth to this new depth
715 * -1 - drop back to untagged operation using host->cmd_per_lun 715 * -1 - drop back to untagged operation using host->cmd_per_lun
716 * as the untagged command depth 716 * as the untagged command depth
717 * 717 *
718 * Might block: no 718 * Might block: no
719 * 719 *
720 * Notes: LLDs may call this at any time and we will do "The Right 720 * Notes: LLDs may call this at any time and we will do "The Right
721 * Thing"; interrupt context safe. 721 * Thing"; interrupt context safe.
722 * 722 *
723 * Defined in: drivers/scsi/scsi.c . 723 * Defined in: drivers/scsi/scsi.c .
724 **/ 724 **/
725 int scsi_track_queue_full(struct scsi_device *sdev, int depth) 725 int scsi_track_queue_full(struct scsi_device *sdev, int depth)
726 726
727 727
728 /** 728 /**
729 * scsi_unblock_requests - allow further commands to be queued to given host 729 * scsi_unblock_requests - allow further commands to be queued to given host
730 * 730 *
731 * @shost: pointer to host to unblock commands on 731 * @shost: pointer to host to unblock commands on
732 * 732 *
733 * Returns nothing 733 * Returns nothing
734 * 734 *
735 * Might block: no 735 * Might block: no
736 * 736 *
737 * Defined in: drivers/scsi/scsi_lib.c . 737 * Defined in: drivers/scsi/scsi_lib.c .
738 **/ 738 **/
739 void scsi_unblock_requests(struct Scsi_Host * shost) 739 void scsi_unblock_requests(struct Scsi_Host * shost)
740 740
741 741
742 /** 742 /**
743 * scsi_unregister - unregister and free memory used by host instance 743 * scsi_unregister - unregister and free memory used by host instance
744 * @shp: pointer to scsi host instance to unregister. 744 * @shp: pointer to scsi host instance to unregister.
745 * 745 *
746 * Returns nothing 746 * Returns nothing
747 * 747 *
748 * Might block: no 748 * Might block: no
749 * 749 *
750 * Notes: Should not be invoked if the "hotplug initialization 750 * Notes: Should not be invoked if the "hotplug initialization
751 * model" is being used. Called internally by exit_this_scsi_driver() 751 * model" is being used. Called internally by exit_this_scsi_driver()
752 * in the "passive initialization model". Hence a LLD has no need to 752 * in the "passive initialization model". Hence a LLD has no need to
753 * call this function directly. 753 * call this function directly.
754 * 754 *
755 * Defined in: drivers/scsi/hosts.c . 755 * Defined in: drivers/scsi/hosts.c .
756 **/ 756 **/
757 void scsi_unregister(struct Scsi_Host * shp) 757 void scsi_unregister(struct Scsi_Host * shp)
758 758
759 759
760 760
761 761
762 Interface Functions 762 Interface Functions
763 =================== 763 ===================
764 Interface functions are supplied (defined) by LLDs and their function 764 Interface functions are supplied (defined) by LLDs and their function
765 pointers are placed in an instance of struct scsi_host_template which 765 pointers are placed in an instance of struct scsi_host_template which
766 is passed to scsi_host_alloc() [or scsi_register() / init_this_scsi_driver()]. 766 is passed to scsi_host_alloc() [or scsi_register() / init_this_scsi_driver()].
767 Some are mandatory. Interface functions should be declared static. The 767 Some are mandatory. Interface functions should be declared static. The
768 accepted convention is that driver "xyz" will declare its slave_configure() 768 accepted convention is that driver "xyz" will declare its slave_configure()
769 function as: 769 function as:
770 static int xyz_slave_configure(struct scsi_device * sdev); 770 static int xyz_slave_configure(struct scsi_device * sdev);
771 and so forth for all interface functions listed below. 771 and so forth for all interface functions listed below.
772 772
773 A pointer to this function should be placed in the 'slave_configure' member 773 A pointer to this function should be placed in the 'slave_configure' member
774 of a "struct scsi_host_template" instance. A pointer to such an instance 774 of a "struct scsi_host_template" instance. A pointer to such an instance
775 should be passed to the mid level's scsi_host_alloc() [or scsi_register() / 775 should be passed to the mid level's scsi_host_alloc() [or scsi_register() /
776 init_this_scsi_driver()]. 776 init_this_scsi_driver()].
777 777
778 The interface functions are also described in the include/scsi/scsi_host.h 778 The interface functions are also described in the include/scsi/scsi_host.h
779 file immediately above their definition point in "struct scsi_host_template". 779 file immediately above their definition point in "struct scsi_host_template".
780 In some cases more detail is given in scsi_host.h than below. 780 In some cases more detail is given in scsi_host.h than below.
781 781
782 The interface functions are listed below in alphabetical order. 782 The interface functions are listed below in alphabetical order.
783 783
784 Summary: 784 Summary:
785 bios_param - fetch head, sector, cylinder info for a disk 785 bios_param - fetch head, sector, cylinder info for a disk
786 detect - detects HBAs this driver wants to control 786 detect - detects HBAs this driver wants to control
787 eh_timed_out - notify the host that a command timer expired 787 eh_timed_out - notify the host that a command timer expired
788 eh_abort_handler - abort given command 788 eh_abort_handler - abort given command
789 eh_bus_reset_handler - issue SCSI bus reset 789 eh_bus_reset_handler - issue SCSI bus reset
790 eh_device_reset_handler - issue SCSI device reset 790 eh_device_reset_handler - issue SCSI device reset
791 eh_host_reset_handler - reset host (host bus adapter) 791 eh_host_reset_handler - reset host (host bus adapter)
792 info - supply information about given host 792 info - supply information about given host
793 ioctl - driver can respond to ioctls 793 ioctl - driver can respond to ioctls
794 proc_info - supports /proc/scsi/{driver_name}/{host_no} 794 proc_info - supports /proc/scsi/{driver_name}/{host_no}
795 queuecommand - queue scsi command, invoke 'done' on completion 795 queuecommand - queue scsi command, invoke 'done' on completion
796 release - release all resources associated with given host 796 release - release all resources associated with given host
797 slave_alloc - prior to any commands being sent to a new device 797 slave_alloc - prior to any commands being sent to a new device
798 slave_configure - driver fine tuning for given device after attach 798 slave_configure - driver fine tuning for given device after attach
799 slave_destroy - given device is about to be shut down 799 slave_destroy - given device is about to be shut down
800 800
801 801
802 Details: 802 Details:
803 803
804 /** 804 /**
805 * bios_param - fetch head, sector, cylinder info for a disk 805 * bios_param - fetch head, sector, cylinder info for a disk
806 * @sdev: pointer to scsi device context (defined in 806 * @sdev: pointer to scsi device context (defined in
807 * include/scsi/scsi_device.h) 807 * include/scsi/scsi_device.h)
808 * @bdev: pointer to block device context (defined in fs.h) 808 * @bdev: pointer to block device context (defined in fs.h)
809 * @capacity: device size (in 512 byte sectors) 809 * @capacity: device size (in 512 byte sectors)
810 * @params: three element array to place output: 810 * @params: three element array to place output:
811 * params[0] number of heads (max 255) 811 * params[0] number of heads (max 255)
812 * params[1] number of sectors (max 63) 812 * params[1] number of sectors (max 63)
813 * params[2] number of cylinders 813 * params[2] number of cylinders
814 * 814 *
815 * Return value is ignored 815 * Return value is ignored
816 * 816 *
817 * Locks: none 817 * Locks: none
818 * 818 *
819 * Calling context: process (sd) 819 * Calling context: process (sd)
820 * 820 *
821 * Notes: an arbitrary geometry (based on READ CAPACITY) is used 821 * Notes: an arbitrary geometry (based on READ CAPACITY) is used
822 * if this function is not provided. The params array is 822 * if this function is not provided. The params array is
823 * pre-initialized with made up values just in case this function 823 * pre-initialized with made up values just in case this function
824 * doesn't output anything. 824 * doesn't output anything.
825 * 825 *
826 * Optionally defined in: LLD 826 * Optionally defined in: LLD
827 **/ 827 **/
828 int bios_param(struct scsi_device * sdev, struct block_device *bdev, 828 int bios_param(struct scsi_device * sdev, struct block_device *bdev,
829 sector_t capacity, int params[3]) 829 sector_t capacity, int params[3])
830 830
831 831
832 /** 832 /**
833 * detect - detects HBAs this driver wants to control 833 * detect - detects HBAs this driver wants to control
834 * @shtp: host template for this driver. 834 * @shtp: host template for this driver.
835 * 835 *
836 * Returns number of hosts this driver wants to control. 0 means no 836 * Returns number of hosts this driver wants to control. 0 means no
837 * suitable hosts found. 837 * suitable hosts found.
838 * 838 *
839 * Locks: none held 839 * Locks: none held
840 * 840 *
841 * Calling context: process [invoked from init_this_scsi_driver()] 841 * Calling context: process [invoked from init_this_scsi_driver()]
842 * 842 *
843 * Notes: First function called from the SCSI mid level on this 843 * Notes: First function called from the SCSI mid level on this
844 * driver. Upper level drivers (e.g. sd) may not (yet) be present. 844 * driver. Upper level drivers (e.g. sd) may not (yet) be present.
845 * For each host found, this method should call scsi_register() 845 * For each host found, this method should call scsi_register()
846 * [see hosts.c]. 846 * [see hosts.c].
847 * 847 *
848 * Defined in: LLD (required if "passive initialization mode" is used, 848 * Defined in: LLD (required if "passive initialization mode" is used,
849 * not invoked in "hotplug initialization mode") 849 * not invoked in "hotplug initialization mode")
850 **/ 850 **/
851 int detect(struct scsi_host_template * shtp) 851 int detect(struct scsi_host_template * shtp)
852 852
853 853
854 /** 854 /**
855 * eh_timed_out - The timer for the command has just fired 855 * eh_timed_out - The timer for the command has just fired
856 * @scp: identifies command timing out 856 * @scp: identifies command timing out
857 * 857 *
858 * Returns: 858 * Returns:
859 * 859 *
860 * EH_HANDLED: I fixed the error, please complete the command 860 * EH_HANDLED: I fixed the error, please complete the command
861 * EH_RESET_TIMER: I need more time, reset the timer and 861 * EH_RESET_TIMER: I need more time, reset the timer and
862 * begin counting again 862 * begin counting again
863 * EH_NOT_HANDLED Begin normal error recovery 863 * EH_NOT_HANDLED Begin normal error recovery
864 * 864 *
865 * 865 *
866 * Locks: None held 866 * Locks: None held
867 * 867 *
868 * Calling context: interrupt 868 * Calling context: interrupt
869 * 869 *
870 * Notes: This is to give the LLD an opportunity to do local recovery. 870 * Notes: This is to give the LLD an opportunity to do local recovery.
871 * This recovery is limited to determining if the outstanding command 871 * This recovery is limited to determining if the outstanding command
872 * will ever complete. You may not abort and restart the command from 872 * will ever complete. You may not abort and restart the command from
873 * this callback. 873 * this callback.
874 * 874 *
875 * Optionally defined in: LLD 875 * Optionally defined in: LLD
876 **/ 876 **/
877 int eh_timed_out(struct scsi_cmnd * scp) 877 int eh_timed_out(struct scsi_cmnd * scp)
878 878
879 879
880 /** 880 /**
881 * eh_abort_handler - abort command associated with scp 881 * eh_abort_handler - abort command associated with scp
882 * @scp: identifies command to be aborted 882 * @scp: identifies command to be aborted
883 * 883 *
884 * Returns SUCCESS if command aborted else FAILED 884 * Returns SUCCESS if command aborted else FAILED
885 * 885 *
886 * Locks: None held 886 * Locks: None held
887 * 887 *
888 * Calling context: kernel thread 888 * Calling context: kernel thread
889 * 889 *
890 * Notes: Invoked from scsi_eh thread. No other commands will be 890 * Notes: Invoked from scsi_eh thread. No other commands will be
891 * queued on current host during eh. 891 * queued on current host during eh.
892 * 892 *
893 * Optionally defined in: LLD 893 * Optionally defined in: LLD
894 **/ 894 **/
895 int eh_abort_handler(struct scsi_cmnd * scp) 895 int eh_abort_handler(struct scsi_cmnd * scp)
896 896
897 897
898 /** 898 /**
899 * eh_bus_reset_handler - issue SCSI bus reset 899 * eh_bus_reset_handler - issue SCSI bus reset
900 * @scp: SCSI bus that contains this device should be reset 900 * @scp: SCSI bus that contains this device should be reset
901 * 901 *
902 * Returns SUCCESS if command aborted else FAILED 902 * Returns SUCCESS if command aborted else FAILED
903 * 903 *
904 * Locks: None held 904 * Locks: None held
905 * 905 *
906 * Calling context: kernel thread 906 * Calling context: kernel thread
907 * 907 *
908 * Notes: Invoked from scsi_eh thread. No other commands will be 908 * Notes: Invoked from scsi_eh thread. No other commands will be
909 * queued on current host during eh. 909 * queued on current host during eh.
910 * 910 *
911 * Optionally defined in: LLD 911 * Optionally defined in: LLD
912 **/ 912 **/
913 int eh_bus_reset_handler(struct scsi_cmnd * scp) 913 int eh_bus_reset_handler(struct scsi_cmnd * scp)
914 914
915 915
916 /** 916 /**
917 * eh_device_reset_handler - issue SCSI device reset 917 * eh_device_reset_handler - issue SCSI device reset
918 * @scp: identifies SCSI device to be reset 918 * @scp: identifies SCSI device to be reset
919 * 919 *
920 * Returns SUCCESS if command aborted else FAILED 920 * Returns SUCCESS if command aborted else FAILED
921 * 921 *
922 * Locks: None held 922 * Locks: None held
923 * 923 *
924 * Calling context: kernel thread 924 * Calling context: kernel thread
925 * 925 *
926 * Notes: Invoked from scsi_eh thread. No other commands will be 926 * Notes: Invoked from scsi_eh thread. No other commands will be
927 * queued on current host during eh. 927 * queued on current host during eh.
928 * 928 *
929 * Optionally defined in: LLD 929 * Optionally defined in: LLD
930 **/ 930 **/
931 int eh_device_reset_handler(struct scsi_cmnd * scp) 931 int eh_device_reset_handler(struct scsi_cmnd * scp)
932 932
933 933
934 /** 934 /**
935 * eh_host_reset_handler - reset host (host bus adapter) 935 * eh_host_reset_handler - reset host (host bus adapter)
936 * @scp: SCSI host that contains this device should be reset 936 * @scp: SCSI host that contains this device should be reset
937 * 937 *
938 * Returns SUCCESS if command aborted else FAILED 938 * Returns SUCCESS if command aborted else FAILED
939 * 939 *
940 * Locks: None held 940 * Locks: None held
941 * 941 *
942 * Calling context: kernel thread 942 * Calling context: kernel thread
943 * 943 *
944 * Notes: Invoked from scsi_eh thread. No other commands will be 944 * Notes: Invoked from scsi_eh thread. No other commands will be
945 * queued on current host during eh. 945 * queued on current host during eh.
946 * With the default eh_strategy in place, if none of the _abort_, 946 * With the default eh_strategy in place, if none of the _abort_,
947 * _device_reset_, _bus_reset_ or this eh handler function are 947 * _device_reset_, _bus_reset_ or this eh handler function are
948 * defined (or they all return FAILED) then the device in question 948 * defined (or they all return FAILED) then the device in question
949 * will be set offline whenever eh is invoked. 949 * will be set offline whenever eh is invoked.
950 * 950 *
951 * Optionally defined in: LLD 951 * Optionally defined in: LLD
952 **/ 952 **/
953 int eh_host_reset_handler(struct scsi_cmnd * scp) 953 int eh_host_reset_handler(struct scsi_cmnd * scp)
954 954
955 955
956 /** 956 /**
957 * info - supply information about given host: driver name plus data 957 * info - supply information about given host: driver name plus data
958 * to distinguish given host 958 * to distinguish given host
959 * @shp: host to supply information about 959 * @shp: host to supply information about
960 * 960 *
961 * Return ASCII null terminated string. [This driver is assumed to 961 * Return ASCII null terminated string. [This driver is assumed to
962 * manage the memory pointed to and maintain it, typically for the 962 * manage the memory pointed to and maintain it, typically for the
963 * lifetime of this host.] 963 * lifetime of this host.]
964 * 964 *
965 * Locks: none 965 * Locks: none
966 * 966 *
967 * Calling context: process 967 * Calling context: process
968 * 968 *
969 * Notes: Often supplies PCI or ISA information such as IO addresses 969 * Notes: Often supplies PCI or ISA information such as IO addresses
970 * and interrupt numbers. If not supplied struct Scsi_Host::name used 970 * and interrupt numbers. If not supplied struct Scsi_Host::name used
971 * instead. It is assumed the returned information fits on one line 971 * instead. It is assumed the returned information fits on one line
972 * (i.e. does not included embedded newlines). 972 * (i.e. does not included embedded newlines).
973 * The SCSI_IOCTL_PROBE_HOST ioctl yields the string returned by this 973 * The SCSI_IOCTL_PROBE_HOST ioctl yields the string returned by this
974 * function (or struct Scsi_Host::name if this function is not 974 * function (or struct Scsi_Host::name if this function is not
975 * available). 975 * available).
976 * In a similar manner, init_this_scsi_driver() outputs to the console 976 * In a similar manner, init_this_scsi_driver() outputs to the console
977 * each host's "info" (or name) for the driver it is registering. 977 * each host's "info" (or name) for the driver it is registering.
978 * Also if proc_info() is not supplied, the output of this function 978 * Also if proc_info() is not supplied, the output of this function
979 * is used instead. 979 * is used instead.
980 * 980 *
981 * Optionally defined in: LLD 981 * Optionally defined in: LLD
982 **/ 982 **/
983 const char * info(struct Scsi_Host * shp) 983 const char * info(struct Scsi_Host * shp)
984 984
985 985
986 /** 986 /**
987 * ioctl - driver can respond to ioctls 987 * ioctl - driver can respond to ioctls
988 * @sdp: device that ioctl was issued for 988 * @sdp: device that ioctl was issued for
989 * @cmd: ioctl number 989 * @cmd: ioctl number
990 * @arg: pointer to read or write data from. Since it points to 990 * @arg: pointer to read or write data from. Since it points to
991 * user space, should use appropriate kernel functions 991 * user space, should use appropriate kernel functions
992 * (e.g. copy_from_user() ). In the Unix style this argument 992 * (e.g. copy_from_user() ). In the Unix style this argument
993 * can also be viewed as an unsigned long. 993 * can also be viewed as an unsigned long.
994 * 994 *
995 * Returns negative "errno" value when there is a problem. 0 or a 995 * Returns negative "errno" value when there is a problem. 0 or a
996 * positive value indicates success and is returned to the user space. 996 * positive value indicates success and is returned to the user space.
997 * 997 *
998 * Locks: none 998 * Locks: none
999 * 999 *
1000 * Calling context: process 1000 * Calling context: process
1001 * 1001 *
1002 * Notes: The SCSI subsystem uses a "trickle down" ioctl model. 1002 * Notes: The SCSI subsystem uses a "trickle down" ioctl model.
1003 * The user issues an ioctl() against an upper level driver 1003 * The user issues an ioctl() against an upper level driver
1004 * (e.g. /dev/sdc) and if the upper level driver doesn't recognize 1004 * (e.g. /dev/sdc) and if the upper level driver doesn't recognize
1005 * the 'cmd' then it is passed to the SCSI mid level. If the SCSI 1005 * the 'cmd' then it is passed to the SCSI mid level. If the SCSI
1006 * mid level does not recognize it, then the LLD that controls 1006 * mid level does not recognize it, then the LLD that controls
1007 * the device receives the ioctl. According to recent Unix standards 1007 * the device receives the ioctl. According to recent Unix standards
1008 * unsupported ioctl() 'cmd' numbers should return -ENOTTY. 1008 * unsupported ioctl() 'cmd' numbers should return -ENOTTY.
1009 * 1009 *
1010 * Optionally defined in: LLD 1010 * Optionally defined in: LLD
1011 **/ 1011 **/
1012 int ioctl(struct scsi_device *sdp, int cmd, void *arg) 1012 int ioctl(struct scsi_device *sdp, int cmd, void *arg)
1013 1013
1014 1014
1015 /** 1015 /**
1016 * proc_info - supports /proc/scsi/{driver_name}/{host_no} 1016 * proc_info - supports /proc/scsi/{driver_name}/{host_no}
1017 * @buffer: anchor point to output to (0==writeto1_read0) or fetch from 1017 * @buffer: anchor point to output to (0==writeto1_read0) or fetch from
1018 * (1==writeto1_read0). 1018 * (1==writeto1_read0).
1019 * @start: where "interesting" data is written to. Ignored when 1019 * @start: where "interesting" data is written to. Ignored when
1020 * 1==writeto1_read0. 1020 * 1==writeto1_read0.
1021 * @offset: offset within buffer 0==writeto1_read0 is actually 1021 * @offset: offset within buffer 0==writeto1_read0 is actually
1022 * interested in. Ignored when 1==writeto1_read0 . 1022 * interested in. Ignored when 1==writeto1_read0 .
1023 * @length: maximum (or actual) extent of buffer 1023 * @length: maximum (or actual) extent of buffer
1024 * @host_no: host number of interest (struct Scsi_Host::host_no) 1024 * @host_no: host number of interest (struct Scsi_Host::host_no)
1025 * @writeto1_read0: 1 -> data coming from user space towards driver 1025 * @writeto1_read0: 1 -> data coming from user space towards driver
1026 * (e.g. "echo some_string > /proc/scsi/xyz/2") 1026 * (e.g. "echo some_string > /proc/scsi/xyz/2")
1027 * 0 -> user what data from this driver 1027 * 0 -> user what data from this driver
1028 * (e.g. "cat /proc/scsi/xyz/2") 1028 * (e.g. "cat /proc/scsi/xyz/2")
1029 * 1029 *
1030 * Returns length when 1==writeto1_read0. Otherwise number of chars 1030 * Returns length when 1==writeto1_read0. Otherwise number of chars
1031 * output to buffer past offset. 1031 * output to buffer past offset.
1032 * 1032 *
1033 * Locks: none held 1033 * Locks: none held
1034 * 1034 *
1035 * Calling context: process 1035 * Calling context: process
1036 * 1036 *
1037 * Notes: Driven from scsi_proc.c which interfaces to proc_fs. proc_fs 1037 * Notes: Driven from scsi_proc.c which interfaces to proc_fs. proc_fs
1038 * support can now be configured out of the scsi subsystem. 1038 * support can now be configured out of the scsi subsystem.
1039 * 1039 *
1040 * Optionally defined in: LLD 1040 * Optionally defined in: LLD
1041 **/ 1041 **/
1042 int proc_info(char * buffer, char ** start, off_t offset, 1042 int proc_info(char * buffer, char ** start, off_t offset,
1043 int length, int host_no, int writeto1_read0) 1043 int length, int host_no, int writeto1_read0)
1044 1044
1045 1045
1046 /** 1046 /**
1047 * queuecommand - queue scsi command, invoke 'done' on completion 1047 * queuecommand - queue scsi command, invoke scp->scsi_done on completion
1048 * @shost: pointer to the scsi host object
1048 * @scp: pointer to scsi command object 1049 * @scp: pointer to scsi command object
1049 * @done: function pointer to be invoked on completion
1050 * 1050 *
1051 * Returns 0 on success. 1051 * Returns 0 on success.
1052 * 1052 *
1053 * If there's a failure, return either: 1053 * If there's a failure, return either:
1054 * 1054 *
1055 * SCSI_MLQUEUE_DEVICE_BUSY if the device queue is full, or 1055 * SCSI_MLQUEUE_DEVICE_BUSY if the device queue is full, or
1056 * SCSI_MLQUEUE_HOST_BUSY if the entire host queue is full 1056 * SCSI_MLQUEUE_HOST_BUSY if the entire host queue is full
1057 * 1057 *
1058 * On both of these returns, the mid-layer will requeue the I/O 1058 * On both of these returns, the mid-layer will requeue the I/O
1059 * 1059 *
1060 * - if the return is SCSI_MLQUEUE_DEVICE_BUSY, only that particular 1060 * - if the return is SCSI_MLQUEUE_DEVICE_BUSY, only that particular
1061 * device will be paused, and it will be unpaused when a command to 1061 * device will be paused, and it will be unpaused when a command to
1062 * the device returns (or after a brief delay if there are no more 1062 * the device returns (or after a brief delay if there are no more
1063 * outstanding commands to it). Commands to other devices continue 1063 * outstanding commands to it). Commands to other devices continue
1064 * to be processed normally. 1064 * to be processed normally.
1065 * 1065 *
1066 * - if the return is SCSI_MLQUEUE_HOST_BUSY, all I/O to the host 1066 * - if the return is SCSI_MLQUEUE_HOST_BUSY, all I/O to the host
1067 * is paused and will be unpaused when any command returns from 1067 * is paused and will be unpaused when any command returns from
1068 * the host (or after a brief delay if there are no outstanding 1068 * the host (or after a brief delay if there are no outstanding
1069 * commands to the host). 1069 * commands to the host).
1070 * 1070 *
1071 * For compatibility with earlier versions of queuecommand, any 1071 * For compatibility with earlier versions of queuecommand, any
1072 * other return value is treated the same as 1072 * other return value is treated the same as
1073 * SCSI_MLQUEUE_HOST_BUSY. 1073 * SCSI_MLQUEUE_HOST_BUSY.
1074 * 1074 *
1075 * Other types of errors that are detected immediately may be 1075 * Other types of errors that are detected immediately may be
1076 * flagged by setting scp->result to an appropriate value, 1076 * flagged by setting scp->result to an appropriate value,
1077 * invoking the 'done' callback, and then returning 0 from this 1077 * invoking the scp->scsi_done callback, and then returning 0
1078 * function. If the command is not performed immediately (and the 1078 * from this function. If the command is not performed
1079 * LLD is starting (or will start) the given command) then this 1079 * immediately (and the LLD is starting (or will start) the given
1080 * function should place 0 in scp->result and return 0. 1080 * command) then this function should place 0 in scp->result and
1081 * return 0.
1081 * 1082 *
1082 * Command ownership. If the driver returns zero, it owns the 1083 * Command ownership. If the driver returns zero, it owns the
1083 * command and must take responsibility for ensuring the 'done' 1084 * command and must take responsibility for ensuring the
1084 * callback is executed. Note: the driver may call done before 1085 * scp->scsi_done callback is executed. Note: the driver may
1085 * returning zero, but after it has called done, it may not 1086 * call scp->scsi_done before returning zero, but after it has
1086 * return any value other than zero. If the driver makes a 1087 * called scp->scsi_done, it may not return any value other than
1087 * non-zero return, it must not execute the command's done 1088 * zero. If the driver makes a non-zero return, it must not
1088 * callback at any time. 1089 * execute the command's scsi_done callback at any time.
1089 * 1090 *
1090 * Locks: struct Scsi_Host::host_lock held on entry (with "irqsave") 1091 * Locks: up to and including 2.6.36, struct Scsi_Host::host_lock
1091 * and is expected to be held on return. 1092 * held on entry (with "irqsave") and is expected to be
1093 * held on return. From 2.6.37 onwards, queuecommand is
1094 * called without any locks held.
1092 * 1095 *
1093 * Calling context: in interrupt (soft irq) or process context 1096 * Calling context: in interrupt (soft irq) or process context
1094 * 1097 *
1095 * Notes: This function should be relatively fast. Normally it will 1098 * Notes: This function should be relatively fast. Normally it
1096 * not wait for IO to complete. Hence the 'done' callback is invoked 1099 * will not wait for IO to complete. Hence the scp->scsi_done
1097 * (often directly from an interrupt service routine) some time after 1100 * callback is invoked (often directly from an interrupt service
1098 * this function has returned. In some cases (e.g. pseudo adapter 1101 * routine) some time after this function has returned. In some
1099 * drivers that manufacture the response to a SCSI INQUIRY) 1102 * cases (e.g. pseudo adapter drivers that manufacture the
1100 * the 'done' callback may be invoked before this function returns. 1103 * response to a SCSI INQUIRY) the scp->scsi_done callback may be
1101 * If the 'done' callback is not invoked within a certain period 1104 * invoked before this function returns. If the scp->scsi_done
1102 * the SCSI mid level will commence error processing. 1105 * callback is not invoked within a certain period the SCSI mid
1103 * If a status of CHECK CONDITION is placed in "result" when the 1106 * level will commence error processing. If a status of CHECK
1104 * 'done' callback is invoked, then the LLD driver should 1107 * CONDITION is placed in "result" when the scp->scsi_done
1105 * perform autosense and fill in the struct scsi_cmnd::sense_buffer 1108 * callback is invoked, then the LLD driver should perform
1109 * autosense and fill in the struct scsi_cmnd::sense_buffer
1106 * array. The scsi_cmnd::sense_buffer array is zeroed prior to 1110 * array. The scsi_cmnd::sense_buffer array is zeroed prior to
1107 * the mid level queuing a command to an LLD. 1111 * the mid level queuing a command to an LLD.
1108 * 1112 *
1109 * Defined in: LLD 1113 * Defined in: LLD
1110 **/ 1114 **/
1111 int queuecommand(struct scsi_cmnd * scp, 1115 int queuecommand(struct Scsi_Host *shost, struct scsi_cmnd * scp)
1112 void (*done)(struct scsi_cmnd *))
1113 1116
1114 1117
1115 /** 1118 /**
1116 * release - release all resources associated with given host 1119 * release - release all resources associated with given host
1117 * @shp: host to be released. 1120 * @shp: host to be released.
1118 * 1121 *
1119 * Return value ignored (could soon be a function returning void). 1122 * Return value ignored (could soon be a function returning void).
1120 * 1123 *
1121 * Locks: none held 1124 * Locks: none held
1122 * 1125 *
1123 * Calling context: process 1126 * Calling context: process
1124 * 1127 *
1125 * Notes: Invoked from scsi_module.c's exit_this_scsi_driver(). 1128 * Notes: Invoked from scsi_module.c's exit_this_scsi_driver().
1126 * LLD's implementation of this function should call 1129 * LLD's implementation of this function should call
1127 * scsi_unregister(shp) prior to returning. 1130 * scsi_unregister(shp) prior to returning.
1128 * Only needed for old-style host templates. 1131 * Only needed for old-style host templates.
1129 * 1132 *
1130 * Defined in: LLD (required in "passive initialization model", 1133 * Defined in: LLD (required in "passive initialization model",
1131 * should not be defined in hotplug model) 1134 * should not be defined in hotplug model)
1132 **/ 1135 **/
1133 int release(struct Scsi_Host * shp) 1136 int release(struct Scsi_Host * shp)
1134 1137
1135 1138
1136 /** 1139 /**
1137 * slave_alloc - prior to any commands being sent to a new device 1140 * slave_alloc - prior to any commands being sent to a new device
1138 * (i.e. just prior to scan) this call is made 1141 * (i.e. just prior to scan) this call is made
1139 * @sdp: pointer to new device (about to be scanned) 1142 * @sdp: pointer to new device (about to be scanned)
1140 * 1143 *
1141 * Returns 0 if ok. Any other return is assumed to be an error and 1144 * Returns 0 if ok. Any other return is assumed to be an error and
1142 * the device is ignored. 1145 * the device is ignored.
1143 * 1146 *
1144 * Locks: none 1147 * Locks: none
1145 * 1148 *
1146 * Calling context: process 1149 * Calling context: process
1147 * 1150 *
1148 * Notes: Allows the driver to allocate any resources for a device 1151 * Notes: Allows the driver to allocate any resources for a device
1149 * prior to its initial scan. The corresponding scsi device may not 1152 * prior to its initial scan. The corresponding scsi device may not
1150 * exist but the mid level is just about to scan for it (i.e. send 1153 * exist but the mid level is just about to scan for it (i.e. send
1151 * and INQUIRY command plus ...). If a device is found then 1154 * and INQUIRY command plus ...). If a device is found then
1152 * slave_configure() will be called while if a device is not found 1155 * slave_configure() will be called while if a device is not found
1153 * slave_destroy() is called. 1156 * slave_destroy() is called.
1154 * For more details see the include/scsi/scsi_host.h file. 1157 * For more details see the include/scsi/scsi_host.h file.
1155 * 1158 *
1156 * Optionally defined in: LLD 1159 * Optionally defined in: LLD
1157 **/ 1160 **/
1158 int slave_alloc(struct scsi_device *sdp) 1161 int slave_alloc(struct scsi_device *sdp)
1159 1162
1160 1163
1161 /** 1164 /**
1162 * slave_configure - driver fine tuning for given device just after it 1165 * slave_configure - driver fine tuning for given device just after it
1163 * has been first scanned (i.e. it responded to an 1166 * has been first scanned (i.e. it responded to an
1164 * INQUIRY) 1167 * INQUIRY)
1165 * @sdp: device that has just been attached 1168 * @sdp: device that has just been attached
1166 * 1169 *
1167 * Returns 0 if ok. Any other return is assumed to be an error and 1170 * Returns 0 if ok. Any other return is assumed to be an error and
1168 * the device is taken offline. [offline devices will _not_ have 1171 * the device is taken offline. [offline devices will _not_ have
1169 * slave_destroy() called on them so clean up resources.] 1172 * slave_destroy() called on them so clean up resources.]
1170 * 1173 *
1171 * Locks: none 1174 * Locks: none
1172 * 1175 *
1173 * Calling context: process 1176 * Calling context: process
1174 * 1177 *
1175 * Notes: Allows the driver to inspect the response to the initial 1178 * Notes: Allows the driver to inspect the response to the initial
1176 * INQUIRY done by the scanning code and take appropriate action. 1179 * INQUIRY done by the scanning code and take appropriate action.
1177 * For more details see the include/scsi/scsi_host.h file. 1180 * For more details see the include/scsi/scsi_host.h file.
1178 * 1181 *
1179 * Optionally defined in: LLD 1182 * Optionally defined in: LLD
1180 **/ 1183 **/
1181 int slave_configure(struct scsi_device *sdp) 1184 int slave_configure(struct scsi_device *sdp)
1182 1185
1183 1186
1184 /** 1187 /**
1185 * slave_destroy - given device is about to be shut down. All 1188 * slave_destroy - given device is about to be shut down. All
1186 * activity has ceased on this device. 1189 * activity has ceased on this device.
1187 * @sdp: device that is about to be shut down 1190 * @sdp: device that is about to be shut down
1188 * 1191 *
1189 * Returns nothing 1192 * Returns nothing
1190 * 1193 *
1191 * Locks: none 1194 * Locks: none
1192 * 1195 *
1193 * Calling context: process 1196 * Calling context: process
1194 * 1197 *
1195 * Notes: Mid level structures for given device are still in place 1198 * Notes: Mid level structures for given device are still in place
1196 * but are about to be torn down. Any per device resources allocated 1199 * but are about to be torn down. Any per device resources allocated
1197 * by this driver for given device should be freed now. No further 1200 * by this driver for given device should be freed now. No further
1198 * commands will be sent for this sdp instance. [However the device 1201 * commands will be sent for this sdp instance. [However the device
1199 * could be re-attached in the future in which case a new instance 1202 * could be re-attached in the future in which case a new instance
1200 * of struct scsi_device would be supplied by future slave_alloc() 1203 * of struct scsi_device would be supplied by future slave_alloc()
1201 * and slave_configure() calls.] 1204 * and slave_configure() calls.]
1202 * 1205 *
1203 * Optionally defined in: LLD 1206 * Optionally defined in: LLD
1204 **/ 1207 **/
1205 void slave_destroy(struct scsi_device *sdp) 1208 void slave_destroy(struct scsi_device *sdp)
1206 1209
1207 1210
1208 1211
1209 Data Structures 1212 Data Structures
1210 =============== 1213 ===============
1211 struct scsi_host_template 1214 struct scsi_host_template
1212 ------------------------- 1215 -------------------------
1213 There is one "struct scsi_host_template" instance per LLD ***. It is 1216 There is one "struct scsi_host_template" instance per LLD ***. It is
1214 typically initialized as a file scope static in a driver's header file. That 1217 typically initialized as a file scope static in a driver's header file. That
1215 way members that are not explicitly initialized will be set to 0 or NULL. 1218 way members that are not explicitly initialized will be set to 0 or NULL.
1216 Member of interest: 1219 Member of interest:
1217 name - name of driver (may contain spaces, please limit to 1220 name - name of driver (may contain spaces, please limit to
1218 less than 80 characters) 1221 less than 80 characters)
1219 proc_name - name used in "/proc/scsi/<proc_name>/<host_no>" and 1222 proc_name - name used in "/proc/scsi/<proc_name>/<host_no>" and
1220 by sysfs in one of its "drivers" directories. Hence 1223 by sysfs in one of its "drivers" directories. Hence
1221 "proc_name" should only contain characters acceptable 1224 "proc_name" should only contain characters acceptable
1222 to a Unix file name. 1225 to a Unix file name.
1223 (*queuecommand)() - primary callback that the mid level uses to inject 1226 (*queuecommand)() - primary callback that the mid level uses to inject
1224 SCSI commands into an LLD. 1227 SCSI commands into an LLD.
1225 The structure is defined and commented in include/scsi/scsi_host.h 1228 The structure is defined and commented in include/scsi/scsi_host.h
1226 1229
1227 *** In extreme situations a single driver may have several instances 1230 *** In extreme situations a single driver may have several instances
1228 if it controls several different classes of hardware (e.g. an LLD 1231 if it controls several different classes of hardware (e.g. an LLD
1229 that handles both ISA and PCI cards and has a separate instance of 1232 that handles both ISA and PCI cards and has a separate instance of
1230 struct scsi_host_template for each class). 1233 struct scsi_host_template for each class).
1231 1234
1232 struct Scsi_Host 1235 struct Scsi_Host
1233 ---------------- 1236 ----------------
1234 There is one struct Scsi_Host instance per host (HBA) that an LLD 1237 There is one struct Scsi_Host instance per host (HBA) that an LLD
1235 controls. The struct Scsi_Host structure has many members in common 1238 controls. The struct Scsi_Host structure has many members in common
1236 with "struct scsi_host_template". When a new struct Scsi_Host instance 1239 with "struct scsi_host_template". When a new struct Scsi_Host instance
1237 is created (in scsi_host_alloc() in hosts.c) those common members are 1240 is created (in scsi_host_alloc() in hosts.c) those common members are
1238 initialized from the driver's struct scsi_host_template instance. Members 1241 initialized from the driver's struct scsi_host_template instance. Members
1239 of interest: 1242 of interest:
1240 host_no - system wide unique number that is used for identifying 1243 host_no - system wide unique number that is used for identifying
1241 this host. Issued in ascending order from 0. 1244 this host. Issued in ascending order from 0.
1242 can_queue - must be greater than 0; do not send more than can_queue 1245 can_queue - must be greater than 0; do not send more than can_queue
1243 commands to the adapter. 1246 commands to the adapter.
1244 this_id - scsi id of host (scsi initiator) or -1 if not known 1247 this_id - scsi id of host (scsi initiator) or -1 if not known
1245 sg_tablesize - maximum scatter gather elements allowed by host. 1248 sg_tablesize - maximum scatter gather elements allowed by host.
1246 0 implies scatter gather not supported by host 1249 0 implies scatter gather not supported by host
1247 max_sectors - maximum number of sectors (usually 512 bytes) allowed 1250 max_sectors - maximum number of sectors (usually 512 bytes) allowed
1248 in a single SCSI command. The default value of 0 leads 1251 in a single SCSI command. The default value of 0 leads
1249 to a setting of SCSI_DEFAULT_MAX_SECTORS (defined in 1252 to a setting of SCSI_DEFAULT_MAX_SECTORS (defined in
1250 scsi_host.h) which is currently set to 1024. So for a 1253 scsi_host.h) which is currently set to 1024. So for a
1251 disk the maximum transfer size is 512 KB when max_sectors 1254 disk the maximum transfer size is 512 KB when max_sectors
1252 is not defined. Note that this size may not be sufficient 1255 is not defined. Note that this size may not be sufficient
1253 for disk firmware uploads. 1256 for disk firmware uploads.
1254 cmd_per_lun - maximum number of commands that can be queued on devices 1257 cmd_per_lun - maximum number of commands that can be queued on devices
1255 controlled by the host. Overridden by LLD calls to 1258 controlled by the host. Overridden by LLD calls to
1256 scsi_adjust_queue_depth(). 1259 scsi_adjust_queue_depth().
1257 unchecked_isa_dma - 1=>only use bottom 16 MB of ram (ISA DMA addressing 1260 unchecked_isa_dma - 1=>only use bottom 16 MB of ram (ISA DMA addressing
1258 restriction), 0=>can use full 32 bit (or better) DMA 1261 restriction), 0=>can use full 32 bit (or better) DMA
1259 address space 1262 address space
1260 use_clustering - 1=>SCSI commands in mid level's queue can be merged, 1263 use_clustering - 1=>SCSI commands in mid level's queue can be merged,
1261 0=>disallow SCSI command merging 1264 0=>disallow SCSI command merging
1262 hostt - pointer to driver's struct scsi_host_template from which 1265 hostt - pointer to driver's struct scsi_host_template from which
1263 this struct Scsi_Host instance was spawned 1266 this struct Scsi_Host instance was spawned
1264 hostt->proc_name - name of LLD. This is the driver name that sysfs uses 1267 hostt->proc_name - name of LLD. This is the driver name that sysfs uses
1265 transportt - pointer to driver's struct scsi_transport_template instance 1268 transportt - pointer to driver's struct scsi_transport_template instance
1266 (if any). FC and SPI transports currently supported. 1269 (if any). FC and SPI transports currently supported.
1267 sh_list - a double linked list of pointers to all struct Scsi_Host 1270 sh_list - a double linked list of pointers to all struct Scsi_Host
1268 instances (currently ordered by ascending host_no) 1271 instances (currently ordered by ascending host_no)
1269 my_devices - a double linked list of pointers to struct scsi_device 1272 my_devices - a double linked list of pointers to struct scsi_device
1270 instances that belong to this host. 1273 instances that belong to this host.
1271 hostdata[0] - area reserved for LLD at end of struct Scsi_Host. Size 1274 hostdata[0] - area reserved for LLD at end of struct Scsi_Host. Size
1272 is set by the second argument (named 'xtr_bytes') to 1275 is set by the second argument (named 'xtr_bytes') to
1273 scsi_host_alloc() or scsi_register(). 1276 scsi_host_alloc() or scsi_register().
1274 vendor_id - a unique value that identifies the vendor supplying 1277 vendor_id - a unique value that identifies the vendor supplying
1275 the LLD for the Scsi_Host. Used most often in validating 1278 the LLD for the Scsi_Host. Used most often in validating
1276 vendor-specific message requests. Value consists of an 1279 vendor-specific message requests. Value consists of an
1277 identifier type and a vendor-specific value. 1280 identifier type and a vendor-specific value.
1278 See scsi_netlink.h for a description of valid formats. 1281 See scsi_netlink.h for a description of valid formats.
1279 1282
1280 The scsi_host structure is defined in include/scsi/scsi_host.h 1283 The scsi_host structure is defined in include/scsi/scsi_host.h
1281 1284
1282 struct scsi_device 1285 struct scsi_device
1283 ------------------ 1286 ------------------
1284 Generally, there is one instance of this structure for each SCSI logical unit 1287 Generally, there is one instance of this structure for each SCSI logical unit
1285 on a host. Scsi devices connected to a host are uniquely identified by a 1288 on a host. Scsi devices connected to a host are uniquely identified by a
1286 channel number, target id and logical unit number (lun). 1289 channel number, target id and logical unit number (lun).
1287 The structure is defined in include/scsi/scsi_device.h 1290 The structure is defined in include/scsi/scsi_device.h
1288 1291
1289 struct scsi_cmnd 1292 struct scsi_cmnd
1290 ---------------- 1293 ----------------
1291 Instances of this structure convey SCSI commands to the LLD and responses 1294 Instances of this structure convey SCSI commands to the LLD and responses
1292 back to the mid level. The SCSI mid level will ensure that no more SCSI 1295 back to the mid level. The SCSI mid level will ensure that no more SCSI
1293 commands become queued against the LLD than are indicated by 1296 commands become queued against the LLD than are indicated by
1294 scsi_adjust_queue_depth() (or struct Scsi_Host::cmd_per_lun). There will 1297 scsi_adjust_queue_depth() (or struct Scsi_Host::cmd_per_lun). There will
1295 be at least one instance of struct scsi_cmnd available for each SCSI device. 1298 be at least one instance of struct scsi_cmnd available for each SCSI device.
1296 Members of interest: 1299 Members of interest:
1297 cmnd - array containing SCSI command 1300 cmnd - array containing SCSI command
1298 cmnd_len - length (in bytes) of SCSI command 1301 cmnd_len - length (in bytes) of SCSI command
1299 sc_data_direction - direction of data transfer in data phase. See 1302 sc_data_direction - direction of data transfer in data phase. See
1300 "enum dma_data_direction" in include/linux/dma-mapping.h 1303 "enum dma_data_direction" in include/linux/dma-mapping.h
1301 request_bufflen - number of data bytes to transfer (0 if no data phase) 1304 request_bufflen - number of data bytes to transfer (0 if no data phase)
1302 use_sg - ==0 -> no scatter gather list, hence transfer data 1305 use_sg - ==0 -> no scatter gather list, hence transfer data
1303 to/from request_buffer 1306 to/from request_buffer
1304 - >0 -> scatter gather list (actually an array) in 1307 - >0 -> scatter gather list (actually an array) in
1305 request_buffer with use_sg elements 1308 request_buffer with use_sg elements
1306 request_buffer - either contains data buffer or scatter gather list 1309 request_buffer - either contains data buffer or scatter gather list
1307 depending on the setting of use_sg. Scatter gather 1310 depending on the setting of use_sg. Scatter gather
1308 elements are defined by 'struct scatterlist' found 1311 elements are defined by 'struct scatterlist' found
1309 in include/asm/scatterlist.h . 1312 in include/asm/scatterlist.h .
1310 done - function pointer that should be invoked by LLD when the 1313 done - function pointer that should be invoked by LLD when the
1311 SCSI command is completed (successfully or otherwise). 1314 SCSI command is completed (successfully or otherwise).
1312 Should only be called by an LLD if the LLD has accepted 1315 Should only be called by an LLD if the LLD has accepted
1313 the command (i.e. queuecommand() returned or will return 1316 the command (i.e. queuecommand() returned or will return
1314 0). The LLD may invoke 'done' prior to queuecommand() 1317 0). The LLD may invoke 'done' prior to queuecommand()
1315 finishing. 1318 finishing.
1316 result - should be set by LLD prior to calling 'done'. A value 1319 result - should be set by LLD prior to calling 'done'. A value
1317 of 0 implies a successfully completed command (and all 1320 of 0 implies a successfully completed command (and all
1318 data (if any) has been transferred to or from the SCSI 1321 data (if any) has been transferred to or from the SCSI
1319 target device). 'result' is a 32 bit unsigned integer that 1322 target device). 'result' is a 32 bit unsigned integer that
1320 can be viewed as 4 related bytes. The SCSI status value is 1323 can be viewed as 4 related bytes. The SCSI status value is
1321 in the LSB. See include/scsi/scsi.h status_byte(), 1324 in the LSB. See include/scsi/scsi.h status_byte(),
1322 msg_byte(), host_byte() and driver_byte() macros and 1325 msg_byte(), host_byte() and driver_byte() macros and
1323 related constants. 1326 related constants.
1324 sense_buffer - an array (maximum size: SCSI_SENSE_BUFFERSIZE bytes) that 1327 sense_buffer - an array (maximum size: SCSI_SENSE_BUFFERSIZE bytes) that
1325 should be written when the SCSI status (LSB of 'result') 1328 should be written when the SCSI status (LSB of 'result')
1326 is set to CHECK_CONDITION (2). When CHECK_CONDITION is 1329 is set to CHECK_CONDITION (2). When CHECK_CONDITION is
1327 set, if the top nibble of sense_buffer[0] has the value 7 1330 set, if the top nibble of sense_buffer[0] has the value 7
1328 then the mid level will assume the sense_buffer array 1331 then the mid level will assume the sense_buffer array
1329 contains a valid SCSI sense buffer; otherwise the mid 1332 contains a valid SCSI sense buffer; otherwise the mid
1330 level will issue a REQUEST_SENSE SCSI command to 1333 level will issue a REQUEST_SENSE SCSI command to
1331 retrieve the sense buffer. The latter strategy is error 1334 retrieve the sense buffer. The latter strategy is error
1332 prone in the presence of command queuing so the LLD should 1335 prone in the presence of command queuing so the LLD should
1333 always "auto-sense". 1336 always "auto-sense".
1334 device - pointer to scsi_device object that this command is 1337 device - pointer to scsi_device object that this command is
1335 associated with. 1338 associated with.
1336 resid - an LLD should set this signed integer to the requested 1339 resid - an LLD should set this signed integer to the requested
1337 transfer length (i.e. 'request_bufflen') less the number 1340 transfer length (i.e. 'request_bufflen') less the number
1338 of bytes that are actually transferred. 'resid' is 1341 of bytes that are actually transferred. 'resid' is
1339 preset to 0 so an LLD can ignore it if it cannot detect 1342 preset to 0 so an LLD can ignore it if it cannot detect
1340 underruns (overruns should be rare). If possible an LLD 1343 underruns (overruns should be rare). If possible an LLD
1341 should set 'resid' prior to invoking 'done'. The most 1344 should set 'resid' prior to invoking 'done'. The most
1342 interesting case is data transfers from a SCSI target 1345 interesting case is data transfers from a SCSI target
1343 device device (i.e. READs) that underrun. 1346 device device (i.e. READs) that underrun.
1344 underflow - LLD should place (DID_ERROR << 16) in 'result' if 1347 underflow - LLD should place (DID_ERROR << 16) in 'result' if
1345 actual number of bytes transferred is less than this 1348 actual number of bytes transferred is less than this
1346 figure. Not many LLDs implement this check and some that 1349 figure. Not many LLDs implement this check and some that
1347 do just output an error message to the log rather than 1350 do just output an error message to the log rather than
1348 report a DID_ERROR. Better for an LLD to implement 1351 report a DID_ERROR. Better for an LLD to implement
1349 'resid'. 1352 'resid'.
1350 1353
1351 The scsi_cmnd structure is defined in include/scsi/scsi_cmnd.h 1354 The scsi_cmnd structure is defined in include/scsi/scsi_cmnd.h
1352 1355
1353 1356
1354 Locks 1357 Locks
1355 ===== 1358 =====
1356 Each struct Scsi_Host instance has a spin_lock called struct 1359 Each struct Scsi_Host instance has a spin_lock called struct
1357 Scsi_Host::default_lock which is initialized in scsi_host_alloc() [found in 1360 Scsi_Host::default_lock which is initialized in scsi_host_alloc() [found in
1358 hosts.c]. Within the same function the struct Scsi_Host::host_lock pointer 1361 hosts.c]. Within the same function the struct Scsi_Host::host_lock pointer
1359 is initialized to point at default_lock. Thereafter lock and unlock 1362 is initialized to point at default_lock. Thereafter lock and unlock
1360 operations performed by the mid level use the struct Scsi_Host::host_lock 1363 operations performed by the mid level use the struct Scsi_Host::host_lock
1361 pointer. Previously drivers could override the host_lock pointer but 1364 pointer. Previously drivers could override the host_lock pointer but
1362 this is not allowed anymore. 1365 this is not allowed anymore.
1363 1366
1364 1367
1365 Autosense 1368 Autosense
1366 ========= 1369 =========
1367 Autosense (or auto-sense) is defined in the SAM-2 document as "the 1370 Autosense (or auto-sense) is defined in the SAM-2 document as "the
1368 automatic return of sense data to the application client coincident 1371 automatic return of sense data to the application client coincident
1369 with the completion of a SCSI command" when a status of CHECK CONDITION 1372 with the completion of a SCSI command" when a status of CHECK CONDITION
1370 occurs. LLDs should perform autosense. This should be done when the LLD 1373 occurs. LLDs should perform autosense. This should be done when the LLD
1371 detects a CHECK CONDITION status by either: 1374 detects a CHECK CONDITION status by either:
1372 a) instructing the SCSI protocol (e.g. SCSI Parallel Interface (SPI)) 1375 a) instructing the SCSI protocol (e.g. SCSI Parallel Interface (SPI))
1373 to perform an extra data in phase on such responses 1376 to perform an extra data in phase on such responses
1374 b) or, the LLD issuing a REQUEST SENSE command itself 1377 b) or, the LLD issuing a REQUEST SENSE command itself
1375 1378
1376 Either way, when a status of CHECK CONDITION is detected, the mid level 1379 Either way, when a status of CHECK CONDITION is detected, the mid level
1377 decides whether the LLD has performed autosense by checking struct 1380 decides whether the LLD has performed autosense by checking struct
1378 scsi_cmnd::sense_buffer[0] . If this byte has an upper nibble of 7 (or 0xf) 1381 scsi_cmnd::sense_buffer[0] . If this byte has an upper nibble of 7 (or 0xf)
1379 then autosense is assumed to have taken place. If it has another value (and 1382 then autosense is assumed to have taken place. If it has another value (and
1380 this byte is initialized to 0 before each command) then the mid level will 1383 this byte is initialized to 0 before each command) then the mid level will
1381 issue a REQUEST SENSE command. 1384 issue a REQUEST SENSE command.
1382 1385
1383 In the presence of queued commands the "nexus" that maintains sense 1386 In the presence of queued commands the "nexus" that maintains sense
1384 buffer data from the command that failed until a following REQUEST SENSE 1387 buffer data from the command that failed until a following REQUEST SENSE
1385 may get out of synchronization. This is why it is best for the LLD 1388 may get out of synchronization. This is why it is best for the LLD
1386 to perform autosense. 1389 to perform autosense.
1387 1390
1388 1391
1389 Changes since lk 2.4 series 1392 Changes since lk 2.4 series
1390 =========================== 1393 ===========================
1391 io_request_lock has been replaced by several finer grained locks. The lock 1394 io_request_lock has been replaced by several finer grained locks. The lock
1392 relevant to LLDs is struct Scsi_Host::host_lock and there is 1395 relevant to LLDs is struct Scsi_Host::host_lock and there is
1393 one per SCSI host. 1396 one per SCSI host.
1394 1397
1395 The older error handling mechanism has been removed. This means the 1398 The older error handling mechanism has been removed. This means the
1396 LLD interface functions abort() and reset() have been removed. 1399 LLD interface functions abort() and reset() have been removed.
1397 The struct scsi_host_template::use_new_eh_code flag has been removed. 1400 The struct scsi_host_template::use_new_eh_code flag has been removed.
1398 1401
1399 In the 2.4 series the SCSI subsystem configuration descriptions were 1402 In the 2.4 series the SCSI subsystem configuration descriptions were
1400 aggregated with the configuration descriptions from all other Linux 1403 aggregated with the configuration descriptions from all other Linux
1401 subsystems in the Documentation/Configure.help file. In the 2.6 series, 1404 subsystems in the Documentation/Configure.help file. In the 2.6 series,
1402 the SCSI subsystem now has its own (much smaller) drivers/scsi/Kconfig 1405 the SCSI subsystem now has its own (much smaller) drivers/scsi/Kconfig
1403 file that contains both configuration and help information. 1406 file that contains both configuration and help information.
1404 1407
1405 struct SHT has been renamed to struct scsi_host_template. 1408 struct SHT has been renamed to struct scsi_host_template.
1406 1409
1407 Addition of the "hotplug initialization model" and many extra functions 1410 Addition of the "hotplug initialization model" and many extra functions
1408 to support it. 1411 to support it.
1409 1412
1410 1413
1411 Credits 1414 Credits
1412 ======= 1415 =======
1413 The following people have contributed to this document: 1416 The following people have contributed to this document:
1414 Mike Anderson <andmike at us dot ibm dot com> 1417 Mike Anderson <andmike at us dot ibm dot com>
1415 James Bottomley <James dot Bottomley at hansenpartnership dot com> 1418 James Bottomley <James dot Bottomley at hansenpartnership dot com>
1416 Patrick Mansfield <patmans at us dot ibm dot com> 1419 Patrick Mansfield <patmans at us dot ibm dot com>
1417 Christoph Hellwig <hch at infradead dot org> 1420 Christoph Hellwig <hch at infradead dot org>
1418 Doug Ledford <dledford at redhat dot com> 1421 Doug Ledford <dledford at redhat dot com>
1419 Andries Brouwer <Andries dot Brouwer at cwi dot nl> 1422 Andries Brouwer <Andries dot Brouwer at cwi dot nl>
1420 Randy Dunlap <rdunlap at xenotime dot net> 1423 Randy Dunlap <rdunlap at xenotime dot net>
1421 Alan Stern <stern at rowland dot harvard dot edu> 1424 Alan Stern <stern at rowland dot harvard dot edu>
1422 1425
1423 1426
1424 Douglas Gilbert 1427 Douglas Gilbert
1425 dgilbert at interlog dot com 1428 dgilbert at interlog dot com