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Commit 75570af1504141316c22dfb6796cd13bf5b11fd2

Authored by Steven Whitehouse
Committed by Dmitry Torokhov
1 parent 374766bc2a
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

Input: fix bug in example code 

The input example driver uses BTN_0 in the later stages of the
example, so this changes the interrupt routine to match.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

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

Documentation/input/input-programming.txt
Diff comments   View file @ 75570af
1 Programming input drivers 1 Programming input drivers
2 ~~~~~~~~~~~~~~~~~~~~~~~~~ 2 ~~~~~~~~~~~~~~~~~~~~~~~~~
3 3
4 1. Creating an input device driver 4 1. Creating an input device driver
5 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6 6
7 1.0 The simplest example 7 1.0 The simplest example
8 ~~~~~~~~~~~~~~~~~~~~~~~~ 8 ~~~~~~~~~~~~~~~~~~~~~~~~
9 9
10 Here comes a very simple example of an input device driver. The device has 10 Here comes a very simple example of an input device driver. The device has
11 just one button and the button is accessible at i/o port BUTTON_PORT. When 11 just one button and the button is accessible at i/o port BUTTON_PORT. When
12 pressed or released a BUTTON_IRQ happens. The driver could look like: 12 pressed or released a BUTTON_IRQ happens. The driver could look like:
13 13
14 #include <linux/input.h> 14 #include <linux/input.h>
15 #include <linux/module.h> 15 #include <linux/module.h>
16 #include <linux/init.h> 16 #include <linux/init.h>
17 17
18 #include <asm/irq.h> 18 #include <asm/irq.h>
19 #include <asm/io.h> 19 #include <asm/io.h>
20 20
21 static struct input_dev *button_dev; 21 static struct input_dev *button_dev;
22 22
23 static void button_interrupt(int irq, void *dummy, struct pt_regs *fp) 23 static void button_interrupt(int irq, void *dummy, struct pt_regs *fp)
24 { 24 {
25 input_report_key(button_dev, BTN_1, inb(BUTTON_PORT) & 1); 25 input_report_key(button_dev, BTN_0, inb(BUTTON_PORT) & 1);
26 input_sync(button_dev); 26 input_sync(button_dev);
27 } 27 }
28 28
29 static int __init button_init(void) 29 static int __init button_init(void)
30 { 30 {
31 int error; 31 int error;
32 32
33 if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) { 33 if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) {
34 printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq); 34 printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
35 return -EBUSY; 35 return -EBUSY;
36 } 36 }
37 37
38 button_dev = input_allocate_device(); 38 button_dev = input_allocate_device();
39 if (!button_dev) { 39 if (!button_dev) {
40 printk(KERN_ERR "button.c: Not enough memory\n"); 40 printk(KERN_ERR "button.c: Not enough memory\n");
41 error = -ENOMEM; 41 error = -ENOMEM;
42 goto err_free_irq; 42 goto err_free_irq;
43 } 43 }
44 44
45 button_dev->evbit[0] = BIT_MASK(EV_KEY); 45 button_dev->evbit[0] = BIT_MASK(EV_KEY);
46 button_dev->keybit[BIT_WORD(BTN_0)] = BIT_MASK(BTN_0); 46 button_dev->keybit[BIT_WORD(BTN_0)] = BIT_MASK(BTN_0);
47 47
48 error = input_register_device(button_dev); 48 error = input_register_device(button_dev);
49 if (error) { 49 if (error) {
50 printk(KERN_ERR "button.c: Failed to register device\n"); 50 printk(KERN_ERR "button.c: Failed to register device\n");
51 goto err_free_dev; 51 goto err_free_dev;
52 } 52 }
53 53
54 return 0; 54 return 0;
55 55
56 err_free_dev: 56 err_free_dev:
57 input_free_device(button_dev); 57 input_free_device(button_dev);
58 err_free_irq: 58 err_free_irq:
59 free_irq(BUTTON_IRQ, button_interrupt); 59 free_irq(BUTTON_IRQ, button_interrupt);
60 return error; 60 return error;
61 } 61 }
62 62
63 static void __exit button_exit(void) 63 static void __exit button_exit(void)
64 { 64 {
65 input_unregister_device(button_dev); 65 input_unregister_device(button_dev);
66 free_irq(BUTTON_IRQ, button_interrupt); 66 free_irq(BUTTON_IRQ, button_interrupt);
67 } 67 }
68 68
69 module_init(button_init); 69 module_init(button_init);
70 module_exit(button_exit); 70 module_exit(button_exit);
71 71
72 1.1 What the example does 72 1.1 What the example does
73 ~~~~~~~~~~~~~~~~~~~~~~~~~ 73 ~~~~~~~~~~~~~~~~~~~~~~~~~
74 74
75 First it has to include the <linux/input.h> file, which interfaces to the 75 First it has to include the <linux/input.h> file, which interfaces to the
76 input subsystem. This provides all the definitions needed. 76 input subsystem. This provides all the definitions needed.
77 77
78 In the _init function, which is called either upon module load or when 78 In the _init function, which is called either upon module load or when
79 booting the kernel, it grabs the required resources (it should also check 79 booting the kernel, it grabs the required resources (it should also check
80 for the presence of the device). 80 for the presence of the device).
81 81
82 Then it allocates a new input device structure with input_allocate_device() 82 Then it allocates a new input device structure with input_allocate_device()
83 and sets up input bitfields. This way the device driver tells the other 83 and sets up input bitfields. This way the device driver tells the other
84 parts of the input systems what it is - what events can be generated or 84 parts of the input systems what it is - what events can be generated or
85 accepted by this input device. Our example device can only generate EV_KEY 85 accepted by this input device. Our example device can only generate EV_KEY
86 type events, and from those only BTN_0 event code. Thus we only set these 86 type events, and from those only BTN_0 event code. Thus we only set these
87 two bits. We could have used 87 two bits. We could have used
88 88
89 set_bit(EV_KEY, button_dev.evbit); 89 set_bit(EV_KEY, button_dev.evbit);
90 set_bit(BTN_0, button_dev.keybit); 90 set_bit(BTN_0, button_dev.keybit);
91 91
92 as well, but with more than single bits the first approach tends to be 92 as well, but with more than single bits the first approach tends to be
93 shorter. 93 shorter.
94 94
95 Then the example driver registers the input device structure by calling 95 Then the example driver registers the input device structure by calling
96 96
97 input_register_device(&button_dev); 97 input_register_device(&button_dev);
98 98
99 This adds the button_dev structure to linked lists of the input driver and 99 This adds the button_dev structure to linked lists of the input driver and
100 calls device handler modules _connect functions to tell them a new input 100 calls device handler modules _connect functions to tell them a new input
101 device has appeared. input_register_device() may sleep and therefore must 101 device has appeared. input_register_device() may sleep and therefore must
102 not be called from an interrupt or with a spinlock held. 102 not be called from an interrupt or with a spinlock held.
103 103
104 While in use, the only used function of the driver is 104 While in use, the only used function of the driver is
105 105
106 button_interrupt() 106 button_interrupt()
107 107
108 which upon every interrupt from the button checks its state and reports it 108 which upon every interrupt from the button checks its state and reports it
109 via the 109 via the
110 110
111 input_report_key() 111 input_report_key()
112 112
113 call to the input system. There is no need to check whether the interrupt 113 call to the input system. There is no need to check whether the interrupt
114 routine isn't reporting two same value events (press, press for example) to 114 routine isn't reporting two same value events (press, press for example) to
115 the input system, because the input_report_* functions check that 115 the input system, because the input_report_* functions check that
116 themselves. 116 themselves.
117 117
118 Then there is the 118 Then there is the
119 119
120 input_sync() 120 input_sync()
121 121
122 call to tell those who receive the events that we've sent a complete report. 122 call to tell those who receive the events that we've sent a complete report.
123 This doesn't seem important in the one button case, but is quite important 123 This doesn't seem important in the one button case, but is quite important
124 for for example mouse movement, where you don't want the X and Y values 124 for for example mouse movement, where you don't want the X and Y values
125 to be interpreted separately, because that'd result in a different movement. 125 to be interpreted separately, because that'd result in a different movement.
126 126
127 1.2 dev->open() and dev->close() 127 1.2 dev->open() and dev->close()
128 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 128 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
129 129
130 In case the driver has to repeatedly poll the device, because it doesn't 130 In case the driver has to repeatedly poll the device, because it doesn't
131 have an interrupt coming from it and the polling is too expensive to be done 131 have an interrupt coming from it and the polling is too expensive to be done
132 all the time, or if the device uses a valuable resource (eg. interrupt), it 132 all the time, or if the device uses a valuable resource (eg. interrupt), it
133 can use the open and close callback to know when it can stop polling or 133 can use the open and close callback to know when it can stop polling or
134 release the interrupt and when it must resume polling or grab the interrupt 134 release the interrupt and when it must resume polling or grab the interrupt
135 again. To do that, we would add this to our example driver: 135 again. To do that, we would add this to our example driver:
136 136
137 static int button_open(struct input_dev *dev) 137 static int button_open(struct input_dev *dev)
138 { 138 {
139 if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) { 139 if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) {
140 printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq); 140 printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
141 return -EBUSY; 141 return -EBUSY;
142 } 142 }
143 143
144 return 0; 144 return 0;
145 } 145 }
146 146
147 static void button_close(struct input_dev *dev) 147 static void button_close(struct input_dev *dev)
148 { 148 {
149 free_irq(IRQ_AMIGA_VERTB, button_interrupt); 149 free_irq(IRQ_AMIGA_VERTB, button_interrupt);
150 } 150 }
151 151
152 static int __init button_init(void) 152 static int __init button_init(void)
153 { 153 {
154 ... 154 ...
155 button_dev->open = button_open; 155 button_dev->open = button_open;
156 button_dev->close = button_close; 156 button_dev->close = button_close;
157 ... 157 ...
158 } 158 }
159 159
160 Note that input core keeps track of number of users for the device and 160 Note that input core keeps track of number of users for the device and
161 makes sure that dev->open() is called only when the first user connects 161 makes sure that dev->open() is called only when the first user connects
162 to the device and that dev->close() is called when the very last user 162 to the device and that dev->close() is called when the very last user
163 disconnects. Calls to both callbacks are serialized. 163 disconnects. Calls to both callbacks are serialized.
164 164
165 The open() callback should return a 0 in case of success or any nonzero value 165 The open() callback should return a 0 in case of success or any nonzero value
166 in case of failure. The close() callback (which is void) must always succeed. 166 in case of failure. The close() callback (which is void) must always succeed.
167 167
168 1.3 Basic event types 168 1.3 Basic event types
169 ~~~~~~~~~~~~~~~~~~~~~ 169 ~~~~~~~~~~~~~~~~~~~~~
170 170
171 The most simple event type is EV_KEY, which is used for keys and buttons. 171 The most simple event type is EV_KEY, which is used for keys and buttons.
172 It's reported to the input system via: 172 It's reported to the input system via:
173 173
174 input_report_key(struct input_dev *dev, int code, int value) 174 input_report_key(struct input_dev *dev, int code, int value)
175 175
176 See linux/input.h for the allowable values of code (from 0 to KEY_MAX). 176 See linux/input.h for the allowable values of code (from 0 to KEY_MAX).
177 Value is interpreted as a truth value, ie any nonzero value means key 177 Value is interpreted as a truth value, ie any nonzero value means key
178 pressed, zero value means key released. The input code generates events only 178 pressed, zero value means key released. The input code generates events only
179 in case the value is different from before. 179 in case the value is different from before.
180 180
181 In addition to EV_KEY, there are two more basic event types: EV_REL and 181 In addition to EV_KEY, there are two more basic event types: EV_REL and
182 EV_ABS. They are used for relative and absolute values supplied by the 182 EV_ABS. They are used for relative and absolute values supplied by the
183 device. A relative value may be for example a mouse movement in the X axis. 183 device. A relative value may be for example a mouse movement in the X axis.
184 The mouse reports it as a relative difference from the last position, 184 The mouse reports it as a relative difference from the last position,
185 because it doesn't have any absolute coordinate system to work in. Absolute 185 because it doesn't have any absolute coordinate system to work in. Absolute
186 events are namely for joysticks and digitizers - devices that do work in an 186 events are namely for joysticks and digitizers - devices that do work in an
187 absolute coordinate systems. 187 absolute coordinate systems.
188 188
189 Having the device report EV_REL buttons is as simple as with EV_KEY, simply 189 Having the device report EV_REL buttons is as simple as with EV_KEY, simply
190 set the corresponding bits and call the 190 set the corresponding bits and call the
191 191
192 input_report_rel(struct input_dev *dev, int code, int value) 192 input_report_rel(struct input_dev *dev, int code, int value)
193 193
194 function. Events are generated only for nonzero value. 194 function. Events are generated only for nonzero value.
195 195
196 However EV_ABS requires a little special care. Before calling 196 However EV_ABS requires a little special care. Before calling
197 input_register_device, you have to fill additional fields in the input_dev 197 input_register_device, you have to fill additional fields in the input_dev
198 struct for each absolute axis your device has. If our button device had also 198 struct for each absolute axis your device has. If our button device had also
199 the ABS_X axis: 199 the ABS_X axis:
200 200
201 button_dev.absmin[ABS_X] = 0; 201 button_dev.absmin[ABS_X] = 0;
202 button_dev.absmax[ABS_X] = 255; 202 button_dev.absmax[ABS_X] = 255;
203 button_dev.absfuzz[ABS_X] = 4; 203 button_dev.absfuzz[ABS_X] = 4;
204 button_dev.absflat[ABS_X] = 8; 204 button_dev.absflat[ABS_X] = 8;
205 205
206 Or, you can just say: 206 Or, you can just say:
207 207
208 input_set_abs_params(button_dev, ABS_X, 0, 255, 4, 8); 208 input_set_abs_params(button_dev, ABS_X, 0, 255, 4, 8);
209 209
210 This setting would be appropriate for a joystick X axis, with the minimum of 210 This setting would be appropriate for a joystick X axis, with the minimum of
211 0, maximum of 255 (which the joystick *must* be able to reach, no problem if 211 0, maximum of 255 (which the joystick *must* be able to reach, no problem if
212 it sometimes reports more, but it must be able to always reach the min and 212 it sometimes reports more, but it must be able to always reach the min and
213 max values), with noise in the data up to +- 4, and with a center flat 213 max values), with noise in the data up to +- 4, and with a center flat
214 position of size 8. 214 position of size 8.
215 215
216 If you don't need absfuzz and absflat, you can set them to zero, which mean 216 If you don't need absfuzz and absflat, you can set them to zero, which mean
217 that the thing is precise and always returns to exactly the center position 217 that the thing is precise and always returns to exactly the center position
218 (if it has any). 218 (if it has any).
219 219
220 1.4 BITS_TO_LONGS(), BIT_WORD(), BIT_MASK() 220 1.4 BITS_TO_LONGS(), BIT_WORD(), BIT_MASK()
221 ~~~~~~~~~~~~~~~~~~~~~~~~~~ 221 ~~~~~~~~~~~~~~~~~~~~~~~~~~
222 222
223 These three macros from bitops.h help some bitfield computations: 223 These three macros from bitops.h help some bitfield computations:
224 224
225 BITS_TO_LONGS(x) - returns the length of a bitfield array in longs for 225 BITS_TO_LONGS(x) - returns the length of a bitfield array in longs for
226 x bits 226 x bits
227 BIT_WORD(x) - returns the index in the array in longs for bit x 227 BIT_WORD(x) - returns the index in the array in longs for bit x
228 BIT_MASK(x) - returns the index in a long for bit x 228 BIT_MASK(x) - returns the index in a long for bit x
229 229
230 1.5 The id* and name fields 230 1.5 The id* and name fields
231 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 231 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
232 232
233 The dev->name should be set before registering the input device by the input 233 The dev->name should be set before registering the input device by the input
234 device driver. It's a string like 'Generic button device' containing a 234 device driver. It's a string like 'Generic button device' containing a
235 user friendly name of the device. 235 user friendly name of the device.
236 236
237 The id* fields contain the bus ID (PCI, USB, ...), vendor ID and device ID 237 The id* fields contain the bus ID (PCI, USB, ...), vendor ID and device ID
238 of the device. The bus IDs are defined in input.h. The vendor and device ids 238 of the device. The bus IDs are defined in input.h. The vendor and device ids
239 are defined in pci_ids.h, usb_ids.h and similar include files. These fields 239 are defined in pci_ids.h, usb_ids.h and similar include files. These fields
240 should be set by the input device driver before registering it. 240 should be set by the input device driver before registering it.
241 241
242 The idtype field can be used for specific information for the input device 242 The idtype field can be used for specific information for the input device
243 driver. 243 driver.
244 244
245 The id and name fields can be passed to userland via the evdev interface. 245 The id and name fields can be passed to userland via the evdev interface.
246 246
247 1.6 The keycode, keycodemax, keycodesize fields 247 1.6 The keycode, keycodemax, keycodesize fields
248 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 248 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
249 249
250 These three fields should be used by input devices that have dense keymaps. 250 These three fields should be used by input devices that have dense keymaps.
251 The keycode is an array used to map from scancodes to input system keycodes. 251 The keycode is an array used to map from scancodes to input system keycodes.
252 The keycode max should contain the size of the array and keycodesize the 252 The keycode max should contain the size of the array and keycodesize the
253 size of each entry in it (in bytes). 253 size of each entry in it (in bytes).
254 254
255 Userspace can query and alter current scancode to keycode mappings using 255 Userspace can query and alter current scancode to keycode mappings using
256 EVIOCGKEYCODE and EVIOCSKEYCODE ioctls on corresponding evdev interface. 256 EVIOCGKEYCODE and EVIOCSKEYCODE ioctls on corresponding evdev interface.
257 When a device has all 3 aforementioned fields filled in, the driver may 257 When a device has all 3 aforementioned fields filled in, the driver may
258 rely on kernel's default implementation of setting and querying keycode 258 rely on kernel's default implementation of setting and querying keycode
259 mappings. 259 mappings.
260 260
261 1.7 dev->getkeycode() and dev->setkeycode() 261 1.7 dev->getkeycode() and dev->setkeycode()
262 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 262 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
263 getkeycode() and setkeycode() callbacks allow drivers to override default 263 getkeycode() and setkeycode() callbacks allow drivers to override default
264 keycode/keycodesize/keycodemax mapping mechanism provided by input core 264 keycode/keycodesize/keycodemax mapping mechanism provided by input core
265 and implement sparse keycode maps. 265 and implement sparse keycode maps.
266 266
267 1.8 Key autorepeat 267 1.8 Key autorepeat
268 ~~~~~~~~~~~~~~~~~~ 268 ~~~~~~~~~~~~~~~~~~
269 269
270 ... is simple. It is handled by the input.c module. Hardware autorepeat is 270 ... is simple. It is handled by the input.c module. Hardware autorepeat is
271 not used, because it's not present in many devices and even where it is 271 not used, because it's not present in many devices and even where it is
272 present, it is broken sometimes (at keyboards: Toshiba notebooks). To enable 272 present, it is broken sometimes (at keyboards: Toshiba notebooks). To enable
273 autorepeat for your device, just set EV_REP in dev->evbit. All will be 273 autorepeat for your device, just set EV_REP in dev->evbit. All will be
274 handled by the input system. 274 handled by the input system.
275 275
276 1.9 Other event types, handling output events 276 1.9 Other event types, handling output events
277 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 277 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
278 278
279 The other event types up to now are: 279 The other event types up to now are:
280 280
281 EV_LED - used for the keyboard LEDs. 281 EV_LED - used for the keyboard LEDs.
282 EV_SND - used for keyboard beeps. 282 EV_SND - used for keyboard beeps.
283 283
284 They are very similar to for example key events, but they go in the other 284 They are very similar to for example key events, but they go in the other
285 direction - from the system to the input device driver. If your input device 285 direction - from the system to the input device driver. If your input device
286 driver can handle these events, it has to set the respective bits in evbit, 286 driver can handle these events, it has to set the respective bits in evbit,
287 *and* also the callback routine: 287 *and* also the callback routine:
288 288
289 button_dev->event = button_event; 289 button_dev->event = button_event;
290 290
291 int button_event(struct input_dev *dev, unsigned int type, unsigned int code, int value); 291 int button_event(struct input_dev *dev, unsigned int type, unsigned int code, int value);
292 { 292 {
293 if (type == EV_SND && code == SND_BELL) { 293 if (type == EV_SND && code == SND_BELL) {
294 outb(value, BUTTON_BELL); 294 outb(value, BUTTON_BELL);
295 return 0; 295 return 0;
296 } 296 }
297 return -1; 297 return -1;
298 } 298 }
299 299
300 This callback routine can be called from an interrupt or a BH (although that 300 This callback routine can be called from an interrupt or a BH (although that
301 isn't a rule), and thus must not sleep, and must not take too long to finish. 301 isn't a rule), and thus must not sleep, and must not take too long to finish.
302 302