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Commit 10569713c78f3c499745651aebc90b0d1c454c28

Authored by Borislav Petkov 2008-04-27 21:38:28 +0800

Committed by Bartlomiej Zolnierkiewicz 2008-04-27 21:38:28 +0800

Exists in master and in 7 other branches

ide-tape: remove comments markup from Documentation/ide/ide-tape.txt

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

Showing 1 changed file with 65 additions and 67 deletions Side-by-side Diff

Documentation/ide/ide-tape.txt

Documentation/ide/ide-tape.txt

Diff comments View file @ 1056971

1		-/*
2		- * IDE ATAPI streaming tape driver.
3		- *
4		- * This driver is a part of the Linux ide driver.
5		- *
6		- * The driver, in co-operation with ide.c, basically traverses the
7		- * request-list for the block device interface. The character device
8		- * interface, on the other hand, creates new requests, adds them
9		- * to the request-list of the block device, and waits for their completion.
10		- *
11		- * The block device major and minor numbers are determined from the
12		- * tape's relative position in the ide interfaces, as explained in ide.c.
13		- *
14		- * The character device interface consists of the following devices:
15		- *
16		- * ht0 major 37, minor 0 first IDE tape, rewind on close.
17		- * ht1 major 37, minor 1 second IDE tape, rewind on close.
18		- * ...
19		- * nht0 major 37, minor 128 first IDE tape, no rewind on close.
20		- * nht1 major 37, minor 129 second IDE tape, no rewind on close.
21		- * ...
22		- *
23		- * The general magnetic tape commands compatible interface, as defined by
24		- * include/linux/mtio.h, is accessible through the character device.
25		- *
26		- * General ide driver configuration options, such as the interrupt-unmask
27		- * flag, can be configured by issuing an ioctl to the block device interface,
28		- * as any other ide device.
29		- *
30		- * Our own ide-tape ioctl's can be issued to either the block device or
31		- * the character device interface.
32		- *
33		- * Maximal throughput with minimal bus load will usually be achieved in the
34		- * following scenario:
35		- *
36		- * 1. ide-tape is operating in the pipelined operation mode.
37		- * 2. No buffering is performed by the user backup program.
38		- *
39		- * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
40		- *
41		- * Here are some words from the first releases of hd.c, which are quoted
42		- * in ide.c and apply here as well:
43		- *
44		- * \| Special care is recommended. Have Fun!
45		- *
46		- * Possible improvements.
47		- *
48		- * 1. Support for the ATAPI overlap protocol.
49		- *
50		- * In order to maximize bus throughput, we currently use the DSC
51		- * overlap method which enables ide.c to service requests from the
52		- * other device while the tape is busy executing a command. The
53		- * DSC overlap method involves polling the tape's status register
54		- * for the DSC bit, and servicing the other device while the tape
55		- * isn't ready.
56		- *
57		- * In the current QIC development standard (December 1995),
58		- * it is recommended that new tape drives will in addition
59		- * implement the ATAPI overlap protocol, which is used for the
60		- * same purpose - efficient use of the IDE bus, but is interrupt
61		- * driven and thus has much less CPU overhead.
62		- *
63		- * ATAPI overlap is likely to be supported in most new ATAPI
64		- * devices, including new ATAPI cdroms, and thus provides us
65		- * a method by which we can achieve higher throughput when
66		- * sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
67		- */
	1	+IDE ATAPI streaming tape driver.
	2	+
	3	+This driver is a part of the Linux ide driver.
	4	+
	5	+The driver, in co-operation with ide.c, basically traverses the
	6	+request-list for the block device interface. The character device
	7	+interface, on the other hand, creates new requests, adds them
	8	+to the request-list of the block device, and waits for their completion.
	9	+
	10	+The block device major and minor numbers are determined from the
	11	+tape's relative position in the ide interfaces, as explained in ide.c.
	12	+
	13	+The character device interface consists of the following devices:
	14	+
	15	+ht0 major 37, minor 0 first IDE tape, rewind on close.
	16	+ht1 major 37, minor 1 second IDE tape, rewind on close.
	17	+...
	18	+nht0 major 37, minor 128 first IDE tape, no rewind on close.
	19	+nht1 major 37, minor 129 second IDE tape, no rewind on close.
	20	+...
	21	+
	22	+The general magnetic tape commands compatible interface, as defined by
	23	+include/linux/mtio.h, is accessible through the character device.
	24	+
	25	+General ide driver configuration options, such as the interrupt-unmask
	26	+flag, can be configured by issuing an ioctl to the block device interface,
	27	+as any other ide device.
	28	+
	29	+Our own ide-tape ioctl's can be issued to either the block device or
	30	+the character device interface.
	31	+
	32	+Maximal throughput with minimal bus load will usually be achieved in the
	33	+following scenario:
	34	+
	35	+ 1. ide-tape is operating in the pipelined operation mode.
	36	+ 2. No buffering is performed by the user backup program.
	37	+
	38	+Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
	39	+
	40	+Here are some words from the first releases of hd.c, which are quoted
	41	+in ide.c and apply here as well:
	42	+
	43	+\| Special care is recommended. Have Fun!
	44	+
	45	+Possible improvements:
	46	+
	47	+1. Support for the ATAPI overlap protocol.
	48	+
	49	+In order to maximize bus throughput, we currently use the DSC
	50	+overlap method which enables ide.c to service requests from the
	51	+other device while the tape is busy executing a command. The
	52	+DSC overlap method involves polling the tape's status register
	53	+for the DSC bit, and servicing the other device while the tape
	54	+isn't ready.
	55	+
	56	+In the current QIC development standard (December 1995),
	57	+it is recommended that new tape drives will in addition
	58	+implement the ATAPI overlap protocol, which is used for the
	59	+same purpose - efficient use of the IDE bus, but is interrupt
	60	+driven and thus has much less CPU overhead.
	61	+
	62	+ATAPI overlap is likely to be supported in most new ATAPI
	63	+devices, including new ATAPI cdroms, and thus provides us
	64	+a method by which we can achieve higher throughput when
	65	+sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.