view Documentation/block/request.txt @ 854:950b9eb27661

usbback: fix urb interval value for interrupt urbs.

Signed-off-by: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Apr 06 13:51:20 2009 +0100 (2009-04-06)
parents 831230e53067
line source
2 struct request documentation
4 Jens Axboe <axboe@suse.de> 27/05/02
6 1.0
7 Index
9 2.0 Struct request members classification
11 2.1 struct request members explanation
13 3.0
16 2.0
17 Short explanation of request members
19 Classification flags:
21 D driver member
22 B block layer member
23 I I/O scheduler member
25 Unless an entry contains a D classification, a device driver must not access
26 this member. Some members may contain D classifications, but should only be
27 access through certain macros or functions (eg ->flags).
29 <linux/blkdev.h>
31 2.1
32 Member Flag Comment
33 ------ ---- -------
35 struct list_head queuelist BI Organization on various internal
36 queues
38 void *elevator_private I I/O scheduler private data
40 unsigned char cmd[16] D Driver can use this for setting up
41 a cdb before execution, see
42 blk_queue_prep_rq
44 unsigned long flags DBI Contains info about data direction,
45 request type, etc.
47 int rq_status D Request status bits
49 kdev_t rq_dev DBI Target device
51 int errors DB Error counts
53 sector_t sector DBI Target location
55 unsigned long hard_nr_sectors B Used to keep sector sane
57 unsigned long nr_sectors DBI Total number of sectors in request
59 unsigned long hard_nr_sectors B Used to keep nr_sectors sane
61 unsigned short nr_phys_segments DB Number of physical scatter gather
62 segments in a request
64 unsigned short nr_hw_segments DB Number of hardware scatter gather
65 segments in a request
67 unsigned int current_nr_sectors DB Number of sectors in first segment
68 of request
70 unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane
72 int tag DB TCQ tag, if assigned
74 void *special D Free to be used by driver
76 char *buffer D Map of first segment, also see
77 section on bouncing SECTION
79 struct completion *waiting D Can be used by driver to get signalled
80 on request completion
82 struct bio *bio DBI First bio in request
84 struct bio *biotail DBI Last bio in request
86 request_queue_t *q DB Request queue this request belongs to
88 struct request_list *rl B Request list this request came from