1
2 struct request documentation
3
4 Jens Axboe <axboe@suse.de> 27/05/02
5
6 1.0
7 Index
8
9 2.0 Struct request members classification
10
11 2.1 struct request members explanation
12
13 3.0
14
15
16 2.0
17 Short explanation of request members
18
19 Classification flags:
20
21 D driver member
22 B block layer member
23 I I/O scheduler member
24
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).
28
29 <linux/blkdev.h>
30
31 2.1
32 Member Flag Comment
33 ------ ---- -------
34
35 struct list_head queuelist BI Organization on various internal
36 queues
37
38 void *elevator_private I I/O scheduler private data
39
40 unsigned char cmd[16] D Driver can use this for setting up
41 a cdb before execution, see
42 blk_queue_prep_rq
43
44 unsigned long flags DBI Contains info about data direction,
45 request type, etc.
46
47 int rq_status D Request status bits
48
49 kdev_t rq_dev DBI Target device
50
51 int errors DB Error counts
52
53 sector_t sector DBI Target location
54
55 unsigned long hard_nr_sectors B Used to keep sector sane
56
57 unsigned long nr_sectors DBI Total number of sectors in request
58
59 unsigned long hard_nr_sectors B Used to keep nr_sectors sane
60
61 unsigned short nr_phys_segments DB Number of physical scatter gather
62 segments in a request
63
64 unsigned short nr_hw_segments DB Number of hardware scatter gather
65 segments in a request
66
67 unsigned int current_nr_sectors DB Number of sectors in first segment
68 of request
69
70 unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane
71
72 int tag DB TCQ tag, if assigned
73
74 void *special D Free to be used by driver
75
76 char *buffer D Map of first segment, also see
77 section on bouncing SECTION
78
79 struct completion *waiting D Can be used by driver to get signalled
80 on request completion
81
82 struct bio *bio DBI First bio in request
83
84 struct bio *biotail DBI Last bio in request
85
86 request_queue_t *q DB Request queue this request belongs to
87
88 struct request_list *rl B Request list this request came from
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