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99 lines
2.5 KiB
99 lines
2.5 KiB
============================ |
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struct request documentation |
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============================ |
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Jens Axboe <[email protected]> 27/05/02 |
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.. FIXME: |
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No idea about what does mean - seems just some noise, so comment it |
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1.0 |
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Index |
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2.0 Struct request members classification |
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2.1 struct request members explanation |
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3.0 |
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2.0 |
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Short explanation of request members |
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==================================== |
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Classification flags: |
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= ==================== |
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D driver member |
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B block layer member |
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I I/O scheduler member |
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= ==================== |
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Unless an entry contains a D classification, a device driver must not access |
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this member. Some members may contain D classifications, but should only be |
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access through certain macros or functions (eg ->flags). |
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<linux/blkdev.h> |
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=============================== ======= ======================================= |
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Member Flag Comment |
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=============================== ======= ======================================= |
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struct list_head queuelist BI Organization on various internal |
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queues |
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``void *elevator_private`` I I/O scheduler private data |
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unsigned char cmd[16] D Driver can use this for setting up |
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a cdb before execution, see |
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blk_queue_prep_rq |
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unsigned long flags DBI Contains info about data direction, |
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request type, etc. |
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int rq_status D Request status bits |
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kdev_t rq_dev DBI Target device |
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int errors DB Error counts |
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sector_t sector DBI Target location |
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unsigned long hard_nr_sectors B Used to keep sector sane |
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unsigned long nr_sectors DBI Total number of sectors in request |
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unsigned long hard_nr_sectors B Used to keep nr_sectors sane |
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unsigned short nr_phys_segments DB Number of physical scatter gather |
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segments in a request |
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unsigned short nr_hw_segments DB Number of hardware scatter gather |
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segments in a request |
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unsigned int current_nr_sectors DB Number of sectors in first segment |
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of request |
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unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane |
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int tag DB TCQ tag, if assigned |
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``void *special`` D Free to be used by driver |
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``char *buffer`` D Map of first segment, also see |
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section on bouncing SECTION |
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``struct completion *waiting`` D Can be used by driver to get signalled |
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on request completion |
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``struct bio *bio`` DBI First bio in request |
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``struct bio *biotail`` DBI Last bio in request |
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``struct request_queue *q`` DB Request queue this request belongs to |
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``struct request_list *rl`` B Request list this request came from |
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=============================== ======= =======================================
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