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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+============================
+struct request documentation
+============================
+
+Jens Axboe <jens.axboe@oracle.com> 27/05/02
+
+
+.. FIXME:
+ No idea about what does mean - seems just some noise, so comment it
+
+ 1.0
+ Index
+
+ 2.0 Struct request members classification
+
+ 2.1 struct request members explanation
+
+ 3.0
+
+
+ 2.0
+
+
+
+Short explanation of request members
+====================================
+
+Classification flags:
+
+ = ====================
+ D driver member
+ B block layer member
+ I I/O scheduler member
+ = ====================
+
+Unless an entry contains a D classification, a device driver must not access
+this member. Some members may contain D classifications, but should only be
+access through certain macros or functions (eg ->flags).
+
+<linux/blkdev.h>
+
+=============================== ======= =======================================
+Member Flag Comment
+=============================== ======= =======================================
+struct list_head queuelist BI Organization on various internal
+ queues
+
+``void *elevator_private`` I I/O scheduler private data
+
+unsigned char cmd[16] D Driver can use this for setting up
+ a cdb before execution, see
+ blk_queue_prep_rq
+
+unsigned long flags DBI Contains info about data direction,
+ request type, etc.
+
+int rq_status D Request status bits
+
+kdev_t rq_dev DBI Target device
+
+int errors DB Error counts
+
+sector_t sector DBI Target location
+
+unsigned long hard_nr_sectors B Used to keep sector sane
+
+unsigned long nr_sectors DBI Total number of sectors in request
+
+unsigned long hard_nr_sectors B Used to keep nr_sectors sane
+
+unsigned short nr_phys_segments DB Number of physical scatter gather
+ segments in a request
+
+unsigned short nr_hw_segments DB Number of hardware scatter gather
+ segments in a request
+
+unsigned int current_nr_sectors DB Number of sectors in first segment
+ of request
+
+unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane
+
+int tag DB TCQ tag, if assigned
+
+``void *special`` D Free to be used by driver
+
+``char *buffer`` D Map of first segment, also see
+ section on bouncing SECTION
+
+``struct completion *waiting`` D Can be used by driver to get signalled
+ on request completion
+
+``struct bio *bio`` DBI First bio in request
+
+``struct bio *biotail`` DBI Last bio in request
+
+``struct request_queue *q`` DB Request queue this request belongs to
+
+``struct request_list *rl`` B Request list this request came from
+=============================== ======= =======================================