Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 99 insertions, 0 deletions

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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
+=============================== ======= =======================================