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d15156138d
After the SG_IO ioctl was copied into the block layer and
later into the bsg driver, subtle differences emerged.
One difference is the way injected commands are queued through
the block layer (i.e. this is not SCSI device queueing nor SATA
NCQ). Summarizing:
- SG_IO on block layer device: blk_exec*(at_head=false)
- sg device SG_IO: at_head=true
- bsg device SG_IO: at_head=true
Some time ago Boaz Harrosh introduced a sg v4 flag called
BSG_FLAG_Q_AT_TAIL to override the bsg driver default. A
recent patch titled: "sg: add SG_FLAG_Q_AT_TAIL flag"
allowed the sg driver default to be overridden. This patch
allows a SG_IO ioctl sent to a block layer device to have
its default overridden.
ChangeLog:
- introduce SG_FLAG_Q_AT_HEAD flag in sg.h to cause
commands that are injected via a block layer
device SG_IO ioctl to set at_head=true
- make comments clearer about queueing in sg.h since the
header is used both by the sg device and block layer
device implementations of the SG_IO ioctl.
- introduce BSG_FLAG_Q_AT_HEAD in bsg.h for compatibility
(it does nothing) and update comments.
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Jens Axboe <axboe@fb.com>
67 lines
2.4 KiB
C
67 lines
2.4 KiB
C
#ifndef _UAPIBSG_H
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#define _UAPIBSG_H
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#include <linux/types.h>
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#define BSG_PROTOCOL_SCSI 0
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#define BSG_SUB_PROTOCOL_SCSI_CMD 0
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#define BSG_SUB_PROTOCOL_SCSI_TMF 1
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#define BSG_SUB_PROTOCOL_SCSI_TRANSPORT 2
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/*
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* For flag constants below:
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* sg.h sg_io_hdr also has bits defined for it's flags member. These
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* two flag values (0x10 and 0x20) have the same meaning in sg.h . For
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* bsg the BSG_FLAG_Q_AT_HEAD flag is ignored since it is the deafult.
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*/
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#define BSG_FLAG_Q_AT_TAIL 0x10 /* default is Q_AT_HEAD */
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#define BSG_FLAG_Q_AT_HEAD 0x20
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struct sg_io_v4 {
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__s32 guard; /* [i] 'Q' to differentiate from v3 */
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__u32 protocol; /* [i] 0 -> SCSI , .... */
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__u32 subprotocol; /* [i] 0 -> SCSI command, 1 -> SCSI task
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management function, .... */
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__u32 request_len; /* [i] in bytes */
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__u64 request; /* [i], [*i] {SCSI: cdb} */
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__u64 request_tag; /* [i] {SCSI: task tag (only if flagged)} */
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__u32 request_attr; /* [i] {SCSI: task attribute} */
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__u32 request_priority; /* [i] {SCSI: task priority} */
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__u32 request_extra; /* [i] {spare, for padding} */
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__u32 max_response_len; /* [i] in bytes */
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__u64 response; /* [i], [*o] {SCSI: (auto)sense data} */
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/* "dout_": data out (to device); "din_": data in (from device) */
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__u32 dout_iovec_count; /* [i] 0 -> "flat" dout transfer else
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dout_xfer points to array of iovec */
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__u32 dout_xfer_len; /* [i] bytes to be transferred to device */
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__u32 din_iovec_count; /* [i] 0 -> "flat" din transfer */
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__u32 din_xfer_len; /* [i] bytes to be transferred from device */
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__u64 dout_xferp; /* [i], [*i] */
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__u64 din_xferp; /* [i], [*o] */
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__u32 timeout; /* [i] units: millisecond */
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__u32 flags; /* [i] bit mask */
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__u64 usr_ptr; /* [i->o] unused internally */
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__u32 spare_in; /* [i] */
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__u32 driver_status; /* [o] 0 -> ok */
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__u32 transport_status; /* [o] 0 -> ok */
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__u32 device_status; /* [o] {SCSI: command completion status} */
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__u32 retry_delay; /* [o] {SCSI: status auxiliary information} */
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__u32 info; /* [o] additional information */
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__u32 duration; /* [o] time to complete, in milliseconds */
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__u32 response_len; /* [o] bytes of response actually written */
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__s32 din_resid; /* [o] din_xfer_len - actual_din_xfer_len */
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__s32 dout_resid; /* [o] dout_xfer_len - actual_dout_xfer_len */
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__u64 generated_tag; /* [o] {SCSI: transport generated task tag} */
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__u32 spare_out; /* [o] */
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__u32 padding;
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};
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#endif /* _UAPIBSG_H */
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