bsg: add sg_io_v4 structure

This patch adds sg_io_v4 structure that Doug proposed last month.

There's one major change from the RFC. I dropped iovec, which needs
compat stuff. The bsg code simply calls blk_rq_map_user against
dout_xferp/din_xferp. So if possible, the page frames are directly
mapped. If not possible, the block layer allocates new page frames and
does memory copies.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/linux/bsg.h

 #ifndef BSG_H
 #define BSG_H
 
+struct sg_io_v4 {
+	int32_t guard;		/* [i] 'Q' to differentiate from v3 */
+	uint32_t protocol;	/* [i] 0 -> SCSI , .... */
+	uint32_t subprotocol;	/* [i] 0 -> SCSI command, 1 -> SCSI task
+				   management function, .... */
+
+	uint32_t request_len;	/* [i] in bytes */
+	uint64_t request;	/* [i], [*i] {SCSI: cdb} */
+	uint32_t request_attr;	/* [i] {SCSI: task attribute} */
+	uint32_t request_tag;	/* [i] {SCSI: task tag (only if flagged)} */
+	uint32_t request_priority;	/* [i] {SCSI: task priority} */
+	uint32_t max_response_len;	/* [i] in bytes */
+	uint64_t response;	/* [i], [*o] {SCSI: (auto)sense data} */
+
+	/* "din_" for data in (from device); "dout_" for data out (to device) */
+	uint32_t dout_xfer_len;	/* [i] bytes to be transferred to device */
+	uint32_t din_xfer_len;	/* [i] bytes to be transferred from device */
+	uint64_t dout_xferp;	/* [i], [*i] */
+	uint64_t din_xferp;	/* [i], [*o] */
+
+	uint32_t timeout;	/* [i] units: millisecond */
+	uint32_t flags;		/* [i] bit mask */
+	uint64_t usr_ptr;	/* [i->o] unused internally */
+	uint32_t spare_in;	/* [i] */
+
+	uint32_t driver_status;	/* [o] 0 -> ok */
+	uint32_t transport_status;	/* [o] 0 -> ok */
+	uint32_t device_status;	/* [o] {SCSI: command completion status} */
+	uint32_t retry_delay;	/* [o] {SCSI: status auxiliary information} */
+	uint32_t info;		/* [o] additional information */
+	uint32_t duration;	/* [o] time to complete, in milliseconds */
+	uint32_t response_len;	/* [o] bytes of response actually written */
+	int32_t din_resid;	/* [o] actual_din_xfer_len - din_xfer_len */
+	uint32_t generated_tag;	/* [o] {SCSI: task tag that transport chose} */
+	uint32_t spare_out;	/* [o] */
+
+	uint32_t padding;
+};
+
+#ifdef __KERNEL__
+
 #if defined(CONFIG_BLK_DEV_BSG)
 struct bsg_class_device {
 	struct class_device *class_dev;
@@ -18,4 +59,6 @@ struct bsg_class_device { };
 #define bsg_unregister_disk(disk)	do { } while (0)
 #endif
 
+#endif /* __KERNEL__ */
+
 #endif