virtio_blk: SG_IO passthru support

Add support for SG_IO passthru to virtio_blk.  We add the scsi command
block after the normal outhdr, and the scsi inhdr with full status
information aswell as the sense buffer before the regular inhdr.

[hch: forward ported, added the VIRTIO_BLK_F_SCSI flags, some comments
 and tested the whole beast]
[axboe: updated to use ->resid and not dual-path the byte count]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (+ checkpatch.pl tweak)
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/virtio_blk.h b/include/linux/virtio_blk.h
index 94c56d29869d..4dbcbc1c3481 100644
--- a/include/linux/virtio_blk.h
+++ b/include/linux/virtio_blk.h
@@ -15,6 +15,7 @@
 #define VIRTIO_BLK_F_GEOMETRY   4       /* Legacy geometry available  */
 #define VIRTIO_BLK_F_RO         5       /* Disk is read-only */
 #define VIRTIO_BLK_F_BLK_SIZE   6       /* Block size of disk is available*/
+#define VIRTIO_BLK_F_SCSI       7       /* Supports scsi command passthru */
 
 struct virtio_blk_config
 {
@@ -55,6 +56,13 @@ struct virtio_blk_outhdr
         __u64 sector;
 };
 
+struct virtio_scsi_inhdr {
+        __u32 errors;
+        __u32 data_len;
+        __u32 sense_len;
+        __u32 residual;
+};
+
 /* And this is the final byte of the write scatter-gather list. */
 #define VIRTIO_BLK_S_OK         0
 #define VIRTIO_BLK_S_IOERR      1