[Qemu-devel] [PATCH 4/4] ISCSI: If the device we open is a SMC device, then force the use of sg. We dont have any medium changer emulation so only passthrough via real sg or scsi-generic via iscsi would work anyway.

[Ronnie Sahlberg]

Forcing sg also makes qemu skip trying to read from the device to guess the 
image format by reading from the device (find_image_format()).
SMC devices do not implement READ6/10/12/16  so it is noit possible to read 
from them.

With this patch I can successfully manage a SMC device wiht iscsi in 
passthrough mode.

Signed-off-by: Ronnie Sahlberg <address@hidden>
---
 block/iscsi.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/block/iscsi.c b/block/iscsi.c
index a015a52..9ce38b5 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1032,6 +1032,15 @@ static int iscsi_open(BlockDriverState *bs, const char 
*filename, int flags)
     if (iscsi_url != NULL) {
         iscsi_destroy_url(iscsi_url);
     }
+
+    /* Medium changer. We dont have any emulation for this so this must
+       be sg ioctl compatible. We force it to be sg, otherwise qemu will try
+       to read from the device to guess the image format.
+     */
+    if (iscsilun->type == TYPE_MEDIUM_CHANGER) {
+            bs->sg = 1;
+    }
+
     return 0;
 
 failed:
-- 
1.7.3.1