scsi-disk: Inquiry with allocation length of CDB < 36 (v4)

According to the SCSI-2 specification,
http://ldkelley.com/SCSI2/SCSI2/SCSI2/SCSI2-08.html#8.2.5 ,
"if the allocation length of the command descriptor block (CDB) is too
small to transfer all of the parameters, the additional length shall
not be adjusted to reflect the truncation."
The 36 mandatory bytes of response are written to outbuf, and then
only the length requested in CDB is transferred.
Signed-off-by: NArtyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

hw/scsi-disk.c

@@ -5,6 +5,12 @@
  * Based on code by Fabrice Bellard
  *
  * Written by Paul Brook
+ * Modifications:
+ *  2009-Dec-12 Artyom Tarasenko : implemented stamdard inquiry for the case
+ *                                 when the allocation length of CDB is smaller
+ *                                 than 36.
+ *  2009-Oct-13 Artyom Tarasenko : implemented the block descriptor in the
+ *                                 MODE SENSE response.
  *
  * This code is licenced under the LGPL.
  *
@@ -406,11 +412,6 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
         return -1;
     }
 
-    if (req->cmd.xfer < 36) {
-        BADF("Error: Inquiry (STANDARD) buffer size %zd "
-             "is less than 36 (TODO: only 5 required)\n", req->cmd.xfer);
-    }
-
     buflen = req->cmd.xfer;
     if (buflen > SCSI_MAX_INQUIRY_LEN)
         buflen = SCSI_MAX_INQUIRY_LEN;
@@ -436,7 +437,15 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
        Some later commands are also implemented. */
     outbuf[2] = 3;
     outbuf[3] = 2; /* Format 2 */
+
+    if (buflen > 36) {
         outbuf[4] = buflen - 5; /* Additional Length = (Len - 1) - 4 */
+    } else {
+        /* If the allocation length of CDB is too small,
+               the additional length is not adjusted */
+        outbuf[4] = 36 - 5;
+    }
+
     /* Sync data transfer and TCQ.  */
     outbuf[7] = 0x10 | (req->bus->tcq ? 0x02 : 0);
     return buflen;