scsi: Introduce scsi_sense_buf_to_errno

This recognizes the "fixed" and "descriptor" format sense data, extracts
the sense key/asc/ascq fields then converts them to an errno.
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-Id: <20170821141008.19383-4-famz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

include/scsi/scsi.h

@@ -15,5 +15,6 @@
 #define QEMU_SCSI_H
 
 int scsi_sense_to_errno(int key, int asc, int ascq);
+int scsi_sense_buf_to_errno(const uint8_t *sense, size_t sense_size);
 
 #endif

util/scsi.c

@@ -58,3 +58,33 @@ int scsi_sense_to_errno(int key, int asc, int ascq)
         return EIO;
     }
 }
+
+int scsi_sense_buf_to_errno(const uint8_t *sense, size_t sense_size)
+{
+    int key, asc, ascq;
+    if (sense_size < 1) {
+        return EIO;
+    }
+    switch (sense[0]) {
+    case 0x70: /* Fixed format sense data. */
+        if (sense_size < 14) {
+            return EIO;
+        }
+        key = sense[2] & 0xF;
+        asc = sense[12];
+        ascq = sense[13];
+        break;
+    case 0x72: /* Descriptor format sense data. */
+        if (sense_size < 4) {
+            return EIO;
+        }
+        key = sense[1] & 0xF;
+        asc = sense[2];
+        ascq = sense[3];
+        break;
+    default:
+        return EIO;
+        break;
+    }
+    return scsi_sense_to_errno(key, asc, ascq);
+}