Index: head/sys/cam/scsi/scsi_da.c
===================================================================
--- head/sys/cam/scsi/scsi_da.c
+++ head/sys/cam/scsi/scsi_da.c
@@ -1469,6 +1469,7 @@
 static int da_default_timeout = DA_DEFAULT_TIMEOUT;
 static sbintime_t da_default_softtimeout = DA_DEFAULT_SOFTTIMEOUT;
 static int da_send_ordered = DA_DEFAULT_SEND_ORDERED;
+static int da_disable_wp_detection = 0;
 
 static SYSCTL_NODE(_kern_cam, OID_AUTO, da, CTLFLAG_RD, 0,
             "CAM Direct Access Disk driver");
@@ -1480,6 +1481,9 @@
            &da_default_timeout, 0, "Normal I/O timeout (in seconds)");
 SYSCTL_INT(_kern_cam_da, OID_AUTO, send_ordered, CTLFLAG_RWTUN,
            &da_send_ordered, 0, "Send Ordered Tags");
+SYSCTL_INT(_kern_cam_da, OID_AUTO, disable_wp_detection, CTLFLAG_RWTUN,
+           &da_disable_wp_detection, 0,
+	   "Disable detection of write-protected disks");
 
 SYSCTL_PROC(_kern_cam_da, OID_AUTO, default_softtimeout,
     CTLTYPE_UINT | CTLFLAG_RW, NULL, 0, dasysctlsofttimeout, "I",
@@ -3336,12 +3340,22 @@
 		void  *mode_buf;
 		int    mode_buf_len;
 
+		if (da_disable_wp_detection) {
+			if ((softc->flags & DA_FLAG_CAN_RC16) != 0)
+				softc->state = DA_STATE_PROBE_RC16;
+			else
+				softc->state = DA_STATE_PROBE_RC;
+			goto skipstate;
+		}
 		mode_buf_len = 192;
 		mode_buf = malloc(mode_buf_len, M_SCSIDA, M_NOWAIT);
 		if (mode_buf == NULL) {
 			xpt_print(periph->path, "Unable to send mode sense - "
 			    "malloc failure\n");
-			softc->state = DA_STATE_PROBE_RC;
+			if ((softc->flags & DA_FLAG_CAN_RC16) != 0)
+				softc->state = DA_STATE_PROBE_RC16;
+			else
+				softc->state = DA_STATE_PROBE_RC;
 			goto skipstate;
 		}
 		scsi_mode_sense_len(&start_ccb->csio,