From cece5972e9630ff2dbf6fe33c5edd6c5a05c0e53 Mon Sep 17 00:00:00 2001
From: krw <krw@openbsd.org>
Date: Tue, 3 Aug 2010 19:37:17 +0000
Subject: [PATCH] Don't attempt to set the read or write caches on usb disks.
 It breaks at least one previously working device, as discovered by naddy@.
 dlg@ confirmed other kernels also avoid attempting this operation on usb
 disks.

ok dlg@ deraadt@
---
 sys/scsi/sd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sys/scsi/sd.c b/sys/scsi/sd.c
index 98a44ad2dc2..29db37f9585 100644
--- a/sys/scsi/sd.c
+++ b/sys/scsi/sd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sd.c,v 1.204 2010/07/07 03:53:07 marco Exp $	*/
+/*	$OpenBSD: sd.c,v 1.205 2010/08/03 19:37:17 krw Exp $	*/
 /*	$NetBSD: sd.c,v 1.111 1997/04/02 02:29:41 mycroft Exp $	*/
 
 /*-
@@ -1040,6 +1040,9 @@ sd_ioctl_cache(struct sd_softc *sc, long cmd, struct dk_cache *dkc)
 	int big;
 	int rv;
 
+	if (ISSET(sc->sc_link->flags, SDEV_UMASS))
+		return (EOPNOTSUPP);
+
 	/* see if the adapter has special handling */
 	rv = scsi_do_ioctl(sc->sc_link, cmd, (caddr_t)dkc, 0);
 	if (rv != ENOTTY) {
-- 
2.20.1