From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.kundenserver.de ([212.227.126.134]:56758 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755323AbdEETsQ (ORCPT ); Fri, 5 May 2017 15:48:16 -0400 From: Arnd Bergmann To: Ben Hutchings Cc: stable@vger.kernel.org, Arnd Bergmann , Greg Kroah-Hartman Subject: [PATCH 3.16-stable 30/87] tty/isicom: fix big-endian compile warning Date: Fri, 5 May 2017 21:46:48 +0200 Message-Id: <20170505194745.3627137-31-arnd@arndb.de> In-Reply-To: <20170505194745.3627137-1-arnd@arndb.de> References: <20170505194745.3627137-1-arnd@arndb.de> Sender: stable-owner@vger.kernel.org List-ID: Commit f3e2d56dce47dbd0bb3f69f84741b439542fef37 upstream. Building an arm allmodconfig kernel triggers a lengthy but harmless warning in the isicom driver: drvers/tty/isicom.c: In function 'isicom_send_break': uapi/linux/swab.h:13:15: warning: integer overflow in expression [-Woverflow] (((__u16)(x) & (__u16)0x00ffU) << 8) | \ ^ uapi/linux/swab.h:107:2: note: in expansion of macro '___constant_swab16' ___constant_swab16(x) : \ ^ uapi/linux/byteorder/big_endian.h:34:43: note: in expansion of macro '__swab16' #define __cpu_to_le16(x) ((__force __le16)__swab16((x))) ^ linux/byteorder/generic.h:89:21: note: in expansion of macro '__cpu_to_le16' #define cpu_to_le16 __cpu_to_le16 ^ include/asm/io.h:270:6: note: in expansion of macro 'cpu_to_le16' cpu_to_le16(v),__io(p)); }) ^ drivers/tty/isicom.c:1058:2: note: in expansion of macro 'outw' outw((length & 0xff00), base); ^ Apparently, the problem is related to the fact that the value 0xff00, when used as a 16-bit number, is negative and passed into bitwise operands of the generic byte swapping code. Marking the input argument as unsigned in both technically correct and avoids the warning. Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman Signed-off-by: Arnd Bergmann --- drivers/tty/isicom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/isicom.c b/drivers/tty/isicom.c index 858291ca889c..c03ecaa0af7f 100644 --- a/drivers/tty/isicom.c +++ b/drivers/tty/isicom.c @@ -1055,7 +1055,7 @@ static int isicom_send_break(struct tty_struct *tty, int length) outw(0x8000 | ((port->channel) << (card->shift_count)) | 0x3, base); outw((length & 0xff) << 8 | 0x00, base); - outw((length & 0xff00), base); + outw((length & 0xff00u), base); InterruptTheCard(base); unlock_card(card); -- 2.9.0