From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbbAMWAT (ORCPT ); Tue, 13 Jan 2015 17:00:19 -0500 Received: from mout.kundenserver.de ([212.227.17.13]:53127 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751608AbbAMWAR (ORCPT ); Tue, 13 Jan 2015 17:00:17 -0500 From: Arnd Bergmann To: gregkh@linuxfoundation.org Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jiri Slaby Subject: [PATCH] tty/isicom: fix big-endian compile warning Date: Tue, 13 Jan 2015 22:59:47 +0100 Message-ID: <2188320.G0IBCG4UeO@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:mVujfDbwWWWRS7ne4lsHaAeFhPBlR3THUeZ/7qoXa6h0I3jryIl PFcPX+uCaVFm+NCxOwTnL053Awqrqo14J2tYSZhOTbyw74w8lvUOeMF6tnWZxgFyrdipZPZ KhbLDaDoCFFQTYMyZiie0PiUaZod2xR7noaUiBruit4Zvi556sPVF8B1qheLRvjkWGcTJQn YzrHu5NmVdlIIs0Zg1faA== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 diff --git a/drivers/tty/isicom.c b/drivers/tty/isicom.c index 59ed783c4bcd..2054427992e0 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);