From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752842AbcBKDi1 (ORCPT ); Wed, 10 Feb 2016 22:38:27 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:59233 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750748AbcBKDiY (ORCPT ); Wed, 10 Feb 2016 22:38:24 -0500 Subject: Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE To: Arnd Bergmann References: <1455030539-10798-1-git-send-email-linux@roeck-us.net> <4571887.rTPndCnv20@wuerfel> <56BAA27A.9050605@roeck-us.net> <2606061.l722KO95iI@wuerfel> Cc: linux-arm-kernel@lists.infradead.org, Greg Kroah-Hartman , Baruch Siach , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Jiri Slaby , kernel-testers@vger.kernel.org, Andrzej Hajda From: Guenter Roeck Message-ID: <56BC022B.7030004@roeck-us.net> Date: Wed, 10 Feb 2016 19:38:19 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <2606061.l722KO95iI@wuerfel> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/10/2016 07:21 AM, Arnd Bergmann wrote: > On Tuesday 09 February 2016 18:37:46 Guenter Roeck wrote: >> On 02/09/2016 07:26 AM, Arnd Bergmann wrote: >>> On Tuesday 09 February 2016 07:08:59 Guenter Roeck wrote: >>>> IS_ERR_VALUE() assumes that its parameter is an unsigned long. >>>> It can not be used to check if an unsigned int reflects an error. >>>> Doing so can result in the following build warning. >>>> >>>> drivers/tty/serial/digicolor-usart.c: In function ‘digicolor_uart_probe’: >>>> include/linux/err.h:21:38: warning: >>>> comparison is always false due to limited range of data type >>>> drivers/tty/serial/digicolor-usart.c:485:6: note: >>>> in expansion of macro ‘IS_ERR_VALUE’ >>>> >>>> If that warning is seen, an error return from platform_get_irq() is missed. >>>> >>>> >>> >>> The patch looks correct to me, but what compiler version and which kernel >>> tree is it that triggered the warning? >>> >>> Andrzej Hajda just modified the definition of IS_ERR_VALUE(), and the >>> changes are still under discussion, but I don't see that warning with >>> any of the versions. >>> >> I see it with gcc 5.1 and 5.2 (and W=1). I did not see / notice Andrzej's patch. >> >> I agree that fixing the problem in IS_ERR_VALUE() is preferrable. >> >> > > Ah, W=1 explains it. We are still debating about the proper solution. Al Viro > pointed out that most users of IS_ERR_VALUE() shouldn't be using it at all, > so your patch is probably best here after all. > Yes, after looking into it some more I agree. Coccinelle should be able to handle most of the conversions automatically. I actually tried to write a script, just for the fun of it, but it misses some of the problem cases in patch mode. Maybe I get it working tonight. Guenter