From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751536AbcBKPNa (ORCPT ); Thu, 11 Feb 2016 10:13:30 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:54213 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306AbcBKPN1 (ORCPT ); Thu, 11 Feb 2016 10:13:27 -0500 Date: Thu, 11 Feb 2016 07:13:22 -0800 From: Guenter Roeck To: Russell King - ARM Linux Cc: Arnd Bergmann , linux-arm-kernel@lists.infradead.org, Baruch Siach , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Andrzej Hajda , linux-serial@vger.kernel.org, Jiri Slaby , kernel-testers@vger.kernel.org Subject: Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE Message-ID: <20160211151322.GA30389@roeck-us.net> References: <1455030539-10798-1-git-send-email-linux@roeck-us.net> <4571887.rTPndCnv20@wuerfel> <56BAA27A.9050605@roeck-us.net> <20160211104650.GU10826@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160211104650.GU10826@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@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: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@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 Thu, Feb 11, 2016 at 10:46:50AM +0000, Russell King - ARM Linux wrote: > On Tue, Feb 09, 2016 at 06:37:46PM -0800, 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. > > I disagree. What happens if (eg) you decide to do this: > > u8 irq; > > irq = platform_get_irq(...); > if (IS_ERR_VALUE(irq)) > ... > > is that the fault of IS_ERR_VALUE() that it will never be true? No, it's > a programming error in the caller, because the caller is using the wrong > type here - in fact, you can't do anything in IS_ERR_VALUE() to correct > that. > Yes, I think we all reached that conclusion by now. Thanks, Guenter