From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE Date: Wed, 10 Feb 2016 19:38:19 -0800 Message-ID: <56BC022B.7030004@roeck-us.net> References: <1455030539-10798-1-git-send-email-linux@roeck-us.net> <4571887.rTPndCnv20@wuerfel> <56BAA27A.9050605@roeck-us.net> <2606061.l722KO95iI@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <2606061.l722KO95iI@wuerfel> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Greg Kroah-Hartman , Baruch Siach , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jiri Slaby , kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrzej Hajda List-Id: linux-serial@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 =E2=80=98digicol= or_uart_probe=E2=80=99: >>>> 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 =E2=80=98IS_ERR_VALUE=E2=80=99 >>>> >>>> If that warning is seen, an error return from platform_get_irq() i= s 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 t= he >>> changes are still under discussion, but I don't see that warning wi= th >>> any of the versions. >>> >> I see it with gcc 5.1 and 5.2 (and W=3D1). I did not see / notice An= drzej's patch. >> >> I agree that fixing the problem in IS_ERR_VALUE() is preferrable. >> >> > > Ah, W=3D1 explains it. We are still debating about the proper solutio= n. Al Viro > pointed out that most users of IS_ERR_VALUE() shouldn't be using it a= t 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 scri= pt, just for the fun of it, but it misses some of the problem cases in patch mod= e. Maybe I get it working tonight. Guenter