From mboxrd@z Thu Jan  1 00:00:00 1970
From: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
Subject: Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE
Date: Tue, 9 Feb 2016 18:37:46 -0800
Message-ID: <56BAA27A.9050605@roeck-us.net>
References: <1455030539-10798-1-git-send-email-linux@roeck-us.net>
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To: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Baruch Siach <baruch-NswTu9S1W3P6gbPvEgmw2w@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jiri Slaby <jslaby-IBi9RG/b67k@public.gmane.org>, kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
List-Id: linux-serial@vger.kernel.org

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=98digicolor=
_uart_probe=E2=80=99:
>> include/linux/err.h:21:38: warning:
>>          comparison is always false due to limited range of data typ=
e
>> 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() is =
missed.
>>
>>
>
> The patch looks correct to me, but what compiler version and which ke=
rnel
> 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=3D1). I did not see / notice Andrz=
ej's patch.

I agree that fixing the problem in IS_ERR_VALUE() is preferrable.

Guenter