Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE

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