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

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 t=
ype
> >> 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 And=
rzej's patch.
>=20
> I agree that fixing the problem in IS_ERR_VALUE() is preferrable.
>=20
>=20

Ah, W=3D1 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.

	Arnd