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 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
