Messages in this thread | | | Subject | Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE | From | Guenter Roeck <> | Date | Wed, 10 Feb 2016 19:38:19 -0800 |
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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 ‘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. >> >> > > Ah, W=1 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. >
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 script, just for the fun of it, but it misses some of the problem cases in patch mode. Maybe I get it working tonight.
Guenter
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