Messages in this thread | | | Date | Wed, 5 Mar 2014 10:33:48 +0800 | Subject | Re: [PATCH] gpio: clamp returned values to the boolean range | From | Linus Walleij <> |
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On Wed, Mar 5, 2014 at 10:22 AM, Alexandre Courbot <gnurou@gmail.com> wrote: > On Wed, Mar 5, 2014 at 11:19 AM, Joe Perches <joe@perches.com> wrote: >> On Wed, 2014-03-05 at 11:14 +0900, Alexandre Courbot wrote: >>> On Wed, Mar 5, 2014 at 11:04 AM, Joe Perches <joe@perches.com> wrote: >>> > On Wed, 2014-03-05 at 09:49 +0800, Linus Walleij wrote: >>> >> On Wed, Feb 26, 2014 at 9:40 AM, Alexandre Courbot <acourbot@nvidia.com> wrote: >>> >> >>> >> > Nothing prevents GPIO drivers from returning values outside the >>> >> > boolean range, and as it turns out a few drivers are actually doing so. >>> >> > These values were passed as-is to unsuspecting consumers and created >>> >> > confusion. >>> >> > >>> >> > This patch makes the internal _gpiod_get_raw_value() function return a >>> >> > bool, effectively clamping the GPIO value to the boolean range no >>> >> > matter what the driver does. >>> >> >>> >> No, that will not be the semantic effect of this patch, bool is just >>> >> another name for an int, maybe some static checkers will be able >>> >> to use it however. >>> > >>> > No, a bool is not an int. >>> > >>> > It's really different. >>> > include/linux/types.h:typedef _Bool bool; >>> >>> It indeed seems that _Bool is an actual boolean type in C99. However I >>> could not find in the C99 standard how ints are supposed to be >>> converted to it. >> >> 6.3.1.2 Boolean type >> >> When any scalar value is converted to _Bool, the result is 0 if the >> value compares equal to 0; otherwise, the result is 1. >> >>> So in the end it is probably safer to perform this >>> change the way Linus suggested. >> >> Not really. > > Ok, you are obviously correct here. Linus, what do you think?
Yeah I was wrong ... too old and not keeping up with standards development :-)
Anyway, the local "value" variable in the function should still be converted to a bool as well right? And the assignment should still be "false" not 0. So I would still add my hunk of code...
Yours, Linus Walleij
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