Hi Laurent,
On 27.12.2015 00:35, Laurent Pinchart wrote:
> Hi Linus,
>
> Thank you for the patch.
>
> On Tuesday 22 December 2015 15:20:09 Linus Walleij wrote:
>> As we want gpio_chip .get() calls to be able to return negative
>> error codes and propagate to drivers, we need to go over all
>> drivers and make sure their return values are clamped to [0,1].
>> We do this by using the ret = !!(val) design pattern.
>
> The patch itself looks good to me, but wouldn't it be easier to patch the
> caller to clamp positive values to [0,1] and propagate negative values
> untouched ?
this has been done in v4.3 e20538b82f1f ("gpio: Propagate errors from
chip->get()"), but the change causes problems with GPIO line id 31 and
the change is temporarily reverted by 45ad7db90b ("gpio: revert get() to
non-errorprogating behaviour").
See also a recent discussion related to this problem
http://www.spinics.net/lists/linux-gpio/msg10677.html
>> Also start returning the error code if something fails, as the
>> end of the series augment the core to support this.
>>
>> Cc: Grygorii Strashko <[email protected]>
>> Cc: George Cherian <[email protected]>
>> Cc: Laurent Pinchart <[email protected]>
>> Signed-off-by: Linus Walleij <[email protected]>
>> ---
>> drivers/gpio/gpio-pcf857x.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpio/gpio-pcf857x.c b/drivers/gpio/gpio-pcf857x.c
>> index bf511c0efa48..f64380a7d004 100644
>> --- a/drivers/gpio/gpio-pcf857x.c
>> +++ b/drivers/gpio/gpio-pcf857x.c
>> @@ -154,7 +154,7 @@ static int pcf857x_get(struct gpio_chip *chip, unsigned
>> offset) int value;
>>
>> value = gpio->read(gpio->client);
>> - return (value < 0) ? 0 : (value & (1 << offset));
>> + return (value < 0) ? value : !!(value & (1 << offset));
>> }
Back to your question, assume here in unmodified version the case of
(offset == 31) [1], on upper level the returned value will be
misapprehended as a negative number.
[1] (offset == 31) may be an invalid GPIO line id in this particular
driver, but some other gpiochip drivers should support line id 31.
--
With best wishes,
Vladimir
>>
>> static int pcf857x_output(struct gpio_chip *chip, unsigned offset, int
>> value)
>
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