Re: setting gpio-line-names in dts for sama5d2 SoC

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

+Cc: Bart, Linus

On Wed, Mar 17, 2021 at 1:22 AM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
>
>
>
> On Tuesday, March 16, 2021, Alexander Dahl <ada@xxxxxxxxxxx> wrote:
>>
>> Hei hei,
>>
>> for a Microchip SAMA5D2 SoC based device I try to set gpio-line-names in .dts file like this:
>>
>> 257 &pioA {
>> 258         gpio-line-names = "",                   /* PA0  */
>> 259                           "",                   /* PA1  */
>> 260                           "",                   /* PA2  */
>> 261                           "FOO",                /* PA3  */
>> 262                           "BAR",                /* PA4  */
>> 263                           "",                   /* PA5  */
>>
>> … and so on for all 4 * 32 GPIO Pins. However when calling `gpioinfo` in userspace, I always get this:
>>
>> $ gpioinfo
>> gpiochip0 - 128 lines:
>>         line   0:        "PA0"       unused   input  active-high
>>         line   1:        "PA1"       unused   input  active-high
>>         line   2:        "PA2"       unused   input  active-high
>>         line   3:        "PA3"       unused   input  active-high
>>         line   4:        "PA4"       unused   input  active-high
>>         line   5:        "PA5"       unused   input  active-high
>>
>> … and so on. Those "PA0" line names are set by the pinctrl driver in drivers/pinctrl/pinctrl-at91-pio4.c before calling gpiochip_add_data() and from reading the code in drivers/gpio/gpiolib.c I suspect devprop_gpiochip_set_names() is never called then, so those names in .dts are simply ignored.
>>
>> Those default names from the at91 pio4 pinctrl driver are certainly correct speaking of pin names, but from a userspace point of view it would be better if I could override those from dts, so an application using libgpiod could look for a name like e.g. "VALVE7_EN" without caring to which pin that's actually connected. Can I override those with a currently present kernel? Or is it a problem in either the at91 pio4 driver or the gpiolib core? Or is that no real usecase and should I do it differently?
>
>
> I would like to know the consequences if allow this, but to me it sounds like a bug in the gpiolib.c.
>
>>
>> Greets
>> Alex
>
>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>


-- 
With Best Regards,
Andy Shevchenko