setting gpio-line-names in dts for sama5d2 SoC

[Alexander Dahl <ada@xxxxxxxxxxx>]

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?

Greets
Alex