On Tue, Mar 24, 2020 at 2:57 PM Geert Uytterhoeven <geert+renesas@xxxxxxxxx> wrote: > Currently a GPIO lookup table can only refer to a specific GPIO by a > tuple, consisting of a GPIO controller label and a GPIO offset inside > the controller. > > However, a GPIO may also carry a line name, defined by DT or ACPI. > If present, the line name is the most use-centric way to refer to a > GPIO. Hence add support for looking up GPIOs by line name. > > Implement this by reusing the existing gpiod_lookup infrastructure. > Rename gpiod_lookup.chip_label to gpiod_lookup.key, to make it clear > that this field can have two meanings, and update the kerneldoc and > GPIO_LOOKUP*() macros. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > Reviewed-by: Ulrich Hecht <uli+renesas@xxxxxxxx> > Reviewed-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx> > Tested-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx> I kind of like this approach, however there are things here that need to be considered: the line name is in no way globally unique, and I think there are already quite a few GPIO chips that have the same line names assigned for every instance of that chip. gpiochip_set_desc_names() only warns if there is a line with the same name on the same gpio_chip. I suppose we need to document that the line name look-up will be on a first-come-first-served basis: whatever line we find first with this name is what you will get a reference to, no matter what chip it is on, and it is possible albeit not recommended that some other chip has a line with the same name. Yours, Linus Walleij
