Re: [PATCH] [RFC] gpiolib: introduce gpio_name() helper

On Tue, Jun 30, 2026, at 18:01, Geert Uytterhoeven wrote:
> On Mon, 29 Jun 2026 at 19:54, Arnd Bergmann <[email protected]> wrote:
>> On Mon, Jun 29, 2026, at 17:29, Geert Uytterhoeven wrote:

>> > Same results for instantiation using sysfs or configfs[1], although
>> > the latter does have optional support for specifying the name.
>>
>> I wonder how many of the other instances have the same problem
>> then. Would it be appropriate for gpiochip_fwd_desc_add() to set
>> a name itself to address this one?
>
> I don't think it would be appropriate for the GPIO aggregator to set
> that name.  What we want to print here (for debugging) is the physical
> GPIO that an aggregator's GPIO is mapped to, not some consumer or line
> name (which is not guaranteed to be unique).

Ok.

> E.g. "<chip-name>.<offset>" would be fine.  As gpiod_name() can only
> return a fixed string or an existing string, it can't return such a
> formatted string, though. And consumers don't have access to chip info?

The gpiod_hwgpio() function is exported to consumers, so they can
already print that instead of desc_to_gpio() if the local number
is sufficient. If we really care about the <chip-name> portion for
any of the debug prints, we could export another function that
returns maybe gpiod_to_chip(gpiod)->label or
dev_name(&gpiod_to_gpio_device(gpiod)->dev), which are both
constant strings we can print.

It looks like we can also replace most of the remaining callers
of desc_to_gpio() with gpiod_hwgpio().

       Arnd