Re: [PATCH v3 2/7] gpio: regmap: add gpio_regmap_get_gpiochip() accessor

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Wed, Jul 01, 2026 at 01:01:10PM +0300, Andy Shevchenko wrote:
> On Wed, Jul 1, 2026 at 11:44 AM Michael Walle <mwalle@kernel.org> wrote:
> > On Fri Jun 19, 2026 at 11:08 PM CEST, Linus Walleij wrote:
> > > On Mon, Jun 8, 2026 at 4:41 PM Michael Walle <mwalle@kernel.org> wrote:
> > >
> > >> >>> Without an accessor like gpio_regmap_get_gpiochip(), we cannot retrieve the
> > >> >>> gpio_chip instantiated inside gpio-regmap.c to fulfill these requirements in our
> > >> >>> map() function.
> > >>
> > >> Why is gpiochip_irq_reqres() called in the first place? Isn't that
> > >> only called if the irq handling is set up via gc->irq.chip and not
> > >> via gpiochip_irqchip_add_domain() like in gpio-regmap?
> > >
> > > Not really, the gpiochip_irq_reqres() is called to mark that a
> > > GPIO line is used for IRQ, so the gpiolib cannot turn this
> > > GPIO into an output line, gpiod_direction_out() will fail
> > > on lines used for IRQ. So it's a failsafe.
> > >
> > > You can live without it of course, but then you don't get
> > > this failsafe.
> >
> > Thanks for the explanation! So did I make a mistake years ago by
> > adding the gpiochip_irqchip_add_domain(), see commit 6a45b0e2589f
> > ("gpiolib: Introduce gpiochip_irqchip_add_domain()")
> >
> > As Yu-Chun found, gpiochip_irq_reqres() expect the irq chip data
> > to be a gpio_chip, which isn't the case (in general) for an
> > externally allocated domain, is it?
> 
> So the whole issue comes from the fact that the IRQ chip is not marked
> as immutable. For immutable IRQ chips (which all GPIO provides should
> have) there is no such issue to begin with, id est there is no
> gpiochip_irq_reqres() callback assigned (and respective _relres).

Ah, for immutable chips we put either custom ones or
GPIOCHIP_IRQ_RESOURCE_HELPERS which actually refers to those callbacks.

So, if the domain is external, it should also provide irq_request_resources
and release callbacks. In the custom case we can wrap gpiochip_reqres_irq()
and gpiochip_relres_irq() respectively.

But we need to have a struct gpio_chip pointer for them. And note, the
IRQ chip data can be anything in that case, so it's not a requirement.

-- 
With Best Regards,
Andy Shevchenko