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 01:42:55PM +0200, Michael Walle wrote:
> On Wed Jul 1, 2026 at 1:38 PM CEST, Andy Shevchenko wrote:
> > On Wed, Jul 01, 2026 at 01:55:11PM +0300, Andy Shevchenko wrote:
> >> 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.
> >
> > And looking back for implementation in v3 the whole mistake was to use
> > GPIOCHIP_IRQ_RESOURCE_HELPERS. It just wanted custom callbacks with
> > the IRQ chip data assigned to whatever from which we may then deduce
> > struct gpio_chip. It does *not* require to be struct gpio_chip.
> > The local driver data structure should keep pointer to struct gpio_regmap.
> > That one can be used in the respective .irq_request_resources() and
> > .irq_release_resources(). The default ones for gpio-regmap may also
> > be provided via a macro, say GPIO_REGMAP_IRQ_RESOURCE_HELPERS.
> >
> > Hence I don't see the need of having gpio_regmap_get_gpiochip() helper
> > and driver can be implemented using gpio-regmap and external IRQ domain.
> >
> > What did I miss?
> 
> IMHO nothing, that's exactly my understanding, too. Except for the
> GPIO_REGMAP_IRQ_RESOURCE_HELPERS. See my previous mail. Because that
> would have to be set by regmap-irq.

There are two cases:
- easy, when the chip is provided by the user
(in this case we just missing a couple of callbacks in gpio-regmap)

- hard, when chip is created by regmap-irq
(in this case regmap-irq missing to setup the callbacks)

So, effectively all GPIO drivers that use regmap-irq facility are
now missing the functionality of tracking "GPIO locked as IRQ".

-- 
With Best Regards,
Andy Shevchenko