Re: how to request gpiochip line which is only valid as an interrupt?

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Wed, Jun 12, 2024 at 11:03 AM Marek Behún <kabel@xxxxxxxxxx> wrote:
>
> On Wed, 12 Jun 2024 10:55:55 +0200
> Marek Behún <kabel@xxxxxxxxxx> wrote:
>
> > > Users can still read the value of this pin but won't be able to set
> > > direction to output.
> >
> > Users are not supposed to read value of this pin, because it is not a
> > GPIO pin. The corresponding bit is not set in gpiochip.valid_mask.
> > It is for example impossible to export it in /sys/class/gpio.
> >
> > This line is valid only as an IRQ (the
> > corresponding bit is set in gpiochip.irq.valid_mask).
>

Ah, I missed the bit about these pins not being marked as valid.

> I am starting to thing that this might be the problem, that the line is
> not valid as GPIO, only as an IRQ. gpiolib seems to be unable to handle
> that.
>
> Indeed, the definition of the function
>   gpiochip_irqchip_irq_valid()
> first checks if the line is valid as gpio:
>
>   static bool gpiochip_irqchip_irq_valid(const struct gpio_chip *gc,
>                                          unsigned int offset)
>   {
>           if (!gpiochip_line_is_valid(gc, offset))
>                   return false;
>           ...
>

TBH Maybe using the GPIO provider APIs for something that isn't a GPIO
doesn't make much sense? They are called GPIO irqchips for a reason
after all? How about handling the non-GPIO interrupts with regular
irqchip code and only exposing actual GPIOs using gpiolib?

What is the exact layout of these pins? Are the GPIOs and non-GPIOs
somehow grouped together? Maybe export several separate GPIO banks?

Bart