Re: [PATCH v1 5/5] gpio: pca953x: Override GpioInt() pin for Intel Galileo Gen 2

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Mon, May 25, 2020 at 04:47:48PM +0300, Mika Westerberg wrote:
> On Mon, May 25, 2020 at 04:01:08PM +0300, Andy Shevchenko wrote:
> > On Mon, May 25, 2020 at 03:21:36PM +0300, Mika Westerberg wrote:
> > > On Mon, May 25, 2020 at 02:35:51PM +0300, Andy Shevchenko wrote:
> > > > On Mon, May 25, 2020 at 02:05:56PM +0300, Mika Westerberg wrote:
> > > > > On Mon, May 25, 2020 at 01:13:35PM +0300, Andy Shevchenko wrote:
> > > > > > Due to parsing of ACPI tables. I don't want to copy'n'paste 25% of
> > > > > > gpiolib-acpi.c in here. I think provided solution is cleaner and (more)
> > > > > > flexible in terms of maintenance.
> > > > > 
> > > > > Hmm, you seem to pass a hard-coded pin number (1) to the core that then
> > > > > passes it back to the driver. Why you can't simple use that number here
> > > > > directly? You don't need to parse anything. What I'm missing? :-)
> > > > 
> > > > Okay, so, AFAIU you are proposing something like this:
> > > > 
> > > > 1) find a GPIO controller by the ACPI path (somehow, I guess by finding a
> > > >    handle followed by physical device behind it); 2) somehow to request a
> > > >    pin from that device by number;
> > > > 3) convert to IRQ and use.
> > > > 
> > > > Is it correct?
> > > 
> > > Well, no. In the first patch you do this:
> > > 
> > >   pin = lookup->info.quirks_data;
> > > 
> > > and this essentially becomes 1 so you know the pin number upfront in the
> > > driver. Why not simply get GPIO number 1 in the driver and use it as an
> > > interrupt? You know already that this particular board with the matching
> > > DMI identifier always uses the this number anyway.
> > 
> > But GPIO (relative!) number is not enough. We need to understand more, i.e.:
> > 1) from which GPIO controller it comes from (okay, for this particular platform I know it);
> > 2) which expander does have this resource (they all have same ACPI HID).
> > 
> > So, second one means to count GpioInt() resources (I don't remember if we have
> > helper for that, probably we can add one). For the first we need to get a GPIO
> > controller something (gpiochip?) And this first one I have no idea how we can
> > perform without talking to the core.
> > 
> > Basically, it may be done by reimplementing acpi_dev_gpio_irq_get(), followed
> > by acpi_get_gpiod_by_index(), followed by acpi_gpio_resource_lookup(), followed
> > by acpi_populate_gpio_lookup(), where at last this quirk should be applied.
> > 
> > It seems for me like an over duplicated solution.
> > 
> > I really don't understand how we can shortcut all these. What am I missing?
> 
> Why for example following would not work? If it is using global GPIO numbers
> anyway.

Because GPIO 1 above and below is not global?
Okay, what we have in the table seems global.
Let me see if this will fly.

> static int pca953x_acpi_interrupt_get_irq(struct device *dev)
> {
>         struct gpio_desc *desc;
>  
>         desc = gpio_to_desc(1);
>         if (!desc)

Okay, this seems have no deferred probe support, but I think it's fine,
it will be unlikely we will have for the certain platform the SoC's GPIO
controller enumerated after the IO expander one.

>                 return -ENODEV;
> 
>         return gpiod_to_irq(desc);
> }

-- 
With Best Regards,
Andy Shevchenko