Re: [PATCH v4 3/9] gpiolib: acpi: Take into account debounce settings

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Sun, Nov 08, 2020 at 10:31:32AM +0100, Hans de Goede wrote:
> On 11/7/20 4:26 PM, Andy Shevchenko wrote:
> > On Sat, Nov 7, 2020 at 4:49 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> >> On 11/6/20 8:22 PM, Andy Shevchenko wrote:

...

> > Thank you very much for the testing! I remember that I fixed debounce
> > for BayTrail, but it seems I have yet to fix Cherry Trail pin control
> > as a prerequisite to this patch.
> > 
> > And like I said this series is definitely not for backporting.
> 
> Independent of fixing the CherryTrail pinctrl driver to support this,
> I strongly believe that -ENOTSUPP should be ignored (treated as success)
> by this patch. Remember ACPI is not only used on x86 but also on ARM
> now a days. We simply cannot guarantee that all pinctrls will support
> (let alone implement) debounce settings. E.g. I'm pretty sure that
> the pinctrl on the popular Allwinner A64 does not support debouncing
> and there are builts using a combination of uboot + EDK2 to boot!
> 
> The documentation for gpiod_set_debounce even explicitly mentioned that
> -ENOTSUPP is an error which one may expect (and thus treat specially).
> 
> The same goes for the bias stuff too.

While for debounce I absolutely agree with you I don't think it applies to
bias. ACPI table is coupled with a platform and setting bias == !PullNone
implies that bias is supported.

If we break something with this it means:
- ACPI table is broken and we need a quirk
- GPIO library is broken on architectural level and needs not to return
  ENOTSUPP for the flags configuration.

I will update this with taking debounce optional support into account.

-- 
With Best Regards,
Andy Shevchenko