Re: [PATCH v1 1/3] gpiolib: acpi: Respect bias settings for GpioInt() resource

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

On Wed, Oct 21, 2020 at 12:58:54PM +0300, Mika Westerberg wrote:
> On Wed, Oct 14, 2020 at 04:31:52PM +0300, Andy Shevchenko wrote:
> > In some cases the GpioInt() resource is coming with bias settings
> > which may affect system functioning. Respect bias settings for
> > GpioInt() resource by calling acpi_gpio_update_gpiod_*flags() API
> > in acpi_dev_gpio_irq_get().
> > 
> > While at it, refactor to configure flags first and, only when succeeded,
> > map the IRQ descriptor.

...

> > -			irq = gpiod_to_irq(desc);
> > -			if (irq < 0)
> > -				return irq;
> > +			acpi_gpio_update_gpiod_flags(&dflags, &info);
> > +			acpi_gpio_update_gpiod_lookup_flags(&lflags, &info);
> >  
> >  			snprintf(label, sizeof(label), "GpioInt() %d", index);
> > -			ret = gpiod_configure_flags(desc, label, lflags, info.flags);
> > +			ret = gpiod_configure_flags(desc, label, lflags, dflags);
> >  			if (ret < 0)
> >  				return ret;
> >  
> > +			irq = gpiod_to_irq(desc);
> > +			if (irq < 0)
> > +				return irq;
> 
> Should the above be undone if the conversion here fails?

But wouldn't it be not good if we changed direction, for example, and then
change it back? (IRQ requires input, which is safer, right?)

This makes me think what gpiod_to_irq() may do for physical state of the pin.
On the brief search it seems there is no side effect on the pin with that
function, so, perhaps the original order has that in mind to not shuffle with
line if mapping can't be established. But if setting flags fail, we may got
into the state which is not equal to the initial one, right?

So, in either case I see no good way to roll back the physical pin state
changes. But I can return ordering of the calls in next version.

What do you think?

> In any case looks good so,
> 
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Thanks!

-- 
With Best Regards,
Andy Shevchenko