Re: [PATCH] gpiolib: acpi: support override broken GPIO number in ACPI table

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Fri, Mar 05, 2021 at 12:08:52PM +0200, Andy Shevchenko wrote:
> On Fri, Mar 05, 2021 at 10:10:50AM +0100, Hans de Goede wrote:
> > On 3/5/21 2:14 AM, Shawn Guo wrote:
> > > On Thu, Mar 04, 2021 at 08:32:14PM +0100, Hans de Goede wrote:
> > >> On 3/3/21 10:47 AM, Andy Shevchenko wrote:
> 
> ...
> 
> > > So we reach a consensus that this is not the right solution for Lenovo
> > > Flex 5G. But what about for Andy's Galileo Gen 2 case, where the GPIO
> > > number in ACPI is truly broken?
> > 
> > Well if the ACPI table truely simply has a wrong number in it, like in
> > this case, then we clearly need a workaround.
> > 
> > >   ba8c90c61847 ("gpio: pca953x: Override IRQ for one of the expanders on Galileo Gen 2")
> > 
> > And we have one in place, so I'm not sure what the question is?
> > 
> > I guess the question is of your generic GPIO renumber patch would not
> > be a better answer to that ?
> > 
> > IMHO no, we want to keep quirks out of the core as much as possible,
> > for example the code which Andy added a quirk to is build as a module
> > in the generic Fedora distro kernel, so for most users the code will
> > not be loaded into memory. Where as if we add it to the core it would
> > use up extra memory for everyone.
> 
> I guess Shawn is referring to my rework of that quirk [1] due to found a flaw
> in the upstreamed variant. I agree, that this is not ideal, but TL;DR: it less
> invasive even to the upstreamed approach and it has no use of any hard coded
> numbering schemes. The Galileo Gen 2 is "broken" in an *understandable* way,
> i.e. ACPI designers put an absolute GPIO numbers (there are two SoC based GPIO
> controllers: SCH and DesignWare which numbers starts at 0) instead of be

"...at 0 and 8 respectively)"

> relative. For the time being only one device has a driver that needs such GPIO
> number, but as I explained in the cover letter, to support it as a quirk I have
> to copy ~10% of the existing (in gpiolib-acpi.c) code.
> 
> I'm all ears for better approach!
> 
> [1]: https://lore.kernel.org/linux-gpio/20210225163320.71267-1-andriy.shevchenko@xxxxxxxxxxxxxxx/T/#u
> 
> > Also if, in the future, we were to ever add a generic GPIO renumber quirk
> > mechanism to the core, then your code would need more work. Because to be
> > truely generic it would need to remap one gpiochip-name:pin-number on
> > another gpiochip-name:pin-number pair. There might very well be a case
> > with multiple gpiochips with pin number 32 being referenced in the DSDT
> > and where we need to remap one of those 32-s to a different number
> > (or possibly even to a different chip + number).
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

-- 
With Best Regards,
Andy Shevchenko