linux-kernel - Re: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate funcs from get

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Message-ID: <CACRpkdbkcX5pEeikkDZAxSGp+M3kJH5SWimxQA6P35iiDAUNdA@mail.gmail.com>
Date: Thu, 27 Feb 2025 23:53:10 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Mark Brown <broonie@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>, 
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, Stefan Wahren <wahrenst@....net>, 
	Liao Chen <liaochen4@...wei.com>, Chen-Yu Tsai <wens@...e.org>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, linux-gpio@...r.kernel.org, 
	linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC/RFT PATCH] pinctrl: bcm2835: don't -EINVAL on alternate
 funcs from get_direction()

On Wed, Feb 19, 2025 at 3:30 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> On Wed, Feb 19, 2025 at 3:27 PM Mark Brown <broonie@...nel.org> wrote:
> >
> > On Wed, Feb 19, 2025 at 11:27:50AM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > >
> > > Since commit 9d846b1aebbe ("gpiolib: check the return value of
> > > gpio_chip::get_direction()") we check the return value of the
> > > get_direction() callback as per its API contract. This driver returns
> > > -EINVAL if the pin in question is set to one of the alternative
> > > (non-GPIO) functions. This isn't really an error that should be
> > > communicated to GPIOLIB so default to returning the "safe" value of
> > > INPUT in this case. The GPIO subsystem does not have the notion of
> > > "unknown" direction.
> >
> > I see this was already tested for these specific boards.  I've also
> > found that Avenger96 is failing with bisect pointing to the same commit
> > this is fixing:
> >
> >     https://lava.sirena.org.uk/scheduler/job/1126314
> >
> > as is the Libretech Potato:
> >
> >     https://lava.sirena.org.uk/scheduler/job/1126285
> >
> > neither of which produce any output before dying, they'll not be fixed
> > by this change.  Seems like an audit of the drivers might be in order?
>
> Right. I don't know if they return EINVAL or some other error so let
> me prepare a change that will not bail-out but simply warn on
> get_direction() errors in gpiochip_add_data() instead.
>
> This patch can still go upstream IMO.

I'm fine to apply it, maybe as non-urgent fix at this point? (for -next)

Do you want to send a non-RFC/RFT version or should I just apply it?

Yours,
Linus Walleij