linux-kernel - Re: [PATCH v2 0/4] gpio: deprecate and track the removal of GPIO workarounds for regulators

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Message-ID: <CAMRc=McFBAG9Gi3UBfsdoQ=78fL3sTK+ZMToXWGF=KOw6zwPiQ@mail.gmail.com>
Date: Thu, 17 Apr 2025 20:57:24 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Mark Brown <broonie@...nel.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 0/4] gpio: deprecate and track the removal of GPIO
 workarounds for regulators

On Tue, Apr 15, 2025 at 11:33 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> Hi Bartosz,
>
> this caused me to think about a thing:
>
> On Wed, Apr 2, 2025 at 12:05 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> > This is bothering me. This is the abstraction reversal I'm talking
> > about. Should the regulator drivers even be concerned about whether
> > they share resources or not?
> (...)
> > The part where "the higher level users want to understand that there
> > is GPIO sharing going on" does not sound correct.
>
> There are precedents for this type of semantic IRQF_SHARED
> is used whenever two devices share the same IRQ line,
> and that is something the drivers have to specify, i.e. the
> driver has to be aware that it may be sharing the IRQ
> with other devices, and whenever it gets an IRQ it has
> to check "was it for me?" and in case it was, return
> IRQ_HANDLED else IRQ_NONE.
>

First: this flag has existed (as SA_SHIRQ) since before git days and
could be considered legacy. But also: it's a bit of a different story
as sometimes you get an interrupt and need to read a specific register
to check from the status bits whether it concerns you. This never
happens with a GPIO so I don't think it's a good argument for this
specific case.

Bartosz