linux-kernel - Re: [RFC] gpio: about the need to manage irq mapping dynamically.

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Message-ID: <CACRpkdZ2cqUgMwOFG+9JVyAOxYTfHYa3+yrUzUozLpYD87KdOQ@mail.gmail.com>
Date:   Wed, 21 Jun 2017 22:50:14 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>,
        Kevin Hilman <khilman@...libre.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] gpio: about the need to manage irq mapping dynamically.

On Tue, Jun 20, 2017 at 7:23 PM, Jerome Brunet <jbrunet@...libre.com> wrote:
> On Tue, 2017-06-20 at 18:37 +0200, Linus Walleij wrote:

>> Eventually gpio_to_irq() should be DELETED and replaced in full with
>> the prepare/unprepare calls.
>
> Woahh, that's not what I meant. gpio_to_irq should stay. Getting rid of it would
> be a mess and it is a useful call.
>
> The gpio_irq_prepare is meant so that the consumer can tell the gpio driver it
> will want to get irq from a particular gpio at some point.
>
> IOW, it's the consumer saying to the gpio driver "please do whatever you need to
> do, if anything, so this gpio can generate an interrupt"
>
> This is a much simpler change. Using devm, all we need is to put a
> devm_gpio_irq_prepare(<gpio_num>) in the probe of the drivers using gpio_to_irq.
>
> Mandating call to gpio_irq_prepare before any call to gpio_to_irq will be fairly
> easy.

So why can't we just return the IRQ from prepare() and be done with it
instead of having two calls? (Plus a third eventual unprepare()).

Clocks, regulators and godknowswhat is managed by two symmetrical
calls, so why shouldn't GPIO IRQs be?

It would be counterintuitive to have a third call in the middle.

Yours,
Linus Walleij