linux-kernel - Re: [PATCH 4/9] pinctrl: meson: allow gpio to request irq

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Date:   Tue, 25 Oct 2016 20:10:00 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH 4/9] pinctrl: meson: allow gpio to request irq

On Tue, Oct 25, 2016 at 4:47 PM, Marc Zyngier <marc.zyngier@....com> wrote:
> On 25/10/16 15:22, Jerome Brunet wrote:

>> There is a few problems to guarantee that gpio == hwirq.
>> 1. We have 2 instances of pinctrl, to guarantee that the linux gpio
>> number == hwirq, we would have to guarantee the order in which they are
>> probed. At least this my understanding
>
> Maybe I wasn't clear enough, and my use of gpio is probably wrong. So
> Linux has a gpio number, which is obviously an abstract number (just
> like the Linux irq number). But the pad number, in the context of given
> SoC, is constant. So we have:
>
>         pad->gpio
>         hwirq->irq
>
> Why can't you have pad == hwirq, always? This is already what you have
> in the irqchip driver. This would simplify a lot of things.

My thought as well.

We usually refer to the local numberspace on the GPIO controller
as "offsets", so line offsets 0...31 on a gpiochip with 31 lines.

The ngpio in struct gpio_chip is the number of lines on that controller,
and should nominally map 1:1 to hwirq sources.

Yours,
Linus Walleij