linux-kernel - Re: [PATCH v2] gpio: Allow setting gpio device id via device tree alias

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Date:   Mon, 28 Mar 2022 01:03:16 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     haibo.chen@....com, Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Cc:     brgl@...ev.pl, andy.shevchenko@...il.com,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: Re: [PATCH v2] gpio: Allow setting gpio device id via device tree alias

On Tue, Mar 22, 2022 at 6:52 AM <haibo.chen@....com> wrote:

> From: Haibo Chen <haibo.chen@....com>
>
> For some SoCs which contain different cores, like few ARM A cores
> and few ARM M cores. Some GPIO controllers like GPIO3/GPIO4/GPIO5
> belong to A core domain, some GPIO controllers like GPIO1/GPIO2
> belong to M core domain. Linux only cover A cores, without gpio
> alias, we can get gpiochip0/gpiochip1/gpiochip2 to map the real
> GPIO3/GPIO4/GPIO5, it's difficult for users to identify this map
> relation, and hardcode the gpio device index. With gpio alias,
> we can easily make gpiochip3 map to GPIO3, gpiochip4 map to GPIO4.
> For GPIO controllers do not claim the alias, it will get one id
> which larger than all the claimed aliases.
>
> Signed-off-by: Haibo Chen <haibo.chen@....com>

This is device tree related, adds semantics to aliases and needs
a prerequisite patch to
Documentation/devicetree/bindings/gpio/gpio.txt
at the very least.

Also that patch needs to CC to devicetree@...r.kernel.org

IIRC this has been suggested in the past.

Yours,
Linus Walleij