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

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Message-ID: <CAHp75VdZ9RVuMrgWXOWqCrmvHBtkz+S=dxXhR44Ri3p6Pj5LMA@mail.gmail.com>
Date:   Tue, 22 Mar 2022 10:45:01 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     BOUGH CHEN <haibo.chen@....com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v2] gpio: Allow setting gpio device id via device tree alias

On Tue, Mar 22, 2022 at 7:52 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,

With the GPIO

> 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

If GPIO

> which larger than all the claimed aliases.

which is

...

I'm not sure I understand the issue. The other GPIO drivers and hence
user space (which is already quite a question why user space needs
this) may distinguish the GPIO chips by labels and device names.
What's wrong with that approach?

-- 
With Best Regards,
Andy Shevchenko