linux-kernel - Re: [PATCH v2 2/5] gpio: syscon: Add gpio-syscon for rockchip

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Date:   Thu, 24 May 2018 10:28:44 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Heiko Stübner <heiko@...ech.de>
Cc:     Rob Herring <robh@...nel.org>, Levin Du <djw@...hip.com.cn>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Wayne Chou <zxf@...hip.com.cn>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 2/5] gpio: syscon: Add gpio-syscon for rockchip

On Wed, May 23, 2018 at 5:12 PM, Heiko Stübner <heiko@...ech.de> wrote:

> So the gpio controller should definitly also be a subnode.
>
> The gpio in question is called "mute", so I'd think the gpio-syscon driver
> should just define a "rockchip,rk3328-gpio-mute" compatible and contain
> all the register voodoo in the driver itself and not define it in the dt.
>
> So it should probably look like
>
> grf: syscon at ff100000 {
>         compatible = "rockchip,rk3328-grf", "syscon", "simple-mfd";
>
>         [all the other syscon sub-devices]
>
>         gpio_mute: gpio-mute {
>                 compatible = "rockchip,rk3328-gpio-mute";
>                 gpio-controller;
>                 #gpio-cells = <2>;
>         };

I'm sceptic.

That doesn't sound like "general purpose input output" at all.

It sounds like special purpose, for a mute button.

Does it use IRQ? I would recommend implementing
drivers/input/keyboard/syscon-keys.c in the same vein
as drivers/leds/leds-syscon.c so you can avoid indirection
through GPIO for no good reason at all.

I already have other good uses for such a generic
input driver.

Yours,
Linus Walleij