linux-kernel - Re: [PATCH 2/2] x86: pcengines apuv2 gpio/leds/keys platform driver

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Date:   Wed, 13 Feb 2019 10:35:11 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86 <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH 2/2] x86: pcengines apuv2 gpio/leds/keys platform driver

On Mon, Feb 11, 2019 at 11:39 AM Enrico Weigelt, metux IT consult
<lkml@...ux.net> wrote:

> struct gpiod_lookup_table gpios_led_table[] = {
>     .dev_id = "leds-gpio.0",
>     .table = {
>         GPIO_LOOKUP_IDX("gpio.0", 0, "led", 0, GPIO_ACTIVE_LOW),
>         GPIO_LOOKUP_IDX("gpio.0", 1, "led", 1, GPIO_ACTIVE_LOW),
>         GPIO_LOOKUP_IDX("gpio.0", 2, "led", 2, GPIO_ACTIVE_LOW),
>     }
> };
>
> But unsure now to determine the correct names for dev_id (the
> leds-gpio instance ?) and the gpio chip. In the example, these
> seem to be autogenerated - how can I retrieve them from my
> actual devices ?

It is a bit tricky.

For the dev_id you need to be aware of the following from
<linux/platform_device.h>:
#define PLATFORM_DEVID_NONE     (-1)
#define PLATFORM_DEVID_AUTO     (-2)

If the platform device has .id set to -1 it will be just "leds-gpio",
if it is -2 it will be whatever, take a chance on .0 or ideally fix
it up. Any positive number like .id = 4 becomes "leds-gpio.4".

So figure out the .id field on the platform device.

Yours,
Linus Walleij