linux-kernel - Re: [PATCH v2] gpio / ACPI: Add label to the gpio request

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Message-ID: <CAAVeFu+dfc3vH73_uhwDftrd0OEYrX0ZiqK1MSAqsCcpKpzRTw@mail.gmail.com>
Date:	Mon, 15 Jun 2015 11:29:04 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Tobias Diedrich <ranma+kernel@...edrich.de>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpio / ACPI: Add label to the gpio request

On Mon, Jun 15, 2015 at 7:00 AM, Tobias Diedrich
<ranma+kernel@...edrich.de> wrote:
> In leds-gpio.c create_gpio_led only the legacy path propagates the label
> by passing it into devm_gpio_request_one. Similarily gpio_keys_polled.c
> also neglects to propagate the name to the gpio subsystem.
>
> On the newer devicetree/acpi path the label is lost as far as the GPIO
> subsystem goes (it is only retained as name in struct gpio_led.
>
> Amend devm_get_gpiod_from_child to take an additonal (optional) label
> argument and propagate it so it will show up in /sys/kernel/debug/gpio.
>
> So instead of:
>
> GPIOs 288-511, platform/PRP0001:00, AMD SBX00:
>  gpio-475 (?                   ) in  hi
>  gpio-477 (?                   ) out hi
>  gpio-478 (?                   ) out lo
>  gpio-479 (?                   ) out hi
>
> we get the much nicer output:
>
> GPIOs 288-511, platform/PRP0001:00, AMD SBX00:
>  gpio-475 (switch1             ) in  hi
>  gpio-477 (led1                ) out hi
>  gpio-478 (led2                ) out lo
>  gpio-479 (led3                ) out hi

We want to reuse higher-level information (like the con_id) as much as
possible to generate labels, but in the case of
devm_get_gpiod_from_child() there is no such information available
anyway, so why not.

Acked-by: Alexandre Courbot <acourbot@...dia.com>

Generally speaking this label thing is almost useless, we should now
be able to trace which device requested a GPIO and for what purpose
and provide that complete information in debugfs.
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