linux-kernel - Re: [PATCH v1 4/4] leds: no longer use unnamed gpios

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Message-ID: <CACRpkdZZxAPecNfADzYLSz8S6tNBi9Jr4st==zxnNp2r2gPC2g@mail.gmail.com>
Date:	Wed, 14 Jan 2015 13:45:16 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Rob Herring <robherring2@...il.com>,
	Olliver Schinagl <oliver@...inagl.nl>,
	Olliver Schinagl <oliver+list@...inagl.nl>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Robin Gong <b38343@...escale.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Grant Likely <grant.likely@...aro.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Alexander Shiyan <shc_work@...l.ru>,
	Jingoo Han <jg1.han@...sung.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>
Subject: Re: [PATCH v1 4/4] leds: no longer use unnamed gpios

On Thu, Jan 8, 2015 at 11:12 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Thu, Jan 08, 2015 at 08:40:20AM -0600, Rob Herring wrote:
>> On Thu, Jan 8, 2015 at 2:45 AM, Olliver Schinagl <oliver@...inagl.nl> wrote:

>> >>> --- a/drivers/leds/leds-gpio.c
>> >>> +++ b/drivers/leds/leds-gpio.c
>> >>> @@ -184,7 +184,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct
>> >>> platform_device *pdev)
>> >>>                 struct gpio_led led = {};
>> >>>                 const char *state = NULL;
>> >>>   -             led.gpiod = devm_get_gpiod_from_child(dev, NULL, child);
>> >>> +               led.gpiod = devm_get_gpiod_from_child(dev, "led", child);
>> >>
>> >> Would not this break existing boards using old bindings? You need to
>> >> handle both cases: if you can't located "led-gpios" then you will have to
>> >> try just "gpios".
>> >
>> > Very true. I was rather even hoping we could update all bindings, I don't
>> > mind going through the available dts files to fix them ... But need to know
>> > that that's the proper way to go before doing the work ;)
>>
>> That will not work. You cannot make changes that require a new dtb
>> with a new kernel. This would also break for the other way around
>> (i.e. a new dtb and old kernel).
>>
>> You would have to search for both led-gpios and gpios. I'm not sure if
>> we can do that generically for all GPIOs. If you had a node with both
>> "blah-gpios" and "gpios", it would break. I would hope there are no
>> such cases like that. We also now have to consider how ACPI identifies
>> GPIOs and whether this makes sense.
>
> I think only the driver itself can know about such "legacy" mappings and
> make a decision.

Yeah leds-gpio.c will need to be patched to check for "led-gpios" first
and then fall back to "gpios" if not found.

Yours,
Linus Walleij
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