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

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Message-ID: <CAL_JsqJE_PCXrejHO3vfdbbtC4FGyuPhJ8W-A=8nZMcu6aBxCw@mail.gmail.com>
Date:	Thu, 8 Jan 2015 08:40:20 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Olliver Schinagl <oliver@...inagl.nl>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	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>,
	Linus Walleij <linus.walleij@...aro.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
Subject: Re: [PATCH v1 4/4] leds: no longer use unnamed gpios

On Thu, Jan 8, 2015 at 2:45 AM, Olliver Schinagl <oliver@...inagl.nl> wrote:
> Hey Dmitry,
>
>
> On 08-01-15 00:55, Dmitry Torokhov wrote:
>>
>> On Wed, Jan 07, 2015 at 10:08:42AM +0100, Olliver Schinagl wrote:
>>>
>>> From: Olliver Schinagl <oliver@...inagl.nl>
>>>
>>> The gpio document says we should not use unnamed bindings for gpios.
>>> This patch uses the 'led-' prefix to the gpios and updates code and
>>> documents. Because the devm_get_gpiod_from_child() falls back to using
>>> old-style unnamed gpios, we can update the code first, and update
>>> dts files as time allows.

[...]

>>> --- 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.

Rob
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