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

[Rob Herring <robherring2@gmail.com>]

On Thu, Jan 8, 2015 at 2:45 AM, Olliver Schinagl <oliver@schinagl.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@schinagl.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