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

[Linus Walleij]

On Thu, Jan 8, 2015 at 11:12 PM, Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> 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@xxxxxxxxxxx> 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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