Re: [PATCH/RFC v10 03/19] DT: leds: Add led-sources property

[Jacek Anaszewski]

On 01/12/2015 02:52 PM, Rob Herring wrote:
> On Mon, Jan 12, 2015 at 2:32 AM, Jacek Anaszewski
> <j.anaszewski@xxxxxxxxxxx> wrote:
> > On 01/09/2015 07:33 PM, Rob Herring wrote:
> > > On Fri, Jan 9, 2015 at 9:22 AM, Jacek Anaszewski
> > > <j.anaszewski@xxxxxxxxxxx> wrote:
> > > > Add a property for defining the device outputs the LED
> > > > represented by the DT child node is connected to.
> > > >
> > > > Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
> > > > Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> > > > Cc: Bryan Wu <cooloney@xxxxxxxxx>
> > > > Cc: Richard Purdie <rpurdie@xxxxxxxxx>
> > > > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > > > Cc: Pawel Moll <pawel.moll@xxxxxxx>
> > > > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > > > Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx>
> > > > Cc: Kumar Gala <galak@xxxxxxxxxxxxxx>
> > > > ---
> > > >    Documentation/devicetree/bindings/leds/common.txt |    5 +++++
> > > >    1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/leds/common.txt
> > > > b/Documentation/devicetree/bindings/leds/common.txt
> > > > index a2c3f7a..29295bf 100644
> > > > --- a/Documentation/devicetree/bindings/leds/common.txt
> > > > +++ b/Documentation/devicetree/bindings/leds/common.txt
> > > > @@ -1,6 +1,10 @@
> > > >    Common leds properties.
> > > >
> > > >    Optional properties for child nodes:
> > > > +- led-sources : Array of bits signifying the LED current regulator
> > > > outputs the
> > > > +               LED represented by the child node is connected to (1 -
> > > > the LED
> > > > +               is connected to the output, 0 - the LED isn't connected
> > > > to the
> > > > +               output).
> > >
> > >
> > > Sorry, I just don't understand this.
> >
> >
> > In some Flash LED devices one LED can be connected to one or more
> > electric current outputs, which allows for multiplying the maximum
> > current allowed for the LED. Each sub-LED is represented by a child
> > node in the DT binding of the Flash LED device and it needs to declare
> > which outputs it is connected to. In the example below the led-sources
> > property is a two element array, which means that the flash LED device
> > has two current outputs, and the bits signify if the LED is connected
> > to the output.
>
> Sounds like a regulator for which we already have bindings for and we
> have a driver for regulator based LEDs (but no binding for it).

Do you think of drivers/leds/leds-regulator.c driver? This driver just
allows for registering an arbitrary regulator device as a LED subsystem
device.

There are however devices that don't fall into this category, i.e. they
have many outputs, that can be connected to a single LED or to many LEDs
and the driver has to know what is the actual arrangement.

> Please use the regulator binding.

> > Do your doubts stem from the ambiguity of the word "current" or the
> > form of the description itself is unclear? Probably there should be
> > explicit explanation added that the size of the array depends on the
> > number of current outputs of the flash LED device.
>
> The size of the array and meaning of array indexes was not clear.

What about this:

led-sources : Array of connection states between all LED current
	      sources exposed by the device and this LED (1 - this LED
	      is connected to the current output with index N, 0 -
	      this LED isn't connected to the current output with
	      index N); the mapping of N-th element of the array to the
	      physical device output should be defined in the LED
	      driver binding.

--
Best Regards,
Jacek Anaszewski
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