Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's

[Jacek Anaszewski]

Hi Pavel,

On 04/01/2016 11:18 PM, Pavel Machek wrote:
> Hi!
>
> > > > It would have the same downsides as in case of having r, g and b in
> > > > separate attributes, i.e. - problems with setting LED colour in
> > > > a consistent way. This way LED blinking in whatever colour couldn't
> > > > be supported reliably. It was one of your primary rationale standing
> > > > behind this design, if I remember correctly. Second - what about
> > > > triggers? We've had a long discussion about it and this design turned
> > > > out to be most fitting.
> > >
> > > Are on/off triggers really that useful for a LED that can produce 16
> > > million colors?
> > >
> > > I believe we should support patterns for RGB LEDs. Something like
> > > [ (time, r, g, b), ... ] . Ok, what about this one?
> > >
> > > Lets say we have
> > >
> > > /sys/class/pattern/lp5533::0
> > > /sys/class/pattern/software::0
> > >
> > > /sys/class/led/n900::red ; default trigger "lp5533::0:0"
> > > /sys/class/led/n900::green ; default trigger "lp5533::0:1"
> > > /sys/class/led/n900::blue ; default trigger "lp5533::0:2"
> > >
> > > Normally, pattern would correspond to one RGB LED. We could have
> > > attribute "/sys/class/pattern/lp5533::0/color" containing R,G,B for
> > > this pattern.

Could you give an example on how to set a color for RGB LED using
this interface? Would it be compatible with LED triggers?
Where the "pattern" class would be implemented?

> > This involves the same issue you were opposed to: three values per
> > sysfs attribute.
>
> And solves a lot of other things. Like actually being backwards
> compatible.
>
> And yes, it involves three values in a file, but now it is array of
> led brightnesses, and that might actually be acceptable. (At least the
> values have uniform meaning).
>
> Plus, it is not "issue you were opposed to" it is "something that is
> not permitted by sysfs maintainers".

--
Best regards,
Jacek Anaszewski