Re: [PATCH v3 1/2] leds: core: Introduce generic pattern interface

[David Lechner]

On 07/18/2018 02:22 PM, Jacek Anaszewski wrote:
> On 07/18/2018 08:54 PM, Jacek Anaszewski wrote:
> > On 07/18/2018 09:56 AM, Pavel Machek wrote:
> > > Hi!
> > >
> > > > > > > > I believe I meant "changing patterns from kernel in response to events
> > > > > > > > is probably overkill"... or something like that.
> > > > > > >
> > > > > > > Anyway -- to clean up the confusion -- I'd like to see
> > > > > > >
> > > > > > > echo pattern > trigger
> > > > > > > echo "1 2 3 4 5 6 7 8" > somewhere
> > > > > >
> > > > > > s/somewhere/pattern/
> > > > > >
> > > > > > pattern trigger should create "pattern" file similarly how ledtrig-timer
> > > > > > creates delay_{on|off} files.
> > >
> > > Yes, that sounds reasonable. v5 still says
> > >
> > > +               Writing non-empty string to this file will activate the pattern,
> > > +               and empty string will disable the pattern.
> > >
> > > I'd deactivate the pattern by simply writing something else to the
> > > trigger file.
> >
> > Please keep in mind that this is ABI documentation for the pattern file
> > to be exposed by LED core, and not by the pattern trigger, that, as we
> > agreed, will be implemented later. In this case, I'd go for
>
> Gosh, I got completely distracted by the recent discussion about
> pattern synchronization.
>
> So, to recap, we need to decide if we are taking Baolin's solution
> or we're opting for implementing pattern trigger.

I think we should take Baolin's solution.

> If we choose the latter, then we will also need some software
> pattern engine in the trigger, to be applied as a software pattern
> fallback for the devices without hardware pattern support.
> It will certainly delay the contribution process, provided that Baolin
> would find time for this work at all.
>
> I'd just take v5 based solution for now (with improved semantics
> of disabling pattern - in this case my reasoning from the message
> I'm replying to is still valid),
>
> > "echo 0 > brightness" as a command disabling pattern. The same operation
> > disables triggers, so later transition to using pattern trigger will be
> > seamless for userspace.