linux-kernel - Re: [PATCH 2/2] dt: bindings: lp55xx: Add predefined LED pattern

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Message-ID: <20210516183135.GA26985@duo.ucw.cz>
Date:   Sun, 16 May 2021 20:31:35 +0200
From:   Pavel Machek <pavel@....cz>
To:     Doug Zobel <dougdev334@...il.com>
Cc:     Rob Herring <robh@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] dt: bindings: lp55xx: Add predefined LED pattern

Hi!

> > I don't know that this belongs in DT though. Won't a user want to create
> > their own patterns? That means there should be a sysfs interface (which
> > we either already have or has been attempted IIRC).
> 
> Yes, there is a sysfs interface for running patterns via the firmware
> loading interface.  The firmware loading interface doesn't seem well
> suited for constantly changing the pattern that the LED driver runs.
> I found it to be slow and unreliable when quickly changing the LED
> pattern.  The existing predef pattern functionality works much better.
> Unfortunately the only way to define the patterns for it is via the
> platform data structure.  Adding the predef patterns to the device
> tree seemed like a good way to make use of the existing functionality
> in the driver.

Take a look at the pattern trigger. That's the way to change patterns
at runtime, no need for firmware loading.

I may even have compiler from that interface to the bytecode lp55xx
uses. Some assembly will be required. Doing so with the RGB LED will
be even more fun. 

We'll want to deprecate the firmware loading interface at some point.

Forget the device tree, that will not help you.

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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