Re: [PATCH v9 01/15] leds: multicolor: Add sysfs interface definition

[Dan Murphy]

Pavel

On 9/26/19 6:10 AM, Pavel Machek wrote:
> Hi!
>
> > diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
> > new file mode 100644
> > index 000000000000..87a1588d7619
> > --- /dev/null
> > +++ b/Documentation/leds/leds-class-multicolor.rst
> > @@ -0,0 +1,96 @@
> > +====================================
> > +Multi Color LED handling under Linux
> > +====================================
> > +
> > +Description
> > +===========
> > +The multi color class groups monochrome LEDs and allows controlling two
> > +aspects of the final combined color: hue and lightness. The former is
> > +controlled via <color>_intensity files and the latter is controlled
> > +via brightness file.
> > +
> > +For more details on hue and lightness notions please refer to
> > +https://en.wikipedia.org/wiki/CIECAM02.
> > +
> > +Note that intensity files only cache the written value and the actual
> > +change of hardware state occurs upon writing brightness file. This
> > +allows for changing many factors of the perceived color in a virtually
> > +unnoticeable way for the human observer.
> So unlike previous versions, userspace will need to write 4 files
> instead of one in the common case.

Request was made here in v5 of the patchset

https://lore.kernel.org/patchwork/patch/1126685/


> > +Directory Layout Example
> > +========================
> > +root:/sys/class/leds/rgb:grouped_leds# ls -lR colors/
> > +-rw-rwxr-- 1 root root 4096 Jul 7 03:10 red_max_intensity
> > +--w--wx-w- 1 root root 4096 Jul 7 03:10 red_intensity
> > +-rw-rwxr-- 1 root root 4096 Jul 7 03:10 green_max_intensity
> > +--w--wx-w- 1 root root 4096 Jul 7 03:10 green_intensity
> > +-rw-rwxr-- 1 root root 4096 Jul 7 03:10 blue_max_intensity
> > +--w--wx-w- 1 root root 4096 Jul 7 03:10 blue_intensity
> Permissions are way off here.
Yes Jacek made a comment in the code about octals.
> > +A user first writes the color LED brightness file with the brightness level that
> > +is necessary to achieve a blueish violet output from the RGB LED group.
> > +
> > +echo 138 > /sys/class/leds/rgb:grouped_leds/red_intensity
> > +echo 43 > /sys/class/leds/rgb:grouped_leds/green_intensity
> > +echo 226 > /sys/class/leds/rgb:grouped_leds/blue_intensity
> No, you can't tell what kind of color this will result in.

I tested this combination on two devices (LP5523 and LP50xx) and it was 
a blueish violet.

> Will you be on ELCE/OSS in Lyon?

Unfortunately no.

Dan

> Best regards,
> 									Pavel