Re: [RFC PATCH] leds: multicolor: Add sysfs interface definition

[Jacek Anaszewski]

Dan,

On 1/30/19 8:59 PM, Dan Murphy wrote:
> Jacek
>
> On 1/30/19 1:37 PM, Jacek Anaszewski wrote:
> > Hi Dan,
> >
> > Thank you for the RFC.
> >
> > One vital thing is missing - documentation of brightness file must
> > be updated to define its semantics for LED multi color class.
> >
> > Either we need brightness-model file returning only "onoff" option
> > available, or, for time being, fix the max_brightness for LED multi
> > color class to 1 (which will map to max intensity level for each color).
>
> I can make max_brightness default to 1 if not set by the LED driver.
>
> But the LP50xx has brightness controls so setting max_brightness from the driver should over ride
> the max of 1 in the upper level.

Yes, so the max_brightness should be updated basing on current
brightness-model. For LEDn_BRIGHTNESS of LP50xx we could have
"hw" or maybe even better just "lp50xx-linear" and "lp50xx-logarithmic"
- I just forgot about that capability of the device.

> For devices that do not support brightness as a separate control we can create a file called
> max_brightness_<color> that defines the max that a specific color can be set to.  If max_brightness
> is set to 1 then create max_brightness_<color>.  If max_brightness > 1 then do not create the files.

Right. We will need dedicated max_brightness for each color.
They should be placed also in the colors directory, next to the color
files.

> I don't think we have fully vetted the brightness-model yet so I prefer to omit
> it and possibly introduce that later.

We need to start from something. It will give better overview of the
whole idea.

Best regards,
Jacek Anaszewski

> Dan
>
> > Best regards,
> > Jacek Anaszewski
> >
> > On 1/30/19 7:30 PM, Dan Murphy wrote:
> > > Add a documentation of LED Multicolor LED class specific
> > > sysfs attributes.
> > >
> > > Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
> > > ---
> > >  Â .../ABI/testing/sysfs-class-led-multicolorÂÂÂ | 38 +++++++++++++++++++
> > >  Â 1 file changed, 38 insertions(+)
> > >  Â create mode 100644 Documentation/ABI/testing/sysfs-class-led-multicolor
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
> > > new file mode 100644
> > > index 000000000000..19f8da9b150e
> > > --- /dev/null
> > > +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> > > @@ -0,0 +1,38 @@
> > > +What:ÂÂÂÂÂÂÂ /sys/class/leds/<led>/color/sync_enable
> > > +Date:ÂÂÂÂÂÂÂ January 2019
> > > +KernelVersion:ÂÂÂ 5.0
> > > +Contact:ÂÂÂ Dan Murphy <dmurphy@xxxxxx>
> > > +Description:ÂÂÂ read/write
> > > +ÂÂÂÂÂÂÂ Writing a 1 to this file will enable the sychronization of all
> > > + the defined color LEDs within the LED node. Writing a 0 to
> > > +ÂÂÂÂÂÂÂ this file will disable syncing.
> > > +
> > > +What:ÂÂÂÂÂÂÂ /sys/class/leds/<led>/color/sync
> > > +Date:ÂÂÂÂÂÂÂ January 2019
> > > +KernelVersion:ÂÂÂ 5.0
> > > +Contact:ÂÂÂ Dan Murphy <dmurphy@xxxxxx>
> > > +Description:ÂÂÂ write only
> > > +ÂÂÂÂÂÂÂ Writing a 1 to this file while sync_enable is set to 1 will
> > > + synchronize all defined LEDs within the LED node. All LEDs
> > > +ÂÂÂÂÂÂÂ defined will be configured based on the brightness that has
> > > +ÂÂÂÂÂÂÂ been requested.
> > > +
> > > +ÂÂÂÂÂÂÂ If sync_enable is set to 0 then writing a 1 to sync has no
> > > +ÂÂÂÂÂÂÂ affect on the LEDs.
> > > +
> > > +What:ÂÂÂÂÂÂÂ /sys/class/leds/<led>/color/<led color>
> > > +Date:ÂÂÂÂÂÂÂ January 2019
> > > +KernelVersion:ÂÂÂ 5.0
> > > +Contact:ÂÂÂ Dan Murphy <dmurphy@xxxxxx>
> > > +Description:ÂÂÂ read/write
> > > +ÂÂÂÂÂÂÂ These files are dynamically created based on the colors defined
> > > +ÂÂÂÂÂÂÂ by the registrar of the class.
> > > +ÂÂÂÂÂÂÂ The led color(s) can be but not limited to red, green, blue,
> > > + white, amber and violet. If sync is enabled then writing the
> > > +ÂÂÂÂÂÂÂ brightness value of the LED is deferred until a 1 is
> > > + written to /sys/class/leds/<led>/color/sync. If syncing is
> > > +ÂÂÂÂÂÂÂ disabled then the LED brightness value will be written
> > > +ÂÂÂÂÂÂÂ immediately to the LED driver.
> > > +
> > > +ÂÂÂÂÂÂÂ The value of the color is from 0 to
> > > +ÂÂÂÂÂÂÂ /sys/class/leds/<led>/max_brightness.