Re: [PATCH v3 2/9] dt: bindings: Add multicolor class dt bindings documention

[Jacek Anaszewski]

On 6/18/19 5:36 PM, Rob Herring wrote:
> On Fri, Jun 14, 2019 at 11:18 AM Dan Murphy <dmurphy@xxxxxx> wrote:
> > Rob
> >
> > Thanks for the review
> >
> > On 6/14/19 12:00 PM, Rob Herring wrote:
> > > On Thu, May 23, 2019 at 02:08:13PM -0500, Dan Murphy wrote:
> > > > Add DT bindings for the LEDs multicolor class framework.
> > > >
> > > > Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
> > > > ---
> > > >    .../bindings/leds/leds-class-multicolor.txt   | 97 +++++++++++++++++++
> > > >    1 file changed, 97 insertions(+)
> > > >    create mode 100644 Documentation/devicetree/bindings/leds/leds-class-multicolor.txt
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/leds/leds-class-multicolor.txt b/Documentation/devicetree/bindings/leds/leds-class-multicolor.txt
> > > > new file mode 100644
> > > > index 000000000000..e2a2ce3279cb
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/leds/leds-class-multicolor.txt
> > > > @@ -0,0 +1,97 @@
> > > > +* Multicolor LED properties
> > > > +
> > > > +Multicolor LEDs can consist of a RGB, RGBW or a RGBA LED clusters.  These devices
> > > > +can be grouped together and also provide a modeling mechanism so that the
> > > > +cluster LEDs can vary in hue and intensity to produce a wide range of colors.
> > > > +
> > > > +The nodes and properties defined in this document are unique to the multicolor
> > > > +LED class.  Common LED nodes and properties are inherited from the common.txt
> > > > +within this documentation directory.
> > > > +
> > > > +Required LED Child properties:
> > > > +    - color : For multicolor LED support this property should be defined as
> > > > +              LED_COLOR_ID_MULTI and further definition can be found in
> > > > +              include/linux/leds/common.h.
> > > > +
> > > > +led-controller@30 {
> > > > +    #address-cells = <1>;
> > > > +    #size-cells = <0>;
> > > > +    compatible = "ti,lp5024";
> > > > +    reg = <0x29>;
> > > > +
> > > > +    multi-led@4 {
> > > Typically we sort by address order.
> >
> > These are not addresses these end up being the "module" number that the
> > LEDs below are associated to.
>
> 'reg' (and the unit-address) is an address in the sense that is how
> you identify a device or sub-device. It doesn't matter what type of
> 'address' it is, DT practice is to sort node in unit-address numerical
> order.
>
> 'module' is a h/w thing, right? A bank or instance within the device?
> If not, using 'reg' here is not appropriate.

In this case reg represents LEDn_BRIGHTNESS register which controls
a group of three LEDs. The thing is that those registers' addresses
start from 0x07, i.e. the formula for calculating the RGB LED module
address is: LEDn_BRIGHTNESS = 0x07 + n.

From the above it seems that we should have multi-led@7 and reg = 0x07
for LED0_BRIGHTNESS register governing the brightness of RGB LED
module 0, right?

And regarding sorting by address order I think that Rob was asking for
placing whole multi-led@4 sub-node after multi-led@2 (here sticking to
the numeration from the patch).

--
Best regards,
Jacek Anaszewski