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

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Date:   Tue, 18 Jun 2019 20:19:57 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Rob Herring <robh@...nel.org>, Dan Murphy <dmurphy@...com>
Cc:     Pavel Machek <pavel@....cz>, devicetree@...r.kernel.org,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/9] dt: bindings: Add multicolor class dt bindings
 documention

On 6/18/19 5:36 PM, Rob Herring wrote:
> On Fri, Jun 14, 2019 at 11:18 AM Dan Murphy <dmurphy@...com> 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@...com>
>>>> ---
>>>>    .../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