linux-kernel - Re: [PATCH v2 3/9] Documentation: dt-bindings: leds: add LM3633 LED binding information

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Date:	Mon, 30 Nov 2015 17:19:03 +0900
From:	"Kim, Milo" <milo.kim@...com>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
CC:	<robh+dt@...nel.org>, <lee.jones@...aro.org>, <broonie@...nel.org>,
	<devicetree@...r.kernel.org>, <linux-leds@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/9] Documentation: dt-bindings: leds: add LM3633 LED
 binding information

Hi Jacek,

On 11/27/2015 8:19 PM, Jacek Anaszewski wrote:
> Hi Milo,
>
> On 11/26/2015 07:56 AM, Milo Kim wrote:
>> LM3633 LED device is one of TI LMU device list.
>>
>> Cc: Rob Herring <robh+dt@...nel.org>
>> Cc: devicetree@...r.kernel.org
>> Cc: Lee Jones <lee.jones@...aro.org>
>> Cc: Jacek Anaszewski <j.anaszewski@...sung.com>
>> Cc: Mark Brown <broonie@...nel.org>
>> Cc: linux-leds@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Milo Kim <milo.kim@...com>
>> ---
>>    .../devicetree/bindings/leds/leds-lm3633.txt       | 24 ++++++++++++++++++++++
>>    1 file changed, 24 insertions(+)
>>    create mode 100644 Documentation/devicetree/bindings/leds/leds-lm3633.txt
>>
>> diff --git a/Documentation/devicetree/bindings/leds/leds-lm3633.txt b/Documentation/devicetree/bindings/leds/leds-lm3633.txt
>> new file mode 100644
>> index 0000000..a553894
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/leds/leds-lm3633.txt
>> @@ -0,0 +1,24 @@
>> +TI LMU LM3633 LED device tree bindings
>> +
>> +Required properties:
>> +  - compatible: "ti,lm3633-leds"
>> +
>> +Child nodes:
>> +  Each node matches with LED control bank.
>> +  Please refer to the datasheet [1].
>
> leds/common.txt documentation says that child nodes represent discrete
> LED elements.
>
>> +  Required properties of a child node:
>> +  - led-sources: List of enabled channels from 0 to 5.
>> +                 Please refer to LED binding [2].
>
> led-sources property should contain always one element -
> a control bank identifier that the iout is to be associated with.
> For example, if there are three LEDs and they should be controlled
> with control bank A, then the bindings should look as follows
> (assuming that control bank identifiers start from 0 [A:0, B:1,
> C:2, etc. - it has to be also explicitly stated in the documentation]:

My understanding is 'led-sources' means output channel rather than 
control bank. Output channel is visible and intuitive - just output LED.
On the other hand, control banks works inside the silicon, LM3633.
I'm not sure other LED devices have control bank or not, but output 
channel is common concept.

>
> lvled1 {
> 	led-sources = <2>;
> 	led-max-microamp = <1000>;
> }
>
> lvled2 {
> 	led-sources = <2>;
> 	led-max-microamp = <29000>;
> }
>
> lvled3 {
> 	led-sources = <2>;
> 	led-max-microamp = <7000>;
> }

For this reason, I don't understand this LED configuration - one output 
channel with multiple LED devices. LED child node should be matched with 
led class device.
If three output channels are controlled by one control bank, then it 
should be represented as below.

lvled-group-A {
	led-sources = <0>, <1>, <2>;
	led-max-microamp = <some value>;
}

Please let me know if I misunderstand.

Best regards,
Milo
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