linux-kernel - Re: [PATCH v3 3/8] dt-bindings: leds: leds-mt6323: Support WLED output

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Date:   Wed, 14 Jun 2023 10:33:09 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, pavel@....cz
Cc:     lee@...nel.org, sean.wang@...iatek.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, matthias.bgg@...il.com,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v3 3/8] dt-bindings: leds: leds-mt6323: Support WLED
 output

Il 13/06/23 08:59, Krzysztof Kozlowski ha scritto:
> On 09/06/2023 09:51, AngeloGioacchino Del Regno wrote:
>> Il 02/06/23 10:32, Krzysztof Kozlowski ha scritto:
>>> On 01/06/2023 13:08, AngeloGioacchino Del Regno wrote:
>>>> Some PMICs have a separated WLED string output: add a property
>>>> `mediatek,is-wled` to indicate which LED string is a WLED.
>>>>
>>>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>>> ---
>>>>    Documentation/devicetree/bindings/leds/leds-mt6323.txt | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/leds/leds-mt6323.txt b/Documentation/devicetree/bindings/leds/leds-mt6323.txt
>>>> index 052dccb8f2ce..904b2222a5fe 100644
>>>> --- a/Documentation/devicetree/bindings/leds/leds-mt6323.txt
>>>> +++ b/Documentation/devicetree/bindings/leds/leds-mt6323.txt
>>>> @@ -30,6 +30,7 @@ Optional properties for the LED child node:
>>>>    - label : See Documentation/devicetree/bindings/leds/common.txt
>>>>    - linux,default-trigger : See Documentation/devicetree/bindings/leds/common.txt
>>>>    - default-state: See Documentation/devicetree/bindings/leds/common.txt
>>>> +- mediatek,is-wled: LED string is connected to WLED output
>>>
>>> Why would it matter to what the output is connected to?
>>
>> When this property is present, the MT6323 LEDs are managed through different
>> hardware registers which are specific to WLEDs: if we have no indication of
>> whether this is a WLED or a LED, we would program the wrong registers.
>>
> 
> OK, so it is rather the choice of output in the device? What is "LED
> string" in this context?
> 

"LED string" is a term that is commonly used to refer to an array of LEDs.
Usually, in the context of displays (so, WLED!), it refers to the LEDs array
that forms the backlight.

And yes, it's choice of output in the HW.

Cheers,
Angelo