linux-kernel - Re: [PATCH v1 1/2] dt-bindings: leds: add binding for aw200xx

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Date:   Sat, 3 Dec 2022 11:44:03 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Dmitry Rokosov <ddrokosov@...rdevices.ru>
Cc:     Martin Kurbanov <MMKurbanov@...rdevices.ru>,
        Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>
Subject: Re: [PATCH v1 1/2] dt-bindings: leds: add binding for aw200xx

On 02/12/2022 19:53, Dmitry Rokosov wrote:
> Hello Krzysztof,
> 
> On Fri, Dec 02, 2022 at 05:41:37PM +0100, Krzysztof Kozlowski wrote:
>> On 28/11/2022 18:43, Martin Kurbanov wrote:
>>> Hi. Thank you for quick reply. 
>>>
>>> On 25.11.2022 11:29, Krzysztof Kozlowski wrote:
>>>>> +
>>>>> +  imax:
>>>>> +    maxItems: 1
>>>>> +    description:
>>>>> +      Maximum supply current, see dt-bindings/leds/leds-aw200xx.h
>>>>
>>>> No. Use existing properties from common.yaml. This looks like
>>>> led-max-microamp and it is per LED, not per entire device.
>>>
>>> The AW200XX LED chip does not support imax setup per led.
>>> Imax is the global parameter over the all leds. I suppose, it's better
>>> to add vendor prefix or take minimum from all subnodes?
>>> How do you think?
>>
>> Have in mind that led-max-microamp is a required property in some cases,
>> so skipping it and using per-device properties does not solve the
>> problem of adjusting proper currents. What if each LED you set for
>> something which in total gives more than your imax?
>>
> 
> You are right. From my point of view too, we must build our solutions from
> HW capabilities. 

And there was no proposal to go around HW capabilities. We talk only
about representation.

> In the current situation, AW200XX chips support global
> Imax value, so it's acceptable decision to use vendor prefix for global
> imax parameter, why not?

Jacek made his statement some time ago quite clear:

https://lore.kernel.org/all/5785F17D.3010108@samsung.com/

"If you question the idea of having different maximum brightness per
sub-LEDs controlled by the same device, then it means that you have
objections to the entire idea of LED subsystem max_brightness property,
whereas it has been broadly accepted and successfully used for years."

Best regards,
Krzysztof