linux-kernel - Re: [PATCH 2/2] dt-binding: leds: Document leds-multi-gpio bindings

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Date:   Sun, 28 Mar 2021 23:46:16 +0300
From:   Vesa Jääskeläinen <dachaac@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Hermes Zhang <chenhui.zhang@...s.com>, dmurphy@...com,
        robh+dt@...nel.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        chenhuiz@...s.com, lkml@...s.com, kernel@...s.com
Subject: Re: [PATCH 2/2] dt-binding: leds: Document leds-multi-gpio bindings

Hi,

On 25.3.2021 20.41, Pavel Machek wrote:
>>> +  led-gpios:
>>> +    description: Array of one or more GPIOs pins used to control the LED.
>>> +    minItems: 1
>>> +    maxItems: 8  # Should be enough
>>
>> We also have a case with multi color LEDs (which is probably a more common
>> than multi intensity LED. So I am wondering how these both could co-exist.
>>
>> From: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/leds/leds-gpio.yaml?h=v5.12-rc4#n58
>>
>>          led-0 {
>>              gpios = <&mcu_pio 0 GPIO_ACTIVE_LOW>;
>>              linux,default-trigger = "disk-activity";
>>              function = LED_FUNCTION_DISK;
>>          };
>>
>> Now 'gpios' (and in LED context) and 'led-gpios' is very close to each other
>> and could easily be confused.
>>
>> Perhaps this could be something like:
>>
>> intensity-gpios = ...
>>
>> or even simplified then just to gpios = <...>
> 
> ...
>> How would this sound?
> 
> Well, not too bad on a quick look.
> 
> Are you willing to implement such multi-color-multi-bit-multi-gpio
> driver?

We have a need for multi color GPIO LED support so I can work on that if 
no one else gets there before me -- I do not have hardware with multiple 
GPIO lines controlling the brightness so that needs a bit more effort in 
order to test that out.

At some point of time I could also revive the PWM stuff if no one else 
beats me to it -- but probably the GPIO variant is easier to get done as 
binary states are easier.

Thanks,
Vesa Jääskeläinen