linux-kernel - Re: [PATCH v8 1/9] leds: multicolor: Add sysfs interface definition

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Date:   Sat, 21 Sep 2019 12:55:11 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Dan Murphy <dmurphy@...com>, pavel@....cz
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 1/9] leds: multicolor: Add sysfs interface definition

Dan,

On 9/20/19 7:41 PM, Dan Murphy wrote:
> Add a documentation of LED Multicolor LED class specific
> sysfs attributes.
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>
> ---
>  .../ABI/testing/sysfs-class-led-multicolor    | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-led-multicolor
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
> new file mode 100644
> index 000000000000..39fc73becfec
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> @@ -0,0 +1,43 @@
> +What:		/sys/class/leds/<led>/brightness
> +Date:		Sept 2019
> +KernelVersion:	5.5
> +Contact:	Dan Murphy <dmurphy@...com>
> +Description:	read/write
> +		Writing to this file will update all LEDs within the group to a
> +		calculated percentage of what each color LED intensity is set
> +		to. The percentage is calculated via the equation below:
> +
> +		led_brightness = requested_value * led_color_intensity/led_color_max_intensity

How about:

led_brightness = brightness * <color>_intensity/<color>_max_intensity

> +
> +		For additional details please refer to
> +		Documentation/leds/leds-class-multicolor.rst.
> +
> +		The value of the color is from 0 to
> +		/sys/class/leds/<led>/max_brightness.
> +
> +What:		/sys/class/leds/<led>/colors/<led_color>_intensity

s/led_color/color/

> +Date:		Sept 2019
> +KernelVersion:	5.5
> +Contact:	Dan Murphy <dmurphy@...com>
> +Description:	read/write
> +		The led_color directory is dynamically created based on the
> +		colors defined by the registrar of the class.
> +		The value for the led_color is defined in the
> +		include/dt-bindings/leds/common.h. There is one directory per
> +		color presented.  The intensity file is created under each
> +		led_color directory and controls the individual LED color
> +		setting.

We no longer have led_color directories so this description needs
to be adjusted.

And I'd not mention where the colors are defined. This is documentation
for the user, who does not need to know about implementation details.

> +
> +		The value of the color is from 0 to
> +		/sys/class/leds/<led>/colors/<led_color>_max_intensity.
> +
> +What:		/sys/class/leds/<led>/colors/<led_color>_max_intensity
> +Date:		Sept 2019
> +KernelVersion:	5.5
> +Contact:	Dan Murphy <dmurphy@...com>
> +Description:	read only
> +		Maximum intensity level for the LED color, default is
> +		255 (LED_FULL).

Mentioning the default value here is pointless IMO. Userspace cannot
change it anyway.

> +
> +		If the LED does not support different intensity levels, this
> +		should be 1.
> 

This is less relevant for MC class, and also it is rather obvious.
I'd skip this sentence.

-- 
Best regards,
Jacek Anaszewski