Re: devicetree bindings for a generic led-based backlight driver

[Pavel Machek <pavel@ucw.cz>]

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Hi!

> >>> A few years ago (2015), Tomi Valkeinen posted a series implementing a
> >>> backlight driver on top of a LED device.
> >>>
> >>> https://patchwork.kernel.org/patch/7293991/
> >>> https://patchwork.kernel.org/patch/7294001/
> >>> https://patchwork.kernel.org/patch/7293981/
> >>>
> >>> The discussion stopped  because he lacked the time to work on it.
> >>>
> >>> I will be taking over the task and, before heading in the wrong
> >>> direction, wanted a confirmation that the binding Tomi last proposed in
> >>> hist last email was indeed the preferred option.
> >>>
> >>> It will probably require some modifications in the LED core to create
> >>> the right kind of led-device (normal, flash or backlight) based on the
> >>> compatible option.
> >> I recall that discussion. I gave my ack for the LED changes but
> >> now we have more LED people that might want to look into that.
> > 
> > Regarding the LED bindings as discussed by Tom and Rob in
> > https://patchwork.kernel.org/patch/7293991/, what do you think of using
> > a 'compatible' string to make a LED device also a backlight or a flash LED ?
> 
> After going through the referenced discussion and refreshing my memory
> it looks to me the most reasonable way to go for backlight case.
> 
> Nevertheless I'd not tamper at LED flash support - if it's not broken,
> don't fix it.
> 
> Best regards,
> Jacek Anaszewski
> 
> > Here is the example from Tomi at the end of the discussion:
> > 
> > /* tlc59108 is an i2c device */
> > tlc59116@40 {
> > 	#address-cells = <1>;
> > 	#size-cells = <0>;
> > 	compatible = "ti,tlc59108";
> > 	reg = <0x40>;
> > 
> > 	wan@0 {
> > 		label = "wrt1900ac:amber:wan";
> > 		reg = <0x0>;
> > 	};
> > 
> > 	bl@2 {
> > 		label = "backlight";
> > 		reg = <0x2>;
> > 
> > 		compatible = "led-backlight";
> > 		brightness-levels = <0 243 245 247 248 249 251 252 255>;
> > 		default-brightness-level = <8>;
> > 
> > 		enable-gpios = <&pcf_lcd 13 GPIO_ACTIVE_LOW>;

So... this needs some kind of reference to display it belongs to,
right?

									Pavel

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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