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Date: Sat, 6 Jul 2019 17:19:41 +0200
From: Pavel Machek <pavel@ucw.cz>
Subject: Re: devicetree bindings for a generic led-based backlight driver
Message-ID: <20190706151941.GB9856@amd>
References: <69f3a300-9e37-448d-e6fa-49c1c9ca0dd6@ti.com>
 <400ac00b-d3c7-b58f-52fa-8b18b6c7e4a2@gmail.com>
 <283a3b7c-c3ed-719e-14e3-fc73e08af880@ti.com>
 <e7c5a500-4107-8895-d0fc-377c71cd3b34@gmail.com>
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In-Reply-To: <e7c5a500-4107-8895-d0fc-377c71cd3b34@gmail.com>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Jean-Jacques Hiblot <jjhiblot@ti.com>, devicetree@vger.kernel.org, linux-leds@vger.kernel.org, robh@kernel.org, "Valkeinen, Tomi" <tomi.valkeinen@ti.com>
List-ID: <devicetree@vger.kernel.org>


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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=A0 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.
> >=20
> > 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 ?
>=20
> After going through the referenced discussion and refreshing my memory
> it looks to me the most reasonable way to go for backlight case.
>=20
> Nevertheless I'd not tamper at LED flash support - if it's not broken,
> don't fix it.
>=20
> Best regards,
> Jacek Anaszewski
>=20
> > Here is the example from Tomi at the end of the discussion:
> >=20
> > /* tlc59108 is an i2c device */
> > tlc59116@40 {
> > 	#address-cells =3D <1>;
> > 	#size-cells =3D <0>;
> > 	compatible =3D "ti,tlc59108";
> > 	reg =3D <0x40>;
> >=20
> > 	wan@0 {
> > 		label =3D "wrt1900ac:amber:wan";
> > 		reg =3D <0x0>;
> > 	};
> >=20
> > 	bl@2 {
> > 		label =3D "backlight";
> > 		reg =3D <0x2>;
> >=20
> > 		compatible =3D "led-backlight";
> > 		brightness-levels =3D <0 243 245 247 248 249 251 252 255>;
> > 		default-brightness-level =3D <8>;
> >=20
> > 		enable-gpios =3D <&pcf_lcd 13 GPIO_ACTIVE_LOW>;

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

									Pavel

--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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