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Author: Sebastian Reichel
To: Pavel Machek
CC: Tony Lindgren, Merlijn Wajer, maemo-leste, Ivaylo Dimitrov
New-Topics: [maemo-leste] Backlight on Droid4 -- was Re: Droid 4 in 5.3-rc1, development boards
Subject: Re: [maemo-leste] Droid 4 in 5.3-rc1, development boards

On Mon, Jul 29, 2019 at 03:55:23PM +0200, Pavel Machek wrote:
> > Oh and the new backlight module comes up blanked right now so it
> > needs to be manually enabled via sysfs.
> Or you can enable ledtrig-backlight and apply this.
> (I know, we need better solution).


The above patchset is the proper solution. It is a backlight
driver, which takes the LED driver as input and exposes a
proper backlight device. This makes it possible to reference
the backlight in DT:

led-node {

backlight-node {
    led = <&led-node>;

panel-node {
    backlight = <&backlight-node>;

That way the kernel has a known link between the LCD panel and the
backlight and eveything should work smoothly :) I suggest to wait
for it to land and carry any Droid 4 specific hacks downstream until
that happens. This will also remove the bogus DSI backlight from sysfs.
Without the backlight reference the panel driver assumes, that native
DSI backlight is used.

-- Sebastian