linux-kernel - Backlight off at boot

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Message-ID: <CABDcavbuF=C8FS8W1NPnXi6TzLBN4KQjdzQmTfAfaY-CAjSF=A@mail.gmail.com>
Date:   Tue, 30 Aug 2016 10:58:16 +0200
From:   Guillermo Rodriguez Garcia <guille.rodriguez@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Backlight off at boot

Hello all,

I have been experiencing an issue with a SAMA5D3 Xplained board where
the attached LCD panel would boot up completely white until an
application that uses DRM is actually started.

After some investigation I found that this happens because by default,
backlight devices are immediately enabled when registered.

A solution involving a new "backlight-boot-off" DT property was
discussed some time ago [1], but was never merged. I think this would
be useful in general; see for example [2]. I know there is a concern
that configuration should not be part of the device tree, but this is
not much different from the "default-brightness-level" property, and
no other solutions have been proposed.

Are there any plans to implement something like this?

 [1]: https://lkml.org/lkml/2014/7/31/259
 [2]: https://groups.google.com/a/chromium.org/forum/#!topic/chromium-os-reviews/NaicvV6KQUs

-- 
Guillermo Rodriguez Garcia
guille.rodriguez@...il.com