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From: Marek Vasut <marex@denx.de>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
	"Meghana Madhyastha" <meghana.madhyastha@gmail.com>,
	"Noralf Trønnes" <noralf@tronnes.org>,
	"Sean Paul" <seanpaul@chromium.org>,
	"Thierry Reding" <treding@nvidia.com>
Subject: Re: [PATCH] video: backlight: Only set maximum brightness for gpio-backlight
Date: Fri, 9 Jul 2021 15:19:47 +0200	[thread overview]
Message-ID: <6330fc87-333e-f507-0a39-3ca1bfa6b39f@denx.de> (raw)
In-Reply-To: <20210709110315.vv5hbngg26o4vj63@maple.lan>

On 7/9/21 1:03 PM, Daniel Thompson wrote:
> On Thu, Jul 08, 2021 at 11:10:58AM +0200, Marek Vasut wrote:
>> The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
>> in backlight.c") says that gpio-backlight uses brightness as power state.
>> Other backlight drivers do not, so limit this workaround to gpio-backlight.
>>
>> This fixes the case where e.g. pwm-backlight can perfectly well be set to
>> brightness 0 on boot in DT, which without this patch leads to the display
>> brightness to be max instead of off.
>>
>> Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> Cc: Daniel Thompson <daniel.thompson@linaro.org>
>> Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>> Cc: Noralf Trønnes <noralf@tronnes.org>
>> Cc: Sean Paul <seanpaul@chromium.org>
>> Cc: Thierry Reding <treding@nvidia.com>
> 
> I have to admit that this patch really does makes it clear just how
> nasty the hack in of_find_backlight() currently is.
> 
> Moreover I think it is also be obsolete. gpio-backlight power mode
> handling was pretty broken when this code was introduced. It was fixed
> in 2019 by ec665b756e6f ("backlight: gpio backlight: Correct initial
> power state handling") by trying to match the behaviour of PWM
> backlight.  The new code always sets the brightness to 1 so I think we
> can just remove the hack from of_find_backlight() since I think it is
> unreachable.

I assume by "new code" you mean the fixed gpio-backlight driver ?

Dropping the whole code after the Note: is fine by me.

  reply	other threads:[~2021-07-09 13:20 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-08  9:10 Marek Vasut
2021-07-09 11:03 ` Daniel Thompson
2021-07-09 13:19   ` Marek Vasut [this message]
2021-07-09 13:25     ` Noralf Trønnes

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