linux-kernel - Re: [PATCH 1/6] backlight: Nuke unused backlight.props.state states

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Message-ID: <f13c6edb-c9c4-0bff-4c74-4b381b088359@linaro.org>
Date:   Wed, 17 Jan 2018 14:56:36 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Meghana Madhyastha <meghana.madhyastha@...il.com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 1/6] backlight: Nuke unused backlight.props.state states

On 17/01/18 14:01, Daniel Vetter wrote:
> The backlight power state handling is supremely confusing. We have:
> - props.power, using FB_BLANK_* defines
> - props.fb_blank, using the same, but deprecated int favour of
>    props.state
> - props.state, using the BL_CORE_* defines
> - and finally a bunch of backlight drivers treat brightness == 0 as
>    off. But of course not all of them.
> 
> This is way too much confusion to fix in a simple patch, but at least
> prevent more hilarity from spreading by removing the unused BL_CORE_*
> defines. I have no idea why exactly anyone would need that.
> 
> Wrt the ideal state, we really just want a boolean state. The 4 power
> saving states that the fbdev subsystem uses are overkill in todays hw
> (this was only relevant for VGA and similar analog circuits like
> TV-out), the new drm atomic modeset api simplified even the uapi to a
> simple bool. And there was never a valid technical reason to have the
> intermediate fbdev power states for backlights (those really only can
> be either off or on).
> 
> Cleanup motivated by Meghana's questions about all this.
> 
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Daniel Thompson <daniel.thompson@...aro.org>
> Cc: Jingoo Han <jingoohan1@...il.com>
> Cc: Meghana Madhyastha <meghana.madhyastha@...il.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>

Acked-by: Daniel Thompson <daniel.thompson@...aro.org>

Daniel: Ack is info for Lee J, not to imply you should take it through
         one of your trees.


Daniel.