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

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Message-ID: <20180430122712.GG5147@dell>
Date:   Mon, 30 Apr 2018 13:27:12 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...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 Wed, 25 Apr 2018, 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.

All applied, thanks.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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