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

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Date:   Thu, 18 Jan 2018 08:32:47 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.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, 17 Jan 2018, Daniel Thompson wrote:

> 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.

Right.  I'd rather take the set as a complete unit once all Acks are
acquired though.  Hence my silence thus far.

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