linux-kernel - Re: [PATCH] drm/i915/panel: Alwyas record the backlight level again (but cleverly)

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Message-ID: <s5hobxkzs02.wl%tiwai@suse.de>
Date:	Thu, 13 Oct 2011 20:05:49 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Keith Packard <keithp@...thp.com>
Cc:	Chris Wilson <chris@...is-wilson.co.uk>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915/panel: Alwyas record the backlight level again (but cleverly)

At Thu, 13 Oct 2011 09:40:29 -0700,
Keith Packard wrote:
> 
> On Thu, 13 Oct 2011 10:57:35 +0200, Takashi Iwai <tiwai@...e.de> wrote:
> 
> > This patch fixes the bug by recording the backlight level always
> > when changed but only when dev_priv->backlight_enabled is set.
> > In this way, the bogus value for disabling backlight can be skipped.
> 
> I think this is better than what we have, but I'm not sure it's quite
> what we want -- the backlight level will only be remembered when it is
> enabled, so requested changes that happen while the backlight is off
> will have no effect. And, requested changes while the panel is disabled
> will still go through to the hardware, which can cause problems with
> panel power sequencing.
> 
> I think intel_panel_set_backlight should always record the level passed
> in, but that intel_panel_disable_backlight and
> intel_panel_enable_backlight should use a lower-level function, shared
> with intel_panel_set_backlight that doesn't record the value:
> 
> intel_panel_actually_set_backlight(dev, level) {
>         <internals of current intel_panel_set_backlight>
> }
> 
> intel_panel_set_backlight(dev, level) {
>         dev_priv->backlight_level = level;
>         if (dev_priv->backlight_enabled)
>                 intel_panel_actually_set_backlight(dev, level);
> }
> 
> intel_panel_enable_backlight(dev) {
>         dev_priv->backlight_enabled = true;
>         intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
> }
> 
> intel_panel_disable_backlight(dev) {
>         dev_priv->backlight_enabled = false;
>         intel_panel_actually_set_backlight(dev, 0);
> }

Yes, this looks more understandable, indeed.
Would you patch it by yourself or should I refresh the patch?
In either way, I'll test tomorrow, as I'm already at home without a
test machine.


thanks,

Takashi
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