linux-kernel - Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

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Date:	Sat, 19 Nov 2011 15:02:16 -0500
From:	Woody Suwalski <terraluna977@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
CC:	Keith Packard <keithp@...thp.com>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, Alex Davis <alex14641@...oo.com>,
	Kamal Mostafa <kamal@...onical.com>, mjg@...hat.com
Subject: Re: [PATCH] drm/i915: Fix inconsistent backlight level during disabled

Takashi Iwai wrote:
> When the brightness property is inquired while the backlight is disabled,
> the driver returns a wrong value (zero) because it probes the value after
> the backlight was turned off.  This caused a black screen even after the
> backlight is enabled again.  It should return the internal backlight_level
> instead, so that it won't be influenced by the backlight-enable state.
>
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=41926
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/872652
>
> Tested-by: Kamal Mostafa<kamal@...onical.com>
> Cc: Alex Davis<alex14641@...oo.com>
> Cc:<stable@...nel.org>
> Signed-off-by: Takashi Iwai<tiwai@...e.de>
> ---
>   drivers/gpu/drm/i915/intel_panel.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 499d4c0..21f60b7 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -326,7 +326,8 @@ static int intel_panel_update_status(struct backlight_device *bd)
>   static int intel_panel_get_brightness(struct backlight_device *bd)
>   {
>   	struct drm_device *dev = bl_get_data(bd);
> -	return intel_panel_get_backlight(dev);
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	return dev_priv->backlight_level;
>   }
>
>   static const struct backlight_ops intel_panel_bl_ops = {
Seems to be fixing a black-screen regression since 3.0 on EeePC devices 
as well...

Thanks, Woody

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