linux-kernel - Re: [PATCH] fix backlight brightness on intel LVDS panel after reopening lid

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Message-ID: <AANLkTik20vCMhXqjxkoebZ1cWFb0zQLP5OZvVx4GWMPb@mail.gmail.com>
Date:	Sat, 19 Feb 2011 13:11:00 +0100
From:	Alex Riesen <raa.lkml@...il.com>
To:	Indan Zupancic <indan@....nu>
Cc:	DRI mailing list <dri-devel@...ts.freedesktop.org>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fix backlight brightness on intel LVDS panel after
 reopening lid

Sorry for this late answer. I only get a very little time for this.

On Fri, Feb 18, 2011 at 05:57, Indan Zupancic <indan@....nu> wrote:
> On Thu, February 17, 2011 23:13, Tino Keitel wrote:
>> with kernel 2.6.37, the display brightness of my ThinkPad X61s was
>> always reduced after lid open, resume from suspend etc.  With this
>> patch on top of 2.6.38-rc5, the problem is gone.  Thanks.
>
> Tino, I think Alex's patch only hides the problem and doesn't properly solve

Could well be. I don't understand what the code is supposed to do.
The patch was created just be looking at diffs.

> the real bug. Can you confirm that this is the bit that fixes it for you?
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index c65992d..c4b1ca4 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -267,6 +235,9 @@ void intel_panel_enable_backlight(struct drm_device *dev)
>  {
>        struct drm_i915_private *dev_priv = dev->dev_private;
>
> +       if (dev_priv->backlight_enabled)
> +               return;
> +
>        if (dev_priv->backlight_level == 0)
>                dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
>
> (Alex's patch edited by hand, offsets might be wrong.)

It is not enough, at least for me.

> The other bits either don't change the logic, or should be harmless, or are
> plain wrong, like setting the brightness to maximum at bootup.

I am not absolutely sure, but I don't think this is what happens on this laptop.

> Lastly, could you verify that my patch at https://lkml.org/lkml/2011/2/16/447 fixes
> it for you too? (Make sure you're at max brightness before rebooting.)

I'll try it now.
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