linux-kernel - Re: [V5 PATCH 2/4] drivers-gpu-drm-i915-panel-invert-brightness-via-parameter.patch

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Message-Id: <aefc95$3ggeaf@orsmga001.jf.intel.com>
Date:	Thu, 15 Mar 2012 15:15:05 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Carsten Emde <C.Emde@...dl.org>, David Airlie <airlied@...ux.ie>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Keith Packard <keithp@...thp.com>,
	Paul Menzel <paulepanter@...rs.sourceforge.net>,
	Carsten Emde <C.Emde@...dl.org>,
	DRI <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [V5 PATCH 2/4] drivers-gpu-drm-i915-panel-invert-brightness-via-parameter.patch

On Thu, 15 Mar 2012 15:56:25 +0100, Carsten Emde <C.Emde@...dl.org> wrote:
> Following the documentation of the Legacy Backlight Brightness (LBB)
> Register in the configuration space of some Intel PCI graphics adapters,
> setting the LBB register with the value 0x0 causes the backlight to be
> turned off, and 0xFF causes the backlight to be set to 100% intensity
> (http://download.intel.com/embedded/processors/Whitepaper/324567.pdf).
> The Acer Aspire 5734Z, however, turns the backlight off at 0xFF and sets
> it to maximum intensity at 0. In consequence, the screen of this systems
> becomes dark at an early boot stage which makes it unusable. The same
> inversion applies to the BLC_PWM_CTL I915 register. This problem was
> introduced in kernel version 2.6.38 when the PCI device of this system
> was first supported by the i915 KMS module.
> 
> This patch adds a parameter to the i915 module to enable inversion of
> the brightness variable (i915.invert_brightness).
> 
> Signed-off-by: Carsten Emde <C.Emde@...dl.org>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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