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From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [V5 PATCH 2/4] drivers-gpu-drm-i915-panel-invert-brightness-via-parameter.patch
To: Carsten Emde <C.Emde@osadl.org>, David Airlie <airlied@linux.ie>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Keith Packard <keithp@keithp.com>,
        Paul Menzel <paulepanter@users.sourceforge.net>,
        Carsten Emde <C.Emde@osadl.org>, DRI <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <20120315145828.308069018@osadl.org>
References: <20120315145623.486070468@osadl.org> <20120315145828.308069018@osadl.org>
Date: Thu, 15 Mar 2012 15:15:05 +0000
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On Thu, 15 Mar 2012 15:56:25 +0100, Carsten Emde <C.Emde@osadl.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@osadl.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre