Am Donnerstag, den 15.03.2012, 00:35 +0100 schrieb Carsten Emde: > Einfaches Textdokument-Anlage > (drivers-gpu-drm-i915-invert-backlight-brightness.patch) quilt also does not adapt the subject line of the message correctly to the one of the patch. > 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). > At least one of our test systems, 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 module parameter to invert the backlight brightness > value before writing and after reading which makes the affected notebook > usable again. > > Signed-off-by: Carsten Emde <C.Emde@xxxxxxxxx> > > --- > Documentation/kernel-parameters.txt | 9 +++++++++ > drivers/gpu/drm/i915/intel_panel.c | 14 ++++++++++++++ > 2 files changed, 23 insertions(+) > > Index: linux-3.3-rc6/Documentation/kernel-parameters.txt > =================================================================== > --- linux-3.3-rc6.orig/Documentation/kernel-parameters.txt > +++ linux-3.3-rc6/Documentation/kernel-parameters.txt > @@ -966,6 +966,15 @@ bytes respectively. Such letter suffixes > > i810= [HW,DRM] > > + i915.invert_brightness > + [DRM] Invert the sense of the variable that is used to > + set the brightness of the panel backlight. Normally a > + value of 0 indicates backlight switched off, and the > + maximum value sets the backlight to maximum brightness. > + If this parameter is specified, a value of 0 sets the > + backlight to maximum brightness, and the maximum value > + switches the backlight off. > + > i8k.ignore_dmi [HW] Continue probing hardware even if DMI data > indicates that the driver is running on unsupported > hardware. > Index: linux-3.3-rc6/drivers/gpu/drm/i915/intel_panel.c > =================================================================== > --- linux-3.3-rc6.orig/drivers/gpu/drm/i915/intel_panel.c > +++ linux-3.3-rc6/drivers/gpu/drm/i915/intel_panel.c > @@ -28,6 +28,7 @@ > * Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > */ > > +#include <linux/moduleparam.h> > #include "intel_drv.h" > > #define PCI_LBPC 0xf4 /* legacy/combination backlight modes */ > @@ -191,6 +192,10 @@ u32 intel_panel_get_max_backlight(struct > return max; > } > > +static bool brightness_inverted; > +MODULE_PARM_DESC(brightness_inverted, "Backlight brightness value is inverted " > + "(0 = max brightness, max value = dark)"); Could you elaborate somewhere for example by giving an example what `dark` means? As a normal user it is not clear to me. > +module_param_named(brightness_inverted, brightness_inverted, bool, 0600); > u32 intel_panel_get_backlight(struct drm_device *dev) > { > struct drm_i915_private *dev_priv = dev->dev_private; > @@ -212,6 +217,10 @@ u32 intel_panel_get_backlight(struct drm > } > > DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val); > + if (brightness_inverted) { > + u32 max = intel_panel_get_max_backlight(dev); > + val = max - val; > + } > return val; > } > > @@ -229,6 +238,11 @@ static void intel_panel_actually_set_bac > > DRM_DEBUG_DRIVER("set backlight PWM = %d\n", level); > > + if (brightness_inverted) { > + u32 max = intel_panel_get_max_backlight(dev); > + level = max - level; > + } > + > if (HAS_PCH_SPLIT(dev)) > return intel_pch_panel_set_backlight(dev, level); Thanks, Paul
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