1 files changed, 27 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 230a141dbea3..cad45ff8251b 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -28,6 +28,9 @@
  *      Chris Wilson <chris@chris-wilson.co.uk>
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/moduleparam.h>
 #include "intel_drv.h"
 
 #define PCI_LBPC 0xf4 /* legacy/combination backlight modes */
@@ -171,7 +174,7 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
                 /* XXX add code here to query mode clock or hardware clock
                  * and program max PWM appropriately.
                  */
-                printk_once(KERN_WARNING "fixme: max PWM is zero.\n");
+                pr_warn_once("fixme: max PWM is zero\n");
                 return 1;
         }
 
@@ -191,6 +194,27 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
         return max;
 }
 
+static int i915_panel_invert_brightness;
+MODULE_PARM_DESC(invert_brightness, "Invert backlight brightness "
+        "(-1 force normal, 0 machine defaults, 1 force inversion), please "
+        "report PCI device ID, subsystem vendor and subsystem device ID "
+        "to dri-devel@lists.freedesktop.org, if your machine needs it. "
+        "It will then be included in an upcoming module version.");
+module_param_named(invert_brightness, i915_panel_invert_brightness, int, 0600);
+static u32 intel_panel_compute_brightness(struct drm_device *dev, u32 val)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        if (i915_panel_invert_brightness < 0)
+                return val;
+
+        if (i915_panel_invert_brightness > 0 ||
+            dev_priv->quirks & QUIRK_INVERT_BRIGHTNESS)
+                return intel_panel_get_max_backlight(dev) - val;
+
+        return val;
+}
+
 u32 intel_panel_get_backlight(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
@@ -211,6 +235,7 @@ u32 intel_panel_get_backlight(struct drm_device *dev)
                 }
         }
 
+        val = intel_panel_compute_brightness(dev, val);
         DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val);
         return val;
 }
@@ -228,6 +253,7 @@ static void intel_panel_actually_set_backlight(struct drm_device *dev, u32 level
         u32 tmp;
 
         DRM_DEBUG_DRIVER("set backlight PWM = %d\n", level);
+        level = intel_panel_compute_brightness(dev, level);
 
         if (HAS_PCH_SPLIT(dev))
                 return intel_pch_panel_set_backlight(dev, level);