[Intel-gfx] [PATCH 1/2] drm/i915: i915.enable_backlight=0 disables intel_backlight

[Kamal Mostafa]

i915.enable_backlight=0 can be used to disable i915 backlight control
and the /sys/class/backlight/intel_backlight interface -- useful for
systems where intel_backight conflicts with BIOS backlight control.

BugLink: https://launchpad.net/bugs/954661
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/i915_drv.c    |    6 ++++++
 drivers/gpu/drm/i915/i915_drv.h    |    1 +
 drivers/gpu/drm/i915/intel_panel.c |   12 ++++++++++++
 3 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index ae8a64f..ddb947b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -112,6 +112,12 @@ module_param_named(i915_enable_ppgtt, i915_enable_ppgtt, int, 0600);
 MODULE_PARM_DESC(i915_enable_ppgtt,
 		"Enable PPGTT (default: true)");
 
+int i915_enable_backlight __read_mostly = -1;
+module_param_named(enable_backlight, i915_enable_backlight, int, 0644);
+MODULE_PARM_DESC(enable_backlight,
+		"Enable backlight control and the intel_backlight interface. "
+		"(default: -1 (auto))");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5fabc6c..6e52a42 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1087,6 +1087,7 @@ extern int i915_enable_rc6 __read_mostly;
 extern int i915_enable_fbc __read_mostly;
 extern bool i915_enable_hangcheck __read_mostly;
 extern int i915_enable_ppgtt __read_mostly;
+extern int i915_enable_backlight __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 48177ec..fcecbd2 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -259,6 +259,9 @@ void intel_panel_disable_backlight(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!i915_enable_backlight)
+		return;
+
 	dev_priv->backlight_enabled = false;
 	intel_panel_actually_set_backlight(dev, 0);
 }
@@ -267,6 +270,9 @@ void intel_panel_enable_backlight(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!i915_enable_backlight)
+		return;
+
 	if (dev_priv->backlight_level == 0)
 		dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
 
@@ -333,6 +339,9 @@ int intel_panel_setup_backlight(struct drm_device *dev)
 	struct backlight_properties props;
 	struct drm_connector *connector;
 
+	if (!i915_enable_backlight)
+		return 0;
+
 	intel_panel_init_backlight(dev);
 
 	if (dev_priv->int_lvds_connector)
@@ -368,6 +377,9 @@ void intel_panel_destroy_backlight(struct drm_device *dev)
 #else
 int intel_panel_setup_backlight(struct drm_device *dev)
 {
+	if (!i915_enable_backlight)
+		return;
+
 	intel_panel_init_backlight(dev);
 	return 0;
 }
-- 
1.7.5.4