[PATCH 2/3] ACPI: Provide config option to control automatic brightness switching

[Matthew Garrett <mjg@redhat.com>]

The ACPI backlight driver will optionally automatically respond to ACPI
brightness key events. This is unique amongst backlight drivers and makes
it more difficult for userspace to provide a consistent backlight policy.
Add support for disabling this behaviour by default.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: linux-acpi@vger.kernel.org
Cc: lenb@kernel.org
---
 drivers/acpi/Kconfig |   11 +++++++++++
 drivers/acpi/video.c |    6 +++++-
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 5354290..27212e0 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -171,6 +171,17 @@ config ACPI_VIDEO_DISABLE_BIOS_POWER_BRIGHTNESS
 	  Many laptops will automatically change brightness on AC/battery
 	  status changes. Choose Y here to disable this.
 
+config ACPI_VIDEO_BRIGHTNESS_SWITCH_ENABLED
+        bool "Automatically change brightness on ACPI key events"
+	depends on ACPI_VIDEO
+	default y
+	help
+	  If this option is enabled the kernel will change brightness
+	  automatically in response to ACPI video key events. If it is
+	  disabled, the keys will be reported to userspace but no further
+	  action will be taken by the kernel. It is then up to userspace
+	  to respond to the events.
+
 config ACPI_FAN
 	tristate "Fan"
 	select THERMAL
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 4b42938..2b85046 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -69,7 +69,11 @@ MODULE_AUTHOR("Bruno Ducrot");
 MODULE_DESCRIPTION("ACPI Video Driver");
 MODULE_LICENSE("GPL");
 
-static bool brightness_switch_enabled = 1;
+#ifdef CONFIG_ACPI_VIDEO_BRIGHTNESS_SWITCH_ENABLED
+static bool brightness_switch_enabled = true;
+#else
+static bool brightness_switch_enabled;
+#endif
 module_param(brightness_switch_enabled, bool, 0644);
 
 /*
-- 
1.7.7.6