acpi-video-detect: Rewrite backlight interface selection logic

Currently we have 2 kernel commandline options + dmi-quirks in 3 places all
interacting (in interesting ways) to select which which backlight interface
to use. On the commandline we've acpi_backlight=[video|vendor] and
video.use_native_backlight=[0|1]. DMI quirks we have in
acpi/video-detect.c, acpi/video.c and drivers/platform/x86/*.c .

This commit is the first step to cleaning this up, replacing the 2 cmdline
options with just acpi_backlight=[video|vendor|native|none], and adds a
new API to video_detect.c to reflect this.

Follow up commits will also move other related code, like unregistering the
acpi_video backlight interface if it was registered before other drivers
which take priority over it are loaded, to video_detect.c where this
logic really belongs.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/acpi/video.h b/include/acpi/video.h
index 843ef1adfbfa..01b5cc78efd8 100644
--- a/include/acpi/video.h
+++ b/include/acpi/video.h
@@ -16,6 +16,14 @@ struct acpi_device;
 #define ACPI_VIDEO_DISPLAY_LEGACY_PANEL   0x0110
 #define ACPI_VIDEO_DISPLAY_LEGACY_TV      0x0200
 
+enum acpi_backlight_type {
+	acpi_backlight_undef = -1,
+	acpi_backlight_none = 0,
+	acpi_backlight_video,
+	acpi_backlight_vendor,
+	acpi_backlight_native,
+};
+
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
 extern int acpi_video_register(void);
 extern void acpi_video_unregister(void);
@@ -23,6 +31,8 @@ extern void acpi_video_unregister_backlight(void);
 extern int acpi_video_get_edid(struct acpi_device *device, int type,
 			       int device_id, void **edid);
 extern bool acpi_video_verify_backlight_support(void);
+extern enum acpi_backlight_type acpi_video_get_backlight_type(void);
+extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);
 #else
 static inline int acpi_video_register(void) { return 0; }
 static inline void acpi_video_unregister(void) { return; }
@@ -33,6 +43,13 @@ static inline int acpi_video_get_edid(struct acpi_device *device, int type,
 	return -ENODEV;
 }
 static inline bool acpi_video_verify_backlight_support(void) { return false; }
+static inline enum acpi_backlight_type acpi_video_get_backlight_type(void)
+{
+	return acpi_backlight_vendor;
+}
+static void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
+{
+}
 #endif
 
 #endif