@@ -715,6 +715,16 @@ static bool google_cros_ec_present(void)
return acpi_dev_found("GOOG0004") || acpi_dev_found("GOOG000C");
}
+/*
+ * Windows 8 and newer no longer use the ACPI video interface, so it often
+ * does not work. So on win8+ systems prefer native brightness control.
+ * Chromebooks should always prefer native backlight control.
+ */
+static bool prefer_native_over_acpi_video(void)
+{
+ return acpi_osi_is_win8() || google_cros_ec_present();
+}
+
/*
* Determine which type of backlight interface to use on this system,
* First check cmdline, then dmi quirks, then do autodetect.
@@ -760,26 +770,14 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
if (apple_gmux_present())
return acpi_backlight_apple_gmux;
- /* Chromebooks should always prefer native backlight control. */
- if (google_cros_ec_present() && native_available)
- return acpi_backlight_native;
+ /* Use ACPI video if available, except when native should be preferred. */
+ if ((video_caps & ACPI_VIDEO_BACKLIGHT) &&
+ !(native_available && prefer_native_over_acpi_video()))
+ return acpi_backlight_video;
- /* On systems with ACPI video use either native or ACPI video. */
- if (video_caps & ACPI_VIDEO_BACKLIGHT) {
- /*
- * Windows 8 and newer no longer use the ACPI video interface,
- * so it often does not work. If the ACPI tables are written
- * for win8 and native brightness ctl is available, use that.
- *
- * The native check deliberately is inside the if acpi-video
- * block on older devices without acpi-video support native
- * is usually not the best choice.
- */
- if (acpi_osi_is_win8() && native_available)
- return acpi_backlight_native;
- else
- return acpi_backlight_video;
- }
+ /* Use native if available */
+ if (native_available && prefer_native_over_acpi_video())
+ return acpi_backlight_native;
/* No ACPI video (old hw), use vendor specific fw methods. */
return acpi_backlight_vendor;
Simplify __acpi_video_get_backlight_type() removing a nested if which makes the flow harder to follow. This also results in having only 1 exit point with return acpi_backlight_native instead of 2. Note this drops the (video_caps & ACPI_VIDEO_BACKLIGHT) check from the if (acpi_osi_is_win8() && native_available) return native path. Windows 8's hardware certification requirements include that there must be ACPI video bus backlight control, so the ACPI_VIDEO_BACKLIGHT check is redundant. Signed-off-by: Hans de Goede <hdegoede@redhat.com> --- drivers/acpi/video_detect.c | 36 +++++++++++++++++------------------- 1 file changed, 17 insertions(+), 19 deletions(-)