ACPI: video: Simplify __acpi_video_get_backlight_type()

[ Upstream commit a5df42521f328b45c9d89c13740e747be08ac66e ]

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>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 13f10fb..0c17ee9 100644 (file)
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -735,6 +735,16 @@ static bool google_cros_ec_present(void)
 }
 
 /*
+ * 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.
  */
@@ -779,26 +789,14 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
        if (apple_gmux_backlight_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;