@@ -1984,6 +1984,7 @@ static int instance;
static int acpi_video_bus_add(struct acpi_device *device)
{
struct acpi_video_bus *video;
+ bool auto_detect;
int error;
acpi_status status;
@@ -2045,10 +2046,20 @@ static int acpi_video_bus_add(struct acpi_device *device)
mutex_unlock(&video_list_lock);
/*
- * The userspace visible backlight_device gets registered separately
- * from acpi_video_register_backlight().
+ * If backlight-type auto-detection is used then a native backlight may
+ * show up later and this may change the result from video to native.
+ * Therefor normally the userspace visible /sys/class/backlight device
+ * gets registered separately by the GPU driver calling
+ * acpi_video_register_backlight() when an internal panel is detected.
+ * Register the backlight now when not using auto-detection, so that
+ * when the kernel cmdline or DMI-quirks are used the backlight will
+ * get registered even if acpi_video_register_backlight() is not called.
*/
acpi_video_run_bcl_for_osi(video);
+ if (__acpi_video_get_backlight_type(false, &auto_detect) == acpi_backlight_video &&
+ !auto_detect)
+ acpi_video_bus_register_backlight(video);
+
acpi_video_bus_add_notify_handler(video);
return 0;
Commit 3dbc80a3e4c5 ("ACPI: video: Make backlight class device registration a separate step (v2)") combined with commit 5aa9d943e9b6 ("ACPI: video: Don't enable fallback path for creating ACPI backlight by default") Means that the video.ko code now fully depends on the GPU driver calling acpi_video_register_backlight() for the acpi_video# backlight class devices to get registered. This means that if the GPU driver does not do this, acpi_backlight=video on the cmdline, or DMI quirks for selecting acpi_video# will not work. This is a problem on for example Apple iMac14,1 all-in-ones where the monitor's LCD panel shows up as a regular DP connection instead of eDP so the GPU driver will not call acpi_video_register_backlight() [1]. Fix this by making video.ko directly register the acpi_video# devices when these have been explicitly requested either on the cmdline or through DMI quirks (rather then auto-detection being used). [1] GPU drivers only call acpi_video_register_backlight() when an internal panel is detected, to avoid non working acpi_video# devices getting registered on desktops which unfortunately is a real issue. Fixes: 5aa9d943e9b6 ("ACPI: video: Don't enable fallback path for creating ACPI backlight by default") Cc: stable@vger.kernel.org Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> --- drivers/acpi/acpi_video.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)