On machines without an Intel video opregion the acpi_video driver immediately probes the ACPI video bus and used to also immediately register acpi_video# backlight devices when supported. Once the drm/kms driver then loaded later and possibly registered a native backlight device then the drivers/acpi/video_detect.c code unregistered the acpi_video0 device to avoid there being 2 backlight devices (when acpi_video_get_backlight_type()==native). This means that userspace used to briefly see 2 devices and the disappearing of acpi_video0 after a brief time confuses the systemd backlight level save/restore code, see e.g.: https://bbs.archlinux.org/viewtopic.php?id=269920 To fix this the ACPI video code has been modified to make backlight class device registration a separate step, relying on the drm/kms driver to ask for the acpi_video backlight registration after it is done setting up its native backlight device. Add a call to the new acpi_video_register_backlight() function after setting up the gma500's native backlight, so that the acpi_video backlight device gets registered on systems where the gma500's native backlight device is not registered. Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/gpu/drm/gma500/psb_drv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/gma500/psb_drv.c b/drivers/gpu/drm/gma500/psb_drv.c index d3dc16193a29..cd9c73f5a64a 100644 --- a/drivers/gpu/drm/gma500/psb_drv.c +++ b/drivers/gpu/drm/gma500/psb_drv.c @@ -398,6 +398,8 @@ static int psb_driver_load(struct drm_device *dev, unsigned long flags) if (gma_encoder->type == INTEL_OUTPUT_LVDS || gma_encoder->type == INTEL_OUTPUT_MIPI) { ret = gma_backlight_init(dev); + if (ret == 0) + acpi_video_register_backlight(); break; } } -- 2.37.3
