Hi Lyude, Thank you for the reviews. On 5/18/22 19:39, Lyude Paul wrote: > On Tue, 2022-05-17 at 17:23 +0200, Hans de Goede wrote: >> Typically the acpi_video driver will initialize before nouveau, which >> used to cause /sys/class/backlight/acpi_video0 to get registered and then >> nouveau would register its own nv_backlight device later. After which >> the drivers/acpi/video_detect.c code unregistered the acpi_video0 device >> to avoid there being 2 backlight devices. >> >> 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() when native backlight >> device registration has failed / was skipped to ensure that there is a >> backlight device available before the drm_device gets registered with >> userspace. >> >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> >> --- >> drivers/gpu/drm/nouveau/nouveau_backlight.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c >> b/drivers/gpu/drm/nouveau/nouveau_backlight.c >> index f56ff797c78c..0ae8793357a4 100644 >> --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c >> +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c >> @@ -436,6 +436,13 @@ nouveau_backlight_init(struct drm_connector *connector) >> >> fail_alloc: >> kfree(bl); >> + /* >> + * If we get here we have an internal panel, but no nv_backlight, >> + * try registering an ACPI video backlight device instead. >> + */ >> + if (ret == 0) >> + acpi_video_register_backlight(); > > Assuming we don't need to return the value of acpi_video_register_backlight() > here: The function return type is void, so no return value to check :) > > Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> > >> + >> return ret; >> } >> >
