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: Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> > + > return ret; > } > -- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat
