Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> On Wed, 2022-08-24 at 14:15 +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. > > Changes in v2: > - Add nouveau_acpi_video_register_backlight() wrapper to avoid unresolved > symbol errors on non X86 > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/gpu/drm/nouveau/nouveau_acpi.c | 5 +++++ > drivers/gpu/drm/nouveau/nouveau_acpi.h | 2 ++ > drivers/gpu/drm/nouveau/nouveau_backlight.c | 7 +++++++ > 3 files changed, 14 insertions(+) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c > index 1592c9cd7750..8cf096f841a9 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_acpi.c > +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c > @@ -391,3 +391,8 @@ bool nouveau_acpi_video_backlight_use_native(void) > { > return acpi_video_backlight_use_native(); > } > + > +void nouveau_acpi_video_register_backlight(void) > +{ > + acpi_video_register_backlight(); > +} > diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.h b/drivers/gpu/drm/nouveau/nouveau_acpi.h > index 3c666c30dfca..e39dd8b94b8b 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_acpi.h > +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.h > @@ -12,6 +12,7 @@ void nouveau_unregister_dsm_handler(void); > void nouveau_switcheroo_optimus_dsm(void); > void *nouveau_acpi_edid(struct drm_device *, struct drm_connector *); > bool nouveau_acpi_video_backlight_use_native(void); > +void nouveau_acpi_video_register_backlight(void); > #else > static inline bool nouveau_is_optimus(void) { return false; }; > static inline bool nouveau_is_v1_dsm(void) { return false; }; > @@ -20,6 +21,7 @@ static inline void nouveau_unregister_dsm_handler(void) {} > static inline void nouveau_switcheroo_optimus_dsm(void) {} > static inline void *nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector) { return NULL; } > static inline bool nouveau_acpi_video_backlight_use_native(void) { return true; } > +static inline void nouveau_acpi_video_register_backlight(void) {} > #endif > > #endif > diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c > index d2b8f8c13db4..a614582779ca 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) > + nouveau_acpi_video_register_backlight(); > + > return ret; > } > -- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat
