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; } -- 2.37.2
