On Tue, Jul 12, 2022 at 3:40 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > On x86/ACPI boards the acpi_video driver will usually initializing before initializing -> initialize > the kms driver (except i915). This causes /sys/class/backlight/acpi_video0 > to show up and then the kms driver registers its own native backlight > device after which the drivers/acpi/video_detect.c code unregisters > the acpi_video0 device (when acpi_video_get_backlight_type()==native). > > This means that userspace briefly sees 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 make backlight class device registration a separate step > done by a new acpi_video_register_backlight() function. The intend is for > this to be called by the drm/kms driver *after* it is done setting up its > own native backlight device. So that acpi_video_get_backlight_type() knows > if a native backlight will be available or not at acpi_video backlight > registration time, avoiding the add + remove dance. > > Note the new acpi_video_register_backlight() function is also called from > a delayed work to ensure that the acpi_video backlight devices does get > registered if necessary even if there is no drm/kms driver or when it is > disabled. > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/acpi/acpi_video.c | 45 ++++++++++++++++++++++++++++++++++++--- > include/acpi/video.h | 2 ++ > 2 files changed, 44 insertions(+), 3 deletions(-) > > diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c > index 6944794797a5..c4c3a9e7ce69 100644 > --- a/drivers/acpi/acpi_video.c > +++ b/drivers/acpi/acpi_video.c > @@ -31,6 +31,12 @@ > #define ACPI_VIDEO_BUS_NAME "Video Bus" > #define ACPI_VIDEO_DEVICE_NAME "Video Device" > > +/* > + * Display probing is known to take up to 5 seconds, so delay the fallback > + * backlight registration by 5 seconds + 3 seconds for some extra margin. > + */ > +#define ACPI_VIDEO_REGISTER_BACKLIGHT_DELAY (8 * HZ) > + > #define MAX_NAME_LEN 20 > > MODULE_AUTHOR("Bruno Ducrot"); > @@ -81,6 +87,9 @@ static LIST_HEAD(video_bus_head); > static int acpi_video_bus_add(struct acpi_device *device); > static int acpi_video_bus_remove(struct acpi_device *device); > static void acpi_video_bus_notify(struct acpi_device *device, u32 event); > +static void acpi_video_bus_register_backlight_work(struct work_struct *ignored); > +static DECLARE_DELAYED_WORK(video_bus_register_backlight_work, > + acpi_video_bus_register_backlight_work); > void acpi_video_detect_exit(void); > > /* > @@ -1865,8 +1874,6 @@ static int acpi_video_bus_register_backlight(struct acpi_video_bus *video) > if (video->backlight_registered) > return 0; > > - acpi_video_run_bcl_for_osi(video); > - > if (acpi_video_get_backlight_type() != acpi_backlight_video) > return 0; > > @@ -2092,7 +2099,11 @@ static int acpi_video_bus_add(struct acpi_device *device) > list_add_tail(&video->entry, &video_bus_head); > mutex_unlock(&video_list_lock); > > - acpi_video_bus_register_backlight(video); > + /* > + * The userspace visible backlight_device gets registered separately > + * from acpi_video_register_backlight(). > + */ > + acpi_video_run_bcl_for_osi(video); > acpi_video_bus_add_notify_handler(video); > > return 0; > @@ -2131,6 +2142,11 @@ static int acpi_video_bus_remove(struct acpi_device *device) > return 0; > } > > +static void acpi_video_bus_register_backlight_work(struct work_struct *ignored) > +{ > + acpi_video_register_backlight(); > +} > + > static int __init is_i740(struct pci_dev *dev) > { > if (dev->device == 0x00D1) > @@ -2241,6 +2257,17 @@ int acpi_video_register(void) > */ > register_count = 1; > > + /* > + * acpi_video_bus_add() skips registering the userspace visible > + * backlight_device. The intend is for this to be registered by the > + * drm/kms driver calling acpi_video_register_backlight() *after* it is > + * done setting up its own native backlight device. The delayed work > + * ensures that acpi_video_register_backlight() always gets called > + * eventually, in case there is no drm/kms driver or it is disabled. > + */ > + schedule_delayed_work(&video_bus_register_backlight_work, > + ACPI_VIDEO_REGISTER_BACKLIGHT_DELAY); > + > leave: > mutex_unlock(®ister_count_mutex); > return ret; > @@ -2251,6 +2278,7 @@ void acpi_video_unregister(void) > { > mutex_lock(®ister_count_mutex); > if (register_count) { > + cancel_delayed_work_sync(&video_bus_register_backlight_work); > acpi_bus_unregister_driver(&acpi_video_bus); > register_count = 0; > has_backlight = false; > @@ -2259,6 +2287,17 @@ void acpi_video_unregister(void) > } > EXPORT_SYMBOL(acpi_video_unregister); > > +void acpi_video_register_backlight(void) > +{ > + struct acpi_video_bus *video; > + > + mutex_lock(&video_list_lock); > + list_for_each_entry(video, &video_bus_head, entry) > + acpi_video_bus_register_backlight(video); > + mutex_unlock(&video_list_lock); > +} > +EXPORT_SYMBOL(acpi_video_register_backlight); > + > void acpi_video_unregister_backlight(void) > { > struct acpi_video_bus *video; > diff --git a/include/acpi/video.h b/include/acpi/video.h > index 4705e339c252..0625806d3bbd 100644 > --- a/include/acpi/video.h > +++ b/include/acpi/video.h > @@ -53,6 +53,7 @@ enum acpi_backlight_type { > #if IS_ENABLED(CONFIG_ACPI_VIDEO) > extern int acpi_video_register(void); > extern void acpi_video_unregister(void); > +extern void acpi_video_register_backlight(void); > extern int acpi_video_get_edid(struct acpi_device *device, int type, > int device_id, void **edid); > extern enum acpi_backlight_type acpi_video_get_backlight_type(void); > @@ -69,6 +70,7 @@ extern int acpi_video_get_levels(struct acpi_device *device, > #else > static inline int acpi_video_register(void) { return -ENODEV; } > static inline void acpi_video_unregister(void) { return; } > +static inline void acpi_video_register_backlight(void) { return; } > static inline int acpi_video_get_edid(struct acpi_device *device, int type, > int device_id, void **edid) > { > -- > 2.36.0 >
