Commit 3dbc80a3 authored by Hans de Goede's avatar Hans de Goede
Browse files

ACPI: video: Make backlight class device registration a separate step (v2) 

On x86/ACPI boards the acpi_video driver will usually initialize before
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.

Changes in v2:
- Make register_backlight_delay a module parameter, mainly so that it can
  be disabled by Nvidia binary driver users

Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
parent 038a8191

drivers/acpi/acpi_video.c

+47 −3
Original line number Diff line number Diff line
@@ -73,6 +73,16 @@ module_param(device_id_scheme, bool, 0444); 
static int only_lcd = -1;

module_param(only_lcd, int, 0444);



/*

 * 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.

 */

static int register_backlight_delay = 8;

module_param(register_backlight_delay, int, 0444);

MODULE_PARM_DESC(register_backlight_delay,

	"Delay in seconds before doing fallback (non GPU driver triggered) "

	"backlight registration, set to 0 to disable.");



static bool may_report_brightness_keys;

static int register_count;

static DEFINE_MUTEX(register_count_mutex);
@@ -81,6 +91,9 @@ 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);



/*
@@ -1859,8 +1872,6 @@ 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;
@@ -2086,7 +2097,11 @@ 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;
@@ -2125,6 +2140,11 @@ 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)
@@ -2235,6 +2255,18 @@ 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.

	 */

	if (register_backlight_delay)

		schedule_delayed_work(&video_bus_register_backlight_work,

				      register_backlight_delay * HZ);



leave:

	mutex_unlock(&register_count_mutex);

	return ret;
@@ -2245,6 +2277,7 @@ void acpi_video_unregister(void) 
{

	mutex_lock(&register_count_mutex);

	if (register_count) {

		cancel_delayed_work_sync(&video_bus_register_backlight_work);

		acpi_bus_unregister_driver(&acpi_video_bus);

		register_count = 0;

		may_report_brightness_keys = false;
@@ -2253,6 +2286,17 @@ 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;

include/acpi/video.h

+2 −0
Original line number Diff line number Diff line
@@ -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)

{