[PATCH v2 25/29] ACPI: video: Remove acpi_video_set_dmi_backlight_type()

[Hans de Goede]

acpi_video_set_dmi_backlight_type() is troublesome because it may end
up getting called after other backlight drivers have already called
acpi_video_get_backlight_type() resulting in the other drivers
already being registered even though they should not.

In case of the acpi_video backlight, acpi_video_set_dmi_backlight_type()
actually calls acpi_video_unregister_backlight() since that is often
probed earlier, leading to userspace seeing the acpi_video0 class
device being briefly available, leading to races in userspace where
udev probe-rules try to access the device and it is already gone.

All callers have been fixed to no longer call it, so remove
acpi_video_set_dmi_backlight_type() now.

This means we now also no longer need acpi_video_unregister_backlight()
for the remove acpi_video backlight after it was wrongly registered hack,
so remove that too.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/acpi/acpi_video.c   | 10 ----------
 drivers/acpi/video_detect.c | 16 ----------------
 include/acpi/video.h        |  4 ----
 3 files changed, 30 deletions(-)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 4fc2a8100865..dc3c037d6313 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2297,16 +2297,6 @@ void acpi_video_register_backlight(void)
 }
 EXPORT_SYMBOL(acpi_video_register_backlight);
 
-void acpi_video_unregister_backlight(void)
-{
-	struct acpi_video_bus *video;
-
-	mutex_lock(&video_list_lock);
-	list_for_each_entry(video, &video_bus_head, entry)
-		acpi_video_bus_unregister_backlight(video);
-	mutex_unlock(&video_list_lock);
-}
-
 bool acpi_video_handles_brightness_key_presses(void)
 {
 	return has_backlight &&
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 84dce2c113ef..351bd6335d7a 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -37,8 +37,6 @@
 #include <linux/workqueue.h>
 #include <acpi/video.h>
 
-void acpi_video_unregister_backlight(void);
-
 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
 
@@ -792,17 +790,3 @@ bool acpi_video_backlight_use_native(void)
 	return __acpi_video_get_backlight_type(true) == acpi_backlight_native;
 }
 EXPORT_SYMBOL(acpi_video_backlight_use_native);
-
-/*
- * Set the preferred backlight interface type based on DMI info.
- * This function allows DMI blacklists to be implemented by external
- * platform drivers instead of putting a big blacklist in video_detect.c
- */
-void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
-{
-	acpi_backlight_dmi = type;
-	/* Remove acpi-video backlight interface if it is no longer desired */
-	if (acpi_video_get_backlight_type() != acpi_backlight_video)
-		acpi_video_unregister_backlight();
-}
-EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
diff --git a/include/acpi/video.h b/include/acpi/video.h
index dbd48cb8bd23..a275c35e5249 100644
--- a/include/acpi/video.h
+++ b/include/acpi/video.h
@@ -60,7 +60,6 @@ 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);
 extern bool acpi_video_backlight_use_native(void);
-extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);
 /*
  * Note: The value returned by acpi_video_handles_brightness_key_presses()
  * may change over time and should not be cached.
@@ -86,9 +85,6 @@ static inline bool acpi_video_backlight_use_native(void)
 {
 	return true;
 }
-static inline void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
-{
-}
 static inline bool acpi_video_handles_brightness_key_presses(void)
 {
 	return false;
-- 
2.36.0