[PATCH v4 27/31] ACPI: video: Remove acpi_video_set_dmi_backlight_type()

Hans de Goede
2022-08-24T12:18:42Z

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.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Hans de Goede <hdegoede@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 d1e41f30c004..a7c3d11e0dac 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2296,16 +2296,6 @@ 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 may_report_brightness_keys &&
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 3861d4121172..67a0211c07b4 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -38,8 +38,6 @@
#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;

@@ -817,17 +815,3 @@ 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;
--
2.37.2