drm/privacy-screen: Add notifier support (v2)

Add support for privacy-screen consumers to register a notifier to
be notified of external (e.g. done by the hw itself on a hotkey press)
state changes.

Changes in v2:
- Drop WARN_ON(mutex_is_locked(&priv->lock)) check in
  drm_privacy_screen_call_notifier_chain() it may be locked by
  another thread, which would lead to a false-positive triggering
  of the check

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-5-hdegoede@redhat.com

1 files changed, 15 insertions, 0 deletions

diff --git a/include/drm/drm_privacy_screen_consumer.h b/include/drm/drm_privacy_screen_consumer.h
index 0cbd23b0453d..7f66a90d15b7 100644
--- a/include/drm/drm_privacy_screen_consumer.h
+++ b/include/drm/drm_privacy_screen_consumer.h
@@ -24,6 +24,11 @@ int drm_privacy_screen_set_sw_state(struct drm_privacy_screen *priv,
 void drm_privacy_screen_get_state(struct drm_privacy_screen *priv,
 				  enum drm_privacy_screen_status *sw_state_ret,
 				  enum drm_privacy_screen_status *hw_state_ret);
+
+int drm_privacy_screen_register_notifier(struct drm_privacy_screen *priv,
+					 struct notifier_block *nb);
+int drm_privacy_screen_unregister_notifier(struct drm_privacy_screen *priv,
+					   struct notifier_block *nb);
 #else
 static inline struct drm_privacy_screen *drm_privacy_screen_get(struct device *dev,
 								const char *con_id)
@@ -45,6 +50,16 @@ static inline void drm_privacy_screen_get_state(struct drm_privacy_screen *priv,
 	*sw_state_ret = PRIVACY_SCREEN_DISABLED;
 	*hw_state_ret = PRIVACY_SCREEN_DISABLED;
 }
+static inline int drm_privacy_screen_register_notifier(struct drm_privacy_screen *priv,
+						       struct notifier_block *nb)
+{
+	return -ENODEV;
+}
+static inline int drm_privacy_screen_unregister_notifier(struct drm_privacy_screen *priv,
+							 struct notifier_block *nb)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif