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, 4 insertions, 0 deletions

diff --git a/include/drm/drm_privacy_screen_driver.h b/include/drm/drm_privacy_screen_driver.h
index 5187ae52eb03..24591b607675 100644
--- a/include/drm/drm_privacy_screen_driver.h
+++ b/include/drm/drm_privacy_screen_driver.h
@@ -54,6 +54,8 @@ struct drm_privacy_screen {
 	struct mutex lock;
 	/** @list: privacy-screen devices list list-entry. */
 	struct list_head list;
+	/** @notifier_head: privacy-screen notifier head. */
+	struct blocking_notifier_head notifier_head;
 	/**
 	 * @ops: &struct drm_privacy_screen_ops for this privacy-screen.
 	 * This is NULL if the driver has unregistered the privacy-screen.
@@ -77,4 +79,6 @@ struct drm_privacy_screen *drm_privacy_screen_register(
 	struct device *parent, const struct drm_privacy_screen_ops *ops);
 void drm_privacy_screen_unregister(struct drm_privacy_screen *priv);
 
+void drm_privacy_screen_call_notifier_chain(struct drm_privacy_screen *priv);
+
 #endif