[PATCH v3 2/7] drm/bridge: add bridge notifier to be notified of bridge addition and removal

Luca Ceresoli
2024-08-09T15:35:49Z

From: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

In preparation for allowing bridges to be added to and removed from a DRM
card without destroying the whole card, add a DRM bridge notifier. Notified
events are addition and removal to/from the global bridge list.

Co-developed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

---

Changes in v3: none
Changes in v2: none
---
drivers/gpu/drm/drm_bridge.c | 35 +++++++++++++++++++++++++++++++++++
include/drm/drm_bridge.h | 19 +++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index d44f055dbe3e..0728a4e0cbfd 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -25,6 +25,7 @@
#include <linux/media-bus-format.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/notifier.h>

#include <drm/drm_atomic_state_helper.h>
#include <drm/drm_bridge.h>
@@ -197,6 +198,36 @@

static DEFINE_MUTEX(bridge_lock);
static LIST_HEAD(bridge_list);
+static BLOCKING_NOTIFIER_HEAD(bridge_notifier);
+
+/**
+ * drm_bridge_notifier_register - add a DRM bridge notifier
+ * @nb: the notifier block to be registered
+ *
+ * The notifier block will be notified of events defined in
+ * &drm_bridge_notifier_event
+ */
+int drm_bridge_notifier_register(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_register(&bridge_notifier, nb);
+}
+EXPORT_SYMBOL(drm_bridge_notifier_register);
+
+/**
+ * drm_bridge_notifier_unregister - remove a DRM bridge notifier
+ * @nb: the notifier block to be unregistered
+ */
+int drm_bridge_notifier_unregister(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_unregister(&bridge_notifier, nb);
+}
+EXPORT_SYMBOL(drm_bridge_notifier_unregister);
+
+static void drm_bridge_notifier_notify(unsigned long event,
+ struct drm_bridge *bridge)
+{
+ blocking_notifier_call_chain(&bridge_notifier, event, bridge);
+}

/**
* drm_bridge_add - add the given bridge to the global bridge list
@@ -210,6 +241,8 @@ void drm_bridge_add(struct drm_bridge *bridge)
mutex_lock(&bridge_lock);
list_add_tail(&bridge->list, &bridge_list);
mutex_unlock(&bridge_lock);
+
+ drm_bridge_notifier_notify(DRM_BRIDGE_NOTIFY_ADD, bridge);
}
EXPORT_SYMBOL(drm_bridge_add);

@@ -243,6 +276,8 @@ EXPORT_SYMBOL(devm_drm_bridge_add);
*/
void drm_bridge_remove(struct drm_bridge *bridge)
{
+ drm_bridge_notifier_notify(DRM_BRIDGE_NOTIFY_REMOVE, bridge);
+
mutex_lock(&bridge_lock);
list_del_init(&bridge->list);
mutex_unlock(&bridge_lock);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 75019d16be64..3748c1011307 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -43,6 +43,22 @@ struct drm_panel;
struct edid;
struct i2c_adapter;

+/**
+ * enum drm_bridge_notifier_event - DRM bridge events
+ */
+enum drm_bridge_notifier_event {
+ /**
+ * @DRM_BRIDGE_NOTIFY_ADD: A bridge has just been added to the
+ * global bridge list. See drm_bridge_add().
+ */
+ DRM_BRIDGE_NOTIFY_ADD,
+ /**
+ * @DRM_BRIDGE_NOTIFY_REMOVE: A bridge is about to be removed from
+ * the global bridge list. See drm_bridge_remove().
+ */
+ DRM_BRIDGE_NOTIFY_REMOVE,
+};
+
/**
* enum drm_bridge_attach_flags - Flags for &drm_bridge_funcs.attach
*/
@@ -862,6 +878,9 @@ drm_priv_to_bridge(struct drm_private_obj *priv)
return container_of(priv, struct drm_bridge, base);
}

+int drm_bridge_notifier_register(struct notifier_block *nb);
+int drm_bridge_notifier_unregister(struct notifier_block *nb);
+
void drm_bridge_add(struct drm_bridge *bridge);
int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge);
void drm_bridge_remove(struct drm_bridge *bridge);

--
2.34.1