[PATCH v6 12/26] drm/bridge: allow bridges to be informed about added and removed bridges

Luca Ceresoli
2025-02-06T18:15:10Z

In preparation for allowing bridges to be added to and removed from a DRM
card without destroying the whole card, add a new DRM bridge function
called on addition and removal of bridges.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

---

Changed in v6:
- rebased fixing conflicts

Changed in v5:
- fixed kerneldoc errors

This patch was added in v4.
---
drivers/gpu/drm/drm_bridge.c | 12 ++++++++++++
include/drm/drm_bridge.h | 23 +++++++++++++++++++++++
2 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index b0834b8644284e5f7751cec81724af849b4180e7..1955a231378050abf1071d74a145831b425c47c5 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -207,12 +207,18 @@ LIST_HEAD(bridge_list);
*/
void drm_bridge_add(struct drm_bridge *bridge)
{
+ struct drm_bridge *br, *tmp;
+
mutex_init(&bridge->hpd_mutex);

if (bridge->ops & DRM_BRIDGE_OP_HDMI)
bridge->ycbcr_420_allowed = !!(bridge->supported_formats &
BIT(HDMI_COLORSPACE_YUV420));

+ list_for_each_entry_safe(br, tmp, &bridge_list, list)
+ if (br->funcs->bridge_event_notify)
+ br->funcs->bridge_event_notify(br, DRM_EVENT_BRIDGE_ADD, bridge);
+
mutex_lock(&bridge_lock);
list_add_tail(&bridge->list, &bridge_list);
mutex_unlock(&bridge_lock);
@@ -249,10 +255,16 @@ EXPORT_SYMBOL(devm_drm_bridge_add);
*/
void drm_bridge_remove(struct drm_bridge *bridge)
{
+ struct drm_bridge *br, *tmp;
+
mutex_lock(&bridge_lock);
list_del_init(&bridge->list);
mutex_unlock(&bridge_lock);

+ list_for_each_entry_safe(br, tmp, &bridge_list, list)
+ if (br->funcs->bridge_event_notify)
+ br->funcs->bridge_event_notify(br, DRM_EVENT_BRIDGE_REMOVE, bridge);
+
mutex_destroy(&bridge->hpd_mutex);
}
EXPORT_SYMBOL(drm_bridge_remove);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 1561347c4991dac6022319774510f9560c9283c3..ad7ba444a13e5ecf16f996de3742e4ac67dc21f1 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -56,6 +56,11 @@ enum drm_bridge_attach_flags {
DRM_BRIDGE_ATTACH_NO_CONNECTOR = BIT(0),
};

+enum drm_bridge_event_type {
+ DRM_EVENT_BRIDGE_ADD,
+ DRM_EVENT_BRIDGE_REMOVE,
+};
+
/**
* struct drm_bridge_funcs - drm_bridge control functions
*/
@@ -729,6 +734,24 @@ struct drm_bridge_funcs {
struct drm_bridge *bridge,
bool enable, int direction);

+ /**
+ * @bridge_event_notify:
+ *
+ * Notify that another bridge is being added or removed.
+ *
+ * This callback is optional. Bridges implementing it must always
+ * check whether the event refers to a bridge they actually need to
+ * interact with.
+ *
+ * @bridge: bridge being notified
+ * @event: event happened (add/remove bridge)
+ * @event_bridge: the bridge mentioned by the event (i.e. the
+ * bridge being added or removed)
+ */
+ void (*bridge_event_notify)(struct drm_bridge *bridge,
+ enum drm_bridge_event_type event,
+ struct drm_bridge *event_bridge);
+
/**
* @debugfs_init:
*

--
2.34.1