From: Petr Oros <poros@redhat.com>

Currently, the DPLL subsystem reports events (creation, deletion, changes)
to userspace via Netlink. However, there is no mechanism for other kernel
components to be notified of these events directly.

Add a raw notifier chain to the DPLL core protected by dpll_lock. This
allows other kernel subsystems or drivers to register callbacks and
receive notifications when DPLL devices or pins are created, deleted,
or modified.

Define the following:
- Registration helpers: {,un}register_dpll_notifier()
- Event types: DPLL_DEVICE_CREATED, DPLL_PIN_CREATED, etc.
- Context structures: dpll_{device,pin}_notifier_info  to pass relevant
  data to the listeners.

The notification chain is invoked alongside the existing Netlink event
generation to ensure in-kernel listeners are kept in sync with the
subsystem state.

Co-developed-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Petr Oros <poros@redhat.com>
---
 drivers/dpll/dpll_core.c    | 57 +++++++++++++++++++++++++++++++++++++
 drivers/dpll/dpll_core.h    |  4 +++
 drivers/dpll/dpll_netlink.c |  6 ++++
 include/linux/dpll.h        | 29 +++++++++++++++++++
 4 files changed, 96 insertions(+)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index fb68b5e19b480..52f2ed888e46c 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -23,6 +23,8 @@ DEFINE_MUTEX(dpll_lock);
 DEFINE_XARRAY_FLAGS(dpll_device_xa, XA_FLAGS_ALLOC);
 DEFINE_XARRAY_FLAGS(dpll_pin_xa, XA_FLAGS_ALLOC);
 
+static RAW_NOTIFIER_HEAD(dpll_notifier_chain);
+
 static u32 dpll_device_xa_id;
 static u32 dpll_pin_xa_id;
 
@@ -46,6 +48,39 @@ struct dpll_pin_registration {
 	void *cookie;
 };
 
+static int call_dpll_notifiers(unsigned long action, void *info)
+{
+	lockdep_assert_held(&dpll_lock);
+	return raw_notifier_call_chain(&dpll_notifier_chain, action, info);
+}
+
+void dpll_device_notify(struct dpll_device *dpll, unsigned long action)
+{
+	struct dpll_device_notifier_info info = {
+		.dpll = dpll,
+		.id = dpll->id,
+		.idx = dpll->device_idx,
+		.clock_id = dpll->clock_id,
+		.type = dpll->type,
+	};
+
+	call_dpll_notifiers(action, &info);
+}
+
+void dpll_pin_notify(struct dpll_pin *pin, unsigned long action)
+{
+	struct dpll_pin_notifier_info info = {
+		.pin = pin,
+		.id = pin->id,
+		.idx = pin->pin_idx,
+		.clock_id = pin->clock_id,
+		.fwnode = pin->fwnode,
+		.prop = &pin->prop,
+	};
+
+	call_dpll_notifiers(action, &info);
+}
+
 struct dpll_device *dpll_device_get_by_id(int id)
 {
 	if (xa_get_mark(&dpll_device_xa, id, DPLL_REGISTERED))
@@ -543,6 +578,28 @@ void dpll_netdev_pin_clear(struct net_device *dev)
 }
 EXPORT_SYMBOL(dpll_netdev_pin_clear);
 
+int register_dpll_notifier(struct notifier_block *nb)
+{
+	int ret;
+
+	mutex_lock(&dpll_lock);
+	ret = raw_notifier_chain_register(&dpll_notifier_chain, nb);
+	mutex_unlock(&dpll_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_dpll_notifier);
+
+int unregister_dpll_notifier(struct notifier_block *nb)
+{
+	int ret;
+
+	mutex_lock(&dpll_lock);
+	ret = raw_notifier_chain_unregister(&dpll_notifier_chain, nb);
+	mutex_unlock(&dpll_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(unregister_dpll_notifier);
+
 /**
  * dpll_pin_get - find existing or create new dpll pin
  * @clock_id: clock_id of creator
diff --git a/drivers/dpll/dpll_core.h b/drivers/dpll/dpll_core.h
index d3e17ff0ecef0..b7b4bb251f739 100644
--- a/drivers/dpll/dpll_core.h
+++ b/drivers/dpll/dpll_core.h
@@ -91,4 +91,8 @@ struct dpll_pin_ref *dpll_xa_ref_dpll_first(struct xarray *xa_refs);
 extern struct xarray dpll_device_xa;
 extern struct xarray dpll_pin_xa;
 extern struct mutex dpll_lock;
+
+void dpll_device_notify(struct dpll_device *dpll, unsigned long action);
+void dpll_pin_notify(struct dpll_pin *pin, unsigned long action);
+
 #endif
diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
index 64944f601ee5a..fe9c3d9073f0f 100644
--- a/drivers/dpll/dpll_netlink.c
+++ b/drivers/dpll/dpll_netlink.c
@@ -742,17 +742,20 @@ dpll_device_event_send(enum dpll_cmd event, struct dpll_device *dpll)
 
 int dpll_device_create_ntf(struct dpll_device *dpll)
 {
+	dpll_device_notify(dpll, DPLL_DEVICE_CREATED);
 	return dpll_device_event_send(DPLL_CMD_DEVICE_CREATE_NTF, dpll);
 }
 
 int dpll_device_delete_ntf(struct dpll_device *dpll)
 {
+	dpll_device_notify(dpll, DPLL_DEVICE_DELETED);
 	return dpll_device_event_send(DPLL_CMD_DEVICE_DELETE_NTF, dpll);
 }
 
 static int
 __dpll_device_change_ntf(struct dpll_device *dpll)
 {
+	dpll_device_notify(dpll, DPLL_DEVICE_CHANGED);
 	return dpll_device_event_send(DPLL_CMD_DEVICE_CHANGE_NTF, dpll);
 }
 
@@ -810,16 +813,19 @@ dpll_pin_event_send(enum dpll_cmd event, struct dpll_pin *pin)
 
 int dpll_pin_create_ntf(struct dpll_pin *pin)
 {
+	dpll_pin_notify(pin, DPLL_PIN_CREATED);
 	return dpll_pin_event_send(DPLL_CMD_PIN_CREATE_NTF, pin);
 }
 
 int dpll_pin_delete_ntf(struct dpll_pin *pin)
 {
+	dpll_pin_notify(pin, DPLL_PIN_DELETED);
 	return dpll_pin_event_send(DPLL_CMD_PIN_DELETE_NTF, pin);
 }
 
 int __dpll_pin_change_ntf(struct dpll_pin *pin)
 {
+	dpll_pin_notify(pin, DPLL_PIN_CHANGED);
 	return dpll_pin_event_send(DPLL_CMD_PIN_CHANGE_NTF, pin);
 }
 
diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index f0c31a111c304..34b005bb4df6f 100644
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -11,6 +11,7 @@
 #include <linux/device.h>
 #include <linux/netlink.h>
 #include <linux/netdevice.h>
+#include <linux/notifier.h>
 #include <linux/rtnetlink.h>
 
 struct dpll_device;
@@ -167,6 +168,30 @@ struct dpll_pin_properties {
 	u32 phase_gran;
 };
 
+#define DPLL_DEVICE_CREATED	1
+#define DPLL_DEVICE_DELETED	2
+#define DPLL_DEVICE_CHANGED	3
+#define DPLL_PIN_CREATED	4
+#define DPLL_PIN_DELETED	5
+#define DPLL_PIN_CHANGED	6
+
+struct dpll_device_notifier_info {
+	struct dpll_device *dpll;
+	u32 id;
+	u32 idx;
+	u64 clock_id;
+	enum dpll_type type;
+};
+
+struct dpll_pin_notifier_info {
+	struct dpll_pin *pin;
+	u32 id;
+	u32 idx;
+	u64 clock_id;
+	const struct fwnode_handle *fwnode;
+	const struct dpll_pin_properties *prop;
+};
+
 #if IS_ENABLED(CONFIG_DPLL)
 void dpll_netdev_pin_set(struct net_device *dev, struct dpll_pin *dpll_pin);
 void dpll_netdev_pin_clear(struct net_device *dev);
@@ -237,4 +262,8 @@ int dpll_device_change_ntf(struct dpll_device *dpll);
 
 int dpll_pin_change_ntf(struct dpll_pin *pin);
 
+int register_dpll_notifier(struct notifier_block *nb);
+
+int unregister_dpll_notifier(struct notifier_block *nb);
+
 #endif
-- 
2.51.2