dpll: Add notifier chain for dpll events

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.

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Co-developed-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Petr Oros <poros@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Link: https://patch.msgid.link/20260203174002.705176-4-ivecera@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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))
@@ -539,6 +574,28 @@ 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

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

drivers/dpll/dpll_netlink.c

@@ -761,17 +761,20 @@ err_free_msg:
 
 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);
 }
 
@@ -829,16 +832,19 @@ err_free_msg:
 
 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);
 }
 

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;
@@ -172,6 +173,30 @@ 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);
@@ -242,4 +267,8 @@ 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