firmware: arm_scmi: Introduce new devres notification ops

Expose to the SCMI drivers a new alternative devres managed notifications
API based on protocol handles.

All drivers still keep using the old API, no functional change.

Link: https://lore.kernel.org/r/20210316124903.35011-6-cristian.marussi@arm.comTested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/notify.c

@@ -1317,7 +1317,7 @@ static int scmi_event_handler_enable_events(struct scmi_event_handler *hndl)
  * Return: 0 on Success
  */
 static int scmi_register_notifier(const struct scmi_handle *handle,
-				  u8 proto_id, u8 evt_id, u32 *src_id,
+				  u8 proto_id, u8 evt_id, const u32 *src_id,
 				  struct notifier_block *nb)
 {
 	int ret = 0;
@@ -1366,7 +1366,7 @@ static int scmi_register_notifier(const struct scmi_handle *handle,
  * Return: 0 on Success
  */
 static int scmi_unregister_notifier(const struct scmi_handle *handle,
-				    u8 proto_id, u8 evt_id, u32 *src_id,
+				    u8 proto_id, u8 evt_id, const u32 *src_id,
 				    struct notifier_block *nb)
 {
 	u32 evt_key;
@@ -1408,6 +1408,129 @@ static int scmi_unregister_notifier(const struct scmi_handle *handle,
 	return 0;
 }
 
+struct scmi_notifier_devres {
+	const struct scmi_handle *handle;
+	u8 proto_id;
+	u8 evt_id;
+	u32 __src_id;
+	u32 *src_id;
+	struct notifier_block *nb;
+};
+
+static void scmi_devm_release_notifier(struct device *dev, void *res)
+{
+	struct scmi_notifier_devres *dres = res;
+
+	scmi_unregister_notifier(dres->handle, dres->proto_id, dres->evt_id,
+				 dres->src_id, dres->nb);
+}
+
+/**
+ * scmi_devm_notifier_register()  - Managed registration of a notifier_block
+ * for an event
+ * @sdev: A reference to an scmi_device whose embedded struct device is to
+ *	  be used for devres accounting.
+ * @proto_id: Protocol ID
+ * @evt_id: Event ID
+ * @src_id: Source ID, when NULL register for events coming form ALL possible
+ *	    sources
+ * @nb: A standard notifier block to register for the specified event
+ *
+ * Generic devres managed helper to register a notifier_block against a
+ * protocol event.
+ */
+static int scmi_devm_notifier_register(struct scmi_device *sdev,
+				       u8 proto_id, u8 evt_id,
+				       const u32 *src_id,
+				       struct notifier_block *nb)
+{
+	int ret;
+	struct scmi_notifier_devres *dres;
+
+	dres = devres_alloc(scmi_devm_release_notifier,
+			    sizeof(*dres), GFP_KERNEL);
+	if (!dres)
+		return -ENOMEM;
+
+	ret = scmi_register_notifier(sdev->handle, proto_id,
+				     evt_id, src_id, nb);
+	if (ret) {
+		devres_free(dres);
+		return ret;
+	}
+
+	dres->handle = sdev->handle;
+	dres->proto_id = proto_id;
+	dres->evt_id = evt_id;
+	dres->nb = nb;
+	if (src_id) {
+		dres->__src_id = *src_id;
+		dres->src_id = &dres->__src_id;
+	} else {
+		dres->src_id = NULL;
+	}
+	devres_add(&sdev->dev, dres);
+
+	return ret;
+}
+
+static int scmi_devm_notifier_match(struct device *dev, void *res, void *data)
+{
+	struct scmi_notifier_devres *dres = res;
+	struct scmi_notifier_devres *xres = data;
+
+	if (WARN_ON(!dres || !xres))
+		return 0;
+
+	return dres->proto_id == xres->proto_id &&
+		dres->evt_id == xres->evt_id &&
+		dres->nb == xres->nb &&
+		((!dres->src_id && !xres->src_id) ||
+		  (dres->src_id && xres->src_id &&
+		   dres->__src_id == xres->__src_id));
+}
+
+/**
+ * scmi_devm_notifier_unregister()  - Managed un-registration of a
+ * notifier_block for an event
+ * @sdev: A reference to an scmi_device whose embedded struct device is to
+ *	  be used for devres accounting.
+ * @proto_id: Protocol ID
+ * @evt_id: Event ID
+ * @src_id: Source ID, when NULL register for events coming form ALL possible
+ *	    sources
+ * @nb: A standard notifier block to register for the specified event
+ *
+ * Generic devres managed helper to explicitly un-register a notifier_block
+ * against a protocol event, which was previously registered using the above
+ * @scmi_devm_notifier_register.
+ */
+static int scmi_devm_notifier_unregister(struct scmi_device *sdev,
+					 u8 proto_id, u8 evt_id,
+					 const u32 *src_id,
+					 struct notifier_block *nb)
+{
+	int ret;
+	struct scmi_notifier_devres dres;
+
+	dres.handle = sdev->handle;
+	dres.proto_id = proto_id;
+	dres.evt_id = evt_id;
+	if (src_id) {
+		dres.__src_id = *src_id;
+		dres.src_id = &dres.__src_id;
+	} else {
+		dres.src_id = NULL;
+	}
+
+	ret = devres_release(&sdev->dev, scmi_devm_release_notifier,
+			     scmi_devm_notifier_match, &dres);
+
+	WARN_ON(ret);
+
+	return ret;
+}
+
 /**
  * scmi_protocols_late_init()  - Worker for late initialization
  * @work: The work item to use associated to the proper SCMI instance
@@ -1465,6 +1588,8 @@ static void scmi_protocols_late_init(struct work_struct *work)
  * directly from an scmi_driver to register its own notifiers.
  */
 static const struct scmi_notify_ops notify_ops = {
+	.devm_event_notifier_register = scmi_devm_notifier_register,
+	.devm_event_notifier_unregister = scmi_devm_notifier_unregister,
 	.register_event_notifier = scmi_register_notifier,
 	.unregister_event_notifier = scmi_unregister_notifier,
 };

include/linux/scmi_protocol.h

@@ -544,6 +544,10 @@ struct scmi_voltage_ops {
 /**
  * struct scmi_notify_ops  - represents notifications' operations provided by
  * SCMI core
+ * @devm_event_notifier_register: Managed registration of a notifier_block for
+ *				  the requested event
+ * @devm_event_notifier_unregister: Managed unregistration of a notifier_block
+ *				    for the requested event
  * @register_event_notifier: Register a notifier_block for the requested event
  * @unregister_event_notifier: Unregister a notifier_block for the requested
  *			       event
@@ -553,7 +557,9 @@ struct scmi_voltage_ops {
  * tuple: (proto_id, evt_id, src_id) using the provided register/unregister
  * interface where:
  *
- * @handle: The handle identifying the platform instance to use
+ * @sdev: The scmi_device to use when calling the devres managed ops devm_
+ * @handle: The handle identifying the platform instance to use, when not
+ *	    calling the managed ops devm_
  * @proto_id: The protocol ID as in SCMI Specification
  * @evt_id: The message ID of the desired event as in SCMI Specification
  * @src_id: A pointer to the desired source ID if different sources are
@@ -576,11 +582,21 @@ struct scmi_voltage_ops {
  * @report: A custom struct describing the specific event delivered
  */
 struct scmi_notify_ops {
+	int (*devm_event_notifier_register)(struct scmi_device *sdev,
+					    u8 proto_id, u8 evt_id,
+					    const u32 *src_id,
+					    struct notifier_block *nb);
+	int (*devm_event_notifier_unregister)(struct scmi_device *sdev,
+					      u8 proto_id, u8 evt_id,
+					      const u32 *src_id,
+					      struct notifier_block *nb);
 	int (*register_event_notifier)(const struct scmi_handle *handle,
-				       u8 proto_id, u8 evt_id, u32 *src_id,
+				       u8 proto_id, u8 evt_id,
+				       const u32 *src_id,
 				       struct notifier_block *nb);
 	int (*unregister_event_notifier)(const struct scmi_handle *handle,
-					 u8 proto_id, u8 evt_id, u32 *src_id,
+					 u8 proto_id, u8 evt_id,
+					 const u32 *src_id,
 					 struct notifier_block *nb);
 };