firmware: arm_scmi: Extend protocol registration interfaces

Extend common protocol registration routines and provide some new generic
protocols get/put helpers that can track protocols usage and automatically
perform the proper initialization and de-initialization on demand when
required.

Convert all standard protocols to use this new registration scheme while
keeping them all still using the usual initialization logic bound to SCMI
devices probing.

Link: https://lore.kernel.org/r/20210316124903.35011-2-cristian.marussi@arm.comTested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/base.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Base Protocol
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications BASE - " fmt
@@ -365,3 +365,11 @@ int scmi_base_protocol_init(struct scmi_handle *h)
 
 	return 0;
 }
+
+static const struct scmi_protocol scmi_base = {
+	.id = SCMI_PROTOCOL_BASE,
+	.init = &scmi_base_protocol_init,
+	.ops = NULL,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(base, scmi_base)

drivers/firmware/arm_scmi/bus.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Message Protocol bus layer
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -51,13 +51,29 @@ static int scmi_dev_match(struct device *dev, struct device_driver *drv)
 	return 0;
 }
 
+const struct scmi_protocol *scmi_protocol_get(int protocol_id)
+{
+	const struct scmi_protocol *proto;
+
+	proto = idr_find(&scmi_protocols, protocol_id);
+	if (!proto) {
+		pr_warn("SCMI Protocol 0x%x not found!\n", protocol_id);
+		return NULL;
+	}
+
+	pr_debug("Found SCMI Protocol 0x%x\n", protocol_id);
+
+	return proto;
+}
+
 static int scmi_protocol_init(int protocol_id, struct scmi_handle *handle)
 {
-	scmi_prot_init_fn_t fn = idr_find(&scmi_protocols, protocol_id);
+	const struct scmi_protocol *proto;
 
-	if (unlikely(!fn))
+	proto = scmi_protocol_get(protocol_id);
+	if (!proto)
 		return -EINVAL;
-	return fn(handle);
+	return proto->init(handle);
 }
 
 static int scmi_protocol_dummy_init(struct scmi_handle *handle)
@@ -194,26 +210,45 @@ void scmi_set_handle(struct scmi_device *scmi_dev)
 	scmi_dev->handle = scmi_handle_get(&scmi_dev->dev);
 }
 
-int scmi_protocol_register(int protocol_id, scmi_prot_init_fn_t fn)
+int scmi_protocol_register(const struct scmi_protocol *proto)
 {
 	int ret;
 
+	if (!proto) {
+		pr_err("invalid protocol\n");
+		return -EINVAL;
+	}
+
+	if (!proto->init && !proto->instance_init) {
+		pr_err("missing init for protocol 0x%x\n", proto->id);
+		return -EINVAL;
+	}
+
 	spin_lock(&protocol_lock);
-	ret = idr_alloc(&scmi_protocols, fn, protocol_id, protocol_id + 1,
-			GFP_ATOMIC);
+	ret = idr_alloc(&scmi_protocols, (void *)proto,
+			proto->id, proto->id + 1, GFP_ATOMIC);
 	spin_unlock(&protocol_lock);
-	if (ret != protocol_id)
-		pr_err("unable to allocate SCMI idr slot, err %d\n", ret);
+	if (ret != proto->id) {
+		pr_err("unable to allocate SCMI idr slot for 0x%x - err %d\n",
+		       proto->id, ret);
+		return ret;
+	}
+
+	pr_debug("Registered SCMI Protocol 0x%x\n", proto->id);
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(scmi_protocol_register);
 
-void scmi_protocol_unregister(int protocol_id)
+void scmi_protocol_unregister(const struct scmi_protocol *proto)
 {
 	spin_lock(&protocol_lock);
-	idr_remove(&scmi_protocols, protocol_id);
+	idr_remove(&scmi_protocols, proto->id);
 	spin_unlock(&protocol_lock);
+
+	pr_debug("Unregistered SCMI Protocol 0x%x\n", proto->id);
+
+	return;
 }
 EXPORT_SYMBOL_GPL(scmi_protocol_unregister);
 

drivers/firmware/arm_scmi/clock.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Clock Protocol
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #include <linux/sort.h>
@@ -366,4 +366,10 @@ static int scmi_clock_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_CLOCK, clock)
+static const struct scmi_protocol scmi_clock = {
+	.id = SCMI_PROTOCOL_CLOCK,
+	.init = &scmi_clock_protocol_init,
+	.ops = &clk_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(clock, scmi_clock)

drivers/firmware/arm_scmi/common.h

@@ -4,7 +4,7 @@
  * driver common header file containing some definitions, structures
  * and function prototypes used in all the different SCMI protocols.
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 #ifndef _SCMI_COMMON_H
 #define _SCMI_COMMON_H
@@ -157,6 +157,24 @@ void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
 				     u8 *prot_imp);
 
 int scmi_base_protocol_init(struct scmi_handle *h);
+typedef int (*scmi_prot_init_fn_t)(struct scmi_handle *);
+
+/**
+ * struct scmi_protocol  - Protocol descriptor
+ * @id: Protocol ID.
+ * @init: Mandatory protocol initialization function.
+ * @instance_init: Optional protocol instance initialization function.
+ * @instance_deinit: Optional protocol de-initialization function.
+ * @ops: Optional reference to the operations provided by the protocol and
+ *	 exposed in scmi_protocol.h.
+ */
+struct scmi_protocol {
+	const u8				id;
+	const scmi_prot_init_fn_t		init;
+	const scmi_prot_init_fn_t		instance_init;
+	const scmi_prot_init_fn_t		instance_deinit;
+	const void				*ops;
+};
 
 int __init scmi_bus_init(void);
 void __exit scmi_bus_exit(void);
@@ -164,6 +182,7 @@ void __exit scmi_bus_exit(void);
 #define DECLARE_SCMI_REGISTER_UNREGISTER(func)		\
 	int __init scmi_##func##_register(void);	\
 	void __exit scmi_##func##_unregister(void)
+DECLARE_SCMI_REGISTER_UNREGISTER(base);
 DECLARE_SCMI_REGISTER_UNREGISTER(clock);
 DECLARE_SCMI_REGISTER_UNREGISTER(perf);
 DECLARE_SCMI_REGISTER_UNREGISTER(power);
@@ -172,17 +191,24 @@ DECLARE_SCMI_REGISTER_UNREGISTER(sensors);
 DECLARE_SCMI_REGISTER_UNREGISTER(voltage);
 DECLARE_SCMI_REGISTER_UNREGISTER(system);
 
-#define DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(id, name) \
-int __init scmi_##name##_register(void) \
-{ \
-	return scmi_protocol_register((id), &scmi_##name##_protocol_init); \
-} \
-\
-void __exit scmi_##name##_unregister(void) \
-{ \
-	scmi_protocol_unregister((id)); \
+#define DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(name, proto)	\
+static const struct scmi_protocol *__this_proto = &(proto);	\
+								\
+int __init scmi_##name##_register(void)				\
+{								\
+	return scmi_protocol_register(__this_proto);		\
+}								\
+								\
+void __exit scmi_##name##_unregister(void)			\
+{								\
+	scmi_protocol_unregister(__this_proto);			\
 }
 
+const struct scmi_protocol *scmi_protocol_get(int protocol_id);
+
+int scmi_protocol_acquire(struct scmi_handle *handle, u8 protocol_id);
+void scmi_protocol_release(struct scmi_handle *handle, u8 protocol_id);
+
 /* SCMI Transport */
 /**
  * struct scmi_chan_info - Structure representing a SCMI channel information

drivers/firmware/arm_scmi/driver.c

@@ -11,11 +11,12 @@
  * various power domain DVFS including the core/cluster, certain system
  * clocks configuration, thermal sensors and many others.
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #include <linux/bitmap.h>
 #include <linux/export.h>
+#include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/ktime.h>
@@ -23,6 +24,7 @@
 #include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/processor.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 
 #include "common.h"
@@ -68,6 +70,21 @@ struct scmi_xfers_info {
 	spinlock_t xfer_lock;
 };
 
+/**
+ * struct scmi_protocol_instance  - Describe an initialized protocol instance.
+ * @proto: A reference to the protocol descriptor.
+ * @gid: A reference for per-protocol devres management.
+ * @users: A refcount to track effective users of this protocol.
+ *
+ * Each protocol is initialized independently once for each SCMI platform in
+ * which is defined by DT and implemented by the SCMI server fw.
+ */
+struct scmi_protocol_instance {
+	const struct scmi_protocol	*proto;
+	void				*gid;
+	refcount_t			users;
+};
+
 /**
  * struct scmi_info - Structure representing a SCMI instance
  *
@@ -80,6 +97,10 @@ struct scmi_xfers_info {
  * @rx_minfo: Universal Receive Message management info
  * @tx_idr: IDR object to map protocol id to Tx channel info pointer
  * @rx_idr: IDR object to map protocol id to Rx channel info pointer
+ * @protocols: IDR for protocols' instance descriptors initialized for
+ *	       this SCMI instance: populated on protocol's first attempted
+ *	       usage.
+ * @protocols_mtx: A mutex to protect protocols instances initialization.
  * @protocols_imp: List of protocols implemented, currently maximum of
  *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
  * @node: List head
@@ -94,6 +115,9 @@ struct scmi_info {
 	struct scmi_xfers_info rx_minfo;
 	struct idr tx_idr;
 	struct idr rx_idr;
+	struct idr protocols;
+	/* Ensure mutual exclusive access to protocols instance array */
+	struct mutex protocols_mtx;
 	u8 *protocols_imp;
 	struct list_head node;
 	int users;
@@ -519,6 +543,150 @@ int scmi_version_get(const struct scmi_handle *handle, u8 protocol,
 	return ret;
 }
 
+/**
+ * scmi_alloc_init_protocol_instance  - Allocate and initialize a protocol
+ * instance descriptor.
+ * @info: The reference to the related SCMI instance.
+ * @proto: The protocol descriptor.
+ *
+ * Allocate a new protocol instance descriptor, using the provided @proto
+ * description, against the specified SCMI instance @info, and initialize it;
+ * all resources management is handled via a dedicated per-protocol devres
+ * group.
+ *
+ * Context: Assumes to be called with @protocols_mtx already acquired.
+ * Return: A reference to a freshly allocated and initialized protocol instance
+ *	   or ERR_PTR on failure.
+ */
+static struct scmi_protocol_instance *
+scmi_alloc_init_protocol_instance(struct scmi_info *info,
+				  const struct scmi_protocol *proto)
+{
+	int ret = -ENOMEM;
+	void *gid;
+	struct scmi_protocol_instance *pi;
+	struct scmi_handle *handle = &info->handle;
+
+	/* Protocol specific devres group */
+	gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
+	if (!gid)
+		goto out;
+
+	pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
+	if (!pi)
+		goto clean;
+
+	pi->gid = gid;
+	pi->proto = proto;
+	refcount_set(&pi->users, 1);
+	/* proto->init is assured NON NULL by scmi_protocol_register */
+	ret = pi->proto->instance_init(handle);
+	if (ret)
+		goto clean;
+
+	ret = idr_alloc(&info->protocols, pi, proto->id, proto->id + 1,
+			GFP_KERNEL);
+	if (ret != proto->id)
+		goto clean;
+
+	devres_close_group(handle->dev, pi->gid);
+	dev_dbg(handle->dev, "Initialized protocol: 0x%X\n", pi->proto->id);
+
+	return pi;
+
+clean:
+	devres_release_group(handle->dev, gid);
+out:
+	return ERR_PTR(ret);
+}
+
+/**
+ * scmi_get_protocol_instance  - Protocol initialization helper.
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * In case the required protocol has never been requested before for this
+ * instance, allocate and initialize all the needed structures while handling
+ * resource allocation with a dedicated per-protocol devres subgroup.
+ *
+ * Return: A reference to an initialized protocol instance or error on failure.
+ */
+static struct scmi_protocol_instance * __must_check
+scmi_get_protocol_instance(struct scmi_handle *handle, u8 protocol_id)
+{
+	struct scmi_protocol_instance *pi;
+	struct scmi_info *info = handle_to_scmi_info(handle);
+
+	mutex_lock(&info->protocols_mtx);
+	pi = idr_find(&info->protocols, protocol_id);
+
+	if (pi) {
+		refcount_inc(&pi->users);
+	} else {
+		const struct scmi_protocol *proto;
+
+		/* Fails if protocol not registered on bus */
+		proto = scmi_protocol_get(protocol_id);
+		if (proto)
+			pi = scmi_alloc_init_protocol_instance(info, proto);
+		else
+			pi = ERR_PTR(-ENODEV);
+	}
+	mutex_unlock(&info->protocols_mtx);
+
+	return pi;
+}
+
+/**
+ * scmi_protocol_acquire  - Protocol acquire
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * Register a new user for the requested protocol on the specified SCMI
+ * platform instance, possibly triggering its initialization on first user.
+ *
+ * Return: 0 if protocol was acquired successfully.
+ */
+int scmi_protocol_acquire(struct scmi_handle *handle, u8 protocol_id)
+{
+	return PTR_ERR_OR_ZERO(scmi_get_protocol_instance(handle, protocol_id));
+}
+
+/**
+ * scmi_protocol_release  - Protocol de-initialization helper.
+ * @handle: A reference to the SCMI platform instance.
+ * @protocol_id: The protocol being requested.
+ *
+ * Remove one user for the specified protocol and triggers de-initialization
+ * and resources de-allocation once the last user has gone.
+ */
+void scmi_protocol_release(struct scmi_handle *handle, u8 protocol_id)
+{
+	struct scmi_info *info = handle_to_scmi_info(handle);
+	struct scmi_protocol_instance *pi;
+
+	mutex_lock(&info->protocols_mtx);
+	pi = idr_find(&info->protocols, protocol_id);
+	if (WARN_ON(!pi))
+		goto out;
+
+	if (refcount_dec_and_test(&pi->users)) {
+		void *gid = pi->gid;
+
+		if (pi->proto->instance_deinit)
+			pi->proto->instance_deinit(handle);
+
+		idr_remove(&info->protocols, protocol_id);
+
+		devres_release_group(handle->dev, gid);
+		dev_dbg(handle->dev, "De-Initialized protocol: 0x%X\n",
+			protocol_id);
+	}
+
+out:
+	mutex_unlock(&info->protocols_mtx);
+}
+
 void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
 				     u8 *prot_imp)
 {
@@ -786,6 +954,8 @@ static int scmi_probe(struct platform_device *pdev)
 	info->dev = dev;
 	info->desc = desc;
 	INIT_LIST_HEAD(&info->node);
+	idr_init(&info->protocols);
+	mutex_init(&info->protocols_mtx);
 
 	platform_set_drvdata(pdev, info);
 	idr_init(&info->tx_idr);
@@ -860,6 +1030,10 @@ static int scmi_remove(struct platform_device *pdev)
 
 	scmi_notification_exit(&info->handle);
 
+	mutex_lock(&info->protocols_mtx);
+	idr_destroy(&info->protocols);
+	mutex_unlock(&info->protocols_mtx);
+
 	/* Safe to free channels since no more users */
 	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
 	idr_destroy(&info->tx_idr);
@@ -942,6 +1116,8 @@ static int __init scmi_driver_init(void)
 {
 	scmi_bus_init();
 
+	scmi_base_register();
+
 	scmi_clock_register();
 	scmi_perf_register();
 	scmi_power_register();
@@ -956,7 +1132,7 @@ subsys_initcall(scmi_driver_init);
 
 static void __exit scmi_driver_exit(void)
 {
-	scmi_bus_exit();
+	scmi_base_unregister();
 
 	scmi_clock_unregister();
 	scmi_perf_unregister();
@@ -966,6 +1142,8 @@ static void __exit scmi_driver_exit(void)
 	scmi_voltage_unregister();
 	scmi_system_unregister();
 
+	scmi_bus_exit();
+
 	platform_driver_unregister(&scmi_driver);
 }
 module_exit(scmi_driver_exit);

drivers/firmware/arm_scmi/perf.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Performance Protocol
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications PERF - " fmt
@@ -900,4 +900,10 @@ static int scmi_perf_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_PERF, perf)
+static const struct scmi_protocol scmi_perf = {
+	.id = SCMI_PROTOCOL_PERF,
+	.init = &scmi_perf_protocol_init,
+	.ops = &perf_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(perf, scmi_perf)

drivers/firmware/arm_scmi/power.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Power Protocol
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications POWER - " fmt
@@ -301,4 +301,10 @@ static int scmi_power_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_POWER, power)
+static const struct scmi_protocol scmi_power = {
+	.id = SCMI_PROTOCOL_POWER,
+	.init = &scmi_power_protocol_init,
+	.ops = &power_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(power, scmi_power)

drivers/firmware/arm_scmi/reset.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Reset Protocol
  *
- * Copyright (C) 2019 ARM Ltd.
+ * Copyright (C) 2019-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications RESET - " fmt
@@ -311,4 +311,10 @@ static int scmi_reset_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_RESET, reset)
+static const struct scmi_protocol scmi_reset = {
+	.id = SCMI_PROTOCOL_RESET,
+	.init = &scmi_reset_protocol_init,
+	.ops = &reset_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(reset, scmi_reset)

drivers/firmware/arm_scmi/sensors.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Sensor Protocol
  *
- * Copyright (C) 2018-2020 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications SENSOR - " fmt
@@ -983,4 +983,10 @@ static int scmi_sensors_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_SENSOR, sensors)
+static const struct scmi_protocol scmi_sensors = {
+	.id = SCMI_PROTOCOL_SENSOR,
+	.init = &scmi_sensors_protocol_init,
+	.ops = &sensor_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(sensors, scmi_sensors)

drivers/firmware/arm_scmi/system.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) System Power Protocol
  *
- * Copyright (C) 2020 ARM Ltd.
+ * Copyright (C) 2020-2021 ARM Ltd.
  */
 
 #define pr_fmt(fmt) "SCMI Notifications SYSTEM - " fmt
@@ -128,4 +128,10 @@ static int scmi_system_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_SYSTEM, system)
+static const struct scmi_protocol scmi_system = {
+	.id = SCMI_PROTOCOL_SYSTEM,
+	.init = &scmi_system_protocol_init,
+	.ops = NULL,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(system, scmi_system)

drivers/firmware/arm_scmi/voltage.c

@@ -2,7 +2,7 @@
 /*
  * System Control and Management Interface (SCMI) Voltage Protocol
  *
- * Copyright (C) 2020 ARM Ltd.
+ * Copyright (C) 2020-2021 ARM Ltd.
  */
 
 #include <linux/scmi_protocol.h>
@@ -377,4 +377,10 @@ static int scmi_voltage_protocol_init(struct scmi_handle *handle)
 	return 0;
 }
 
-DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_VOLTAGE, voltage)
+static const struct scmi_protocol scmi_voltage = {
+	.id = SCMI_PROTOCOL_VOLTAGE,
+	.init = &scmi_voltage_protocol_init,
+	.ops = &voltage_ops,
+};
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(voltage, scmi_voltage)

include/linux/scmi_protocol.h

@@ -2,7 +2,7 @@
 /*
  * SCMI Message Protocol driver header
  *
- * Copyright (C) 2018 ARM Ltd.
+ * Copyright (C) 2018-2021 ARM Ltd.
  */
 
 #ifndef _LINUX_SCMI_PROTOCOL_H
@@ -712,9 +712,9 @@ static inline void scmi_driver_unregister(struct scmi_driver *driver) {}
 #define module_scmi_driver(__scmi_driver)	\
 	module_driver(__scmi_driver, scmi_register, scmi_unregister)
 
-typedef int (*scmi_prot_init_fn_t)(struct scmi_handle *);
-int scmi_protocol_register(int protocol_id, scmi_prot_init_fn_t fn);
-void scmi_protocol_unregister(int protocol_id);
+struct scmi_protocol;
+int scmi_protocol_register(const struct scmi_protocol *proto);
+void scmi_protocol_unregister(const struct scmi_protocol *proto);
 
 /* SCMI Notification API - Custom Event Reports */
 enum scmi_notification_events {