[PATCH v4 05/20] firmware: arm_scmi: add scmi protocol bus to enumerate protocol devices

[Sudeep Holla]

The SCMI specification encompasses various protocols. However, not every
protocol has to be present on a given platform/implementation as not
every protocol is relevant for it.

Furthermore, the platform chooses which protocols it exposes to a given
agent. The only protocol that must be implemented is the base protocol.
The base protocol is used by an agent to discover which protocols are
available to it.

In order to enumerate the discovered implemented protocols, this patch
adds support for a separate scmi protocol bus. It also adds mechanism to
register support for different protocols.

Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
 drivers/firmware/arm_scmi/Makefile |   3 +-
 drivers/firmware/arm_scmi/bus.c    | 232 +++++++++++++++++++++++++++++++++++++
 drivers/firmware/arm_scmi/common.h |   1 +
 include/linux/scmi_protocol.h      |  62 ++++++++++
 4 files changed, 297 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/arm_scmi/bus.c

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index 5d9c7ef35f0f..5f4ec2613db6 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -1,3 +1,4 @@
-obj-y	= scmi-driver.o scmi-protocols.o
+obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o
+scmi-bus-y = bus.o
 scmi-driver-y = driver.o
 scmi-protocols-y = base.o
diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
new file mode 100644
index 000000000000..40c72a35fc99
--- /dev/null
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -0,0 +1,232 @@
+/*
+ * System Control and Management Interface (SCMI) Message Protocol bus layer
+ *
+ * Copyright (C) 2017 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+
+#include "common.h"
+
+static DEFINE_IDA(scmi_bus_id);
+static DEFINE_IDR(scmi_protocols);
+static DEFINE_SPINLOCK(protocol_lock);
+
+static const struct scmi_device_id *
+scmi_dev_match_id(struct scmi_device *scmi_dev, struct scmi_driver *scmi_drv)
+{
+	const struct scmi_device_id *id = scmi_drv->id_table;
+
+	if (!id)
+		return NULL;
+
+	for (; id->protocol_id; id++)
+		if (id->protocol_id == scmi_dev->protocol_id)
+			return id;
+
+	return NULL;
+}
+
+static int scmi_dev_match(struct device *dev, struct device_driver *drv)
+{
+	struct scmi_driver *scmi_drv = to_scmi_driver(drv);
+	struct scmi_device *scmi_dev = to_scmi_dev(dev);
+	const struct scmi_device_id *id;
+
+	id = scmi_dev_match_id(scmi_dev, scmi_drv);
+	if (id)
+		return 1;
+
+	return 0;
+}
+
+static int scmi_protocol_init(int protocol_id, struct scmi_handle *handle)
+{
+	scmi_prot_init_fn_t fn = idr_find(&scmi_protocols, protocol_id);
+
+	if (unlikely(!fn))
+		return -EINVAL;
+	return fn(handle);
+}
+
+static int scmi_dev_probe(struct device *dev)
+{
+	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
+	struct scmi_device *scmi_dev = to_scmi_dev(dev);
+	const struct scmi_device_id *id;
+	int ret;
+
+	id = scmi_dev_match_id(scmi_dev, scmi_drv);
+	if (!id)
+		return -ENODEV;
+
+	if (!scmi_dev->handle)
+		return -EPROBE_DEFER;
+
+	ret = scmi_protocol_init(scmi_dev->protocol_id, scmi_dev->handle);
+	if (ret)
+		return ret;
+
+	return scmi_drv->probe(scmi_dev);
+}
+
+static int scmi_dev_remove(struct device *dev)
+{
+	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
+	struct scmi_device *scmi_dev = to_scmi_dev(dev);
+
+	if (scmi_drv->remove)
+		scmi_drv->remove(scmi_dev);
+
+	return 0;
+}
+
+static struct bus_type scmi_bus_type = {
+	.name =	"scmi_protocol",
+	.match = scmi_dev_match,
+	.probe = scmi_dev_probe,
+	.remove = scmi_dev_remove,
+};
+
+int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
+			 const char *mod_name)
+{
+	int retval;
+
+	driver->driver.bus = &scmi_bus_type;
+	driver->driver.name = driver->name;
+	driver->driver.owner = owner;
+	driver->driver.mod_name = mod_name;
+
+	retval = driver_register(&driver->driver);
+	if (!retval)
+		pr_debug("registered new scmi driver %s\n", driver->name);
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(scmi_driver_register);
+
+void scmi_driver_unregister(struct scmi_driver *driver)
+{
+	driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(scmi_driver_unregister);
+
+struct scmi_device *
+scmi_device_create(struct device_node *np, struct device *parent, int protocol)
+{
+	int id, retval;
+	struct scmi_device *scmi_dev;
+
+	id = ida_simple_get(&scmi_bus_id, 1, 0, GFP_KERNEL);
+	if (id < 0)
+		return NULL;
+
+	scmi_dev = kzalloc(sizeof(*scmi_dev), GFP_KERNEL);
+	if (!scmi_dev)
+		goto no_mem;
+
+	scmi_dev->id = id;
+	scmi_dev->protocol_id = protocol;
+	scmi_dev->dev.parent = parent;
+	scmi_dev->dev.of_node = np;
+	scmi_dev->dev.bus = &scmi_bus_type;
+	dev_set_name(&scmi_dev->dev, "scmi_dev.%d", id);
+
+	retval = device_register(&scmi_dev->dev);
+	if (!retval)
+		return scmi_dev;
+
+	put_device(&scmi_dev->dev);
+	kfree(scmi_dev);
+no_mem:
+	ida_simple_remove(&scmi_bus_id, id);
+	return NULL;
+}
+
+void scmi_device_destroy(struct scmi_device *scmi_dev)
+{
+	scmi_handle_put(scmi_dev->handle);
+	device_unregister(&scmi_dev->dev);
+	ida_simple_remove(&scmi_bus_id, scmi_dev->id);
+	kfree(scmi_dev);
+}
+
+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 ret;
+
+	spin_lock(&protocol_lock);
+	ret = idr_alloc(&scmi_protocols, fn, protocol_id, protocol_id + 1,
+			GFP_KERNEL);
+	if (ret != protocol_id)
+		pr_err("unable to allocate SCMI idr slot, err %d\n", ret);
+	spin_unlock(&protocol_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(scmi_protocol_register);
+
+void scmi_protocol_unregister(int protocol_id)
+{
+	spin_lock(&protocol_lock);
+	idr_remove(&scmi_protocols, protocol_id);
+	spin_unlock(&protocol_lock);
+}
+EXPORT_SYMBOL_GPL(scmi_protocol_unregister);
+
+static int __scmi_devices_unregister(struct device *dev, void *data)
+{
+	struct scmi_device *scmi_dev = to_scmi_dev(dev);
+
+	scmi_device_destroy(scmi_dev);
+	return 0;
+}
+
+static void scmi_devices_unregister(void)
+{
+	bus_for_each_dev(&scmi_bus_type, NULL, NULL, __scmi_devices_unregister);
+}
+
+static int __init scmi_bus_init(void)
+{
+	int retval;
+
+	retval = bus_register(&scmi_bus_type);
+	if (retval)
+		pr_err("scmi protocol bus register failed (%d)\n", retval);
+
+	return retval;
+}
+subsys_initcall(scmi_bus_init);
+
+void __exit scmi_bus_exit(void)
+{
+	scmi_devices_unregister();
+	bus_unregister(&scmi_bus_type);
+	ida_destroy(&scmi_bus_id);
+}
+module_exit(scmi_bus_exit);
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index bc767f4997e0..f1eeacaef57b 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -107,6 +107,7 @@ int scmi_one_xfer_init(const struct scmi_handle *h, u8 msg_id, u8 prot_id,
 		       size_t tx_size, size_t rx_size, struct scmi_xfer **p);
 int scmi_handle_put(const struct scmi_handle *handle);
 struct scmi_handle *scmi_handle_get(struct device *dev);
+void scmi_set_handle(struct scmi_device *scmi_dev);
 int scmi_version_get(const struct scmi_handle *h, u8 protocol, u32 *version);
 void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
 				     u8 *prot_imp);
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 664da3d763f2..7b72c75cb560 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -15,6 +15,7 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */
+#include <linux/device.h>
 #include <linux/types.h>
 
 #define SCMI_MAX_STR_SIZE	16
@@ -62,3 +63,64 @@ enum scmi_std_protocol {
 	SCMI_PROTOCOL_CLOCK = 0x14,
 	SCMI_PROTOCOL_SENSOR = 0x15,
 };
+
+struct scmi_device {
+	u32 id;
+	u8 protocol_id;
+	struct device dev;
+	struct scmi_handle *handle;
+};
+
+#define to_scmi_dev(d) container_of(d, struct scmi_device, dev)
+
+struct scmi_device *
+scmi_device_create(struct device_node *np, struct device *parent, int protocol);
+void scmi_device_destroy(struct scmi_device *scmi_dev);
+
+struct scmi_device_id {
+	u8 protocol_id;
+};
+
+struct scmi_driver {
+	const char *name;
+	int (*probe)(struct scmi_device *);
+	void (*remove)(struct scmi_device *);
+	const struct scmi_device_id *id_table;
+
+	struct device_driver driver;
+};
+
+#define to_scmi_driver(d) container_of(d, struct scmi_driver, driver)
+
+#ifdef CONFIG_ARM_SCMI_PROTOCOL
+int scmi_driver_register(struct scmi_driver *driver,
+			 struct module *owner, const char *mod_name);
+void scmi_driver_unregister(struct scmi_driver *driver);
+#else
+static int scmi_driver_register(struct scmi_driver *driver,
+				struct module *owner, const char *mod_name)
+{
+	return -EINVAL;
+}
+static void scmi_driver_unregister(struct scmi_driver *driver) {}
+#endif /* CONFIG_ARM_SCMI_PROTOCOL */
+
+#define scmi_register(driver) \
+	scmi_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+#define scmi_unregister(driver) \
+	scmi_driver_unregister(driver)
+
+/**
+ * module_scmi_driver() - Helper macro for registering a scmi driver
+ * @__scmi_driver: scmi_driver structure
+ *
+ * Helper macro for scmi drivers to set up proper module init / exit
+ * functions.  Replaces module_init() and module_exit() and keeps people from
+ * printing pointless things to the kernel log when their driver is loaded.
+ */
+#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);
-- 
2.7.4