tee: add bus driver framework for TEE based devices

Introduce a generic TEE bus driver concept for TEE based kernel drivers
which would like to communicate with TEE based devices/services. Also
add support in module device table for these new TEE based devices.

In this TEE bus concept, devices/services are identified via Universally
Unique Identifier (UUID) and drivers register a table of device UUIDs
which they can support.

So this TEE bus framework registers following apis:
- match(): Iterates over the driver UUID table to find a corresponding
  match for device UUID. If a match is found, then this particular device
  is probed via corresponding probe api registered by the driver. This
  process happens whenever a device or a driver is registered with TEE
  bus.
- uevent(): Notifies user-space (udev) whenever a new device is registered
  on this bus for auto-loading of modularized drivers.

Also this framework allows for device enumeration to be specific to
corresponding TEE implementation like OP-TEE etc.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/tee_core.c

@@ -15,7 +15,6 @@
 #define pr_fmt(fmt) "%s: " fmt, __func__
 
 #include <linux/cdev.h>
-#include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/idr.h>
 #include <linux/module.h>
@@ -1040,6 +1039,39 @@ int tee_client_invoke_func(struct tee_context *ctx,
 }
 EXPORT_SYMBOL_GPL(tee_client_invoke_func);
 
+static int tee_client_device_match(struct device *dev,
+				   struct device_driver *drv)
+{
+	const struct tee_client_device_id *id_table;
+	struct tee_client_device *tee_device;
+
+	id_table = to_tee_client_driver(drv)->id_table;
+	tee_device = to_tee_client_device(dev);
+
+	while (!uuid_is_null(&id_table->uuid)) {
+		if (uuid_equal(&tee_device->id.uuid, &id_table->uuid))
+			return 1;
+		id_table++;
+	}
+
+	return 0;
+}
+
+static int tee_client_device_uevent(struct device *dev,
+				    struct kobj_uevent_env *env)
+{
+	uuid_t *dev_id = &to_tee_client_device(dev)->id.uuid;
+
+	return add_uevent_var(env, "MODALIAS=tee:%pUb", dev_id);
+}
+
+struct bus_type tee_bus_type = {
+	.name		= "tee",
+	.match		= tee_client_device_match,
+	.uevent		= tee_client_device_uevent,
+};
+EXPORT_SYMBOL_GPL(tee_bus_type);
+
 static int __init tee_init(void)
 {
 	int rc;
@@ -1053,18 +1085,32 @@ static int __init tee_init(void)
 	rc = alloc_chrdev_region(&tee_devt, 0, TEE_NUM_DEVICES, "tee");
 	if (rc) {
 		pr_err("failed to allocate char dev region\n");
-		class_destroy(tee_class);
-		tee_class = NULL;
+		goto out_unreg_class;
 	}
 
+	rc = bus_register(&tee_bus_type);
+	if (rc) {
+		pr_err("failed to register tee bus\n");
+		goto out_unreg_chrdev;
+	}
+
+	return 0;
+
+out_unreg_chrdev:
+	unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);
+out_unreg_class:
+	class_destroy(tee_class);
+	tee_class = NULL;
+
 	return rc;
 }
 
 static void __exit tee_exit(void)
 {
+	bus_unregister(&tee_bus_type);
+	unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);
 	class_destroy(tee_class);
 	tee_class = NULL;
-	unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);
 }
 
 subsys_initcall(tee_init);