Introduce a generic TEE bus driver concept for TEE based kernel drivers
which would like to communicate with TEE based devices/services.

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 a match() callback function which
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.

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

Signed-off-by: Sumit Garg <redacted>
---
  drivers/tee/tee_core.c  | 43 ++++++++++++++++++++++++++++++++++++++++---
  include/linux/tee_drv.h | 36 ++++++++++++++++++++++++++++++++++++
  2 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 7b2bb4c..a685940 100644
--- a/drivers/tee/tee_core.c
+++ b/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>

@@ -1027,6 +1026,30 @@ 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)
+{
+	struct tee_client_device *tee_device;
+	const struct tee_client_device_id *id_table;
+
+	tee_device = to_tee_client_device(dev);
+	id_table = to_tee_client_driver(drv)->id_table;
+
+	while (!uuid_is_null(&id_table->uuid)) {
+		if (uuid_equal(&tee_device->id.uuid, &id_table->uuid))
+			return 1;
+		id_table++;
+	}
+
+	return 0;
+}
+
+struct bus_type tee_bus_type = {
+	.name		= "tee",
+	.match		= tee_client_device_match,
+};
+EXPORT_SYMBOL_GPL(tee_bus_type);
+
  static int __init tee_init(void)
  {
  	int rc;

@@ -1040,10 +1063,23 @@ 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 chrdev_err;
  	}
  
+	rc = bus_register(&tee_bus_type);
+	if (rc) {
+		pr_err("failed to register tee bus\n");
+		goto bus_err;
+	}
+
+	return 0;
+
+bus_err:
+	unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);
+chrdev_err:
+	class_destroy(tee_class);
+	tee_class = NULL;
+

  	return rc;
  }
  

@@ -1052,6 +1088,7 @@ static void __exit tee_exit(void)
  	class_destroy(tee_class);
  	tee_class = NULL;
  	unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);
+	bus_unregister(&tee_bus_type);

  }
  
  subsys_initcall(tee_init);

diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
index 6cfe058..ed16bf1 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h

@@ -20,6 +20,8 @@
  #include <linux/kref.h>
  #include <linux/list.h>
  #include <linux/tee.h>
+#include <linux/device.h>
+#include <linux/uuid.h>

  
  /*
   * The file describes the API provided by the generic TEE driver to the

@@ -538,4 +540,38 @@ static inline bool tee_param_is_memref(struct tee_param *param)
  	}
  }
  
+extern struct bus_type tee_bus_type;
+
+/**
+ * struct tee_client_device_id - tee based device identifier
+ * @uuid:		For TEE based client devices we use the device uuid
+ *			as the identifier.
+ */
+struct tee_client_device_id {
+	uuid_t uuid;
+};