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 <[email protected]>
Reviewed-by: Daniel Thompson <[email protected]>
Reviewed-by: Bhupesh Sharma <[email protected]>
Signed-off-by: Jens Wiklander <[email protected]>

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);

include/linux/mod_devicetable.h

@@ -779,4 +779,13 @@ struct typec_device_id {
 	kernel_ulong_t driver_data;
 };
 
+/**
+ * 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;
+};
+
 #endif /* LINUX_MOD_DEVICETABLE_H */

include/linux/tee_drv.h

@@ -15,11 +15,14 @@
 #ifndef __TEE_DRV_H
 #define __TEE_DRV_H
 
-#include <linux/types.h>
+#include <linux/device.h>
 #include <linux/idr.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/mod_devicetable.h>
 #include <linux/tee.h>
+#include <linux/types.h>
+#include <linux/uuid.h>
 
 /*
  * The file describes the API provided by the generic TEE driver to the
@@ -544,4 +547,31 @@ static inline bool tee_param_is_memref(struct tee_param *param)
 	}
 }
 
+extern struct bus_type tee_bus_type;
+
+/**
+ * struct tee_client_device - tee based device
+ * @id:			device identifier
+ * @dev:		device structure
+ */
+struct tee_client_device {
+	struct tee_client_device_id id;
+	struct device dev;
+};
+
+#define to_tee_client_device(d) container_of(d, struct tee_client_device, dev)
+
+/**
+ * struct tee_client_driver - tee client driver
+ * @id_table:		device id table supported by this driver
+ * @driver:		driver structure
+ */
+struct tee_client_driver {
+	const struct tee_client_device_id *id_table;
+	struct device_driver driver;
+};
+
+#define to_tee_client_driver(d) \
+		container_of(d, struct tee_client_driver, driver)
+
 #endif /*__TEE_DRV_H*/

scripts/mod/devicetable-offsets.c

@@ -225,5 +225,8 @@ int main(void)
 	DEVID_FIELD(typec_device_id, svid);
 	DEVID_FIELD(typec_device_id, mode);
 
+	DEVID(tee_client_device_id);
+	DEVID_FIELD(tee_client_device_id, uuid);
+
 	return 0;
 }

scripts/mod/file2alias.c

@@ -37,6 +37,9 @@ typedef unsigned char	__u8;
 typedef struct {
 	__u8 b[16];
 } uuid_le;
+typedef struct {
+	__u8 b[16];
+} uuid_t;
 
 /* Big exception to the "don't include kernel headers into userspace, which
  * even potentially has different endianness and word sizes, since
@@ -1287,6 +1290,21 @@ static int do_typec_entry(const char *filename, void *symval, char *alias)
 	return 1;
 }
 
+/* Looks like: tee:uuid */
+static int do_tee_entry(const char *filename, void *symval, char *alias)
+{
+	DEF_FIELD(symval, tee_client_device_id, uuid);
+
+	sprintf(alias, "tee:%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+		uuid.b[0], uuid.b[1], uuid.b[2], uuid.b[3], uuid.b[4],
+		uuid.b[5], uuid.b[6], uuid.b[7], uuid.b[8], uuid.b[9],
+		uuid.b[10], uuid.b[11], uuid.b[12], uuid.b[13], uuid.b[14],
+		uuid.b[15]);
+
+	add_wildcard(alias);
+	return 1;
+}
+
 /* Does namelen bytes of name exactly match the symbol? */
 static bool sym_is(const char *name, unsigned namelen, const char *symbol)
 {
@@ -1357,6 +1375,7 @@ static const struct devtable devtable[] = {
 	{"fslmc", SIZE_fsl_mc_device_id, do_fsl_mc_entry},
 	{"tbsvc", SIZE_tb_service_id, do_tbsvc_entry},
 	{"typec", SIZE_typec_device_id, do_typec_entry},
+	{"tee", SIZE_tee_client_device_id, do_tee_entry},
 };
 
 /* Create MODULE_ALIAS() statements.