Merge tag 'tee-bus-for-5.1' of https://git.linaro.org/people/jens.wiklander/linux-tee into arm/drivers

Introduce TEE bus driver framework

- supp_nowait flag for non-blocking tee requests
- The tee bus driver framework
- OP-TEE TEE bus device enumeration support
- An OP-TEE based rng driver

* tag 'tee-bus-for-5.1' of https://git.linaro.org/people/jens.wiklander/linux-tee:
  hwrng: add OP-TEE based rng driver
  tee: optee: add TEE bus device enumeration support
  tee: add bus driver framework for TEE based devices
  tee: add supp_nowait flag in tee_context struct

9 files changed, 549 insertions, 5 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index dac895dc01b9..25a7d8ffdb5d 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -424,6 +424,21 @@ config HW_RANDOM_EXYNOS
 	  will be called exynos-trng.
 
 	  If unsure, say Y.
+
+config HW_RANDOM_OPTEE
+	tristate "OP-TEE based Random Number Generator support"
+	depends on OPTEE
+	default HW_RANDOM
+	help
+	  This  driver provides support for OP-TEE based Random Number
+	  Generator on ARM SoCs where hardware entropy sources are not
+	  accessible to normal world (Linux).
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called optee-rng.
+
+	  If unsure, say Y.
+
 endif # HW_RANDOM
 
 config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index e35ec3ce3a20..7c9ef4a7667f 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -38,3 +38,4 @@ obj-$(CONFIG_HW_RANDOM_CAVIUM) += cavium-rng.o cavium-rng-vf.o
 obj-$(CONFIG_HW_RANDOM_MTK)	+= mtk-rng.o
 obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o
 obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o
+obj-$(CONFIG_HW_RANDOM_OPTEE) += optee-rng.o
diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
new file mode 100644
index 000000000000..2b9fc8ac5500
--- /dev/null
+++ b/drivers/char/hw_random/optee-rng.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018-2019 Linaro Ltd.
+ */
+
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/hw_random.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/tee_drv.h>
+#include <linux/uuid.h>
+
+#define DRIVER_NAME "optee-rng"
+
+#define TEE_ERROR_HEALTH_TEST_FAIL	0x00000001
+
+/*
+ * TA_CMD_GET_ENTROPY - Get Entropy from RNG
+ *
+ * param[0] (inout memref) - Entropy buffer memory reference
+ * param[1] unused
+ * param[2] unused
+ * param[3] unused
+ *
+ * Result:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ * TEE_ERROR_NOT_SUPPORTED - Requested entropy size greater than size of pool
+ * TEE_ERROR_HEALTH_TEST_FAIL - Continuous health testing failed
+ */
+#define TA_CMD_GET_ENTROPY		0x0
+
+/*
+ * TA_CMD_GET_RNG_INFO - Get RNG information
+ *
+ * param[0] (out value) - value.a: RNG data-rate in bytes per second
+ *                        value.b: Quality/Entropy per 1024 bit of data
+ * param[1] unused
+ * param[2] unused
+ * param[3] unused
+ *
+ * Result:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ */
+#define TA_CMD_GET_RNG_INFO		0x1
+
+#define MAX_ENTROPY_REQ_SZ		(4 * 1024)
+
+/**
+ * struct optee_rng_private - OP-TEE Random Number Generator private data
+ * @dev:		OP-TEE based RNG device.
+ * @ctx:		OP-TEE context handler.
+ * @session_id:		RNG TA session identifier.
+ * @data_rate:		RNG data rate.
+ * @entropy_shm_pool:	Memory pool shared with RNG device.
+ * @optee_rng:		OP-TEE RNG driver structure.
+ */
+struct optee_rng_private {
+	struct device *dev;
+	struct tee_context *ctx;
+	u32 session_id;
+	u32 data_rate;
+	struct tee_shm *entropy_shm_pool;
+	struct hwrng optee_rng;
+};
+
+#define to_optee_rng_private(r) \
+		container_of(r, struct optee_rng_private, optee_rng)
+
+static size_t get_optee_rng_data(struct optee_rng_private *pvt_data,
+				 void *buf, size_t req_size)
+{
+	u32 ret = 0;
+	u8 *rng_data = NULL;
+	size_t rng_size = 0;
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+
+	/* Invoke TA_CMD_GET_ENTROPY function of Trusted App */
+	inv_arg.func = TA_CMD_GET_ENTROPY;
+	inv_arg.session = pvt_data->session_id;
+	inv_arg.num_params = 4;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT;
+	param[0].u.memref.shm = pvt_data->entropy_shm_pool;
+	param[0].u.memref.size = req_size;
+	param[0].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(pvt_data->ctx, &inv_arg, param);
+	if ((ret < 0) || (inv_arg.ret != 0)) {
+		dev_err(pvt_data->dev, "TA_CMD_GET_ENTROPY invoke err: %x\n",
+			inv_arg.ret);
+		return 0;
+	}
+
+	rng_data = tee_shm_get_va(pvt_data->entropy_shm_pool, 0);
+	if (IS_ERR(rng_data)) {
+		dev_err(pvt_data->dev, "tee_shm_get_va failed\n");
+		return 0;
+	}
+
+	rng_size = param[0].u.memref.size;
+	memcpy(buf, rng_data, rng_size);
+
+	return rng_size;
+}
+
+static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+{
+	struct optee_rng_private *pvt_data = to_optee_rng_private(rng);
+	size_t read = 0, rng_size = 0;
+	int timeout = 1;
+	u8 *data = buf;
+
+	if (max > MAX_ENTROPY_REQ_SZ)
+		max = MAX_ENTROPY_REQ_SZ;
+
+	while (read == 0) {
+		rng_size = get_optee_rng_data(pvt_data, data, (max - read));
+
+		data += rng_size;
+		read += rng_size;
+
+		if (wait) {
+			if (timeout-- == 0)
+				return read;
+			msleep((1000 * (max - read)) / pvt_data->data_rate);
+		} else {
+			return read;
+		}
+	}
+
+	return read;
+}
+
+static int optee_rng_init(struct hwrng *rng)
+{
+	struct optee_rng_private *pvt_data = to_optee_rng_private(rng);
+	struct tee_shm *entropy_shm_pool = NULL;
+
+	entropy_shm_pool = tee_shm_alloc(pvt_data->ctx, MAX_ENTROPY_REQ_SZ,
+					 TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+	if (IS_ERR(entropy_shm_pool)) {
+		dev_err(pvt_data->dev, "tee_shm_alloc failed\n");
+		return PTR_ERR(entropy_shm_pool);
+	}
+
+	pvt_data->entropy_shm_pool = entropy_shm_pool;
+
+	return 0;
+}
+
+static void optee_rng_cleanup(struct hwrng *rng)
+{
+	struct optee_rng_private *pvt_data = to_optee_rng_private(rng);
+
+	tee_shm_free(pvt_data->entropy_shm_pool);
+}
+
+static struct optee_rng_private pvt_data = {
+	.optee_rng = {
+		.name		= DRIVER_NAME,
+		.init		= optee_rng_init,
+		.cleanup	= optee_rng_cleanup,
+		.read		= optee_rng_read,
+	}
+};
+
+static int get_optee_rng_info(struct device *dev)
+{
+	u32 ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+
+	/* Invoke TA_CMD_GET_RNG_INFO function of Trusted App */
+	inv_arg.func = TA_CMD_GET_RNG_INFO;
+	inv_arg.session = pvt_data.session_id;
+	inv_arg.num_params = 4;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT;
+
+	ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
+	if ((ret < 0) || (inv_arg.ret != 0)) {
+		dev_err(dev, "TA_CMD_GET_RNG_INFO invoke err: %x\n",
+			inv_arg.ret);
+		return -EINVAL;
+	}
+
+	pvt_data.data_rate = param[0].u.value.a;
+	pvt_data.optee_rng.quality = param[0].u.value.b;
+
+	return 0;
+}
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	if (ver->impl_id == TEE_IMPL_ID_OPTEE)
+		return 1;
+	else
+		return 0;
+}
+
+static int optee_rng_probe(struct device *dev)
+{
+	struct tee_client_device *rng_device = to_tee_client_device(dev);
+	int ret = 0, err = -ENODEV;
+	struct tee_ioctl_open_session_arg sess_arg = {0};
+
+	/* Open context with TEE driver */
+	pvt_data.ctx = tee_client_open_context(NULL, optee_ctx_match, NULL,
+					       NULL);
+	if (IS_ERR(pvt_data.ctx))
+		return -ENODEV;
+
+	/* Open session with hwrng Trusted App */
+	memcpy(sess_arg.uuid, rng_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
+	sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
+	sess_arg.num_params = 0;
+
+	ret = tee_client_open_session(pvt_data.ctx, &sess_arg, NULL);
+	if ((ret < 0) || (sess_arg.ret != 0)) {
+		dev_err(dev, "tee_client_open_session failed, err: %x\n",
+			sess_arg.ret);
+		err = -EINVAL;
+		goto out_ctx;
+	}
+	pvt_data.session_id = sess_arg.session;
+
+	err = get_optee_rng_info(dev);
+	if (err)
+		goto out_sess;
+
+	err = hwrng_register(&pvt_data.optee_rng);
+	if (err) {
+		dev_err(dev, "hwrng registration failed (%d)\n", err);
+		goto out_sess;
+	}
+
+	pvt_data.dev = dev;
+
+	return 0;
+
+out_sess:
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+out_ctx:
+	tee_client_close_context(pvt_data.ctx);
+
+	return err;
+}
+
+static int optee_rng_remove(struct device *dev)
+{
+	hwrng_unregister(&pvt_data.optee_rng);
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+	tee_client_close_context(pvt_data.ctx);
+
+	return 0;
+}
+
+const struct tee_client_device_id optee_rng_id_table[] = {
+	{UUID_INIT(0xab7a617c, 0xb8e7, 0x4d8f,
+		   0x83, 0x01, 0xd0, 0x9b, 0x61, 0x03, 0x6b, 0x64)},
+	{}
+};
+
+MODULE_DEVICE_TABLE(tee, optee_rng_id_table);
+
+static struct tee_client_driver optee_rng_driver = {
+	.id_table	= optee_rng_id_table,
+	.driver		= {
+		.name		= DRIVER_NAME,
+		.bus		= &tee_bus_type,
+		.probe		= optee_rng_probe,
+		.remove		= optee_rng_remove,
+	},
+};
+
+static int __init optee_rng_mod_init(void)
+{
+	return driver_register(&optee_rng_driver.driver);
+}
+
+static void __exit optee_rng_mod_exit(void)
+{
+	driver_unregister(&optee_rng_driver.driver);
+}
+
+module_init(optee_rng_mod_init);
+module_exit(optee_rng_mod_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sumit Garg <sumit.garg@linaro.org>");
+MODULE_DESCRIPTION("OP-TEE based random number generator driver");
diff --git a/drivers/tee/optee/Makefile b/drivers/tee/optee/Makefile
index 48d262ae2f04..56263ae3b1d7 100644
--- a/drivers/tee/optee/Makefile
+++ b/drivers/tee/optee/Makefile
@@ -5,3 +5,4 @@ optee-objs += call.o
 optee-objs += rpc.o
 optee-objs += supp.o
 optee-objs += shm_pool.o
+optee-objs += device.o
diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
index e5efce3c08e2..ac59c77841a4 100644
--- a/drivers/tee/optee/core.c
+++ b/drivers/tee/optee/core.c
@@ -634,6 +634,10 @@ static struct optee *optee_probe(struct device_node *np)
 	if (optee->sec_caps & OPTEE_SMC_SEC_CAP_DYNAMIC_SHM)
 		pr_info("dynamic shared memory is enabled\n");
 
+	rc = optee_enumerate_devices();
+	if (rc)
+		goto err;
+
 	pr_info("initialized driver\n");
 	return optee;
 err:
diff --git a/drivers/tee/optee/device.c b/drivers/tee/optee/device.c
new file mode 100644
index 000000000000..5e4938bbef2b
--- /dev/null
+++ b/drivers/tee/optee/device.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/tee_drv.h>
+#include <linux/uuid.h>
+#include "optee_private.h"
+
+/*
+ * Get device UUIDs
+ *
+ * [out]     memref[0]        Array of device UUIDs
+ *
+ * Return codes:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ * TEE_ERROR_SHORT_BUFFER - Output buffer size less than required
+ */
+#define PTA_CMD_GET_DEVICES		0x0
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	if (ver->impl_id == TEE_IMPL_ID_OPTEE)
+		return 1;
+	else
+		return 0;
+}
+
+static int get_devices(struct tee_context *ctx, u32 session,
+		       struct tee_shm *device_shm, u32 *shm_size)
+{
+	u32 ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+
+	/* Invoke PTA_CMD_GET_DEVICES function */
+	inv_arg.func = PTA_CMD_GET_DEVICES;
+	inv_arg.session = session;
+	inv_arg.num_params = 4;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = device_shm;
+	param[0].u.memref.size = *shm_size;
+	param[0].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(ctx, &inv_arg, param);
+	if ((ret < 0) || ((inv_arg.ret != TEEC_SUCCESS) &&
+			  (inv_arg.ret != TEEC_ERROR_SHORT_BUFFER))) {
+		pr_err("PTA_CMD_GET_DEVICES invoke function err: %x\n",
+		       inv_arg.ret);
+		return -EINVAL;
+	}
+
+	*shm_size = param[0].u.memref.size;
+
+	return 0;
+}
+
+static int optee_register_device(const uuid_t *device_uuid, u32 device_id)
+{
+	struct tee_client_device *optee_device = NULL;
+	int rc;
+
+	optee_device = kzalloc(sizeof(*optee_device), GFP_KERNEL);
+	if (!optee_device)
+		return -ENOMEM;
+
+	optee_device->dev.bus = &tee_bus_type;
+	dev_set_name(&optee_device->dev, "optee-clnt%u", device_id);
+	uuid_copy(&optee_device->id.uuid, device_uuid);
+
+	rc = device_register(&optee_device->dev);
+	if (rc) {
+		pr_err("device registration failed, err: %d\n", rc);
+		kfree(optee_device);
+	}
+
+	return rc;
+}
+
+int optee_enumerate_devices(void)
+{
+	const uuid_t pta_uuid =
+		UUID_INIT(0x7011a688, 0xddde, 0x4053,
+			  0xa5, 0xa9, 0x7b, 0x3c, 0x4d, 0xdf, 0x13, 0xb8);
+	struct tee_ioctl_open_session_arg sess_arg = {0};
+	struct tee_shm *device_shm = NULL;
+	const uuid_t *device_uuid = NULL;
+	struct tee_context *ctx = NULL;
+	u32 shm_size = 0, idx, num_devices = 0;
+	int rc;
+
+	/* Open context with OP-TEE driver */
+	ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
+	if (IS_ERR(ctx))
+		return -ENODEV;
+
+	/* Open session with device enumeration pseudo TA */
+	memcpy(sess_arg.uuid, pta_uuid.b, TEE_IOCTL_UUID_LEN);
+	sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
+	sess_arg.num_params = 0;
+
+	rc = tee_client_open_session(ctx, &sess_arg, NULL);
+	if ((rc < 0) || (sess_arg.ret != TEEC_SUCCESS)) {
+		/* Device enumeration pseudo TA not found */
+		rc = 0;
+		goto out_ctx;
+	}
+
+	rc = get_devices(ctx, sess_arg.session, NULL, &shm_size);
+	if (rc < 0 || !shm_size)
+		goto out_sess;
+
+	device_shm = tee_shm_alloc(ctx, shm_size,
+				   TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+	if (IS_ERR(device_shm)) {
+		pr_err("tee_shm_alloc failed\n");
+		rc = PTR_ERR(device_shm);
+		goto out_sess;
+	}
+
+	rc = get_devices(ctx, sess_arg.session, device_shm, &shm_size);
+	if (rc < 0)
+		goto out_shm;
+
+	device_uuid = tee_shm_get_va(device_shm, 0);
+	if (IS_ERR(device_uuid)) {
+		pr_err("tee_shm_get_va failed\n");
+		rc = PTR_ERR(device_uuid);
+		goto out_shm;
+	}
+
+	num_devices = shm_size / sizeof(uuid_t);
+
+	for (idx = 0; idx < num_devices; idx++) {
+		rc = optee_register_device(&device_uuid[idx], idx);
+		if (rc)
+			goto out_shm;
+	}
+
+out_shm:
+	tee_shm_free(device_shm);
+out_sess:
+	tee_client_close_session(ctx, sess_arg.session);
+out_ctx:
+	tee_client_close_context(ctx);
+
+	return rc;
+}
diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
index 35e79386c556..a5e84afd5013 100644
--- a/drivers/tee/optee/optee_private.h
+++ b/drivers/tee/optee/optee_private.h
@@ -28,6 +28,7 @@
 #define TEEC_ERROR_BAD_PARAMETERS	0xFFFF0006
 #define TEEC_ERROR_COMMUNICATION	0xFFFF000E
 #define TEEC_ERROR_OUT_OF_MEMORY	0xFFFF000C
+#define TEEC_ERROR_SHORT_BUFFER		0xFFFF0010
 
 #define TEEC_ORIGIN_COMMS		0x00000002
 
@@ -181,6 +182,8 @@ void optee_free_pages_list(void *array, size_t num_entries);
 void optee_fill_pages_list(u64 *dst, struct page **pages, int num_pages,
 			   size_t page_offset);
 
+int optee_enumerate_devices(void);
+
 /*
  * Small helpers
  */
diff --git a/drivers/tee/optee/supp.c b/drivers/tee/optee/supp.c
index 43626e15703a..92f56b8645e3 100644
--- a/drivers/tee/optee/supp.c
+++ b/drivers/tee/optee/supp.c
@@ -88,10 +88,18 @@ u32 optee_supp_thrd_req(struct tee_context *ctx, u32 func, size_t num_params,
 {
 	struct optee *optee = tee_get_drvdata(ctx->teedev);
 	struct optee_supp *supp = &optee->supp;
-	struct optee_supp_req *req = kzalloc(sizeof(*req), GFP_KERNEL);
+	struct optee_supp_req *req;
 	bool interruptable;
 	u32 ret;
 
+	/*
+	 * Return in case there is no supplicant available and
+	 * non-blocking request.
+	 */
+	if (!supp->ctx && ctx->supp_nowait)
+		return TEEC_ERROR_COMMUNICATION;
+
+	req = kzalloc(sizeof(*req), GFP_KERNEL);
 	if (!req)
 		return TEEC_ERROR_OUT_OF_MEMORY;
 
diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 7b2bb4c50058..25f3b9cc8908 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>
@@ -106,6 +105,11 @@ static int tee_open(struct inode *inode, struct file *filp)
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
+	/*
+	 * Default user-space behaviour is to wait for tee-supplicant
+	 * if not present for any requests in this context.
+	 */
+	ctx->supp_nowait = false;
 	filp->private_data = ctx;
 	return 0;
 }
@@ -982,6 +986,14 @@ tee_client_open_context(struct tee_context *start,
 	} while (IS_ERR(ctx) && PTR_ERR(ctx) != -ENOMEM);
 
 	put_device(put_dev);
+	/*
+	 * Default behaviour for in kernel client is to not wait for
+	 * tee-supplicant if not present for any requests in this context.
+	 * Also this flag could be configured again before call to
+	 * tee_client_open_session() if any in kernel client requires
+	 * different behaviour.
+	 */
+	ctx->supp_nowait = true;
 	return ctx;
 }
 EXPORT_SYMBOL_GPL(tee_client_open_context);
@@ -1027,6 +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;
@@ -1040,18 +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);