Re: [Tee-dev] [PATCH v3 1/4] tee: add bus driver framework for TEE based devices

Hi Sumit,

Thanks for the patch. Some nitpicks in-line:

On 01/11/2019 05:17 PM, Sumit Garg wrote:

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 sumit.garg@linaro.org

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;

Hmm.. these error paths/labels look out-of-order. See 'drivers/i2c/i2c-dev.c' for example.

Normally our error paths in an __init function is of the same order as the __exit function implementation. So this should be changed to something like:

+out_unreg_class: + class_destroy(tee_class); + tee_class = NULL; +out_unreg_chrdev: + unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);

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);

Since the __exit function order is the reverse of the __init one, lets reorder this as:

+ bus_unregister(&tee_bus_type); class_destroy(tee_class); tee_class = NULL; unregister_chrdev_region(tee_devt, TEE_NUM_DEVICES);

See 'drivers/i2c/i2c-dev.c' for example.

} 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>

If possible, let's keep alphabetical order of header files when making changes in the patch.

/*

• 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;

+};

Hmm.. Do we really need a struct for a single element, rather lets use a simple typedef here.

+/**

• • 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;

+};

Add a blank line here.

+#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;

+};

Add a blank line here.

+#define to_tee_client_driver(d) \

• container_of(d, struct tee_client_driver, driver)
  

• #endif /*__TEE_DRV_H*/

Thanks, Bhupesh