linux-kernel - Re: [PATCH v2 1/4] tee: add bus driver framework for TEE based devices

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Date:   Thu, 10 Jan 2019 14:06:30 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, jens.wiklander@...aro.org,
        mpm@...enic.com, herbert@...dor.apana.org.au, robh+dt@...nel.org,
        mark.rutland@....com, arnd@...db.de, gregkh@...uxfoundation.org,
        ard.biesheuvel@...aro.org, bhsharma@...hat.com,
        tee-dev@...ts.linaro.org
Subject: Re: [PATCH v2 1/4] tee: add bus driver framework for TEE based
 devices

On Thu, Jan 10, 2019 at 05:54:54PM +0530, 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@...aro.org>
> ---
>  drivers/tee/tee_core.c  | 41 ++++++++++++++++++++++++++++++++++++++---
>  include/linux/tee_drv.h | 36 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 74 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 7b2bb4c..9ddb89e 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 +1063,21 @@ 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 class_err;
>  	}
>  
> +	rc = bus_register(&tee_bus_type);
> +	if (rc) {
> +		pr_err("failed to register tee bus\n");
> +		goto class_err;

There is an unregister_chrdev_region() in tee_exit(). Why isn't it
needed on this error path?


> +	}
> +
> +	return 0;
> +
> +class_err:
> +	class_destroy(tee_class);
> +	tee_class = NULL;
> +
>  	return rc;
>  }
>  
> @@ -1052,6 +1086,7 @@ 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;
> +};
> +
> +/**
> + * 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*/
> -- 
> 2.7.4
>