On Fri, 11 Jan 2019 at 20:39, Bhupesh Sharma [off-list ref] wrote:

Hi Sumit,

Thanks for the patch. Some nitpicks in-line:

Apologies for delay in my response as I was on leave. Please find my
comments inline.

Will include these nitpicks in v4 but let me wait for any further
major comments.

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

quoted

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;
+

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);

It seems that prior to this patch also allocation order in __init
function differed from release order in __exit function. Will correct
that too along with this.

quoted

      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);

Ok.

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

quoted

  }

  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.

Ok.

quoted

  /*
   * 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.

Agree, will rather use typedef here.

quoted

+
+/**
+ * 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.

Ok.

quoted

+#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.

Ok.

-Sumit

quoted

+#define to_tee_client_driver(d) \
+             container_of(d, struct tee_client_driver, driver)
+
  #endif /*__TEE_DRV_H*/

Thanks,
Bhupesh

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