linux-kernel - Re: [PATCHv5 2/3] optee: use uuid for sysfs driver entry

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Message-ID: <CAFA6WYM3cg2Z2aB=0oO5mp6tXhVtvGZSTr5DTeaBvnpekH8aBA@mail.gmail.com>
Date:   Mon, 1 Jun 2020 15:47:49 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Maxim Uvarov <maxim.uvarov@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>,
        peterhuewe@....de,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        linux-integrity@...r.kernel.org, Arnd Bergmann <arnd@...aro.org>
Subject: Re: [PATCHv5 2/3] optee: use uuid for sysfs driver entry

On Fri, 29 May 2020 at 13:57, Maxim Uvarov <maxim.uvarov@...aro.org> wrote:
>
> OP-TEE device names for sysfs need to be unique
> and it's better if they will mean something. UUID for name
> looks like good solution:
> /sys/bus/tee/devices/optee-ta-<uuid>
>

I think this description is a little vague here which fails to explain
why we are doing this. How about:

=======
With the evolving use-cases for TEE bus, now it's required to support
multi-stage enumeration process. But using a simple index doesn't
suffice this requirement and instead leads to duplicate sysfs entries.
So instead switch to use more informative device UUID for sysfs entry
like:

/sys/bus/tee/devices/optee-ta-<uuid>
========

> Signed-off-by: Maxim Uvarov <maxim.uvarov@...aro.org>
> ---
>  Documentation/ABI/testing/sysfs-bus-optee-devices | 8 ++++++++
>  MAINTAINERS                                       | 2 ++
>  drivers/tee/optee/device.c                        | 6 +++---
>  3 files changed, 13 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-optee-devices
>

I think this patch belongs as patch #1 in this series given the dependency.

> diff --git a/Documentation/ABI/testing/sysfs-bus-optee-devices b/Documentation/ABI/testing/sysfs-bus-optee-devices
> new file mode 100644
> index 000000000000..0ae04ae5374a
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-optee-devices
> @@ -0,0 +1,8 @@
> +What:          /sys/bus/tee/devices/optee-ta-<uuid>/
> +Date:           May 2020
> +KernelVersion   5.7
> +Contact:        tee-dev@...ts.linaro.org
> +Description:
> +               OP-TEE bus provides reference to registered drivers under this directory. The <uuid>
> +               matches Trusted Application (TA) driver and corresponding TA in secure OS. Drivers
> +               are free to create needed API under optee-ta-<uuid> directory.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ecc0749810b0..52717ede29fc 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12516,8 +12516,10 @@ OP-TEE DRIVER
>  M:     Jens Wiklander <jens.wiklander@...aro.org>
>  L:     tee-dev@...ts.linaro.org
>  S:     Maintained
> +F:     Documentation/ABI/testing/sysfs-bus-optee-devices
>  F:     drivers/tee/optee/
>
> +

Unnecessary blank line.

-Sumit

>  OP-TEE RANDOM NUMBER GENERATOR (RNG) DRIVER
>  M:     Sumit Garg <sumit.garg@...aro.org>
>  L:     tee-dev@...ts.linaro.org
> diff --git a/drivers/tee/optee/device.c b/drivers/tee/optee/device.c
> index d4931dad07aa..2eb1c0283aec 100644
> --- a/drivers/tee/optee/device.c
> +++ b/drivers/tee/optee/device.c
> @@ -65,7 +65,7 @@ static int get_devices(struct tee_context *ctx, u32 session,
>         return 0;
>  }
>
> -static int optee_register_device(const uuid_t *device_uuid, u32 device_id)
> +static int optee_register_device(const uuid_t *device_uuid)
>  {
>         struct tee_client_device *optee_device = NULL;
>         int rc;
> @@ -75,7 +75,7 @@ static int optee_register_device(const uuid_t *device_uuid, u32 device_id)
>                 return -ENOMEM;
>
>         optee_device->dev.bus = &tee_bus_type;
> -       dev_set_name(&optee_device->dev, "optee-clnt%u", device_id);
> +       dev_set_name(&optee_device->dev, "optee-ta-%pUl", device_uuid);
>         uuid_copy(&optee_device->id.uuid, device_uuid);
>
>         rc = device_register(&optee_device->dev);
> @@ -144,7 +144,7 @@ static int __optee_enumerate_devices(u32 func)
>         num_devices = shm_size / sizeof(uuid_t);
>
>         for (idx = 0; idx < num_devices; idx++) {
> -               rc = optee_register_device(&device_uuid[idx], idx);
> +               rc = optee_register_device(&device_uuid[idx]);
>                 if (rc)
>                         goto out_shm;
>         }
> --
> 2.17.1
>