Re: [PATCH v3 2/2] ftpm: add documentation for ftpm driver

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Mon, Apr 15, 2019 at 11:56:36AM -0400, Sasha Levin wrote:
> This patch adds basic documentation to describe the new fTPM driver.
> 
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
> ---
>  Documentation/security/tpm/index.rst        |  1 +
>  Documentation/security/tpm/tpm_ftpm_tee.rst | 31 +++++++++++++++++++++
>  2 files changed, 32 insertions(+)
>  create mode 100644 Documentation/security/tpm/tpm_ftpm_tee.rst
> 
> diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst
> index af77a7bbb070..15783668644f 100644
> --- a/Documentation/security/tpm/index.rst
> +++ b/Documentation/security/tpm/index.rst
> @@ -4,4 +4,5 @@ Trusted Platform Module documentation
>  
>  .. toctree::
>  
> +   tpm_ftpm_tee
>     tpm_vtpm_proxy
> diff --git a/Documentation/security/tpm/tpm_ftpm_tee.rst b/Documentation/security/tpm/tpm_ftpm_tee.rst
> new file mode 100644
> index 000000000000..29c2f8b5ed10
> --- /dev/null
> +++ b/Documentation/security/tpm/tpm_ftpm_tee.rst
> @@ -0,0 +1,31 @@
> +=============================================
> +Firmware TPM Driver
> +=============================================
> +
> +| Authors:
> +| Thirupathaiah Annapureddy <thiruan@microsoft.com>
> +| Sasha Levin <sashal@kernel.org>
> +
> +This document describes the firmware Trusted Platform Module (fTPM)
> +device driver.
> +
> +Introduction
> +============
> +
> +This driver is a shim for a firmware implemented in ARM's TrustZone
> +environment. The driver allows programs to interact with the TPM in the same
> +way the would interact with a hardware TPM.
> +
> +Design
> +======
> +
> +The driver acts as a thin layer that passes commands to and from a TPM
> +implemented in firmware. The driver itself doesn't contain much logic and is
> +used more like a dumb pipe between firmware and kernel/userspace.
> +
> +The firmware itself is based on the following paper:
> +https://www.microsoft.com/en-us/research/wp-content/uploads/2017/06/ftpm1.pdf
> +
> +When the driver is loaded it will expose ``/dev/tpmX`` character devices to
> +userspace which will enable userspace to communicate with the firmware tpm
> +through this device.
> -- 
> 2.19.1
> 

Actually this would a better place at least with some words to describe
what is TEE. I'm, for example, confused whether there is only single TEE
in existence always used with TZ or is this some MS specific TEE.

Otherwise, looks legit.

/Jarkko