linux-kernel - Re: [PATCH] Documentation: tee: Document TEE kernel interface

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Message-ID: <CAFA6WYNm+5NGODemHKxQXSNk4m+0P60kr=btTwp9q-6d_6-QPw@mail.gmail.com>
Date:   Thu, 4 Jun 2020 12:07:19 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Maxim Uvarov <maxim.uvarov@...aro.org>
Cc:     Jens Wiklander <jens.wiklander@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        "tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        op-tee@...ts.trustedfirmware.org
Subject: Re: [PATCH] Documentation: tee: Document TEE kernel interface

On Wed, 3 Jun 2020 at 20:05, Maxim Uvarov <maxim.uvarov@...aro.org> wrote:
>
> Hello Sumit,
>
> if this doc is for driver developers it might be useful to add some
> code examples how to register drivers on tee bus.

Sure, will add an example TEE client driver snippet for reference.

-Sumit

>
> Best regards,
> Maxim.
>
> On Wed, 3 Jun 2020 at 14:31, Sumit Garg <sumit.garg@...aro.org> wrote:
> >
> > Update documentation with TEE bus infrastructure which provides an
> > interface for kernel client drivers to communicate with corresponding
> > Trusted Application.
> >
> > Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
> > ---
> >  Documentation/tee.txt | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/Documentation/tee.txt b/Documentation/tee.txt
> > index c8fad81..428d3b5 100644
> > --- a/Documentation/tee.txt
> > +++ b/Documentation/tee.txt
> > @@ -53,6 +53,28 @@ clients, forward them to the TEE and send back the results. In the case of
> >  supplicants the communication goes in the other direction, the TEE sends
> >  requests to the supplicant which then sends back the result.
> >
> > +The TEE kernel interface
> > +========================
> > +
> > +Kernel provides a TEE bus infrastructure where a Trusted Application is
> > +represented as a device identified via Universally Unique Identifier (UUID) and
> > +client drivers register a table of supported device UUIDs.
> > +
> > +TEE bus infrastructure registers following APIs:
> > +-  match(): iterates over the client 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 client driver. This
> > +   process happens whenever a device or a client driver is registered with TEE
> > +   bus.
> > +-  uevent(): notifies user-space (udev) whenever a new device is registered on
> > +   TEE bus for auto-loading of modularized client drivers.
> > +
> > +TEE bus device enumeration is specific to underlying TEE implementation, so it
> > +is left open for TEE drivers to provide corresponding implementation.
> > +
> > +Then TEE client driver can talk to a matched Trusted Application using APIs
> > +listed in include/linux/tee_drv.h.
> > +
> >  OP-TEE driver
> >  =============
> >
> > @@ -112,6 +134,14 @@ kernel are handled by the kernel driver. Other RPC messages will be forwarded to
> >  tee-supplicant without further involvement of the driver, except switching
> >  shared memory buffer representation.
> >
> > +OP-TEE device enumeration
> > +-------------------------
> > +
> > +OP-TEE provides a pseudo Trusted Application: drivers/tee/optee/device.c in
> > +order to support device enumeration. In other words, OP-TEE driver invokes this
> > +application to retrieve a list of Trusted Applications which can be registered
> > +as devices on the TEE bus.
> > +
> >  AMD-TEE driver
> >  ==============
> >
> > --
> > 2.7.4
> >