linux-kernel - Re: [PATCH RFC 1/3] firmware: qcom: implement object invoke support

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Message-ID: <CAA8EJprp2veCaQq8GsYv4Mu1HQbx8nWv0XWtxcE4cu5kxkA16w@mail.gmail.com>
Date: Thu, 4 Jul 2024 10:34:28 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Amirreza Zarrabi <quic_azarrabi@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Sumit Semwal <sumit.semwal@...aro.org>, Christian König <christian.koenig@....com>, 
	srinivas.kandagatla@...aro.org, bartosz.golaszewski@...aro.org, 
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH RFC 1/3] firmware: qcom: implement object invoke support

On Thu, 4 Jul 2024 at 00:40, Amirreza Zarrabi <quic_azarrabi@...cinc.com> wrote:
>
>
>
> On 7/3/2024 10:13 PM, Dmitry Baryshkov wrote:
> > On Tue, Jul 02, 2024 at 10:57:36PM GMT, Amirreza Zarrabi wrote:
> >> Qualcomm TEE hosts Trusted Applications and Services that run in the
> >> secure world. Access to these resources is provided using object
> >> capabilities. A TEE client with access to the capability can invoke
> >> the object and request a service. Similarly, TEE can request a service
> >> from nonsecure world with object capabilities that are exported to secure
> >> world.
> >>
> >> We provide qcom_tee_object which represents an object in both secure
> >> and nonsecure world. TEE clients can invoke an instance of qcom_tee_object
> >> to access TEE. TEE can issue a callback request to nonsecure world
> >> by invoking an instance of qcom_tee_object in nonsecure world.
> >
> > Please see Documentation/process/submitting-patches.rst on how to write
> > commit messages.
>
> Ack.
>
> >
> >>
> >> Any driver in nonsecure world that is interested to export a struct (or a
> >> service object) to TEE, requires to embed an instance of qcom_tee_object in
> >> the relevant struct and implements the dispatcher function which is called
> >> when TEE invoked the service object.
> >>
> >> We also provids simplified API which implements the Qualcomm TEE transport
> >> protocol. The implementation is independent from any services that may
> >> reside in nonsecure world.
> >
> > "also" usually means that it should go to a separate commit.
>
> I will split this patch to multiple smaller ones.
>

[...]

> >
> >> +    } in, out;
> >> +};
> >> +
> >> +int qcom_tee_object_do_invoke(struct qcom_tee_object_invoke_ctx *oic,
> >> +    struct qcom_tee_object *object, unsigned long op, struct qcom_tee_arg u[], int *result);
> >
> > What's the difference between a result that gets returned by the
> > function and the result that gets retuned via the pointer?
>
> The function result, is local to kernel, for instance memory allocation failure,
> or failure to issue the smc call. The result in pointer, is the remote result,
> for instance return value from TA, or the TEE itself.
>
> I'll use better name, e.g. 'remote_result'?

See how this is handled by other parties. For example, PSCI. If you
have a standard set of return codes, translate them to -ESOMETHING in
your framework and let everybody else see only the standard errors.


-- 
With best wishes
Dmitry