Simplified OCALL

[jenswi-linaro]

Hi all,

This relates the ongoing OCALL work (#3673, linaro-swg/linux#72, OP-TEE/optee_client#171 and linaro-swg/optee_examples#64) where the Linux kernel driver implementation has become a bottleneck due to its complexity.

I'm proposing an alternative design with more focus on keeping down the complexity in the kernel driver implementation. The TEE Client API exposed to the client is supposed to be left more or less as it is in OP-TEE/optee_client#171. Same goes for the TA API exposed to the TA in #3673.

The design is currently just a rough sketch but I hope it should be enough to get the idea. This is described in the document Simplified OCALL, feel free to comment in the document or here whatever is most convenient for you.

[github-actions]

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