GSoC Weekly Report #5

Weekly Report #5
Submitted on 2010-06-21
Covers 2010-06-14 to 2010-06-21
Corresponding Draft Schedule Item:
Create the RPC framework that can call functions on the GPP side from the DSP and return values back to the DSP.  Implement and unit-test the POSIX function wrappers according to the planned order.

Status and Accomplishments

• we now have a marshaller which takes a function name, signature and a variable number of arguments and packs them neatly into a buffer to be transferred via DSP/Link (as well as the corresponding unmarshaller :))
• all DSP-side stubs are reduced to three lines: rpc_marshal, rpc_invoke and return result, quite suitable for automation
• looked into shared memory issues some more without any fruitful effort; for now we'll enforce the user to pass buffer parameters allocated from shared areas only, and develop a better method later

Plans and Tasks

• unfortunately I managed to break C6RunApp's existing RTS I/O while trying to integrate the RPC server, I'll work on fixing this - it'll be nice to have both working, see issues section regarding possible shift of focus to general RPC instead of POSIX
• the static jump table design used for resolving rpc calls on the GPP right now is awful, write an assembly function launcher similar to the one in C6RunLib

Risks, issues, blockers

• shared memory issues continue, but for now we can overlook them since we can force the user to pass only buffers allocated from shared areas (POOL or CMEM). PROC address translation is there but we have to avoid segfaults / protection issues, this'll need a bit more time
• as I worked more and more with C6RunApp and the existing RTS C library implementation, I've realized that the available functionality is quite sufficient for prototyping purposes. so instead of replacing this with RPC POSIX calls, we can have both methods and leave the choice to the user. it also may be appropriate to shift the focus of the project on RPC issues, providing a library of examples which can be built up to useful code, or focusing on other ease-of-development issues.