I2C sub-system

[Ivan-Velickovic]

I2C sub-system

• REQ_BUF_CLIENT and REQ_BUF_ADDR should be part of the shared ring buffer protocol instead as metadata.
• Too many files exist, it should really just be driver.c and server.c
• Clean up example system description file - lots of unused memory regions, needs comments as well
• Getting timeout IRQs way too frequently - these should never happen if everything is going smoothly
  to my understanding. (only happens on the card reader though)
• The I2C server needs to be fully designed and implemented. Right now the client talks directly to the driver.
• Remove all @ivanv notes.
  * [ ] Currently the I2C driver is responsible for setting up the clocks, etc. This is obviously wrong and should be
  done in pinctrl/regulator/clock drivers. However, this is not something we have right now.
• Should we abstract over doing things like writing to an I2C bus (e.g setting up all the transaction tokens)
• We should write a little client side API for claiming and release a bus.
  sDDF I2C example should use queue Makefile no more queue.c, no more Makefile!

Example client notes

• Timer driver integrated so we're not busy-waiting
• Figure out that extra response dequeue when we read_response
• What to do about just copying libco into the source
• More error-checking and cleanup is needed
• We are running out of return buffers fairly quickly, we must have a leak somewhere.
• Remove all warnings when compiling the example.

Driver notes

• Get rid of popBufRet abstractions, etc
• Too much global state and it's too fragile

Documentation

• The documentation is a great start but is a bit too verbose.
• Need picture of card-reader working and exactly what card reader is used (with links)
• Need to document that the card-reader client code is based of the Arduino PN532 library.