I2CMasterSlaveDriver: add write_read command.

[Vagabond]

Pull Request Overview

This pull request adds a libtock wrapper for the i2c write_read trait because previously it was not possible to call it from userland.

Testing Strategy

I tested using a Salae and the NRF52:

This was a i2c write-read transaction against a i2c EEPROM peripheral.

TODO or Help Wanted

This pull request should be ready to merge. The only question is the buffer overwrite behaviour of write_read. It is not clear if the received bytes are written to the beginning of the buffer, or written after the bytes that were transmitted. Currently we assume the received bytes are written starting at index 0 of the buffer.

Documentation Updated

• Kernel: The relevant files in /docs have been updated or no updates are required.
• Userland: The application README has been added, updated, or no updates are required.

Formatting

• make formatall has been run.

@JayKickliter also contributed to this.

[alevy]

Currently we assume the received bytes are written starting at index 0 of the buffer.

Reading the code for the SAM4L, this indeed appears to be the case. Sorry this isn't documented better 😞

[alevy]

LGTM!