Design and implement OBD-II userspace daemon

[ejvaughan]

Overview

The communication layer of the OBD-II API uses the ISO-TP transport protocol when creating a CAN socket. Only one process can be bound to a given send/receive ID pair at one time. As a result, multiple processes cannot use the API simultaneously. We can remedy this problem by implementing a userspace daemon that vends the API to interested clients.

Approach

We will use dbus to vend the OBD-II functionality to interested clients.

Example clients

• A logger that periodically logs diagnostic data to a file
• A command line interface that provides interactive querying of diagnostic data

Design

The dbus API that is exposed by the daemon still needs to be designed.

[ejvaughan]

The initial design and implementation of the userspace daemon is finished (2499b8dbe1a1305a6f3882d9243968c3b16bba21). We've opted not to use dbus. Instead, the daemon uses an extremely simple binary protocol documented in daemon.md.