A CAN bus controller driver using virtio.
We want to provide access to a CAN controllers to guests running on a hypervisor. Some of these guests may be real-time systems, so the specification of the virtio interface for CAN must contain informations allowing a deterministic usage.
This driver is the Linux device driver for the virtio-can virtual device, it will be the starting point to specify the virtio-can interface.
What we need is an API abstracting the inner working of a CAN controller to a virtualized device while still having a good performance.
We have to provide the guest module with some information about its paramaters provided by the host:
- Number of mailboxes
- Endianness
- CAN-id filters
Currently, these parameters will be statically defined in a device-tree file, or as a module loading parameter.
One of the things to keep in mind is that we want to run real-time tasks at some time, so the TX FIFOs have to be implemented in the host to provide the guests with a good responsivity. For the systems that don't support FIFOs, we can use the built-in virtio ring buffer to share the device while writing.
This driver will connect to the virtual device, setup the queues and mailboxes according to the parameters, and manage the network device for the SocketCAN subsystem.
This project has a 'code now, specify after' approach. After the Linux driver is done, it will be easier to create the spec based on the behaviour of the code.