Port virtio media simple device as a vhost user media device.

[ser-io]

Port virtio media reference device simple_device as a vhost user implementation.

First iteration of simple_device/src/simple_device.rs is the same as in virtio-media upstream https://github.com/chromeos/virtio-media/blob/main/device/src/devices/simple_device.rs.

cargo run --bin simple_device  -- --socket-path /tmp/simple_device.sock

cargo run --features "media" -- --log-level=debug run --cpus 4 --mem 4096 \
  --rwdisk /path/to/debian-12.img \
  --params "root=/dev/vda1" \
  --vhost-user media,socket=/tmp/simple_device.sock \
  /path/to/bzImage

v4l2-compliance -d0 -s

Bug: 445229097

[jemoreira]

Port virtio media reference device simple_device as a vhost user implementation.

First iteration of simple_device/src/simple_device.rs is the same as in virtio-media upstream https://github.com/chromeos/virtio-media/blob/main/device/src/devices/simple_device.rs.

Why are you copying this code here instead of depending on it? Would it be possible to contribute changes upstream and only implement the cuttlefish-specific changes here?

[ser-io]

Port virtio media reference device simple_device as a vhost user implementation.
First iteration of simple_device/src/simple_device.rs is the same as in virtio-media upstream https://github.com/chromeos/virtio-media/blob/main/device/src/devices/simple_device.rs.

Why are you copying this code here instead of depending on it? Would it be possible to contribute changes upstream and only implement the cuttlefish-specific changes here?

Removed the copy depending on the upstream implementation.

[Databean]

Some of the comments apply in multiple places, like reducing map_err usage in favor of automatic conversion with From.

[Databean]

The documentation for VirtioMediaDeviceSession writes

The preferred way to use this trait is to wrap implementations in a VirtioMediaDeviceRunner, which takes care of reading and dispatching commands.

The implementation of VirtioMediaDeviceRunner::handle_command looks quite similar to process_commandq_requests. Is it possible to use this common utility?

[Databean]

I can't really tell here, but is it possible to use a Box<dyn Xyz> for any of these traits? e.g.

sessions: HashMap<u32, Box<dyn VirtioMediaDeviceSession>>,
device: Option<Box<dyn for<'a> VirtioMediaDevice<Reader<'a>, Writer<'a>>>>,
create_device_fn: Box<dyn Fn(EventQueue, HostMemoryMapper) -> Box<dyn for<'a> VirtioMediaDevice<Reader<'a>, Writer<'a>>>>