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.

[ser-io]

I'll remove this once rust-vmm/vhost/pull/339 is merged in.

[Databean]

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

[Databean]

What do you think of using the combined use x::{y, z} syntax more?

It supports multiple levels of nesting, e.g.

use std::{collections::HashMap, convert, io, os::{fd::BorrowedFd, unix::io::AsRawFd}};
...
use log::{error, info};
...

It's even possible to combine everything into a single use statement:

use {
  std::collection::HashMap,
  ...
  libc::{_SC_PAGESIZE, sysconf},
  log::{error, info},
};

The style guide also has some opinions, though they don't seem like strict rules.

[ser-io]

Done.

Preferred using multiple imports rather than a multi-line import and avoided modules within brackets as it makes it complicated to trace back the full import path for a given element.