vhost-device-sound: Add controls field in VirtioSoundConfig

This commit introduces a new controls field in
VirtioSoundConfig to represent the total number of
available control elements. It's based on the recent
changes to the virtio-snd header file in QEMU.

Fixes this issue:
https://gitlab.com/qemu-project/qemu/-/issues/2805

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>

vhost-device-sound/CHANGELOG.md

@@ -3,6 +3,7 @@
 
 ### Added
 
+- [[#806]](https://github.com/rust-vmm/vhost-device/pull/806) Add controls field in VirtioSoundConfig
 - [[#746]](https://github.com/rust-vmm/vhost-device/pull/746) Add new sampling rates 12000Hz and 24000Hz
 
 ### Changed

vhost-device-sound/src/device.rs

@@ -573,6 +573,7 @@ impl VhostUserSoundBackend {
                 jacks: 0.into(),
                 streams: Le32::from(streams_no as u32),
                 chmaps: 1.into(),
+                controls: 0.into(),
             },
             exit_event: EventFd::new(EFD_NONBLOCK).map_err(Error::EventFdCreate)?,
             audio_backend: RwLock::new(audio_backend),

vhost-device-sound/src/virtio_sound.rs

@@ -163,6 +163,8 @@ pub struct VirtioSoundConfig {
     pub streams: Le32,
     /// total number of all available channel maps
     pub chmaps: Le32,
+    /// total number of all available control elements
+    pub controls: Le32,
 }
 
 // SAFETY: The layout of the structure is fixed and can be initialized by
@@ -350,8 +352,9 @@ mod tests {
         let val = VirtioSoundConfig::default();
 
         let debug_output = format!("{:?}", val);
-        let expected_debug =
-            "VirtioSoundConfig { jacks: Le32(0), streams: Le32(0), chmaps: Le32(0) }".to_string();
+        let expected_debug = "VirtioSoundConfig { jacks: Le32(0), streams: Le32(0), chmaps: \
+                              Le32(0), controls: Le32(0) }"
+            .to_string();
         assert_eq!(debug_output, expected_debug);
 
         let val = VirtioSoundHeader::default();