From 05a959d7039d10af00dc4585825357439df22800 Mon Sep 17 00:00:00 2001
From: Dorinda Bassey <dbassey@redhat.com>
Date: Fri, 26 May 2023 17:44:05 +0200
Subject: [PATCH] sound: add PipeWire backend skeleton

to enable the pipewire backend feature, build with `--features pw-backend`

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>
---
 Cargo.lock                                    | 346 +++++++++++++++++-
 crates/sound/Cargo.toml                       |   6 +
 crates/sound/src/audio_backends.rs            |   7 +
 crates/sound/src/audio_backends/pw_backend.rs |  28 ++
 crates/sound/src/virtio_sound.rs              |   2 +-
 5 files changed, 370 insertions(+), 19 deletions(-)
 create mode 100644 crates/sound/src/audio_backends/pw_backend.rs

diff --git a/Cargo.lock b/Cargo.lock
index b22025e..f5f0a78 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11,6 +11,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.71"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
+
 [[package]]
 name = "arc-swap"
 version = "1.6.0"
@@ -45,6 +51,28 @@ dependencies = [
  "which",
 ]
 
+[[package]]
+name = "bindgen"
+version = "0.64.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4243e6031260db77ede97ad86c27e501d646a27ab57b59a574f725d98ab1fb4"
+dependencies = [
+ "bitflags",
+ "cexpr",
+ "clang-sys",
+ "lazy_static",
+ "lazycell",
+ "log",
+ "peeking_take_while",
+ "proc-macro2",
+ "quote",
+ "regex",
+ "rustc-hash",
+ "shlex",
+ "syn",
+ "which",
+]
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -72,6 +100,16 @@ dependencies = [
  "nom",
 ]
 
+[[package]]
+name = "cfg-expr"
+version = "0.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c8790cf1286da485c72cf5fc7aeba308438800036ec67d89425924c4807268c9"
+dependencies = [
+ "smallvec",
+ "target-lexicon",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -126,6 +164,12 @@ dependencies = [
  "os_str_bytes",
 ]
 
+[[package]]
+name = "cookie-factory"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "396de984970346b0d9e93d1415082923c679e5ae5c3ee3dcbd104f5610af126b"
+
 [[package]]
 name = "dashmap"
 version = "5.4.0"
@@ -179,6 +223,17 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "errno"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4bcfec3a70f97c962c307b2d2c56e358cf1d00b558d74262b5f929ee8cc7e73a"
+dependencies = [
+ "errno-dragonfly",
+ "libc",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "errno-dragonfly"
 version = "0.1.2"
@@ -338,6 +393,16 @@ version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
 
+[[package]]
+name = "indexmap"
+version = "1.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bd070e393353796e801d209ad339e89596eb4c8d430d18ede6a1cced8fafbd99"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.12"
@@ -399,7 +464,7 @@ name = "libgpiod"
 version = "0.1.0"
 source = "git+https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/?rev=d8d3a84b2ddf#d8d3a84b2ddfc29670430fc73ff8483a44b8f61e"
 dependencies = [
- "errno",
+ "errno 0.2.8",
  "intmap",
  "libc",
  "libgpiod-sys",
@@ -411,7 +476,7 @@ name = "libgpiod-sys"
 version = "0.1.0"
 source = "git+https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/?rev=d8d3a84b2ddf#d8d3a84b2ddfc29670430fc73ff8483a44b8f61e"
 dependencies = [
- "bindgen",
+ "bindgen 0.63.0",
  "cc",
 ]
 
@@ -425,6 +490,33 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "libspa"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "667dfbb50c3d1f7ee1d33afdc04d1255923ece7642db3303046e7d63d997d77d"
+dependencies = [
+ "bitflags",
+ "cc",
+ "cookie-factory",
+ "errno 0.3.1",
+ "libc",
+ "libspa-sys",
+ "nom",
+ "system-deps",
+]
+
+[[package]]
+name = "libspa-sys"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "79cf5b88f52534df7ca88d451ae9628e22124e3cc5c60966465a7db479534c7a"
+dependencies = [
+ "bindgen 0.64.0",
+ "cc",
+ "system-deps",
+]
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.1.4"
@@ -456,12 +548,35 @@ version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 
+[[package]]
+name = "memoffset"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5de893c32cde5f383baa4c04c5d6dbdd735cfd4a794b0debdb2bb1b421da5ff4"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
 
+[[package]]
+name = "nix"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bfdda3d196821d6af13126e40375cdf7da646a96114af134d5f417a9a1dc8e1a"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "libc",
+ "memoffset",
+ "pin-utils",
+ "static_assertions",
+]
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -535,6 +650,41 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
+[[package]]
+name = "pipewire"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc2180a4a84b855be86e6cd72fa6fd4318278871d2b1082e7cd05fe64b135ccb"
+dependencies = [
+ "anyhow",
+ "bitflags",
+ "errno 0.3.1",
+ "libc",
+ "libspa",
+ "libspa-sys",
+ "nix",
+ "once_cell",
+ "pipewire-sys",
+ "thiserror",
+]
+
+[[package]]
+name = "pipewire-sys"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a95290eedb7fb6aa3922fdc0261cd0ddeb940abcdbdef28778928106554d2123"
+dependencies = [
+ "bindgen 0.64.0",
+ "libspa-sys",
+ "system-deps",
+]
+
+[[package]]
+name = "pkg-config"
+version = "0.3.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26072860ba924cbfa98ea39c8c19b4dd6a4a25423dbdf219c1eca91aa0cf6964"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.17"
@@ -652,7 +802,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fd5c6ff11fecd55b40746d1995a02f2eb375bf8c00d192d521ee09f42bef37bc"
 dependencies = [
  "bitflags",
- "errno",
+ "errno 0.2.8",
  "io-lifetimes",
  "libc",
  "linux-raw-sys",
@@ -665,6 +815,21 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "serde"
+version = "1.0.163"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2113ab51b87a539ae008b5c6c02dc020ffa39afd2d83cffcb3f4eb2722cebec2"
+
+[[package]]
+name = "serde_spanned"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93107647184f6027e3b7dcb2e11034cf95ffa1e3a682c67951963ac69c1c007d"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "serial_test"
 version = "1.0.0"
@@ -711,6 +876,12 @@ version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
 
+[[package]]
+name = "static_assertions"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
+
 [[package]]
 name = "strsim"
 version = "0.10.0"
@@ -728,6 +899,25 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "system-deps"
+version = "6.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5fa6fb9ee296c0dc2df41a656ca7948546d061958115ddb0bcaae43ad0d17d2"
+dependencies = [
+ "cfg-expr",
+ "heck",
+ "pkg-config",
+ "toml",
+ "version-compare",
+]
+
+[[package]]
+name = "target-lexicon"
+version = "0.12.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd1ba337640d60c3e96bc6f0638a939b9c9a7f2c316a1598c279828b3d1dc8c5"
+
 [[package]]
 name = "tempfile"
 version = "3.4.0"
@@ -770,12 +960,52 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "toml"
+version = "0.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6135d499e69981f9ff0ef2167955a5333c35e36f6937d382974566b3d5b94ec"
+dependencies = [
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_edit",
+]
+
+[[package]]
+name = "toml_datetime"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a76a9312f5ba4c2dec6b9161fdf25d87ad8a09256ccea5a556fef03c706a10f"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "toml_edit"
+version = "0.19.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2380d56e8670370eee6566b0bfd4265f65b3f432e8c6d85623f728d4fa31f739"
+dependencies = [
+ "indexmap",
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "winnow",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "84a22b9f218b40614adcb3f4ff08b703773ad44fa9423e4e0d346d5db86e4ebc"
 
+[[package]]
+name = "version-compare"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "579a42fc0b8e0c63b76519a339be31bed574929511fa53c1a3acae26eb258f29"
+
 [[package]]
 name = "version_check"
 version = "0.9.4"
@@ -868,9 +1098,14 @@ dependencies = [
 name = "vhost-user-sound"
 version = "0.1.0"
 dependencies = [
+ "bindgen 0.64.0",
  "clap",
  "env_logger",
+ "libspa",
+ "libspa-sys",
  "log",
+ "pipewire",
+ "pipewire-sys",
  "serial_test",
  "thiserror",
  "vhost",
@@ -1011,13 +1246,13 @@ version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
 dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.42.1",
+ "windows_aarch64_msvc 0.42.2",
+ "windows_i686_gnu 0.42.1",
+ "windows_i686_msvc 0.42.1",
+ "windows_x86_64_gnu 0.42.1",
+ "windows_x86_64_gnullvm 0.42.2",
+ "windows_x86_64_msvc 0.42.1",
 ]
 
 [[package]]
@@ -1026,7 +1261,16 @@ version = "0.45.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "75283be5efb2831d37ea142365f009c02ec203cd29a3ebecbc093d52315b66d0"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.42.1",
+]
+
+[[package]]
+name = "windows-sys"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
+dependencies = [
+ "windows-targets 0.48.0",
 ]
 
 [[package]]
@@ -1035,13 +1279,28 @@ version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8e2522491fbfcd58cc84d47aeb2958948c4b8982e9a2d8a2a35bbaed431390e7"
 dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.42.1",
+ "windows_aarch64_msvc 0.42.2",
+ "windows_i686_gnu 0.42.1",
+ "windows_i686_msvc 0.42.1",
+ "windows_x86_64_gnu 0.42.1",
+ "windows_x86_64_gnullvm 0.42.2",
+ "windows_x86_64_msvc 0.42.1",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b1eb6f0cd7c80c79759c929114ef071b87354ce476d9d94271031c0497adfd5"
+dependencies = [
+ "windows_aarch64_gnullvm 0.48.0",
+ "windows_aarch64_msvc 0.48.0",
+ "windows_i686_gnu 0.48.0",
+ "windows_i686_msvc 0.48.0",
+ "windows_x86_64_gnu 0.48.0",
+ "windows_x86_64_gnullvm 0.48.0",
+ "windows_x86_64_msvc 0.48.0",
 ]
 
 [[package]]
@@ -1050,38 +1309,89 @@ version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8c9864e83243fdec7fc9c5444389dcbbfd258f745e7853198f365e3c4968a608"
 
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91ae572e1b79dba883e0d315474df7305d12f569b400fcf90581b06062f7e1bc"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e08e8864a60f06ef0d0ff4ba04124db8b0fb3be5776a5cd47641e942e58c4d43"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2ef27e0d7bdfcfc7b868b317c1d32c641a6fe4629c171b8928c7b08d98d7cf3"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "de3887528ad530ba7bdbb1faa8275ec7a1155a45ffa57c37993960277145d640"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "622a1962a7db830d6fd0a69683c80a18fda201879f0f447f065a3b7467daa241"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bf4d1122317eddd6ff351aa852118a2418ad4214e6613a50e0191f7004372605"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4542c6e364ce21bf45d69fdd2a8e455fa38d316158cfd43b3ac1c5b1b19f8e00"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c1040f221285e17ebccbc2591ffdc2d44ee1f9186324dd3e84e99ac68d699c45"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca2b8a661f7628cbd23440e50b05d705db3686f894fc9580820623656af974b1"
+
 [[package]]
 name = "windows_x86_64_gnullvm"
 version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "26d41b46a36d453748aedef1486d5c7a85db22e56aff34643984ea85514e94a3"
 
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7896dbc1f41e08872e9d5e8f8baa8fdd2677f29468c4e156210174edc7f7b953"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.42.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "447660ad36a13288b1db4d4248e857b510e8c3a225c822ba4fb748c0aafecffd"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a515f5799fe4961cb532f983ce2b23082366b898e52ffbce459c86f67c8378a"
+
+[[package]]
+name = "winnow"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61de7bac303dc551fe038e2b3cef0f571087a47571ea6e79a87692ac99b99699"
+dependencies = [
+ "memchr",
+]
diff --git a/crates/sound/Cargo.toml b/crates/sound/Cargo.toml
index 0d36703..927aa40 100644
--- a/crates/sound/Cargo.toml
+++ b/crates/sound/Cargo.toml
@@ -12,6 +12,7 @@ edition = "2018"
 [features]
 default = ["null-backend"]
 null-backend = []
+pw-backend = ["pipewire", "libspa", "pipewire-sys", "libspa-sys", "bindgen"]
 
 [dependencies]
 clap = { version = "4.1",  features = ["derive"] }
@@ -23,6 +24,11 @@ vhost-user-backend = "0.8"
 virtio-bindings = "0.2"
 vm-memory = "0.10"
 vmm-sys-util = "0.11"
+pipewire = { version = "0.6.0", optional = true }
+libspa = { version = "0.6.0", optional = true }
+pipewire-sys = { version = "0.6.0", optional = true }
+libspa-sys = { version = "0.6.0", optional = true }
+bindgen = { version = "0.64.0", optional = true }
 
 [dev-dependencies]
 serial_test = "1.0"
diff --git a/crates/sound/src/audio_backends.rs b/crates/sound/src/audio_backends.rs
index 2ac2db4..18f3bed 100644
--- a/crates/sound/src/audio_backends.rs
+++ b/crates/sound/src/audio_backends.rs
@@ -3,8 +3,13 @@
 #[cfg(feature = "null-backend")]
 mod null;
 
+#[cfg(feature = "pw-backend")]
+mod pw_backend;
+
 #[cfg(feature = "null-backend")]
 use self::null::NullBackend;
+#[cfg(feature = "pw-backend")]
+use self::pw_backend::PwBackend;
 use crate::{Error, Result, SoundRequest};
 
 pub trait AudioBackend {
@@ -17,6 +22,8 @@ pub fn alloc_audio_backend(name: String) -> Result<Box<dyn AudioBackend + Send +
     match name.as_str() {
         #[cfg(feature = "null-backend")]
         "null" => Ok(Box::new(NullBackend::new())),
+        #[cfg(feature = "pw-backend")]
+        "pipewire" => Ok(Box::new(PwBackend::new())),
         _ => Err(Error::AudioBackendNotSupported),
     }
 }
diff --git a/crates/sound/src/audio_backends/pw_backend.rs b/crates/sound/src/audio_backends/pw_backend.rs
new file mode 100644
index 0000000..a939365
--- /dev/null
+++ b/crates/sound/src/audio_backends/pw_backend.rs
@@ -0,0 +1,28 @@
+// Pipewire backend device
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use super::AudioBackend;
+use crate::{Error, Result, SoundRequest};
+
+pub struct PwBackend {}
+
+impl PwBackend {
+    pub fn new() -> Self {
+        PwBackend {}
+    }
+}
+
+impl AudioBackend for PwBackend {
+    fn write(&self, _req: &SoundRequest) -> Result<()> {
+        Ok(())
+    }
+
+    fn read(&self, req: &mut SoundRequest) -> Result<()> {
+        let buf = req.data_slice().ok_or(Error::SoundReqMissingData)?;
+        let zero_mem = vec![0u8; buf.len()];
+
+        buf.copy_from(&zero_mem);
+
+        Ok(())
+    }
+}
diff --git a/crates/sound/src/virtio_sound.rs b/crates/sound/src/virtio_sound.rs
index e38ddc7..484c06e 100644
--- a/crates/sound/src/virtio_sound.rs
+++ b/crates/sound/src/virtio_sound.rs
@@ -342,4 +342,4 @@ pub struct VirtioSoundChmapInfo {
 }
 // SAFETY: The layout of the structure is fixed and can be initialized by
 // reading its content from byte array.
-unsafe impl ByteValued for VirtioSoundChmapInfo {}
\ No newline at end of file
+unsafe impl ByteValued for VirtioSoundChmapInfo {}