ac97: switch to ShmStreamSource

Convert playback and capture for the AC97 device to use the zero-copy
ShmStreamSource instead of the old StreamSource.

In the process, rework start_playback and start_capture unit tests so
they rely less on sleep statements.

BUG=chromium:968724
BUG=chromium:1006035
TEST="sox -n -r 48000 -b 16 output.raw synth 5 sine 330 &&
     aplay -f dat output.raw" within a VM, check that sine wave is played
     accurately.

Change-Id: Ie9cddbc5285a9505872c9951a8a1da01de70eb88
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1749950
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Fletcher Woodruff <fletcherw@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Chih-Yang Hsia <paulhsia@chromium.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/sys_util/src/guest_memory.rs b/sys_util/src/guest_memory.rs
index 6399f8c..2390b92 100644
--- a/sys_util/src/guest_memory.rs
+++ b/sys_util/src/guest_memory.rs
@@ -4,6 +4,7 @@
 
 //! Track memory regions that are mapped to the guest VM.
 
+use std::convert::AsRef;
 use std::convert::TryFrom;
 use std::fmt::{self, Display};
 use std::os::unix::io::{AsRawFd, RawFd};
@@ -107,6 +108,12 @@ impl AsRawFd for GuestMemory {
     }
 }
 
+impl AsRef<SharedMemory> for GuestMemory {
+    fn as_ref(&self) -> &SharedMemory {
+        &self.memfd
+    }
+}
+
 impl GuestMemory {
     /// Creates backing memfd for GuestMemory regions
     fn create_memfd(ranges: &[(GuestAddress, u64)]) -> Result<SharedMemory> {