Implement VirtIO sound device capture

Implement VirtIO sound device capture, with adding notice
that the capture usually doesn't work for the reason of 'semu'
emulation part.

Author: Cuda-Chen

.ci/test-sound.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# Source common functions and settings
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+export SCRIPT_DIR
+source "${SCRIPT_DIR}/common.sh"
+
+SAMPLE_SOUND="/usr/share/sounds/alsa/Front_Center.wav"
+
+TEST_SOUND() {
+    ASSERT expect <<DONE
+    set timeout ${TIMEOUT}
+    spawn make check
+    expect "buildroot login:" { send "root\\n" } timeout { exit 1 }
+    expect "# " { send "uname -a\\n" } timeout { exit 2 }
+
+    expect "riscv32 GNU/Linux" { send "aplay ${SAMPLE_SOUND} --fatal-errors > /dev/null\\n"} timeout { exit 3 }
+    expect "# " { send "aplay -C -d 3 --fatal-errors -f S16_LE > /dev/null"} timeout { exit 4 }
+    expect "# " { } timeout { exit 5 }
+DONE
+}
+
+# Clean up any existing semu processes before starting tests
+cleanup
+
+# Test sound device
+TEST_SOUND
+echo "✓ sound test passed"
+
+exit 0

.github/workflows/main.yml

@@ -69,6 +69,10 @@ jobs:
       run: sudo .ci/test-netdev.sh
       shell: bash
       timeout-minutes: 10
+    - name: sound test
+      run: .ci/test-sound.sh
+      shell: bash
+      timeout-minutes: 5
 
   semu-macOS:
     runs-on: macos-latest
@@ -118,6 +122,10 @@ jobs:
       shell: bash
       timeout-minutes: 20
       if: ${{ success() }}
+    - name: sound test
+      run: .ci/test-sound.sh
+      shell: bash
+      timeout-minutes: 20
 
   coding_style:
     runs-on: ubuntu-24.04

README.md

@@ -12,12 +12,13 @@ A minimalist RISC-V system emulator capable of running Linux the kernel and corr
 - Three types of I/O support using VirtIO standard:
     - virtio-blk acquires disk image from the host.
     - virtio-net is mapped as TAP interface.
-    - virtio-snd uses [PortAudio](https://github.com/PortAudio/portaudio) for sound playback on the host with one limitations:
-        - As some unknown issues in guest Linux OS (confirmed in v6.7 and v6.12), you need
-          to adjust the buffer size to more than four times of period size, or
-          the program cannot write the PCM frames into guest OS ALSA stack.
+    - virtio-snd uses [PortAudio](https://github.com/PortAudio/portaudio) for sound playback and capture on the host with one limitations:
+        - As a confirmed issue that `semu` cannot send/receive PCM frames in time, causing
+          the ALSA stack stuck in XRUN state until `semu` being rebooted.
+        - For playback, you can try to adjust the buffer size to more than four times of period size.
             - For instance, the following buffer/period size settings on `aplay` has been tested
               with broken and stutter effects yet complete with no any errors: `aplay --buffer-size=32768 --period-size=4096 /usr/share/sounds/alsa/Front_Center.wav`.
+        - For capture, ALSA usually stucks in XRUN state, so you may try more times and pray for your own luck. 
 
 ## Prerequisites