feat(audio): track a Feature Unit per stream direction

Associate one directly connected Feature Unit with each capture and playback stream. This lets applications control microphone and speaker paths independently.

Signed-off-by: HiFiPHile <[email protected]>

2 files changed, 10 insertions, 5 deletions

diff --git a/examples/host/audio_host/README.md b/examples/host/audio_host/README.md
index 2ad3f40d6..c7cad5bfa 100644
--- a/examples/host/audio_host/README.md
+++ b/examples/host/audio_host/README.md
@@ -20,6 +20,11 @@ This example supports any UAC 1.0 compliant USB audio device with a discrete sam
 
 The echo needs a matching S16_LE playback stream at the capture sample rate; devices without one run capture-only. The sample rate and channel preferences are configured by the `SAMPLE_RATES` / `AUDIO_MAX_CHANNELS` macros in `src/audio_app.c` (48 kHz stereo by default). Continuous sampling-frequency ranges are exposed as a single configuration at the range's highest frequency (e.g. a 8000–48000 Hz speaker appears as 48000 Hz); non-PCM formats are rejected by the driver.
 
+## Limitations and trade-offs
+
+- The Feature Unit API exposes one directly connected Feature Unit per logical capture/playback stream. If several Feature Units map to the same logical stream, the first mapping is retained.
+- The UAC1 `MaxPacketsOnly` endpoint attribute is not supported. OUT transfers are not padded to `wMaxPacketSize`, and padding in IN transfers is not removed from the reported audio data.
+
 ## Building
 
 ### Using CMake (recommended)
diff --git a/examples/host/audio_host/src/audio_app.c b/examples/host/audio_host/src/audio_app.c
index c3bd59abf..6639b7ec5 100644
--- a/examples/host/audio_host/src/audio_app.c
+++ b/examples/host/audio_host/src/audio_app.c
@@ -243,12 +243,12 @@ void led_blinking_task(void) {
 #if 0
   // Print the current Feature Unit volume, which is set to 0x0600 in mic_configured() and can be changed by the device.
   uint16_t volume = 0x0001;
-  tuh_audio_feature_unit_get_sync(audio_idx, AUDIO10_FU_CTRL_VOLUME, 0, &volume);
+  tuh_audio_feature_unit_get_sync(audio_idx, cap_stream_idx, AUDIO10_FU_CTRL_VOLUME, 0, &volume);
   printf("  Feature Unit volume get: 0x%04x\r\n", (unsigned int)volume);
   uint16_t mute = 0x0000;
-  tuh_audio_feature_unit_get_sync(audio_idx, AUDIO10_FU_CTRL_MUTE, 0, &mute);
+  tuh_audio_feature_unit_get_sync(audio_idx, cap_stream_idx, AUDIO10_FU_CTRL_MUTE, 0, &mute);
   mute=!mute; // toggle mute for demonstration
-  tuh_audio_feature_unit_set_sync(audio_idx, AUDIO10_FU_CTRL_MUTE, 0, mute);
+  tuh_audio_feature_unit_set_sync(audio_idx, cap_stream_idx, AUDIO10_FU_CTRL_MUTE, 0, mute);
   printf("  Feature Unit mute set: 0x%04x\r\n", (unsigned int)mute);
 #endif
 }
@@ -368,10 +368,10 @@ static void mic_configured(uint8_t idx, uint8_t stream_idx, tusb_xfer_result_t r
     mic_ready = tuh_audio_start(idx, stream_idx);
 
     uint16_t volume = 0x0600;
-    result          = tuh_audio_feature_unit_set_sync(idx, AUDIO10_FU_CTRL_VOLUME, 0, volume);
+    result          = tuh_audio_feature_unit_set_sync(idx, stream_idx, AUDIO10_FU_CTRL_VOLUME, 0, volume);
     if (result == XFER_RESULT_SUCCESS) {
       printf("  Feature Unit volume set:volume 0x%04x\r\n", (unsigned int)volume);
-      tuh_audio_feature_unit_get_sync(idx, AUDIO10_FU_CTRL_VOLUME, 0, &volume);
+      tuh_audio_feature_unit_get_sync(idx, stream_idx, AUDIO10_FU_CTRL_VOLUME, 0, &volume);
       printf("  Feature Unit volume get: 0x%04x\r\n", (unsigned int)volume);
     } else {
       printf("  Setting Feature Unit volume FAILED: result=%u\r\n", result);