feat: A2DP bluetooth audio working

kernel/src/Drivers/USB/Bluetooth/A2dp.hpp

@@ -38,8 +38,10 @@ namespace Drivers::USB::Bluetooth::A2dp {
     // Process an AVDTP signaling packet
     void ProcessAvdtp(const uint8_t* data, uint16_t len);
 
-    // Process an SDP response packet (on the SDP L2CAP channel)
-    void ProcessSdp(const uint8_t* data, uint16_t len);
+    // Process an SDP packet (on any SDP L2CAP channel).  Dispatches by PDU:
+    // requests (the headset querying OUR services) are answered by the minimal
+    // SDP server; responses on our outgoing client channel complete DoSdpQuery.
+    void ProcessSdp(uint16_t localCid, const uint8_t* data, uint16_t len);
 
     // Configure a stream for the given PCM parameters
     bool ConfigureStream(uint32_t sampleRate, uint8_t channels, uint8_t bitsPerSample);
@@ -47,13 +49,21 @@ namespace Drivers::USB::Bluetooth::A2dp {
     // Start streaming
     bool StartStream();
 
-    // Stop streaming
-    bool StopStream();
+    // Stop streaming.  flushQueued drops any PCM still queued in the media
+    // ring: pass true when closing the stream (track change / app exit),
+    // false for a pause so resume continues gaplessly.
+    bool StopStream(bool flushQueued = true);
 
-    // Write PCM audio data to the Bluetooth audio stream
-    // Returns number of bytes consumed
+    // Write PCM audio data to the Bluetooth audio stream.  Copies into the
+    // media ring and returns immediately (never blocks); returns the number
+    // of bytes accepted (0 = ring full, retry later).
     int WriteAudio(const uint8_t* pcmData, uint32_t pcmLen);
 
+    // Encode + send queued PCM, paced to the audio clock and gated on ACL TX
+    // readiness.  Called from the idle-loop event pump and from WriteAudio;
+    // self-serializing, cheap no-op when not streaming.
+    void PumpMedia();
+
     // Get current state
     State GetState();