Decouple hardware specific code from generic, agnostic code

src/avclan/mediacontrol.h

@@ -16,27 +16,25 @@
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-// Media-control actuator: emulates play/pause and skip button presses on the
-// audio source by toggling MIC_CONTROL (PB1/WO1) with TCA0 in FRQ mode.
+// Media-control: route/handle head-unit button presses to the audio source.
 
 #ifndef MEDIACONTROL_H
 #define MEDIACONTROL_H
 
-#include <stdbool.h>
+#include <stdint.h>
 
-// One-time hardware bring-up for the mic/button-press driver (TCA0 + PB1).
+// Actions list
+typedef enum : uint8_t {
+  MEDIA_PLAY_PAUSE = 0,
+  MEDIA_SKIP_FORWARD,
+  MEDIA_SKIP_BACKWARD,
+} AVCLAN_media_fn_t;
+
+// One-time hardware bring-up for the media driver.
 void mediacontrol_init();
 
-// Emulate a single play/pause button press on the source device.
-void AVCLAN_micPlayPause();
-// Emulate skip-forward/backward button presses
-void AVCLAN_micSkipForward();
-void AVCLAN_micSkipBackward();
-
-// Keep the press waveform roughly in sync while a bus transaction has masked
-// interrupts. MUST be called with interrupts disabled (e.g. from within the
-// frame layer's AVCLAN_stopEvent ATOMIC_BLOCK).
-void mediacontrol_syncDuringMask();
+// Emulate a button press on the source device.
+void AVCLAN_mediaFunction(AVCLAN_media_fn_t fn);
 
 #ifndef NDEBUG
 bool AVCLAN_micToggle();