Added callbacks for asserting/deasserting the mfi audio sync signal (zephyrproject-rtos#23)

Adds in callbacks into the lower link layer code for asserting and de-asserting the sync signal code inside of the ISR handling RX radio packets. If it's an audio packet and it's not a re-transmit, toggle the sync signal pin.

Author: kevin-whisper

subsys/bluetooth/controller/ll_sw/lll_mfi_audio_internal.h

@@ -0,0 +1,11 @@
+#ifndef LLL_MFI_AUDIO_INTERNAL_H
+#define LLL_MFI_AUDIO_INTERNAL_H
+
+// *** Whisper added for MFI.  Register callbacks for triggering the audio
+// sync signal to the ezairo
+typedef void (*mfi_audio_sync_assert_cb_fn)(void);
+typedef void (*mfi_audio_sync_deassert_cb_fn)(void);
+void lll_mfi_audio_sync_register_cb(mfi_audio_sync_assert_cb_fn mfi_audio_sync_assert_cb,
+                                    mfi_audio_sync_deassert_cb_fn mfi_audio_sync_deassert_cb);
+
+#endif // LLL_MFI_AUDIO_INTERNAL_H

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_conn.c

@@ -32,6 +32,7 @@
 #include "lll_df.h"
 #include "lll_conn.h"
 
+#include "lll_mfi_audio_internal.h"
 #include "lll_internal.h"
 #include "lll_df_internal.h"
 #include "lll_tim_internal.h"
@@ -106,6 +107,16 @@ static uint8_t force_md_cnt;
 #define FORCE_MD_CNT_SET()
 #endif /* !CONFIG_BT_CTLR_FORCE_MD_COUNT */
 
+// *** Whisper added for MFI
+static mfi_audio_sync_assert_cb_fn lll_mfi_audio_sync_assert_cb = NULL;
+static mfi_audio_sync_deassert_cb_fn lll_mfi_audio_sync_deassert_cb = NULL;
+void lll_mfi_audio_sync_register_cb(mfi_audio_sync_assert_cb_fn mfi_audio_sync_assert_cb,
+                               mfi_audio_sync_deassert_cb_fn mfi_audio_sync_deassert_cb)
+{
+  lll_mfi_audio_sync_assert_cb = mfi_audio_sync_assert_cb;
+  lll_mfi_audio_sync_deassert_cb = mfi_audio_sync_deassert_cb;
+}
+
 int lll_conn_init(void)
 {
 	int err;
@@ -1011,6 +1022,14 @@ static inline int isr_rx_pdu(struct lll_conn *lll, struct pdu_data *pdu_data_rx,
 
 				// Whisper added for MFI
 				if (lll->mode2_rx_enabled) {
+					// if this is an audio packet and the primary transmit slot, assert the sync signal
+					// for the ezairo
+					if((pdu_data_rx->ll_id == PDU_DATA_LLID_RESV) && 
+					   (pdu_data_rx->sn == 0) && 
+					    lll_mfi_audio_sync_assert_cb) {
+						lll_mfi_audio_sync_assert_cb();
+					}
+
 					// decrypt apple's mode 2 encryption packet via a soft decrypt routine
 					// first get the encrypted packet
 					struct pdu_data *scratch_pkt = radio_pkt_scratch_get();
@@ -1038,6 +1057,14 @@ static inline int isr_rx_pdu(struct lll_conn *lll, struct pdu_data *pdu_data_rx,
 
 					// there's no MIC with mode 2 encryption so set this to false
 					mic_failure = false;
+					
+					// if this is an audio packet and the primary transmit slot, deassert the sync signal
+					// for the ezairo
+					if((pdu_data_rx->ll_id == PDU_DATA_LLID_RESV) && 
+					   (pdu_data_rx->sn == 0) && 
+					    lll_mfi_audio_sync_deassert_cb) {
+						lll_mfi_audio_sync_deassert_cb();
+					}
 				}
 
 				if (mic_failure &&