Bluetooth: BAP: Sink: Move mod_src_param to RAM

The mod_src_param was several places stored on the stack.
However this is a complex paramater struct that has
2 Kconfig options that can significantly increase the size,
and the maximum size of the parameter is nearly 8 KiB, and
was always place the in the BT RX thread's stack.

For this reason, the param is now stored in a single
static variable in RAM instead, so that the BT RX thread's stack
does not need to be increased based on the Kconfig options,
as that is quite difficult for users to be aware of.

The add_src_param has been left as is, as that stored in
the calling thread, and it is easier for an application
to determine if the calling thread needs additional stack
space.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

Author: Thalley

subsys/bluetooth/audio/bap_broadcast_sink.c

@@ -63,6 +63,11 @@ struct codec_cap_lookup_id_data {
 
 static sys_slist_t sink_cbs = SYS_SLIST_STATIC_INIT(&sink_cbs);
 
+/* The mod_src_param is and shall only be used by the BT RX thread. It is statically defined due to
+ * the size of it, and that it's configurable in size, and can cause stack overflow issues otherwise
+ */
+static struct bt_bap_scan_delegator_mod_src_param mod_src_param;
+
 static void broadcast_sink_cleanup(struct bt_bap_broadcast_sink *sink);
 
 static bool find_recv_state_by_sink_cb(const struct bt_bap_scan_delegator_recv_state *recv_state,
@@ -103,7 +108,6 @@ static bool find_recv_state_by_pa_sync_cb(const struct bt_bap_scan_delegator_rec
 static void update_recv_state_big_synced(const struct bt_bap_broadcast_sink *sink)
 {
 	const struct bt_bap_scan_delegator_recv_state *recv_state;
-	struct bt_bap_scan_delegator_mod_src_param mod_src_param = {0};
 	int err;
 
 	recv_state = bt_bap_scan_delegator_find_state(find_recv_state_by_sink_cb, (void *)sink);
@@ -113,6 +117,8 @@ static void update_recv_state_big_synced(const struct bt_bap_broadcast_sink *sin
 		return;
 	}
 
+	(void)memset(&mod_src_param, 0, sizeof(mod_src_param));
+
 	mod_src_param.num_subgroups = sink->subgroup_count;
 	for (uint8_t i = 0U; i < sink->subgroup_count; i++) {
 		struct bt_bap_bass_subgroup *subgroup_param = &mod_src_param.subgroups[i];
@@ -145,7 +151,6 @@ static void update_recv_state_big_synced(const struct bt_bap_broadcast_sink *sin
 static void update_recv_state_big_cleared(const struct bt_bap_broadcast_sink *sink,
 					  uint8_t reason)
 {
-	struct bt_bap_scan_delegator_mod_src_param mod_src_param = { 0 };
 	const struct bt_bap_scan_delegator_recv_state *recv_state;
 	int err;
 
@@ -157,6 +162,8 @@ static void update_recv_state_big_cleared(const struct bt_bap_broadcast_sink *si
 		return;
 	}
 
+	(void)memset(&mod_src_param, 0, sizeof(mod_src_param));
+
 	if ((recv_state->encrypt_state == BT_BAP_BIG_ENC_STATE_BCODE_REQ ||
 	     recv_state->encrypt_state == BT_BAP_BIG_ENC_STATE_DEC) &&
 	    reason == BT_HCI_ERR_TERM_DUE_TO_MIC_FAIL) {
@@ -488,7 +495,6 @@ static void broadcast_sink_add_src(struct bt_bap_broadcast_sink *sink)
 
 static bool base_subgroup_meta_cb(const struct bt_bap_base_subgroup *subgroup, void *user_data)
 {
-	struct bt_bap_scan_delegator_mod_src_param *mod_src_param = user_data;
 	struct bt_bap_bass_subgroup *subgroup_param;
 	uint8_t *meta;
 	int ret;
@@ -498,19 +504,18 @@ static bool base_subgroup_meta_cb(const struct bt_bap_base_subgroup *subgroup, v
 		return false;
 	}
 
-	subgroup_param = &mod_src_param->subgroups[mod_src_param->num_subgroups++];
+	subgroup_param = &mod_src_param.subgroups[mod_src_param.num_subgroups++];
 	subgroup_param->metadata_len = (uint8_t)ret;
 	memcpy(subgroup_param->metadata, meta, subgroup_param->metadata_len);
 
 	return true;
 }
 
-static int update_recv_state_base_copy_meta(const struct bt_bap_base *base,
-					    struct bt_bap_scan_delegator_mod_src_param *param)
+static int update_recv_state_base_copy_meta(const struct bt_bap_base *base)
 {
 	int err;
 
-	err = bt_bap_base_foreach_subgroup(base, base_subgroup_meta_cb, param);
+	err = bt_bap_base_foreach_subgroup(base, base_subgroup_meta_cb, NULL);
 	if (err != 0) {
 		LOG_DBG("Failed to parse subgroups: %d", err);
 		return err;
@@ -522,7 +527,6 @@ static int update_recv_state_base_copy_meta(const struct bt_bap_base *base,
 static void update_recv_state_base(const struct bt_bap_broadcast_sink *sink,
 				   const struct bt_bap_base *base)
 {
-	struct bt_bap_scan_delegator_mod_src_param mod_src_param = { 0 };
 	const struct bt_bap_scan_delegator_recv_state *recv_state;
 	int err;
 
@@ -533,7 +537,9 @@ static void update_recv_state_base(const struct bt_bap_broadcast_sink *sink,
 		return;
 	}
 
-	err = update_recv_state_base_copy_meta(base, &mod_src_param);
+	(void)memset(&mod_src_param, 0, sizeof(mod_src_param));
+
+	err = update_recv_state_base_copy_meta(base);
 	if (err != 0) {
 		LOG_WRN("Failed to modify Receive State for sink %p: %d", sink, err);
 		return;
@@ -740,7 +746,6 @@ static void pa_term_cb(struct bt_le_per_adv_sync *sync,
 
 static void update_recv_state_encryption(const struct bt_bap_broadcast_sink *sink)
 {
-	struct bt_bap_scan_delegator_mod_src_param mod_src_param = { 0 };
 	const struct bt_bap_scan_delegator_recv_state *recv_state;
 	int err;
 
@@ -753,6 +758,8 @@ static void update_recv_state_encryption(const struct bt_bap_broadcast_sink *sin
 		return;
 	}
 
+	(void)memset(&mod_src_param, 0, sizeof(mod_src_param));
+
 	/* Only change the encrypt state, and leave the rest as is */
 	if (atomic_test_bit(sink->flags,
 			    BT_BAP_BROADCAST_SINK_FLAG_BIG_ENCRYPTED)) {