bl00mbox: less aggressive plugin gc

if a plugin is unreachable in userland but another reachable plugin or channel still sources data from it that plugin is considered reachable

this should prevent any existing applications from breaking

components/bl00mbox/micropython/mp_sys_bl00mbox.c

@@ -26,6 +26,8 @@ typedef struct _channel_core_obj_t {
     // will be NULLed on original if channel has been manually deleted
     bl00mbox_channel_t *chan;
     mp_obj_t channel_plugin;
+    // list of all sources connect to the mixer to avoid gc
+    mp_obj_t sources_mx;
 #ifdef BL00MBOX_CALLBACKS_FUNSAFE
     // the channel may be become reachable after having been unreachable.
     // if the callback was collected during this phase it results in a
@@ -49,6 +51,8 @@ typedef struct _plugin_core_obj_t {
     // that might trigger a gc (like creating objects) you need to check this
     // pointer for NULL again.
     bl00mbox_plugin_t *plugin;
+    // list of all source plugins to avoid gc
+    mp_obj_t sources;
 } plugin_core_obj_t;
 
 STATIC const mp_obj_type_t plugin_core_type;
@@ -94,6 +98,38 @@ static void bl00mbox_error_unwrap(bl00mbox_error_t error) {
     }
 }
 
+void bl00mbox_disconnect_rx_callback(void *rx, uint16_t signal_index) {
+    plugin_core_obj_t *self = rx;
+    mp_obj_list_t *list = MP_OBJ_TO_PTR(self->sources);
+    if (signal_index < list->len) {
+        list->items[signal_index] = mp_const_none;
+    } else {
+        bl00mbox_log_error("plugin signal list too short");
+    }
+}
+
+void bl00mbox_connect_rx_callback(void *rx, void *tx, uint16_t signal_index) {
+    plugin_core_obj_t *self = rx;
+    mp_obj_list_t *list = MP_OBJ_TO_PTR(self->sources);
+    if (signal_index < list->len) {
+        list->items[signal_index] = MP_OBJ_FROM_PTR(tx);
+    } else {
+        bl00mbox_log_error("plugin signal list too short");
+    }
+}
+
+void bl00mbox_disconnect_mx_callback(void *chan, void *tx) {
+    channel_core_obj_t *self = chan;
+    // don't have to check for duplicates, bl00mbox_user does that for us
+    mp_obj_list_remove(self->sources_mx, MP_OBJ_FROM_PTR(tx));
+}
+
+void bl00mbox_connect_mx_callback(void *chan, void *tx) {
+    channel_core_obj_t *self = chan;
+    // don't have to check for duplicates, bl00mbox_user does that for us
+    mp_obj_list_append(self->sources_mx, MP_OBJ_FROM_PTR(tx));
+}
+
 static char *strdup_raise(char *str) {
     char *ret = strdup(str);
     if (!ret) bl00mbox_error_unwrap(BL00MBOX_ERROR_OOM);
@@ -207,6 +243,12 @@ static mp_obj_t create_channel_plugin(bl00mbox_channel_t *chan) {
     self->plugin = chan->channel_plugin;
     self->plugin->parent = self;
     self->plugin->parent_self_ref = &self->plugin;
+
+    size_t num_signals = self->plugin->rugin->len_signals;
+    mp_obj_t nones[num_signals];
+    for (size_t i = 0; i < num_signals; i++) nones[i] = mp_const_none;
+    self->sources = mp_obj_new_list(num_signals, nones);
+
     return MP_OBJ_FROM_PTR(self);
 }
 
@@ -214,7 +256,9 @@ STATIC mp_obj_t channel_core_make_new(const mp_obj_type_t *type, size_t n_args,
                                       size_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 1, 1, false);
     channel_core_obj_t *self = m_new_obj_with_finaliser(channel_core_obj_t);
+
     self->base.type = &channel_core_type;
+    self->sources_mx = mp_obj_new_list(0, NULL);
     const char *name = strdup_raise(mp_obj_str_get_str(args[0]));
 
     bl00mbox_channel_t *chan = bl00mbox_channel_create();
@@ -234,6 +278,7 @@ STATIC mp_obj_t channel_core_make_new(const mp_obj_type_t *type, size_t n_args,
     bl00mbox_log_info("created channel %s", chan->name);
     return MP_OBJ_FROM_PTR(self);
 }
+
 STATIC mp_obj_t mp_channel_core_make_fake(mp_obj_t self_in) {
     channel_core_obj_t *fake = m_new_obj_with_finaliser(channel_core_obj_t);
     fake->base.type = &channel_core_type;
@@ -241,6 +286,7 @@ STATIC mp_obj_t mp_channel_core_make_fake(mp_obj_t self_in) {
     channel_core_obj_t *self = MP_OBJ_TO_PTR(self_in);
     channel_core_verify(self);
 
+    fake->sources_mx = mp_const_none;
     fake->chan = self->chan;
     fake->chan_ref = self->chan_ref;
     fake->fake = true;
@@ -431,6 +477,7 @@ STATIC mp_obj_t plugin_core_make_new(const mp_obj_type_t *type, size_t n_args,
     if (chan_core->base.type != &channel_core_type) {
         mp_raise_TypeError(MP_ERROR_TEXT("first argument must be ChannelCore"));
     }
+    channel_core_verify(chan_core);
     bl00mbox_channel_t *chan = chan_core->chan;
     int plugin_kind = mp_obj_get_int(args[1]);
     int init_var = mp_obj_get_int(args[2]);
@@ -443,6 +490,13 @@ STATIC mp_obj_t plugin_core_make_new(const mp_obj_type_t *type, size_t n_args,
     self->plugin = plugin;
     plugin->parent = self;
     plugin->parent_self_ref = &self->plugin;
+
+    // create empty source list
+    size_t num_signals = plugin->rugin->len_signals;
+    mp_obj_t nones[num_signals];
+    for (size_t i = 0; i < num_signals; i++) nones[i] = mp_const_none;
+    self->sources = mp_obj_new_list(num_signals, nones);
+
     bl00mbox_log_info("created plugin %s",
                       self->plugin->rugin->descriptor->name);
     return MP_OBJ_FROM_PTR(self);