1 files changed, 42 insertions, 2 deletions

diff --git a/src/comm.h b/src/comm.h
index 75f098b..e4579eb 100644
--- a/src/comm.h
+++ b/src/comm.h
@@ -6,6 +6,7 @@
 
 #include "attributes.h"
 
+#include "lv2/atom/atom.h"
 #include "lv2/urid/urid.h"
 #include "zix/ring.h"
 #include "zix/status.h"
@@ -16,6 +17,47 @@ JALV_BEGIN_DECLS
 
 // Communication between the audio and main threads via rings
 
+/// Type of an internal message in a communication ring
+typedef enum {
+  NO_MESSAGE,          ///< Sentinel type for uninitialized messages
+  CONTROL_PORT_CHANGE, ///< Value change for a control port (float)
+  EVENT_TRANSFER,      ///< Event transfer for a sequence port (atom)
+} JalvMessageType;
+
+/**
+   Message between the audio thread and the main thread.
+
+   This is the general header for any type of message in a communication ring.
+   The type determines how the message must be handled by the receiver.  This
+   header is followed immediately by `size` bytes of data in the ring.
+*/
+typedef struct {
+  JalvMessageType type; ///< Type of this message
+  uint32_t        size; ///< Size of payload following this header in bytes
+} JalvMessageHeader;
+
+/**
+   The payload of a CONTROL_PORT_CHANGE message.
+
+   This message has a fixed sized, and is described in its entirety by this
+   struct.
+*/
+typedef struct {
+  uint32_t port_index; ///< Control port index
+  float    value;      ///< Control value
+} JalvControlChange;
+
+/**
+   The start of the payload of an EVENT_TRANSFER message.
+
+   This message has a variable size, the start described by this struct is
+   followed immediately by `atom.size` bytes of data (the atom body).
+*/
+typedef struct {
+  uint32_t port_index; ///< Sequence port index
+  LV2_Atom atom;       ///< Event payload header
+} JalvEventTransfer;
+
 /**
    Write a message in two parts to a ring.
 
@@ -43,7 +85,6 @@ jalv_write_split_message(ZixRing*    target,
 
    @param target Communication ring (jalv->plugin_to_ui or jalv->ui_to_plugin).
    @param port_index Index of the port this change is for.
-   @param protocol Port protocol (0 for float control, or atom:eventTransfer).o
    @param size Size of body in bytes.
    @param type Atom type URID.
    @param body Atom body.
@@ -52,7 +93,6 @@ jalv_write_split_message(ZixRing*    target,
 ZixStatus
 jalv_write_event(ZixRing*    target,
                  uint32_t    port_index,
-                 uint32_t    protocol,
                  uint32_t    size,
                  LV2_URID    type,
                  const void* body);