Index: src/plug_io.h
===================================================================
--- src/plug_io.h	(revision 2222)
+++ src/plug_io.h	(revision 2223)
@@ -36,6 +36,12 @@
 	plug_io_t *next;
 	void *plugin_data;
 
+	/* Check if the plugin supports format fmt, for writing (if wr != 0) or for
+	   reading (if wr == 0). Return 0 if not supported or an integer priority
+	   if supported. The higher the prio is the more likely the plugin gets
+	   the next operation on the file. Base prio should be 100 for native formats. */
+	int (*fmt_support_prio)(int wr, const char *fmt);
+
 	/* Attempt to load a pcb design from Filename to Ptr.
 	   Conf subtree at settings_dest is replaced by settings loaded from the
 	   file unless it's CFR_invalid.
Index: src_plugins/io_kicad_legacy/io_kicad_legacy.c
===================================================================
--- src_plugins/io_kicad_legacy/io_kicad_legacy.c	(revision 2222)
+++ src_plugins/io_kicad_legacy/io_kicad_legacy.c	(revision 2223)
@@ -31,6 +31,15 @@
 
 static plug_io_t io_kicad_legacy;
 
+int io_kicad_legacy_fmt(int wr, const char *fmt)
+{
+	if (strcmp(fmt, "kicadl") != 0)
+		return 0;
+	if (wr)
+		return 100;
+	return 0; /* no read support yet */
+}
+
 static void hid_io_kicad_legacy_uninit(void)
 {
 	/* Runs once when the plugin is unloaded. TODO: free plugin-globals here. */
@@ -41,6 +50,7 @@
 
 	/* register the IO hook */
 	io_kicad_legacy.plugin_data = NULL;
+	io_kicad_legacy.fmt_support_prio = io_kicad_legacy_fmt;
 	io_kicad_legacy.parse_pcb = NULL;
 	io_kicad_legacy.parse_element = NULL;
 	io_kicad_legacy.parse_font = NULL;
Index: src_plugins/io_pcb/io_pcb.c
===================================================================
--- src_plugins/io_pcb/io_pcb.c	(revision 2222)
+++ src_plugins/io_pcb/io_pcb.c	(revision 2223)
@@ -31,6 +31,13 @@
 
 static plug_io_t io_pcb;
 
+int io_pcb_fmt(int wr, const char *fmt)
+{
+	if (strcmp(fmt, "pcb") != 0)
+		return 0;
+	return 100; /* read-write */
+}
+
 extern void yylex_destroy(void);
 static void hid_io_pcb_uninit(void)
 {
@@ -43,6 +50,7 @@
 
 	/* register the IO hook */
 	io_pcb.plugin_data = NULL;
+	io_pcb.fmt_support_prio = io_pcb_fmt;
 	io_pcb.parse_pcb = io_pcb_ParsePCB;
 	io_pcb.parse_element = io_pcb_ParseElement;
 	io_pcb.parse_font = io_pcb_ParseFont;