* Make total stack size available as a symbol

* Implement SWI handler to enable/disable interrupts
* Implement event system to deal with kicking non-interrupt code

event.c

@@ -0,0 +1,74 @@
+#include "event.h"
+#include "interrupt.h"
+#include "types.h"
+
+event_handler *event_handler_table[EVENT_MAX+1];
+
+#define EVENT_WORDS ((EVENT_MAX+1+31)/32)
+
+unsigned int event_pending[EVENT_WORDS];
+
+#define EVENT_WORDLEN	32
+#define EVENT_WORD(x)	(x/EVENT_WORDLEN)
+#define EVENT_BIT(x)	(x%EVENT_WORDLEN)
+#define EVENT_MASK(x)	(1<<EVENT_BIT(x))
+
+void event_set(unsigned int event)
+{
+	if (event > EVENT_MAX)
+		return;
+
+	interrupt_block();
+	event_pending[EVENT_WORD(event)] |= EVENT_MASK(event);
+	interrupt_unblock();
+}
+
+static int bitset(unsigned int x)
+{
+	x = 0xffffffff - (x-1);
+	x = x - ((x >> 1) & 0x55555555);
+	x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
+	x = (x + (x >> 4)) & 0x0F0F0F0F;
+	x = x + (x << 8);
+	x = x + (x << 16);
+	return 32 - (x >> 24);
+}
+
+bool event_get(unsigned int *event)
+{
+	int i;
+	unsigned int p;
+
+	for (i = 0; i < EVENT_WORDS; i++) {
+		if ((p = event_pending[i]) != 0) {
+			p = p & (-p);
+			*event = bitset(p) + EVENT_WORDLEN*i;
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+void event_clear(unsigned int event)
+{
+	interrupt_block();
+	event_pending[EVENT_WORD(event)] &= ~EVENT_MASK(event);
+	interrupt_unblock();
+}
+
+void event_dispatch(void)
+{
+	unsigned int event;
+
+	if (event_get(&event)) {
+		event_clear(event);
+		(event_handler_table[event])();
+	}
+}
+
+void event_register(unsigned int event, event_handler *handler)
+{
+	if (event > EVENT_MAX)
+		return;
+	event_handler_table[event] = handler;
+}