[target] add a optional led api for simple debugging

currently set up to show when anything other than the idle thread is running.

include/target.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008 Travis Geiselbrecht
+ * Copyright (c) 2008-2012 Travis Geiselbrecht
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files
@@ -29,4 +29,13 @@ void target_early_init(void);
 /* later init, after the kernel has come up */
 void target_init(void);
 
+/* a target can optionally define a set of debug leds that can be used
+ * in various locations in the system.
+ */
+#if TARGET_HAS_DEBUG_LED
+void target_set_debug_led(unsigned int led, bool on);
+#else
+#define target_set_debug_led(led, on) ((void)(0))
+#endif
+
 #endif

kernel/thread.c

@@ -40,6 +40,7 @@
 #include <kernel/timer.h>
 #include <kernel/dpc.h>
 #include <platform.h>
+#include <target.h>
 
 #if DEBUGLEVEL > 1
 #define THREAD_CHECKS 1
@@ -368,6 +369,9 @@ void thread_resched(void)
 	}
 #endif
 
+	/* set some optional target debug leds */
+	target_set_debug_led(0, newthread != idle_thread);
+
 	/* do the switch */
 	oldthread->saved_critical_section_count = critical_section_count;
 	current_thread = newthread;

target/init.c

@@ -38,3 +38,7 @@ __WEAK void target_init(void)
 {
 }
 
+__WEAK void target_set_led(unsigned int led, bool on)
+{
+}
+