4 files changed, 46 insertions, 3 deletions

diff --git a/kernel/task/idle.c b/kernel/task/idle.c
new file mode 100644
index 0000000..6bd8494
--- /dev/null
+++ b/kernel/task/idle.c
@@ -0,0 +1,18 @@
+#include <avr/power.h>
+#include <avr/interrupt.h>
+#include <avr/sleep.h>
+#include <avr/power.h>
+#include "task/idle.h"
+#include "task/task.h"
+
+void idle_entry(char args) {
+  while(1) {
+    set_sleep_mode(SLEEP_MODE_IDLE);
+    cli();
+    sleep_enable();
+    sei();
+    sleep_cpu();
+    sleep_disable();
+  };
+}
+
diff --git a/kernel/task/include/task/sched.h b/kernel/task/include/task/sched.h
index c14a85b..6dcd67c 100644
--- a/kernel/task/include/task/sched.h
+++ b/kernel/task/include/task/sched.h
@@ -19,7 +19,7 @@ extern struct list_head ready;
 
 /**
  * Stack pointer for operations performed out of task context, including any
- * calls made after SAVE_CONTEXT().
+ * calls made after context save.
  */
 extern void* volatile kstack;
 
diff --git a/kernel/task/include/task/task.h b/kernel/task/include/task/task.h
index 40f18a0..99f16dc 100644
--- a/kernel/task/include/task/task.h
+++ b/kernel/task/include/task/task.h
@@ -4,6 +4,18 @@
 #include "collection/list.h"
 
 /**
+ * Wakeup sources define the minimum power level
+ * at which a task that is waiting in a queue
+ * can be woken up
+ */
+enum wakeup_src {
+   WAKEUP_SRC_OFF = 0, //processor off, external interrupts may trigger this source
+   WAKEUP_SRC_CLOCK = 1, //main clock required
+   WAKEUP_SRC_IDLE = 2, //processor can be put in idle state
+   WAKEUP_SRC_ON = 3 //processor must stay on
+};
+
+/**
  * Task control block, contains runtime
  * information about tasks.
  */
@@ -23,8 +35,12 @@ struct tcb_t {
   /** Current wait queue that this task is in.*/
   struct list_head queue;
 
+  /** ID of task. */
   char id;
 
+
+  enum wakeup_src wakeup_src;
+
 };
 
 /**
@@ -39,7 +55,8 @@ struct tcb_t {
     .mem_high = _declared_stack_##name + stack_size - 1, \
     .entry = entry_function, \
     .queue = {}, \
-    .id = pid \
+    .id = pid, \
+    .wakeup_src = WAKEUP_SRC_ON \
   };
 
 #endif
\ No newline at end of file
diff --git a/kernel/task/sched.c b/kernel/task/sched.c
index ceaf9bb..1ffd369 100644
--- a/kernel/task/sched.c
+++ b/kernel/task/sched.c
@@ -7,6 +7,8 @@
 
 struct tcb_t* volatile current = 0;
 
+static struct tcb_t* volatile idle = 0;
+
 struct list_head ready = LIST_HEAD_INIT(ready);
 
 void* volatile kstack;
@@ -17,6 +19,12 @@ void spawn(struct tcb_t* const tcb) {
   list_add_tail(&tcb->queue, &ready);
 }
 
+void spawn_idle(struct tcb_t* const tcb) {
+  spawn(tcb);
+  list_del(&tcb->queue);
+  idle = tcb;
+}
+
 void yield(void) {
   cli();
   context_save();
@@ -50,6 +58,6 @@ void schedule() {
     current = list_entry(ready.next, struct tcb_t, queue);
     list_move_tail(ready.next, &ready);
   } else {
-    panic();
+    current = idle;
   }
 }
\ No newline at end of file