libtock-sync: alarm sleep_for: use yield-waitfor

libtock-sync/services/alarm.c

@@ -1,27 +1,22 @@
 #include "alarm.h"
 
+// Declare non-public export of helper from libtock.
+uint32_t _ms_to_ticks(uint32_t ms);
+
 struct alarm_cb_data {
   bool fired;
 };
 
-static struct alarm_cb_data delay_data = { .fired = false };
-
-static void delay_cb(__attribute__ ((unused)) uint32_t now,
-                     __attribute__ ((unused)) uint32_t scheduled,
-                     __attribute__ ((unused)) void*    opaque) {
-  delay_data.fired = true;
-}
-
 int libtocksync_alarm_delay_ms(uint32_t ms) {
-  delay_data.fired = false;
-  libtock_alarm_t alarm;
   int rc;
-
-  if ((rc = libtock_alarm_in_ms(ms, delay_cb, NULL, &alarm)) != RETURNCODE_SUCCESS) {
+  uint32_t ticks = _ms_to_ticks(ms);
+  if ((rc = libtock_alarm_command_set_relative_blind(ticks)) != RETURNCODE_SUCCESS) {
     return rc;
   }
 
-  yield_for(&delay_data.fired);
+  yield_waitfor_return_t yval = yield_wait_for(DRIVER_NUM_ALARM, 1);
+  if (yval.data0 != RETURNCODE_SUCCESS) return yval.data0;
+
   return rc;
 }
 

libtock-sync/services/alarm.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <libtock/peripherals/syscalls/alarm_syscalls.h>
 #include <libtock/services/alarm.h>
 #include <libtock/tock.h>
 

libtock/peripherals/syscalls/alarm_syscalls.c

@@ -29,6 +29,11 @@ int libtock_alarm_command_set_relative(uint32_t dt, uint32_t* actual) {
   return tock_command_return_u32_to_returncode(rval, actual);
 }
 
+int libtock_alarm_command_set_relative_blind(uint32_t dt) {
+  syscall_return_t rval = command(DRIVER_NUM_ALARM, 5, dt, 0);
+  return tock_command_return_novalue_to_returncode(rval);
+}
+
 int libtock_alarm_command_set_absolute(uint32_t reference, uint32_t dt) {
   syscall_return_t rval = command(DRIVER_NUM_ALARM, 6, reference, dt);
   uint32_t unused;

libtock/peripherals/syscalls/alarm_syscalls.h

@@ -46,6 +46,15 @@ int libtock_alarm_command_stop(void);
  */
 int libtock_alarm_command_set_relative(uint32_t dt, uint32_t* actual);
 
+/*
+ * Starts a oneshot alarm
+ *
+ * expiration - relative expiration value from when kernel handles syscall.
+ *
+ * Side-effects: cancels any existing/outstanding alarms
+ */
+int libtock_alarm_command_set_relative_blind(uint32_t dt);
+
 /*
  * Starts a oneshot alarm
  *

libtock/services/alarm.c

@@ -64,6 +64,18 @@ static uint32_t ms_to_ticks(uint32_t ms) {
   return ticks;
 }
 
+
+// Declare non-public export of helper for libtock-sync.
+uint32_t _ms_to_ticks(uint32_t ms);
+/** \brief Private export of ms->ticks helper to libtock-sync
+ *
+ * This is a non-stable, non-public interface for a helper
+ * function which is also useful to libtock-sync.
+ */
+uint32_t _ms_to_ticks(uint32_t ms) {
+  return ms_to_ticks(ms);
+}
+
 uint32_t libtock_alarm_ticks_to_ms(uint32_t ticks) {
   // `ticks_to_ms`'s conversion will be accurate to within the range
   // 0 to 1 milliseconds less than the exact conversion