chore(light_sensor) make start and stop functions silently pass if nothing to do

epicardium/epicardium.h

@@ -403,14 +403,15 @@ API(API_DISP_CIRC,
 
 /**
  * Start continuous readout of the light sensor. Will read light level
- * at preconfigured interval and make it available via `epic_light_sensor_get()`
+ * at preconfigured interval and make it available via `epic_light_sensor_get()`.
+ *
+ * If the continuous readout was already running, this function will silently pass.
+ *
  *
  * :return: `0` if the start was successful or a negative error value
  *      if an error occured. Possible errors:
  *
  *      - ``-EBUSY``: The timer could not be scheduled.
- *      - ``-EALREADY``: The continuous readout is already running. You can ignore
- *      this error and safely use `epic_light_sensor_get()` anyways.
  */
 API(API_LIGHT_SENSOR_RUN, int epic_light_sensor_run());
 
@@ -429,12 +430,12 @@ API(API_LIGHT_SENSOR_GET, int epic_light_sensor_get(uint16_t* value));
 /**
  * Stop continuous readout of the light sensor.
  *
+ * If the continuous readout wasn't running, this function will silently pass.
+ *
  * :return: `0` if the stop was sucessful or a negative error value
  *      if an error occured. Possible errors:
  *
  *      - ``-EBUSY``: The timer stop could not be scheduled.
- *      - ``-EINVAL``: The continuous readout was not running. The continuous
- *          readout can be safely restarted.
  */
 API(API_LIGHT_SENSOR_STOP, int epic_light_sensor_stop());
 

epicardium/modules/light_sensor.c

@@ -45,20 +45,19 @@ int epic_light_sensor_run()
 		// since &poll_timer_buffer is not NULL, xTimerCreateStatic should allways succeed, so
 		// we don't need to check for poll_timer being NULL.
 	}
-	if (xTimerIsTimerActive(poll_timer) == pdTRUE) {
-		return -EALREADY;
-	} else {
+	if (xTimerIsTimerActive(poll_timer) == pdFALSE) {
 		if (xTimerStart(poll_timer, 0) != pdPASS) {
 			return -EBUSY;
 		}
-		return 0;
 	}
+	return 0;
 }
 
 int epic_light_sensor_stop()
 {
 	if (!poll_timer || xTimerIsTimerActive(poll_timer) == pdFALSE) {
-		return -EINVAL;
+		// timer wasn't running (or never started), just silently pass
+		return 0;
 	}
 
 	if (xTimerStop(poll_timer, 0) != pdPASS) {