Add devctl_process_running() so that power management system driver

can check whether devd(8) is running.

MFC after:	1 week

sys/kern/subr_bus.c

@@ -508,6 +508,15 @@ devpoll(struct cdev *dev, int events, d_thread_t *td)
 	return (revents);
 }
 
+/**
+ * @brief Return whether the userland process is running
+ */
+boolean_t
+devctl_process_running(void)
+{
+	return (devsoftc.async_proc != NULL);
+}
+
 /**
  * @brief Queue data to be read from the devctl device
  *

sys/sys/bus.h

@@ -83,6 +83,7 @@ struct u_device {
  * hook to send the message.  However, devctl_queue_data is also
  * included in case devctl_notify isn't sufficiently general.
  */
+boolean_t devctl_process_running(void);
 void devctl_notify(const char *__system, const char *__subsystem,
     const char *__type, const char *__data);
 void devctl_queue_data(char *__data);