diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -717,6 +717,10 @@
     if ((error = acpi_machdep_init(dev)))
 	goto out;
 
+    /* Initialize power resource subsystem. */
+    if ((error = acpi_powerres_init()))
+	goto out;
+
     /*
      * Setup our sysctl tree.
      *
diff --git a/sys/dev/acpica/acpi_powerres.c b/sys/dev/acpica/acpi_powerres.c
--- a/sys/dev/acpica/acpi_powerres.c
+++ b/sys/dev/acpica/acpi_powerres.c
@@ -34,6 +34,7 @@
 #include <contrib/dev/acpica/include/acpi.h>
 #include <contrib/dev/acpica/include/accommon.h>
 
+#include <dev/acpica/acpiio.h>
 #include <dev/acpica/acpivar.h>
 
 /*
@@ -120,6 +121,59 @@
 static struct acpi_powerconsumer
 			*acpi_pwr_find_consumer(ACPI_HANDLE consumer);
 
+static int
+acpi_powerres_ioctl(u_long cmd, caddr_t addr, void *arg)
+{
+	struct acpi_pwr_get_d_state_arg *get_d_state_arg;
+	struct acpi_powerconsumer *pc;
+	ACPI_STATUS status;
+	ACPI_HANDLE handle;
+	int err = ENXIO;
+
+	switch (cmd) {
+	case ACPIIO_PWR_GET_D_STATE:
+		get_d_state_arg = arg;
+		get_d_state_arg->path[sizeof(get_d_state_arg->path) - 1] = '\0';
+		status = AcpiGetHandle(ACPI_ROOT_OBJECT, get_d_state_arg->path,
+		    &handle);
+		if (ACPI_FAILURE(status)) {
+			err = ENOENT;
+			break;
+		}
+
+		ACPI_SERIAL_BEGIN(powerres);
+		pc = acpi_pwr_find_consumer(handle);
+		if (pc == NULL) {
+			err = ENOENT;
+			ACPI_SERIAL_END(powerres);
+			break;
+		}
+		get_d_state_arg->d_state = pc->ac_state; /* TODO */
+		ACPI_SERIAL_END(powerres);
+
+		err = 0;
+		break;
+	default:
+		err = EINVAL;
+	}
+
+	return (err);
+}
+
+int
+acpi_powerres_init(void)
+{
+	int err = 0;
+
+	ACPI_SERIAL_BEGIN(powerres);
+
+	err = acpi_register_ioctl(ACPIIO_PWR_GET_D_STATE, acpi_powerres_ioctl,
+	    NULL);
+
+	ACPI_SERIAL_END(powerres);
+	return (err);
+}
+
 /*
  * Register a power resource.
  *
diff --git a/sys/dev/acpica/acpiio.h b/sys/dev/acpica/acpiio.h
--- a/sys/dev/acpica/acpiio.h
+++ b/sys/dev/acpica/acpiio.h
@@ -201,6 +201,15 @@
 /* Get AC adapter status. */
 #define ACPIIO_ACAD_GET_STATUS	  _IOR('A', 1, int)
 
+/* Power resource ioctls */
+struct acpi_pwr_get_d_state_arg {
+	char	path[256];	/* in: ACPI namespace path */
+	int	d_state;	/* out: D-state (ACPI_STATE_Dx or
+				   ACPI_STATE_UNKNOWN) */
+};
+
+#define	ACPIIO_PWR_GET_D_STATE	_IOR('R', 1, struct acpi_pwr_get_d_state_arg)
+
 #ifdef _KERNEL
 typedef int	(*acpi_ioctl_fn)(u_long cmd, caddr_t addr, void *arg);
 extern int	acpi_register_ioctl(u_long cmd, acpi_ioctl_fn fn, void *arg);
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -474,6 +474,7 @@
 EVENTHANDLER_DECLARE(acpi_pre_dev_resume, acpi_event_handler_t);
 
 /* Device power control. */
+int		acpi_powerres_init(void);
 ACPI_STATUS	acpi_pwr_wake_enable(ACPI_HANDLE consumer, int enable);
 ACPI_STATUS	acpi_pwr_switch_consumer(ACPI_HANDLE consumer, int state);
 acpi_pwr_for_sleep_t	acpi_device_pwr_for_sleep;