Index: lib/libdevctl/devctl.h
===================================================================
--- lib/libdevctl/devctl.h
+++ lib/libdevctl/devctl.h
@@ -38,5 +38,6 @@
 int	devctl_suspend(const char *device);
 int	devctl_resume(const char *device);
 int	devctl_set_driver(const char *device, const char *driver, bool force);
+int	devctl_rescan(const char *device);
 
 #endif /* !__DEVCTL_H__ */
Index: lib/libdevctl/devctl.3
===================================================================
--- lib/libdevctl/devctl.3
+++ lib/libdevctl/devctl.3
@@ -34,6 +34,7 @@
 .Nm devctl_detach ,
 .Nm devctl_disable ,
 .Nm devctl_enable ,
+.Nm devctl_rescan ,
 .Nm devctl_resume ,
 .Nm devctl_set_driver ,
 .Nm devctl_suspend
@@ -51,6 +52,8 @@
 .Ft int
 .Fn devctl_enable "const char *device"
 .Ft int
+.Fn devctl_rescan "const char *device"
+.Ft int
 .Fn devctl_resume "const char *device"
 .Ft int
 .Fn devctl_set_driver "const char *device" "const char *driver" "bool force"
@@ -149,9 +152,14 @@
 is true,
 the device will be detached from its current device driver before it is
 attached to the new device driver.
+.Pp
+The
+.Fn devctl_rescan
+function rescans a bus device checking for devices that have been added or
+removed.
 .Sh RETURN VALUES
 .Rv -std devctl_attach devctl_detach devctl_disable devctl_enable \
-devctl_suspend devctl_resume devctl_set_driver
+devctl_suspend devctl_rescan devctl_resume devctl_set_driver
 .Sh ERRORS
 In addition to specific errors noted below,
 all of the
@@ -280,6 +288,16 @@
 .It Bq Er ENXIO
 The new device driver failed to attach.
 .El
+.Pp
+The
+.Fn devctl_rescan
+function may fail if:
+.Bl -tag -width Er
+.It Bq Er ENXIO
+The device is not attached to a driver.
+.It Bq Er ENXIO
+The bus driver does not support rescanning.
+.El
 .Sh SEE ALSO
 .Xr devinfo 3 ,
 .Xr devstat 3 ,
Index: lib/libdevctl/devctl.c
===================================================================
--- lib/libdevctl/devctl.c
+++ lib/libdevctl/devctl.c
@@ -122,3 +122,10 @@
 		req.dr_flags |= DEVF_SET_DRIVER_DETACH;
 	return (devctl_request(DEV_SET_DRIVER, &req));
 }
+
+int
+devctl_rescan(const char *device)
+{
+
+	return (devctl_simple_request(DEV_RESCAN, device, 0));
+}
Index: share/man/man9/BUS_RESCAN.9
===================================================================
--- /dev/null
+++ share/man/man9/BUS_RESCAN.9
@@ -0,0 +1,51 @@
+.\" -*- nroff -*-
+.\"
+.\" Copyright (c) 2016 John H. Baldwin <jhb@FreeBSD.org>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd April 19, 2016
+.Dt BUS_RESCAN 9
+.Os
+.Sh NAME
+.Nm BUS_RESCAN
+.Nd "rescan a bus checking for devices that have been added or removed"
+.Sh SYNOPSIS
+.In sys/param.h
+.In sys/bus.h
+.Ft void
+.Fn BUS_RESCAN "device_t dev"
+.Sh DESCRIPTION
+The
+.Fn BUS_RESCAN
+method is called to request a rescan of the child devices on a bus device.
+The method should add any devices that have been added since the previous
+scan and remove devices that have been removed.
+This method is not required to re-examine existing devices to determine if
+their properties have changed.
+This method is also not required to propagate the rescan request to child
+devices.
+.Sh SEE ALSO
+.Xr device 9
Index: share/man/man9/Makefile
===================================================================
--- share/man/man9/Makefile
+++ share/man/man9/Makefile
@@ -44,6 +44,7 @@
 	BUS_NEW_PASS.9 \
 	BUS_PRINT_CHILD.9 \
 	BUS_READ_IVAR.9 \
+	BUS_RESCAN.9 \
 	bus_release_resource.9 \
 	bus_set_pass.9 \
 	bus_set_resource.9 \
Index: sys/kern/bus_if.m
===================================================================
--- sys/kern/bus_if.m
+++ sys/kern/bus_if.m
@@ -232,6 +232,19 @@
 } DEFAULT null_add_child;
 
 /**
+ * @brief Rescan the bus
+ *
+ * This method is called by a parent bridge or devctl to trigger a bus
+ * rescan.  The rescan should delete devices no longer present and
+ * enumerate devices that have newly arrived.
+ *
+ * @param _dev		the bus device
+ */
+METHOD int rescan {
+	device_t _dev;
+}
+
+/**
  * @brief Allocate a system resource
  *
  * This method is called by child devices of a bus to allocate resources.
Index: sys/kern/subr_bus.c
===================================================================
--- sys/kern/subr_bus.c
+++ sys/kern/subr_bus.c
@@ -5203,6 +5203,7 @@
 	case DEV_SUSPEND:
 	case DEV_RESUME:
 	case DEV_SET_DRIVER:
+	case DEV_RESCAN:
 		error = priv_check(td, PRIV_DRIVER);
 		if (error == 0)
 			error = find_device(req, &dev);
@@ -5366,6 +5367,13 @@
 		error = device_probe_and_attach(dev);
 		break;
 	}
+	case DEV_RESCAN:
+		if (!device_is_attached(dev)) {
+			error = ENXIO;
+			break;
+		}
+		error = BUS_RESCAN(dev);
+		break;
 	}
 	mtx_unlock(&Giant);
 	return (error);
Index: sys/sys/bus.h
===================================================================
--- sys/sys/bus.h
+++ sys/sys/bus.h
@@ -117,6 +117,7 @@
 #define	DEV_SUSPEND	_IOW('D', 5, struct devreq)
 #define	DEV_RESUME	_IOW('D', 6, struct devreq)
 #define	DEV_SET_DRIVER	_IOW('D', 7, struct devreq)
+#define	DEV_RESCAN	_IOW('D', 9, struct devreq)
 
 /* Flags for DEV_DETACH and DEV_DISABLE. */
 #define	DEVF_FORCE_DETACH	0x0000001
Index: usr.sbin/devctl/devctl.8
===================================================================
--- usr.sbin/devctl/devctl.8
+++ usr.sbin/devctl/devctl.8
@@ -56,6 +56,9 @@
 .Cm set driver
 .Op Fl f
 .Ar device driver
+.Nm
+.Cm rescan
+.Ar device
 .Sh DESCRIPTION
 The
 .Nm
@@ -126,6 +129,9 @@
 .Fl f
 flag is not specified,
 the device will not be changed.
+.It Cm rescan Ar device
+Rescan a bus device checking for devices that have been added or
+removed.
 .El
 .Sh SEE ALSO
 .Xr devctl 3 ,
Index: usr.sbin/devctl/devctl.c
===================================================================
--- usr.sbin/devctl/devctl.c
+++ usr.sbin/devctl/devctl.c
@@ -259,6 +259,18 @@
 }
 DEVCTL_COMMAND(set, driver, set_driver);
 
+static int
+rescan(int ac, char **av)
+{
+
+	if (ac != 2)
+		usage();
+	if (devctl_rescan(av[1]) < 0)
+		err(1, "Failed to rescan %s", av[1]);
+	return (0);
+}
+DEVCTL_COMMAND(top, rescan, rescan);
+
 int
 main(int ac, char *av[])
 {