[usb] Add basic support for USB devices

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 1648 insertions, 0 deletions

diff --git a/src/drivers/bus/usb.c b/src/drivers/bus/usb.c
new file mode 100644
index 00000000..5209c4d0
--- /dev/null
+++ b/src/drivers/bus/usb.c
@@ -0,0 +1,1648 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <assert.h>
+#include <byteswap.h>
+#include <ipxe/usb.h>
+
+/** @file
+ *
+ * Universal Serial Bus (USB)
+ *
+ */
+
+/******************************************************************************
+ *
+ * Utility functions
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Get USB endpoint name (for debugging)
+ *
+ * @v address		Endpoint address
+ * @ret name		Endpoint name
+ */
+static inline const char * usb_endpoint_name ( unsigned int address ) {
+	static char buf[ 9 /* "EPxx OUT" + NUL */ ];
+
+	snprintf ( buf, sizeof ( buf ), "EP%d%s",
+		   ( address & USB_ENDPOINT_MAX ),
+		   ( address ?
+		     ( ( address & USB_ENDPOINT_IN ) ? " IN" : " OUT" ) : "" ));
+	return buf;
+}
+
+/**
+ * Get USB speed name (for debugging)
+ *
+ * @v speed		Speed
+ * @ret name		Speed name
+ */
+static inline const char * usb_speed_name ( unsigned int speed ) {
+	static const char *exponents[4] = { "", "k", "M", "G" };
+	static char buf[ 10 /* "xxxxxXbps" + NUL */ ];
+	unsigned int mantissa;
+	unsigned int exponent;
+
+	/* Extract mantissa and exponent */
+	mantissa = USB_SPEED_MANTISSA ( speed );
+	exponent = USB_SPEED_EXPONENT ( speed );
+
+	/* Name speed */
+	switch ( speed ) {
+	case USB_SPEED_NONE:		return "DETACHED";
+	case USB_SPEED_LOW:		return "low";
+	case USB_SPEED_FULL:		return "full";
+	case USB_SPEED_HIGH:		return "high";
+	case USB_SPEED_SUPER:		return "super";
+	default:
+		snprintf ( buf, sizeof ( buf ), "%d%sbps",
+			   mantissa, exponents[exponent] );
+		return buf;
+	}
+}
+
+/**
+ * Transcribe USB BCD-coded value (for debugging)
+ *
+ * @v bcd		BCD-coded value
+ * @ret string		Transcribed value
+ */
+static inline const char * usb_bcd ( uint16_t bcd ) {
+	static char buf[ 6 /* "xx.xx" + NUL */ ];
+	uint8_t high = ( bcd >> 8 );
+	uint8_t low = ( bcd >> 0 );
+
+	snprintf ( buf, sizeof ( buf ), "%x.%02x", high, low );
+	return buf;
+}
+
+/******************************************************************************
+ *
+ * USB descriptors
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Locate USB interface association descriptor
+ *
+ * @v config		Configuraton descriptor
+ * @v first		First interface number
+ * @ret desc		Interface association descriptor, or NULL if not found
+ */
+static struct usb_interface_association_descriptor *
+usb_interface_association_descriptor ( struct usb_configuration_descriptor
+								       *config,
+				       unsigned int first ) {
+	struct usb_interface_association_descriptor *desc;
+
+	/* Find a matching interface association descriptor */
+	for_each_config_descriptor ( desc, config ) {
+		if ( ( desc->header.type ==
+		       USB_INTERFACE_ASSOCIATION_DESCRIPTOR ) &&
+		     ( desc->first == first ) )
+			return desc;
+	}
+	return NULL;
+}
+
+/**
+ * Locate USB interface descriptor
+ *
+ * @v config		Configuraton descriptor
+ * @v interface		Interface number
+ * @v alternate		Alternate setting
+ * @ret desc		Interface descriptor, or NULL if not found
+ */
+struct usb_interface_descriptor *
+usb_interface_descriptor ( struct usb_configuration_descriptor *config,
+			   unsigned int interface, unsigned int alternate ) {
+	struct usb_interface_descriptor *desc;
+
+	/* Find a matching interface descriptor */
+	for_each_config_descriptor ( desc, config ) {
+		if ( ( desc->header.type == USB_INTERFACE_DESCRIPTOR ) &&
+		     ( desc->interface == interface ) &&
+		     ( desc->alternate == alternate ) )
+			return desc;
+	}
+	return NULL;
+}
+
+/**
+ * Locate USB endpoint descriptor
+ *
+ * @v config		Configuration descriptor
+ * @v interface		Interface descriptor
+ * @v type		Endpoint (internal) type
+ * @v index		Endpoint index
+ * @ret desc		Descriptor, or NULL if not found
+ */
+struct usb_endpoint_descriptor *
+usb_endpoint_descriptor ( struct usb_configuration_descriptor *config,
+			  struct usb_interface_descriptor *interface,
+			  unsigned int type, unsigned int index ) {
+	struct usb_endpoint_descriptor *desc;
+	unsigned int attributes = ( type & USB_ENDPOINT_ATTR_TYPE_MASK );
+	unsigned int direction = ( type & USB_DIR_IN );
+
+	/* Find a matching endpoint descriptor */
+	for_each_interface_descriptor ( desc, config, interface ) {
+		if ( ( desc->header.type == USB_ENDPOINT_DESCRIPTOR ) &&
+		     ( ( desc->attributes &
+			 USB_ENDPOINT_ATTR_TYPE_MASK ) == attributes ) &&
+		     ( ( desc->endpoint & USB_DIR_IN ) == direction ) &&
+		     ( index-- == 0 ) )
+			return desc;
+	}
+	return NULL;
+}
+
+/**
+ * Locate USB endpoint companion descriptor
+ *
+ * @v config		Configuration descriptor
+ * @v desc		Endpoint descriptor
+ * @ret descx		Companion descriptor, or NULL if not found
+ */
+struct usb_endpoint_companion_descriptor *
+usb_endpoint_companion_descriptor ( struct usb_configuration_descriptor *config,
+				    struct usb_endpoint_descriptor *desc ) {
+	struct usb_endpoint_companion_descriptor *descx;
+
+	/* Get companion descriptor, if present */
+	descx = container_of ( usb_next_descriptor ( &desc->header ),
+			       struct usb_endpoint_companion_descriptor,
+			       header );
+	return ( ( usb_is_within_config ( config, &descx->header ) &&
+		   descx->header.type == USB_ENDPOINT_COMPANION_DESCRIPTOR )
+		 ? descx : NULL );
+}
+
+/******************************************************************************
+ *
+ * USB endpoint
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Describe USB endpoint from device configuration
+ *
+ * @v ep		USB endpoint
+ * @v config		Configuration descriptor
+ * @v interface		Interface descriptor
+ * @v type		Endpoint (internal) type
+ * @v index		Endpoint index
+ * @ret rc		Return status code
+ */
+int usb_endpoint_described ( struct usb_endpoint *ep,
+			     struct usb_configuration_descriptor *config,
+			     struct usb_interface_descriptor *interface,
+			     unsigned int type, unsigned int index ) {
+	struct usb_endpoint_descriptor *desc;
+	struct usb_endpoint_companion_descriptor *descx;
+	unsigned int sizes;
+	unsigned int burst;
+	size_t mtu;
+
+	/* Locate endpoint descriptor */
+	desc = usb_endpoint_descriptor ( config, interface, type, index );
+	if ( ! desc )
+		return -ENOENT;
+
+	/* Locate companion descriptor, if any */
+	descx = usb_endpoint_companion_descriptor ( config, desc );
+
+	/* Calculate MTU and burst size */
+	sizes = le16_to_cpu ( desc->sizes );
+	mtu = USB_ENDPOINT_MTU ( sizes );
+	burst = ( descx ? descx->burst : USB_ENDPOINT_BURST ( sizes ) );
+
+	/* Describe endpoint */
+	usb_endpoint_describe ( ep, desc->endpoint, desc->attributes,
+				mtu, burst );
+	return 0;
+}
+
+/**
+ * Open USB endpoint
+ *
+ * @v ep		USB endpoint
+ * @ret rc		Return status code
+ */
+int usb_endpoint_open ( struct usb_endpoint *ep ) {
+	struct usb_device *usb = ep->usb;
+	unsigned int idx = USB_ENDPOINT_IDX ( ep->address );
+	int rc;
+
+	/* Populate host controller operations */
+	ep->host = &usb->port->hub->bus->op->endpoint;
+
+	/* Add to endpoint list */
+	if ( usb->ep[idx] != NULL ) {
+		DBGC ( usb, "USB %s %s is already open\n",
+		       usb->name, usb_endpoint_name ( ep->address ) );
+		rc = -EALREADY;
+		goto err_already;
+	}
+	usb->ep[idx] = ep;
+
+	/* Clear any stale error status */
+	ep->rc = 0;
+
+	/* Open endpoint */
+	if ( ( rc = ep->host->open ( ep ) ) != 0 ) {
+		DBGC ( usb, "USB %s %s could not open: %s\n", usb->name,
+		       usb_endpoint_name ( ep->address ), strerror ( rc ) );
+		goto err_open;
+	}
+	ep->open = 1;
+
+	DBGC2 ( usb, "USB %s %s opened with MTU %zd (burst %d)\n", usb->name,
+		usb_endpoint_name ( ep->address ), ep->mtu, ep->burst );
+	return 0;
+
+	ep->open = 0;
+	ep->host->close ( ep );
+ err_open:
+	usb->ep[idx] = NULL;
+ err_already:
+	return rc;
+}
+
+/**
+ * Close USB endpoint
+ *
+ * @v ep		USB endpoint
+ */
+void usb_endpoint_close ( struct usb_endpoint *ep ) {
+	struct usb_device *usb = ep->usb;
+	unsigned int idx = USB_ENDPOINT_IDX ( ep->address );
+
+	/* Sanity checks */
+	assert ( usb->ep[idx] == ep );
+
+	/* Close endpoint */
+	ep->open = 0;
+	ep->host->close ( ep );
+
+	/* Remove from endpoint list */
+	usb->ep[idx] = NULL;
+}
+
+/**
+ * Reset USB endpoint
+ *
+ * @v ep		USB endpoint
+ * @ret rc		Return status code
+ */
+static int usb_endpoint_reset ( struct usb_endpoint *ep ) {
+	struct usb_device *usb = ep->usb;
+	unsigned int type;
+	int rc;
+
+	/* Reset endpoint */
+	if ( ( rc = ep->host->reset ( ep ) ) != 0 ) {
+		DBGC ( usb, "USB %s %s could not reset: %s\n",
+		       usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	/* Clear endpoint halt, if applicable */
+	type = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );
+	if ( ( type != USB_ENDPOINT_ATTR_CONTROL ) &&
+	     ( ( rc = usb_clear_feature ( usb, USB_RECIP_ENDPOINT,
+					  USB_ENDPOINT_HALT,
+					  ep->address ) ) != 0 ) ) {
+		DBGC ( usb, "USB %s %s could not clear endpoint halt: %s\n",
+		       usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	/* Clear recorded error */
+	ep->rc = 0;
+
+	DBGC ( usb, "USB %s %s reset\n",
+	       usb->name, usb_endpoint_name ( ep->address ) );
+	return 0;
+}
+
+/**
+ * Update endpoint MTU
+ *
+ * @v ep		USB endpoint
+ * @v mtu		New MTU
+ * @ret rc		Return status code
+ */
+static int usb_endpoint_mtu ( struct usb_endpoint *ep, size_t mtu ) {
+	struct usb_device *usb = ep->usb;
+	int rc;
+
+	/* Update MTU */
+	ep->mtu = mtu;
+	if ( ( rc = ep->host->mtu ( ep ) ) != 0 ) {
+		DBGC ( usb, "USB %s %s could not update MTU: %s\n",
+		       usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Enqueue USB message transfer
+ *
+ * @v ep		USB endpoint
+ * @v request		Request
+ * @v value		Value parameter
+ * @v index		Index parameter
+ * @v iobuf		I/O buffer
+ * @ret rc		Return status code
+ */
+int usb_message ( struct usb_endpoint *ep, unsigned int request,
+		  unsigned int value, unsigned int index,
+		  struct io_buffer *iobuf ) {
+	struct usb_device *usb = ep->usb;
+	struct usb_port *port = usb->port;
+	struct usb_setup_packet packet;
+	size_t len = iob_len ( iobuf );
+	int rc;
+
+	/* Fail immediately if device has been unplugged */
+	if ( port->speed == USB_SPEED_NONE )
+		return -ENODEV;
+
+	/* Reset endpoint if required */
+	if ( ( ep->rc != 0 ) && ( ( rc = usb_endpoint_reset ( ep ) ) != 0 ) )
+		return rc;
+
+	/* Zero input data buffer (if applicable) */
+	if ( request & USB_DIR_IN )
+		memset ( iobuf->data, 0, len );
+
+	/* Construct setup packet */
+	packet.request = cpu_to_le16 ( request );
+	packet.value = cpu_to_le16 ( value );
+	packet.index = cpu_to_le16 ( index );
+	packet.len = cpu_to_le16 ( len );
+
+	/* Enqueue message transfer */
+	if ( ( rc = ep->host->message ( ep, &packet, iobuf ) ) != 0 ) {
+		DBGC ( usb, "USB %s %s could not enqueue message transfer: "
+		       "%s\n", usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Enqueue USB stream transfer
+ *
+ * @v ep		USB endpoint
+ * @v iobuf		I/O buffer
+ * @ret rc		Return status code
+ */
+int usb_stream ( struct usb_endpoint *ep, struct io_buffer *iobuf ) {
+	struct usb_device *usb = ep->usb;
+	struct usb_port *port = usb->port;
+	int rc;
+
+	/* Fail immediately if device has been unplugged */
+	if ( port->speed == USB_SPEED_NONE )
+		return -ENODEV;
+
+	/* Reset endpoint if required */
+	if ( ( ep->rc != 0 ) && ( ( rc = usb_endpoint_reset ( ep ) ) != 0 ) )
+		return rc;
+
+	/* Enqueue stream transfer */
+	if ( ( rc = ep->host->stream ( ep, iobuf ) ) != 0 ) {
+		DBGC ( usb, "USB %s %s could not enqueue stream transfer: %s\n",
+		       usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Complete transfer (possibly with error)
+ *
+ * @v ep		USB endpoint
+ * @v iobuf		I/O buffer
+ * @v rc		Completion status code
+ */
+void usb_complete_err ( struct usb_endpoint *ep, struct io_buffer *iobuf,
+			int rc ) {
+	struct usb_device *usb = ep->usb;
+
+	/* Record error (if any) */
+	ep->rc = rc;
+	if ( ( rc != 0 ) && ep->open ) {
+		DBGC ( usb, "USB %s %s completion failed: %s\n",
+		       usb->name, usb_endpoint_name ( ep->address ),
+		       strerror ( rc ) );
+	}
+
+	/* Report completion */
+	ep->driver->complete ( ep, iobuf, rc );
+}
+
+/******************************************************************************
+ *
+ * Control endpoint
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Complete USB control transfer
+ *
+ * @v ep		USB endpoint
+ * @v iobuf		I/O buffer
+ * @v rc		Completion status code
+ */
+static void usb_control_complete ( struct usb_endpoint *ep,
+				   struct io_buffer *iobuf, int rc ) {
+	struct usb_device *usb = ep->usb;
+
+	/* Check for failures */
+	if ( rc != 0 ) {
+		DBGC ( usb, "USB %s control transaction failed: %s\n",
+		       usb->name, strerror ( rc ) );
+		free_iob ( iobuf );
+		return;
+	}
+
+	/* Add to list of completed I/O buffers */
+	list_add_tail ( &iobuf->list, &usb->complete );
+}
+
+/** USB control endpoint driver operations */
+static struct usb_endpoint_driver_operations usb_control_operations = {
+	.complete = usb_control_complete,
+};
+
+/**
+ * Issue USB control transaction
+ *
+ * @v usb		USB device
+ * @v request		Request
+ * @v value		Value parameter
+ * @v index		Index parameter
+ * @v data		Data buffer (if any)
+ * @v len		Length of data
+ * @ret rc		Return status code
+ */
+int usb_control ( struct usb_device *usb, unsigned int request,
+		  unsigned int value, unsigned int index, void *data,
+		  size_t len ) {
+	struct usb_bus *bus = usb->port->hub->bus;
+	struct usb_endpoint *ep = &usb->control;
+	struct io_buffer *iobuf;
+	struct io_buffer *cmplt;
+	unsigned int i;
+	int rc;
+
+	/* Allocate I/O buffer */
+	iobuf = alloc_iob ( len );
+	if ( ! iobuf ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	iob_put ( iobuf, len );
+	if ( request & USB_DIR_IN ) {
+		memset ( data, 0, len );
+	} else {
+		memcpy ( iobuf->data, data, len );
+	}
+
+	/* Enqueue message */
+	if ( ( rc = usb_message ( ep, request, value, index, iobuf ) ) != 0 )
+		goto err_message;
+
+	/* Wait for completion */
+	for ( i = 0 ; i < USB_CONTROL_MAX_WAIT_MS ; i++ ) {
+
+		/* Poll bus */
+		usb_poll ( bus );
+
+		/* Check for completion */
+		while ( ( cmplt = list_first_entry ( &usb->complete,
+						     struct io_buffer,
+						     list ) ) ) {
+
+			/* Remove from completion list */
+			list_del ( &cmplt->list );
+
+			/* Discard stale completions */
+			if ( cmplt != iobuf ) {
+				DBGC ( usb, "USB %s stale control "
+				       "completion:\n", usb->name );
+				DBGC_HDA ( usb, 0, cmplt->data,
+					   iob_len ( cmplt ) );
+				free_iob ( cmplt );
+				continue;
+			}
+
+			/* Copy completion to data buffer, if applicable */
+			assert ( iob_len ( cmplt ) <= len );
+			if ( request & USB_DIR_IN )
+				memcpy ( data, cmplt->data, iob_len ( cmplt ) );
+			free_iob ( cmplt );
+			return 0;
+		}
+
+		/* Fail immediately if endpoint is in an error state */
+		if ( ep->rc )
+			return ep->rc;
+
+		/* Delay */
+		mdelay ( 1 );
+	}
+
+	DBGC ( usb, "USB %s timed out waiting for control transaction\n",
+	       usb->name );
+	return -ETIMEDOUT;
+
+ err_message:
+	free_iob ( iobuf );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Get USB string descriptor
+ *
+ * @v usb		USB device
+ * @v index		String index
+ * @v language		Language ID
+ * @v buf		Data buffer
+ * @v len		Length of buffer
+ * @ret len		String length (excluding NUL), or negative error
+ */
+int usb_get_string_descriptor ( struct usb_device *usb, unsigned int index,
+				unsigned int language, char *buf, size_t len ) {
+	size_t max = ( len ? ( len - 1 /* NUL */ ) : 0 );
+	struct {
+		struct usb_descriptor_header header;
+		uint16_t character[max];
+	} __attribute__ (( packed )) *desc;
+	unsigned int actual;
+	unsigned int i;
+	int rc;
+
+	/* Allocate buffer for string */
+	desc = malloc ( sizeof ( *desc ) );
+	if ( ! desc ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+
+	/* Get descriptor */
+	if ( ( rc = usb_get_descriptor ( usb, 0, USB_STRING_DESCRIPTOR, index,
+					 language, &desc->header,
+					 sizeof ( *desc ) ) ) != 0 )
+		goto err_get_descriptor;
+
+	/* Copy to buffer */
+	actual = ( ( desc->header.len - sizeof ( desc->header ) ) /
+		   sizeof ( desc->character[0] ) );
+	for ( i = 0 ; ( ( i < actual ) && ( i < max ) ) ; i++ )
+		buf[i] = le16_to_cpu ( desc->character[i] );
+	if ( len )
+		buf[i] = '\0';
+
+	/* Free buffer */
+	free ( desc );
+
+	return actual;
+
+ err_get_descriptor:
+	free ( desc );
+ err_alloc:
+	return rc;
+}
+
+/******************************************************************************
+ *
+ * USB device driver
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Describe USB function
+ *
+ * @v func		USB function
+ * @v config		Configuration descriptor
+ * @v first		First interface number
+ * @ret rc		Return status code
+ */
+static int usb_function ( struct usb_function *func,
+			  struct usb_configuration_descriptor *config,
+			  unsigned int first ) {
+	struct usb_device *usb = func->usb;
+	struct usb_interface_association_descriptor *association;
+	struct usb_interface_descriptor *interface;
+	unsigned int i;
+
+	/* First, look for an interface association descriptor */
+	association = usb_interface_association_descriptor ( config, first );
+	if ( association ) {
+
+		/* Sanity check */
+		if ( ( association->first + association->count ) >
+		     config->interfaces ) {
+			DBGC ( usb, "USB %s has invalid association [%d-%d)\n",
+			       func->name, association->first,
+			       ( association->first + association->count ) );
+			return -ERANGE;
+		}
+
+		/* Describe function */
+		memcpy ( &func->class, &association->class,
+			 sizeof ( func->class ) );
+		func->count = association->count;
+		for ( i = 0 ; i < association->count ; i++ )
+			func->interface[i] = ( association->first + i );
+		return 0;
+	}
+
+	/* Next, look for an interface descriptor */
+	interface = usb_interface_descriptor ( config, first, 0 );
+	if ( ! interface ) {
+		DBGC ( usb, "USB %s has no interface descriptor\n",
+		       func->name );
+		return -ENOENT;
+	}
+
+	/* Describe function */
+	memcpy ( &func->class, &interface->class, sizeof ( func->class ) );
+	func->count = 1;
+	func->interface[0] = first;
+	return 0;
+}
+
+/**
+ * Check for a USB device ID match
+ *
+ * @v func		USB function
+ * @v id		Device ID
+ * @ret matches		Device ID matches
+ */
+static int
+usb_device_id_matches ( struct usb_function *func, struct usb_device_id *id ) {
+
+	return ( ( ( id->vendor == func->dev.desc.vendor ) ||
+		   ( id->vendor == USB_ANY_ID ) ) &&
+		 ( ( id->product == func->dev.desc.device ) ||
+		   ( id->product == USB_ANY_ID ) ) &&
+		 ( id->class.class == func->class.class ) &&
+		 ( id->class.subclass == func->class.subclass ) &&
+		 ( id->class.protocol == func->class.protocol ) );
+}
+
+/**
+ * Probe USB device driver
+ *
+ * @v func		USB function
+ * @v config		Configuration descriptor
+ * @ret rc		Return status code
+ */
+static int usb_probe ( struct usb_function *func,
+		       struct usb_configuration_descriptor *config ) {
+	struct usb_device *usb = func->usb;
+	struct usb_driver *driver;
+	struct usb_device_id *id;
+	unsigned int i;
+	int rc;
+
+	/* Look for a matching driver */
+	for_each_table_entry ( driver, USB_DRIVERS ) {
+		for ( i = 0 ; i < driver->id_count ; i++ ) {
+
+			/* Check for a matching ID */
+			id = &driver->ids[i];
+			if ( ! usb_device_id_matches ( func, id ) )
+				continue;
+
+			/* Probe driver */
+			if ( ( rc = driver->probe ( func, config ) ) != 0 ) {
+				DBGC ( usb, "USB %s failed to probe driver %s: "
+				       "%s\n", func->name, id->name,
+				       strerror ( rc ) );
+				/* Continue trying other drivers */
+				continue;
+			}
+
+			/* Record driver */
+			func->driver = driver;
+			func->dev.driver_name = id->name;
+			return 0;
+		}
+	}
+
+	/* No driver found */
+	DBGC ( usb, "USB %s %04x:%04x class %d:%d:%d has no driver\n",
+	       func->name, func->dev.desc.vendor, func->dev.desc.device,
+	       func->class.class, func->class.subclass, func->class.protocol );
+	return -ENOENT;
+}
+
+/**
+ * Remove USB device driver
+ *
+ * @v func		USB function
+ */
+static void usb_remove ( struct usb_function *func ) {
+
+	/* Remove driver */
+	func->driver->remove ( func );
+}
+
+/**
+ * Probe all USB device drivers
+ *
+ * @v usb		USB device
+ * @v config		Configuration descriptor
+ */
+static void
+usb_probe_all ( struct usb_device *usb,
+		struct usb_configuration_descriptor *config ) {
+	struct usb_bus *bus = usb->port->hub->bus;
+	struct usb_function *func;
+	uint8_t used[config->interfaces];
+	unsigned int first;
+	unsigned int i;
+	int rc;
+
+	/* Identify each function in turn */
+	memset ( used, 0, sizeof ( used ) );
+	for ( first = 0 ; first < config->interfaces ; first++ ) {
+
+		/* Skip interfaces already used */
+		if ( used[first] )
+			continue;
+
+		/* Allocate and initialise structure */
+		func = zalloc ( sizeof ( *func ) +
+				( config->interfaces *
+				  sizeof ( func->interface[0] ) ) );
+		if ( ! func )
+			goto err_alloc;
+		func->name = func->dev.name;
+		func->usb = usb;
+		func->dev.desc.bus_type = BUS_TYPE_USB;
+		func->dev.desc.location = usb->address;
+		func->dev.desc.vendor = le16_to_cpu ( usb->device.vendor );
+		func->dev.desc.device = le16_to_cpu ( usb->device.product );
+		snprintf ( func->dev.name, sizeof ( func->dev.name ),
+			   "%s-%d", usb->name, first );
+		INIT_LIST_HEAD ( &func->dev.children );
+		func->dev.parent = bus->dev;
+
+		/* Identify function */
+		if ( ( rc = usb_function ( func, config, first ) ) != 0 )
+			goto err_function;
+		assert ( func->count <= config->interfaces );
+
+		/* Mark interfaces as used */
+		for ( i = 0 ; i < func->count ; i++ ) {
+			assert ( func->interface[i] < config->interfaces );
+			used[ func->interface[i] ] = 1;
+		}
+
+		/* Probe device driver */
+		if ( ( rc = usb_probe ( func, config ) ) != 0 )
+			goto err_probe;
+		DBGC ( usb, "USB %s %04x:%04x class %d:%d:%d interfaces ",
+		       func->name, func->dev.desc.vendor, func->dev.desc.device,
+		       func->class.class, func->class.subclass,
+		       func->class.protocol );
+		for ( i = 0 ; i < func->count ; i++ )
+			DBGC ( usb, "%s%d", ( i ? "," : "" ),
+			       func->interface[i] );
+		DBGC ( usb, " using driver %s\n", func->dev.driver_name );
+
+		/* Add to list of functions */
+		list_add ( &func->list, &usb->functions );
+
+		/* Add to device hierarchy */
+		list_add_tail ( &func->dev.siblings, &bus->dev->children );
+
+		continue;
+
+		list_del ( &func->dev.siblings );
+		list_del ( &func->list );
+		usb_remove ( func );
+	err_probe:
+		free ( func );
+	err_alloc:
+	err_function:
+		/* Continue registering other functions */
+		continue;
+	}
+}
+
+/**
+ * Remove all device drivers
+ *
+ * @v usb		USB device
+ */
+static void usb_remove_all ( struct usb_device *usb ) {
+	struct usb_function *func;
+	struct usb_function *tmp;
+
+	/* Remove all functions */
+	list_for_each_entry_safe ( func, tmp, &usb->functions, list ) {
+
+		/* Remove device driver */
+		usb_remove ( func );
+
+		/* Remove from device hierarchy */
+		assert ( list_empty ( &func->dev.children ) );
+		list_del ( &func->dev.siblings );
+
+		/* Remove from list of functions */
+		list_del ( &func->list );
+
+		/* Free function */
+		free ( func );
+	}
+}
+
+/******************************************************************************
+ *
+ * USB device
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Allocate USB device
+ *
+ * @v port		USB port
+ * @ret usb		USB device, or NULL on allocation failure
+ */
+static struct usb_device * alloc_usb ( struct usb_port *port ) {
+	struct usb_hub *hub = port->hub;
+	struct usb_bus *bus = hub->bus;
+	struct usb_device *usb;
+
+	/* Allocate and initialise structure */
+	usb = zalloc ( sizeof ( *usb ) );
+	if ( ! usb )
+		return NULL;
+	snprintf ( usb->name, sizeof ( usb->name ), "%s%c%d", hub->name,
+		   ( hub->usb ? '.' : '-' ), port->address );
+	usb->port = port;
+	INIT_LIST_HEAD ( &usb->functions );
+	usb->host = &bus->op->device;
+	usb_endpoint_init ( &usb->control, usb, &usb_control_operations );
+	INIT_LIST_HEAD ( &usb->complete );
+
+	return usb;
+}
+
+/**
+ * Register USB device
+ *
+ * @v usb		USB device
+ * @ret rc		Return status code
+ */
+static int register_usb ( struct usb_device *usb ) {
+	struct usb_port *port = usb->port;
+	struct usb_hub *hub = port->hub;
+	struct usb_bus *bus = hub->bus;
+	struct usb_configuration_descriptor partial;
+	struct usb_configuration_descriptor *config;
+	unsigned int protocol;
+	size_t mtu;
+	size_t len;
+	int rc;
+
+	/* Add to port */
+	if ( port->usb != NULL ) {
+		DBGC ( hub, "USB hub %s port %d is already registered to %s\n",
+		       hub->name, port->address, port->usb->name );
+		rc = -EALREADY;
+		goto err_already;
+	}
+	port->usb = usb;
+
+	/* Add to bus device list */
+	list_add_tail ( &usb->list, &bus->devices );
+
+	/* Enable device */
+	if ( ( rc = hub->driver->enable ( hub, port ) ) != 0 ) {
+		DBGC ( hub, "USB hub %s port %d could not enable: %s\n",
+		       hub->name, port->address, strerror ( rc ) );
+		goto err_enable;
+	}
+
+	/* Get device speed */
+	if ( ( rc = hub->driver->speed ( hub, port ) ) != 0 ) {
+		DBGC ( hub, "USB hub %s port %d could not get speed: %s\n",
+		       hub->name, port->address, strerror ( rc ) );
+		goto err_speed;
+	}
+	DBGC2 ( usb, "USB %s attached as %s-speed device\n",
+		usb->name, usb_speed_name ( port->speed ) );
+
+	/* Open device */
+	if ( ( rc = usb->host->open ( usb ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not open: %s\n",
+		       usb->name, strerror ( rc ) );
+		goto err_open;
+	}
+
+	/* Describe control endpoint */
+	mtu = USB_EP0_DEFAULT_MTU ( port->speed );
+	usb_endpoint_describe ( &usb->control, USB_EP0_ADDRESS,
+				USB_EP0_ATTRIBUTES, mtu, USB_EP0_BURST );
+
+	/* Open control endpoint */
+	if ( ( rc = usb_endpoint_open ( &usb->control ) ) != 0 )
+		goto err_open_control;
+	assert ( usb_endpoint ( usb, USB_EP0_ADDRESS ) == &usb->control );
+
+	/* Assign device address */
+	if ( ( rc = usb->host->address ( usb ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not set address: %s\n",
+		       usb->name, strerror ( rc ) );
+		goto err_address;
+	}
+	DBGC2 ( usb, "USB %s assigned address %d\n", usb->name, usb->address );
+
+	/* Read first part of device descriptor to get EP0 MTU */
+	if ( ( rc = usb_get_mtu ( usb, &usb->device ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not get MTU: %s\n",
+		       usb->name, strerror ( rc ) );
+		goto err_get_mtu;
+	}
+
+	/* Calculate EP0 MTU */
+	protocol = le16_to_cpu ( usb->device.protocol );
+	mtu = ( ( protocol < USB_PROTO_3_0 ) ?
+		usb->device.mtu : ( 1 << usb->device.mtu ) );
+	DBGC2 ( usb, "USB %s has control MTU %zd (guessed %zd)\n",
+		usb->name, mtu, usb->control.mtu );
+
+	/* Update MTU */
+	if ( ( rc = usb_endpoint_mtu ( &usb->control, mtu ) ) != 0 )
+		goto err_mtu;
+
+	/* Read whole device descriptor */
+	if ( ( rc = usb_get_device_descriptor ( usb, &usb->device ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not get device descriptor: %s\n",
+		       usb->name, strerror ( rc ) );
+		goto err_get_device_descriptor;
+	}
+	DBGC ( usb, "USB %s addr %d %04x:%04x class %d:%d:%d (v%s, %s-speed, "
+	       "MTU %zd)\n", usb->name, usb->address,
+	       le16_to_cpu ( usb->device.vendor ),
+	       le16_to_cpu ( usb->device.product ), usb->device.class.class,
+	       usb->device.class.subclass, usb->device.class.protocol,
+	       usb_bcd ( le16_to_cpu ( usb->device.protocol ) ),
+	       usb_speed_name ( port->speed ), usb->control.mtu );
+
+	/* Read first part of configuration descriptor to get size */
+	if ( ( rc = usb_get_config_descriptor ( usb, 0, &partial,
+						sizeof ( partial ) ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not get configuration descriptor: "
+		       "%s\n", usb->name, strerror ( rc ) );
+		goto err_get_partial;
+	}
+	len = le16_to_cpu ( partial.len );
+	if ( len < sizeof ( partial ) ) {
+		DBGC ( usb, "USB %s underlength configuraton descriptor\n",
+		       usb->name );
+		rc = -EINVAL;
+		goto err_partial_len;
+	}
+
+	/* Allocate buffer for whole configuration descriptor */
+	config = malloc ( len );
+	if ( ! config ) {
+		rc = -ENOMEM;
+		goto err_alloc_config;
+	}
+
+	/* Read whole configuration descriptor */
+	if ( ( rc = usb_get_config_descriptor ( usb, 0, config, len ) ) != 0 ) {
+		DBGC ( usb, "USB %s could not get configuration descriptor: "
+		       "%s\n", usb->name, strerror ( rc ) );
+		goto err_get_config_descriptor;
+	}
+	if ( config->len != partial.len ) {
+		DBGC ( usb, "USB %s bad configuration descriptor length\n",
+		       usb->name );
+		rc = -EINVAL;
+		goto err_config_len;
+	}
+
+	/* Set configuration */
+	if ( ( rc = usb_set_configuration ( usb, config->config ) ) != 0){
+		DBGC ( usb, "USB %s could not set configuration %#02x: %s\n",
+		       usb->name, config->config, strerror ( rc ) );
+		goto err_set_configuration;
+	}
+
+	/* Probe USB device drivers */
+	usb_probe_all ( usb, config );
+
+	/* Free configuration descriptor */
+	free ( config );
+
+	return 0;
+
+	usb_remove_all ( usb );
+	usb_set_configuration ( usb, 0 );
+ err_set_configuration:
+ err_config_len:
+ err_get_config_descriptor:
+	free ( config );
+ err_alloc_config:
+ err_partial_len:
+ err_get_partial:
+ err_get_device_descriptor:
+ err_mtu:
+ err_get_mtu:
+ err_address:
+	usb_endpoint_close ( &usb->control );
+ err_open_control:
+	usb->host->close ( usb );
+ err_open:
+ err_speed:
+	hub->driver->disable ( hub, port );
+ err_enable:
+	list_del ( &usb->list );
+	port->usb = NULL;
+ err_already:
+	return rc;
+}
+
+/**
+ * Unregister USB device
+ *
+ * @v usb		USB device
+ */
+static void unregister_usb ( struct usb_device *usb ) {
+	struct usb_port *port = usb->port;
+	struct usb_hub *hub = port->hub;
+	struct io_buffer *iobuf;
+	struct io_buffer *tmp;
+	unsigned int i;
+
+	/* Remove device drivers */
+	usb_remove_all ( usb );
+
+	/* Sanity checks */
+	for ( i = 0 ; i < ( sizeof ( usb->ep ) / sizeof ( usb->ep[0] ) ) ; i++){
+		if ( i != USB_ENDPOINT_IDX ( USB_EP0_ADDRESS ) )
+			assert ( usb->ep[i] == NULL );
+	}
+	assert ( port->usb == usb );
+
+	/* Clear device configuration */
+	usb_set_configuration ( usb, 0 );
+
+	/* Close control endpoint */
+	usb_endpoint_close ( &usb->control );
+
+	/* Discard any stale control completions */
+	list_for_each_entry_safe ( iobuf, tmp, &usb->complete, list ) {
+		list_del ( &iobuf->list );
+		free_iob ( iobuf );
+	}
+
+	/* Close device */
+	usb->host->close ( usb );
+
+	/* Disable port */
+	hub->driver->disable ( hub, port );
+
+	/* Remove from bus device list */
+	list_del ( &usb->list );
+
+	/* Remove from port */
+	port->usb = NULL;
+}
+
+/**
+ * Free USB device
+ *
+ * @v usb		USB device
+ */
+static void free_usb ( struct usb_device *usb ) {
+	unsigned int i;
+
+	/* Sanity checks */
+	for ( i = 0 ; i < ( sizeof ( usb->ep ) / sizeof ( usb->ep[0] ) ) ; i++ )
+		assert ( usb->ep[i] == NULL );
+	assert ( list_empty ( &usb->functions ) );
+	assert ( list_empty ( &usb->complete ) );
+
+	/* Free device */
+	free ( usb );
+}
+
+/******************************************************************************
+ *
+ * USB device hotplug event handling
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Handle newly attached USB device
+ *
+ * @v port		USB port
+ * @ret rc		Return status code
+ */
+static int usb_attached ( struct usb_port *port ) {
+	struct usb_device *usb;
+	int rc;
+
+	/* Sanity checks */
+	assert ( port->usb == NULL );
+
+	/* Allocate USB device */
+	usb = alloc_usb ( port );
+	if ( ! usb ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+
+	/* Register USB device */
+	if ( ( rc = register_usb ( usb ) ) != 0 )
+		goto err_register;
+
+	return 0;
+
+	unregister_usb ( usb );
+ err_register:
+	free_usb ( usb );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Handle newly detached USB device
+ *
+ * @v port		USB port
+ */
+static void usb_detached ( struct usb_port *port ) {
+	struct usb_device *usb = port->usb;
+
+	/* Sanity checks */
+	assert ( port->usb != NULL );
+
+	/* Unregister USB device */
+	unregister_usb ( usb );
+
+	/* Free USB device */
+	free_usb ( usb );
+}
+
+/**
+ * Handle newly attached or detached USB devices
+ *
+ * @v port		USB port
+ * @ret rc		Return status code
+ */
+static int usb_hotplug ( struct usb_port *port ) {
+	struct usb_hub *hub = port->hub;
+	int rc;
+
+	/* Get current port speed */
+	if ( ( rc = hub->driver->speed ( hub, port ) ) != 0 ) {
+		DBGC ( hub, "USB hub %s port %d could not get speed: %s\n",
+		       hub->name, port->address, strerror ( rc ) );
+		return rc;
+	}
+
+	/* Handle attached/detached device as applicable */
+	if ( port->speed && ! port->usb ) {
+		/* Newly attached device */
+		return usb_attached ( port );
+	} else if ( port->usb && ! port->speed ) {
+		/* Newly detached device */
+		usb_detached ( port );
+		return 0;
+	} else {
+		/* Ignore */
+		return 0;
+	}
+}
+
+/******************************************************************************
+ *
+ * USB process
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Report port status change
+ *
+ * @v port		USB port
+ */
+void usb_port_changed ( struct usb_port *port ) {
+	struct usb_hub *hub = port->hub;
+	struct usb_bus *bus = hub->bus;
+
+	/* Record hub port status change */
+	list_del ( &port->list );
+	list_add_tail ( &port->list, &bus->changed );
+}
+
+/**
+ * USB process
+ *
+ * @v bus		USB bus
+ */
+static void usb_step ( struct usb_bus *bus ) {
+	struct usb_port *port;
+
+	/* Poll bus */
+	usb_poll ( bus );
+
+	/* Handle any changed ports, allowing for the fact that the
+	 * port list may change as we perform hotplug actions.
+	 */
+	while ( ! list_empty ( &bus->changed ) ) {
+
+		/* Get first changed port */
+		port = list_first_entry ( &bus->changed, struct usb_port, list);
+		assert ( port != NULL );
+
+		/* Remove from list of changed ports */
+		list_del ( &port->list );
+		INIT_LIST_HEAD ( &port->list );
+
+		/* Perform appropriate hotplug action */
+		usb_hotplug ( port );
+	}
+}
+
+/** USB process */
+static struct process_descriptor usb_process_desc =
+	PROC_DESC ( struct usb_bus, process, usb_step );
+
+/******************************************************************************
+ *
+ * USB hub
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Allocate USB hub
+ *
+ * @v bus		USB bus
+ * @v usb		Underlying USB device, if any
+ * @v ports		Number of ports
+ * @v driver		Hub driver operations
+ * @ret hub		USB hub, or NULL on allocation failure
+ */
+struct usb_hub * alloc_usb_hub ( struct usb_bus *bus, struct usb_device *usb,
+				 unsigned int ports,
+				 struct usb_hub_driver_operations *driver ) {
+	struct usb_hub *hub;
+	struct usb_port *port;
+	unsigned int i;
+
+	/* Allocate and initialise structure */
+	hub = zalloc ( sizeof ( *hub ) + ( ports * sizeof ( hub->port[0] ) ) );
+	if ( ! hub )
+		return NULL;
+	hub->name = ( usb ? usb->name : bus->name );
+	hub->bus = bus;
+	hub->usb = usb;
+	if ( usb )
+		hub->protocol = usb->port->protocol;
+	hub->ports = ports;
+	hub->driver = driver;
+
+	/* Initialise port list */
+	for ( i = 1 ; i <= hub->ports ; i++ ) {
+		port = usb_port ( hub, i );
+		port->hub = hub;
+		port->address = i;
+		if ( usb )
+			port->protocol = usb->port->protocol;
+		INIT_LIST_HEAD ( &port->list );
+	}
+
+	return hub;
+}
+
+/**
+ * Register USB hub
+ *
+ * @v hub		USB hub
+ * @ret rc		Return status code
+ */
+int register_usb_hub ( struct usb_hub *hub ) {
+	struct usb_bus *bus = hub->bus;
+	struct usb_port *port;
+	unsigned int i;
+	int rc;
+
+	/* Add to hub list */
+	list_add_tail ( &hub->list, &bus->hubs );
+
+	/* Open hub */
+	if ( ( rc = hub->driver->open ( hub ) ) != 0 ) {
+		DBGC ( hub, "USB hub %s could not open: %s\n",
+		       hub->name, strerror ( rc ) );
+		goto err_open;
+	}
+
+	/* Delay to allow ports to stabilise */
+	mdelay ( USB_PORT_DELAY_MS );
+
+	/* Attach any devices already present */
+	for ( i = 1 ; i <= hub->ports ; i++ ) {
+		port = usb_port ( hub, i );
+		usb_hotplug ( port );
+	}
+
+	/* Some hubs seem to defer reporting device connections until
+	 * their interrupt endpoint is polled for the first time.
+	 * Poll the bus once now in order to pick up any such
+	 * connections.
+	 */
+	usb_step ( bus );
+
+	return 0;
+
+	hub->driver->close ( hub );
+ err_open:
+	list_del ( &hub->list );
+	return rc;
+}
+
+/**
+ * Unregister USB hub
+ *
+ * @v hub		USB hub
+ */
+void unregister_usb_hub ( struct usb_hub *hub ) {
+	struct usb_port *port;
+	unsigned int i;
+
+	/* Detach all devices */
+	for ( i = 1 ; i <= hub->ports ; i++ ) {
+		port = usb_port ( hub, i );
+		if ( port->usb )
+			usb_detached ( port );
+	}
+
+	/* Close hub */
+	hub->driver->close ( hub );
+
+	/* Cancel any pending port status changes */
+	for ( i = 1 ; i <= hub->ports ; i++ ) {
+		port = usb_port ( hub, i );
+		list_del ( &port->list );
+		INIT_LIST_HEAD ( &port->list );
+	}
+
+	/* Remove from hub list */
+	list_del ( &hub->list );
+}
+
+/**
+ * Free USB hub
+ *
+ * @v hub		USB hub
+ */
+void free_usb_hub ( struct usb_hub *hub ) {
+	struct usb_port *port;
+	unsigned int i;
+
+	/* Sanity checks */
+	for ( i = 1 ; i <= hub->ports ; i++ ) {
+		port = usb_port ( hub, i );
+		assert ( port->usb == NULL );
+		assert ( list_empty ( &port->list ) );
+	}
+
+	/* Free hub */
+	free ( hub );
+}
+
+/******************************************************************************
+ *
+ * USB bus
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Allocate USB bus
+ *
+ * @v dev		Underlying hardware device
+ * @v ports		Number of root hub ports
+ * @v op		Host controller operations
+ * @ret bus		USB bus, or NULL on allocation failure
+ */
+struct usb_bus * alloc_usb_bus ( struct device *dev, unsigned int ports,
+				 struct usb_host_operations *op ) {
+	struct usb_bus *bus;
+
+	/* Allocate and initialise structure */
+	bus = zalloc ( sizeof ( *bus ) );
+	if ( ! bus )
+		goto err_alloc_bus;
+	bus->name = dev->name;
+	bus->dev = dev;
+	bus->op = op;
+	INIT_LIST_HEAD ( &bus->devices );
+	INIT_LIST_HEAD ( &bus->hubs );
+	INIT_LIST_HEAD ( &bus->changed );
+	process_init_stopped ( &bus->process, &usb_process_desc, NULL );
+	bus->host = &bus->op->bus;
+
+	/* Allocate root hub */
+	bus->hub = alloc_usb_hub ( bus, NULL, ports, &op->hub );
+	if ( ! bus->hub )
+		goto err_alloc_hub;
+
+	return bus;
+
+	free_usb_hub ( bus->hub );
+ err_alloc_hub:
+	free ( bus );
+ err_alloc_bus:
+	return NULL;
+}
+
+/**
+ * Register USB bus
+ *
+ * @v bus		USB bus
+ * @ret rc		Return status code
+ */
+int register_usb_bus ( struct usb_bus *bus ) {
+	int rc;
+
+	/* Sanity checks */
+	assert ( bus->hub != NULL );
+
+	/* Open bus */
+	if ( ( rc = bus->host->open ( bus ) ) != 0 )
+		goto err_open;
+
+	/* Register root hub */
+	if ( ( rc = register_usb_hub ( bus->hub ) ) != 0 )
+		goto err_register_hub;
+
+	/* Start bus process */
+	process_add ( &bus->process );
+
+	return 0;
+
+	unregister_usb_hub ( bus->hub );
+ err_register_hub:
+	bus->host->close ( bus );
+ err_open:
+	return rc;
+}
+
+/**
+ * Unregister USB bus
+ *
+ * @v bus		USB bus
+ */
+void unregister_usb_bus ( struct usb_bus *bus ) {
+
+	/* Sanity checks */
+	assert ( bus->hub != NULL );
+	assert ( process_running ( &bus->process ) );
+
+	/* Stop bus process */
+	process_del ( &bus->process );
+
+	/* Unregister root hub */
+	unregister_usb_hub ( bus->hub );
+
+	/* Close bus */
+	bus->host->close ( bus );
+
+	/* Sanity checks */
+	assert ( list_empty ( &bus->devices ) );
+	assert ( list_empty ( &bus->hubs ) );
+	assert ( ! process_running ( &bus->process ) );
+}
+
+/**
+ * Free USB bus
+ *
+ * @v bus		USB bus
+ */
+void free_usb_bus ( struct usb_bus *bus ) {
+
+	/* Sanity checks */
+	assert ( list_empty ( &bus->devices ) );
+	assert ( list_empty ( &bus->hubs ) );
+	assert ( ! process_running ( &bus->process ) );
+
+	/* Free root hub */
+	free_usb_hub ( bus->hub );
+
+	/* Free bus */
+	free ( bus );
+}
+
+/******************************************************************************
+ *
+ * USB bus topology
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Get USB route string
+ *
+ * @v usb		USB device
+ * @ret route		USB route string
+ */
+unsigned int usb_route_string ( struct usb_device *usb ) {
+	unsigned int route;
+
+	/* Navigate up to root hub, constructing route string as we go */
+	for ( route = 0 ; usb->port->hub->usb ; usb = usb->port->hub->usb ) {
+		route <<= 4;
+		route |= ( ( usb->port->address > 0xf ) ?
+			   0xf : usb->port->address );
+	}
+	return route;
+}
+
+/**
+ * Get USB depth
+ *
+ * @v usb		USB device
+ * @ret depth		Hub depth
+ */
+unsigned int usb_depth ( struct usb_device *usb ) {
+	unsigned int depth;
+
+	/* Navigate up to root hub, constructing depth as we go */
+	for ( depth = 0 ; usb->port->hub->usb ; usb = usb->port->hub->usb )
+		depth++;
+
+	return depth;
+}
+
+/**
+ * Get USB root hub port
+ *
+ * @v usb		USB device
+ * @ret port		Root hub port
+ */
+struct usb_port * usb_root_hub_port ( struct usb_device *usb ) {
+
+	/* Navigate up to root hub */
+	while ( usb->port->hub->usb )
+		usb = usb->port->hub->usb;
+
+	return usb->port;
+}