[spice-gtk,v3,1/3] usb-redir: isolate usage of libusb and usbredirhost

Submitted by Frediano Ziglio on July 10, 2019, 9:49 a.m.

Details

Message ID 20190710094924.17350-2-fziglio@redhat.com
State Accepted
Commit 2e19014e99681a1e6ca8b4f517659500c6aefaab
Headers show
Series "Implementation of USB backend layer" ( rev: 3 ) in Spice

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Commit Message

Frediano Ziglio July 10, 2019, 9:49 a.m.
From: Yuri Benditovich <yuri.benditovich@daynix.com>

As a step toward possibility to present emulated USB devices
to the guest, we remove the knowledge about libusb and
usbredirhost (which depends on libusb) from all the modules
and concentrate it in one (usb backend) which presents
abstract USB objects and internal API to all other modules.
Internal API presents following types of objects:
* SpiceUsbBackend: supports enumeration of local USB devices
  (Windows), hot plug/unplug callbacks (Linux) and events
  handling. It wraps libusb_context
* SpiceUsbBackendDevice: represent local USB device, provides
  access to cached properties of the device, wraps libusb_device
* SpiceUsbBackendChannel: accumulates redirection functionality,
  wraps usbredirhost

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
---
 src/channel-usbredir-priv.h   |  12 +-
 src/channel-usbredir.c        | 236 ++----------
 src/meson.build               |   2 +
 src/usb-backend.c             | 657 ++++++++++++++++++++++++++++++++++
 src/usb-backend.h             | 102 ++++++
 src/usb-device-manager-priv.h |   1 -
 src/usb-device-manager.c      | 336 ++++++-----------
 src/win-usb-dev.c             | 103 ++----
 src/win-usb-dev.h             |   5 +-
 9 files changed, 946 insertions(+), 508 deletions(-)
 create mode 100644 src/usb-backend.c
 create mode 100644 src/usb-backend.h

Patch hide | download patch | download mbox

diff --git a/src/channel-usbredir-priv.h b/src/channel-usbredir-priv.h
index 1ea8a196..80cd31f6 100644
--- a/src/channel-usbredir-priv.h
+++ b/src/channel-usbredir-priv.h
@@ -23,9 +23,8 @@ 
 
 #ifdef USE_USBREDIR
 
-#include <libusb.h>
-#include <usbredirfilter.h>
 #include "spice-client.h"
+#include "usb-backend.h"
 
 G_BEGIN_DECLS
 
@@ -33,7 +32,7 @@  G_BEGIN_DECLS
    context should not be destroyed before the last device has been
    disconnected */
 void spice_usbredir_channel_set_context(SpiceUsbredirChannel *channel,
-                                        libusb_context       *context);
+                                        SpiceUsbBackend      *context);
 
 void spice_usbredir_channel_disconnect_device_async(SpiceUsbredirChannel *channel,
                                                     GCancellable *cancellable,
@@ -48,7 +47,7 @@  gboolean spice_usbredir_channel_disconnect_device_finish(SpiceUsbredirChannel *c
    (through spice_channel_connect()), before calling this. */
 void spice_usbredir_channel_connect_device_async(
                                         SpiceUsbredirChannel *channel,
-                                        libusb_device        *device,
+                                        SpiceUsbBackendDevice *device,
                                         SpiceUsbDevice       *spice_device,
                                         GCancellable         *cancellable,
                                         GAsyncReadyCallback   callback,
@@ -60,7 +59,7 @@  gboolean spice_usbredir_channel_connect_device_finish(
 
 void spice_usbredir_channel_disconnect_device(SpiceUsbredirChannel *channel);
 
-libusb_device *spice_usbredir_channel_get_device(SpiceUsbredirChannel *channel);
+SpiceUsbBackendDevice *spice_usbredir_channel_get_device(SpiceUsbredirChannel *channel);
 
 void spice_usbredir_channel_lock(SpiceUsbredirChannel *channel);
 
@@ -71,6 +70,9 @@  void spice_usbredir_channel_get_guest_filter(
                           const struct usbredirfilter_rule  **rules_ret,
                           int                                *rules_count_ret);
 
+/* Callback for USB backend */
+int spice_usbredir_write_callback(SpiceUsbredirChannel *channel, uint8_t *data, int count);
+
 G_END_DECLS
 
 #endif /* USE_USBREDIR */
diff --git a/src/channel-usbredir.c b/src/channel-usbredir.c
index a54f67b7..76534180 100644
--- a/src/channel-usbredir.c
+++ b/src/channel-usbredir.c
@@ -23,7 +23,6 @@ 
 
 #ifdef USE_USBREDIR
 #include <glib/gi18n-lib.h>
-#include <usbredirhost.h>
 #ifdef USE_LZ4
 #include <lz4.h>
 #endif
@@ -63,15 +62,10 @@  enum SpiceUsbredirChannelState {
 };
 
 struct _SpiceUsbredirChannelPrivate {
-    libusb_device *device;
+    SpiceUsbBackendDevice *device;
     SpiceUsbDevice *spice_device;
-    libusb_context *context;
-    struct usbredirhost *host;
-    /* To catch usbredirhost error messages and report them as a GError */
-    GError **catch_error;
-    /* Data passed from channel handle msg to the usbredirhost read cb */
-    const uint8_t *read_buf;
-    int read_buf_size;
+    SpiceUsbBackend *context;
+    SpiceUsbBackendChannel *host;
     enum SpiceUsbredirChannelState state;
 #ifdef USE_POLKIT
     GTask *task;
@@ -87,16 +81,6 @@  static void spice_usbredir_channel_dispose(GObject *obj);
 static void spice_usbredir_channel_finalize(GObject *obj);
 static void usbredir_handle_msg(SpiceChannel *channel, SpiceMsgIn *in);
 
-static void usbredir_log(void *user_data, int level, const char *msg);
-static int usbredir_read_callback(void *user_data, uint8_t *data, int count);
-static int usbredir_write_callback(void *user_data, uint8_t *data, int count);
-static void usbredir_write_flush_callback(void *user_data);
-static uint64_t usbredir_buffered_output_size_callback(void *user_data);
-
-static void *usbredir_alloc_lock(void);
-static void usbredir_lock_lock(void *user_data);
-static void usbredir_unlock_lock(void *user_data);
-static void usbredir_free_lock(void *user_data);
 
 G_DEFINE_TYPE_WITH_PRIVATE(SpiceUsbredirChannel, spice_usbredir_channel, SPICE_TYPE_CHANNEL)
 
@@ -115,7 +99,7 @@  static void _channel_reset_finish(SpiceUsbredirChannel *channel, gboolean migrat
 
     spice_usbredir_channel_lock(channel);
 
-    usbredirhost_close(priv->host);
+    spice_usb_backend_channel_delete(priv->host);
     priv->host = NULL;
 
     /* Call set_context to re-create the host */
@@ -221,7 +205,7 @@  static void spice_usbredir_channel_finalize(GObject *obj)
     SpiceUsbredirChannel *channel = SPICE_USBREDIR_CHANNEL(obj);
 
     if (channel->priv->host)
-        usbredirhost_close(channel->priv->host);
+        spice_usb_backend_channel_delete(channel->priv->host);
     g_mutex_clear(&channel->priv->device_connect_mutex);
 
     /* Chain up to the parent class */
@@ -244,30 +228,17 @@  static void channel_set_handlers(SpiceChannelClass *klass)
 
 G_GNUC_INTERNAL
 void spice_usbredir_channel_set_context(SpiceUsbredirChannel *channel,
-                                        libusb_context       *context)
+                                        SpiceUsbBackend      *context)
 {
     SpiceUsbredirChannelPrivate *priv = channel->priv;
 
     g_return_if_fail(priv->host == NULL);
 
     priv->context = context;
-    priv->host = usbredirhost_open_full(
-                                   context, NULL,
-                                   usbredir_log,
-                                   usbredir_read_callback,
-                                   usbredir_write_callback,
-                                   usbredir_write_flush_callback,
-                                   usbredir_alloc_lock,
-                                   usbredir_lock_lock,
-                                   usbredir_unlock_lock,
-                                   usbredir_free_lock,
-                                   channel, PACKAGE_STRING,
-                                   spice_util_get_debug() ? usbredirparser_debug : usbredirparser_warning,
-                                   usbredirhost_fl_write_cb_owns_buffer);
+    priv->host = spice_usb_backend_channel_new(context, channel);
     if (!priv->host)
-        g_error("Out of memory allocating usbredirhost");
+        g_error("Out of memory initializing redirection support");
 
-    usbredirhost_set_buffered_output_size_cb(priv->host, usbredir_buffered_output_size_callback);
 #ifdef USE_LZ4
     spice_channel_set_capability(channel, SPICE_SPICEVMC_CAP_DATA_COMPRESS_LZ4);
 #endif
@@ -278,8 +249,6 @@  static gboolean spice_usbredir_channel_open_device(
 {
     SpiceUsbredirChannelPrivate *priv = channel->priv;
     SpiceSession *session;
-    libusb_device_handle *handle = NULL;
-    int rc, status;
     SpiceUsbDeviceManager *manager;
 
     g_return_val_if_fail(priv->state == STATE_DISCONNECTED
@@ -288,19 +257,11 @@  static gboolean spice_usbredir_channel_open_device(
 #endif
                          , FALSE);
 
-    rc = libusb_open(priv->device, &handle);
-    if (rc != 0) {
-        g_set_error(err, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
-                    "Could not open usb device: %s [%i]",
-                    libusb_strerror(rc), rc);
-        return FALSE;
-    }
-
-    priv->catch_error = err;
-    status = usbredirhost_set_device(priv->host, handle);
-    priv->catch_error = NULL;
-    if (status != usb_redir_success) {
-        g_return_val_if_fail(err == NULL || *err != NULL, FALSE);
+    if (!spice_usb_backend_channel_attach(priv->host, priv->device, err)) {
+        if (*err == NULL) {
+            g_set_error(err, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
+                "Error attaching device: (no error information)");
+        }
         return FALSE;
     }
 
@@ -310,7 +271,7 @@  static gboolean spice_usbredir_channel_open_device(
 
     priv->usb_device_manager = g_object_ref(manager);
     if (!spice_usb_device_manager_start_event_listening(priv->usb_device_manager, err)) {
-        usbredirhost_set_device(priv->host, NULL);
+        spice_usb_backend_channel_detach(priv->host);
         return FALSE;
     }
 
@@ -341,8 +302,7 @@  static void spice_usbredir_channel_open_acl_cb(
         spice_usbredir_channel_open_device(channel, &err);
     }
     if (err) {
-        libusb_unref_device(priv->device);
-        priv->device = NULL;
+        g_clear_pointer(&priv->device, spice_usb_backend_device_unref);
         g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
         priv->spice_device = NULL;
         priv->state  = STATE_DISCONNECTED;
@@ -373,8 +333,7 @@  _open_device_async_cb(GTask *task,
     spice_usbredir_channel_lock(channel);
 
     if (!spice_usbredir_channel_open_device(channel, &err)) {
-        libusb_unref_device(priv->device);
-        priv->device = NULL;
+        g_clear_pointer(&priv->device, spice_usb_backend_device_unref);
         g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
         priv->spice_device = NULL;
     }
@@ -392,13 +351,16 @@  _open_device_async_cb(GTask *task,
 G_GNUC_INTERNAL
 void spice_usbredir_channel_connect_device_async(
                                           SpiceUsbredirChannel *channel,
-                                          libusb_device        *device,
+                                          SpiceUsbBackendDevice *device,
                                           SpiceUsbDevice       *spice_device,
                                           GCancellable         *cancellable,
                                           GAsyncReadyCallback   callback,
                                           gpointer              user_data)
 {
     SpiceUsbredirChannelPrivate *priv = channel->priv;
+#ifdef USE_POLKIT
+    const UsbDeviceInformation *info = spice_usb_backend_device_get_info(device);
+#endif
     GTask *task;
 
     g_return_if_fail(SPICE_IS_USBREDIR_CHANNEL(channel));
@@ -425,7 +387,7 @@  void spice_usbredir_channel_connect_device_async(
         goto done;
     }
 
-    priv->device = libusb_ref_device(device);
+    priv->device = spice_usb_backend_device_ref(device);
     priv->spice_device = g_boxed_copy(spice_usb_device_get_type(),
                                       spice_device);
 #ifdef USE_POLKIT
@@ -435,8 +397,8 @@  void spice_usbredir_channel_connect_device_async(
     g_object_set(spice_channel_get_session(SPICE_CHANNEL(channel)),
                  "inhibit-keyboard-grab", TRUE, NULL);
     spice_usb_acl_helper_open_acl_async(priv->acl_helper,
-                                        libusb_get_bus_number(device),
-                                        libusb_get_device_address(device),
+                                        info->bus,
+                                        info->address,
                                         cancellable,
                                         spice_usbredir_channel_open_acl_cb,
                                         channel);
@@ -494,9 +456,8 @@  void spice_usbredir_channel_disconnect_device(SpiceUsbredirChannel *channel)
         g_clear_object(&priv->usb_device_manager);
 
         /* This also closes the libusb handle we passed from open_device */
-        usbredirhost_set_device(priv->host, NULL);
-        libusb_unref_device(priv->device);
-        priv->device = NULL;
+        spice_usb_backend_channel_detach(priv->host);
+        g_clear_pointer(&priv->device, spice_usb_backend_device_unref);
         g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
         priv->spice_device = NULL;
         priv->state  = STATE_DISCONNECTED;
@@ -547,7 +508,7 @@  spice_usbredir_channel_get_spice_usb_device(SpiceUsbredirChannel *channel)
 #endif
 
 G_GNUC_INTERNAL
-libusb_device *spice_usbredir_channel_get_device(SpiceUsbredirChannel *channel)
+SpiceUsbBackendDevice *spice_usbredir_channel_get_device(SpiceUsbredirChannel *channel)
 {
     return channel->priv->device;
 }
@@ -562,91 +523,18 @@  void spice_usbredir_channel_get_guest_filter(
 
     g_return_if_fail(priv->host != NULL);
 
-    usbredirhost_get_guest_filter(priv->host, rules_ret, rules_count_ret);
+    spice_usb_backend_channel_get_guest_filter(priv->host, rules_ret, rules_count_ret);
 }
 
 /* ------------------------------------------------------------------ */
 /* callbacks (any context)                                            */
 
-static uint64_t usbredir_buffered_output_size_callback(void *user_data)
-{
-    g_return_val_if_fail(SPICE_IS_USBREDIR_CHANNEL(user_data), 0);
-    return spice_channel_get_queue_size(SPICE_CHANNEL(user_data));
-}
-
-/* Note that this function must be re-entrant safe, as it can get called
-   from both the main thread as well as from the usb event handling thread */
-static void usbredir_write_flush_callback(void *user_data)
-{
-    SpiceUsbredirChannel *channel = SPICE_USBREDIR_CHANNEL(user_data);
-    SpiceUsbredirChannelPrivate *priv = channel->priv;
-
-    if (spice_channel_get_state(SPICE_CHANNEL(channel)) !=
-            SPICE_CHANNEL_STATE_READY)
-        return;
-
-    if (!priv->host)
-        return;
-
-    usbredirhost_write_guest_data(priv->host);
-}
-
-static void usbredir_log(void *user_data, int level, const char *msg)
-{
-    SpiceUsbredirChannel *channel = user_data;
-    SpiceUsbredirChannelPrivate *priv = channel->priv;
-
-    if (priv->catch_error && level == usbredirparser_error) {
-        CHANNEL_DEBUG(channel, "%s", msg);
-        /* Remove "usbredirhost: " prefix from usbredirhost messages */
-        if (strncmp(msg, "usbredirhost: ", 14) == 0)
-            g_set_error_literal(priv->catch_error, SPICE_CLIENT_ERROR,
-                                SPICE_CLIENT_ERROR_FAILED, msg + 14);
-        else
-            g_set_error_literal(priv->catch_error, SPICE_CLIENT_ERROR,
-                                SPICE_CLIENT_ERROR_FAILED, msg);
-        return;
-    }
-
-    switch (level) {
-        case usbredirparser_error:
-            g_critical("%s", msg);
-            break;
-        case usbredirparser_warning:
-            g_warning("%s", msg);
-            break;
-        default:
-            CHANNEL_DEBUG(channel, "%s", msg);
-    }
-}
-
-static int usbredir_read_callback(void *user_data, uint8_t *data, int count)
-{
-    SpiceUsbredirChannel *channel = user_data;
-    SpiceUsbredirChannelPrivate *priv = channel->priv;
-
-    count = MIN(priv->read_buf_size, count);
-
-    if (count != 0) {
-        memcpy(data, priv->read_buf, count);
-    }
-
-    priv->read_buf_size -= count;
-    if (priv->read_buf_size) {
-        priv->read_buf += count;
-    } else {
-        priv->read_buf = NULL;
-    }
-
-    return count;
-}
-
 static void usbredir_free_write_cb_data(uint8_t *data, void *user_data)
 {
     SpiceUsbredirChannel *channel = user_data;
     SpiceUsbredirChannelPrivate *priv = channel->priv;
 
-    usbredirhost_free_write_buffer(priv->host, data);
+    spice_usb_backend_return_write_data(priv->host, data);
 }
 
 #ifdef USE_LZ4
@@ -711,14 +599,14 @@  static int try_write_compress_LZ4(SpiceUsbredirChannel *channel, uint8_t *data,
 }
 #endif
 
-static int usbredir_write_callback(void *user_data, uint8_t *data, int count)
+G_GNUC_INTERNAL
+int spice_usbredir_write_callback(SpiceUsbredirChannel *channel, uint8_t *data, int count)
 {
-    SpiceUsbredirChannel *channel = user_data;
     SpiceMsgOut *msg_out;
 
 #ifdef USE_LZ4
     if (try_write_compress_LZ4(channel, data, count)) {
-        usbredirhost_free_write_buffer(channel->priv->host, data);
+        spice_usb_backend_return_write_data(channel->priv->host, data);
         return count;
     }
 #endif
@@ -731,15 +619,6 @@  static int usbredir_write_callback(void *user_data, uint8_t *data, int count)
     return count;
 }
 
-static void *usbredir_alloc_lock(void) {
-    GMutex *mutex;
-
-    mutex = g_new0(GMutex, 1);
-    g_mutex_init(mutex);
-
-    return mutex;
-}
-
 G_GNUC_INTERNAL
 void spice_usbredir_channel_lock(SpiceUsbredirChannel *channel)
 {
@@ -752,25 +631,6 @@  void spice_usbredir_channel_unlock(SpiceUsbredirChannel *channel)
     g_mutex_unlock(&channel->priv->device_connect_mutex);
 }
 
-static void usbredir_lock_lock(void *user_data) {
-    GMutex *mutex = user_data;
-
-    g_mutex_lock(mutex);
-}
-
-static void usbredir_unlock_lock(void *user_data) {
-    GMutex *mutex = user_data;
-
-    g_mutex_unlock(mutex);
-}
-
-static void usbredir_free_lock(void *user_data) {
-    GMutex *mutex = user_data;
-
-    g_mutex_clear(mutex);
-    g_free(mutex);
-}
-
 /* --------------------------------------------------------------------- */
 
 typedef struct device_error_data {
@@ -809,7 +669,7 @@  static void spice_usbredir_channel_up(SpiceChannel *c)
 
     g_return_if_fail(priv->host != NULL);
     /* Flush any pending writes */
-    usbredirhost_write_guest_data(priv->host);
+    spice_usb_backend_channel_flush_writes(priv->host);
 }
 
 static int try_handle_compressed_msg(SpiceMsgCompressedData *compressed_data_msg,
@@ -859,26 +719,20 @@  static void usbredir_handle_msg(SpiceChannel *c, SpiceMsgIn *in)
 
     g_return_if_fail(priv->host != NULL);
 
-    /* No recursion allowed! */
-    g_return_if_fail(priv->read_buf == NULL);
-
     if (spice_msg_in_type(in) == SPICE_MSG_SPICEVMC_COMPRESSED_DATA) {
         SpiceMsgCompressedData *compressed_data_msg = spice_msg_in_parsed(in);
         if (try_handle_compressed_msg(compressed_data_msg, &buf, &size)) {
-            priv->read_buf_size = size;
-            priv->read_buf = buf;
+            /* uncompressed ok*/
         } else {
-            r = usbredirhost_read_parse_error;
+            r = USB_REDIR_ERROR_READ_PARSE;
         }
     } else { /* Regular SPICE_MSG_SPICEVMC_DATA msg */
         buf = spice_msg_in_raw(in, &size);
-        priv->read_buf_size = size;
-        priv->read_buf = buf;
     }
 
     spice_usbredir_channel_lock(channel);
     if (r == 0)
-        r = usbredirhost_read_guest_data(priv->host);
+        r = spice_usb_backend_read_guest_data(priv->host, buf, size);
     if (r != 0) {
         SpiceUsbDevice *spice_device = priv->spice_device;
         device_error_data err_data;
@@ -891,25 +745,7 @@  static void usbredir_handle_msg(SpiceChannel *c, SpiceMsgIn *in)
         }
 
         desc = spice_usb_device_get_description(spice_device, NULL);
-        switch (r) {
-        case usbredirhost_read_parse_error:
-            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
-                              _("usbredir protocol parse error for %s"), desc);
-            break;
-        case usbredirhost_read_device_rejected:
-            err = g_error_new(SPICE_CLIENT_ERROR,
-                              SPICE_CLIENT_ERROR_USB_DEVICE_REJECTED,
-                              _("%s rejected by host"), desc);
-            break;
-        case usbredirhost_read_device_lost:
-            err = g_error_new(SPICE_CLIENT_ERROR,
-                              SPICE_CLIENT_ERROR_USB_DEVICE_LOST,
-                              _("%s disconnected (fatal IO error)"), desc);
-            break;
-        default:
-            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
-                              _("Unknown error (%d) for %s"), r, desc);
-        }
+        err = spice_usb_backend_get_error_details(r, desc);
         g_free(desc);
 
         CHANNEL_DEBUG(c, "%s", err->message);
diff --git a/src/meson.build b/src/meson.build
index 5365f054..a51d0a96 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -121,6 +121,8 @@  spice_client_glib_sources = [
   'usb-device-manager-priv.h',
   'usbutil.c',
   'usbutil.h',
+  'usb-backend.c',
+  'usb-backend.h',
   'vmcstream.c',
   'vmcstream.h',
 ]
diff --git a/src/usb-backend.c b/src/usb-backend.c
new file mode 100644
index 00000000..48a62cd1
--- /dev/null
+++ b/src/usb-backend.c
@@ -0,0 +1,657 @@ 
+/* -*- Mode: C; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/*
+    Copyright (C) 2012-2018 Red Hat, Inc.
+
+    Red Hat Authors:
+    Yuri Benditovich<ybendito@redhat.com>
+    Hans de Goede <hdegoede@redhat.com>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library 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
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "config.h"
+
+#ifdef USE_USBREDIR
+
+#include <glib-object.h>
+#include <inttypes.h>
+#include <gio/gio.h>
+#include <glib/gi18n-lib.h>
+#include <errno.h>
+#include <libusb.h>
+#include <string.h>
+#include <fcntl.h>
+#include "usbredirhost.h"
+#include "usbredirparser.h"
+#include "spice-util.h"
+#include "usb-backend.h"
+#include "channel-usbredir-priv.h"
+#include "spice-channel-priv.h"
+
+#define LOUD_DEBUG(x, ...)
+
+struct _SpiceUsbBackendDevice
+{
+    libusb_device *libusb_device;
+    gint ref_count;
+    SpiceUsbBackendChannel *attached_to;
+    UsbDeviceInformation device_info;
+};
+
+struct _SpiceUsbBackend
+{
+    libusb_context *libusb_context;
+    usb_hot_plug_callback hotplug_callback;
+    void *hotplug_user_data;
+    libusb_hotplug_callback_handle hotplug_handle;
+};
+
+struct _SpiceUsbBackendChannel
+{
+    struct usbredirhost *usbredirhost;
+    uint8_t *read_buf;
+    int read_buf_size;
+    struct usbredirfilter_rule *rules;
+    int rules_count;
+    SpiceUsbBackendDevice *attached;
+    SpiceUsbredirChannel  *user_data;
+    GError **error;
+};
+
+/* lock functions for usbredirhost and usbredirparser */
+static void *usbredir_alloc_lock(void) {
+    GMutex *mutex;
+
+    mutex = g_new0(GMutex, 1);
+    g_mutex_init(mutex);
+
+    return mutex;
+}
+
+static void usbredir_free_lock(void *user_data) {
+    GMutex *mutex = user_data;
+
+    g_mutex_clear(mutex);
+    g_free(mutex);
+}
+
+static void usbredir_lock_lock(void *user_data) {
+    GMutex *mutex = user_data;
+
+    g_mutex_lock(mutex);
+}
+
+static void usbredir_unlock_lock(void *user_data) {
+    GMutex *mutex = user_data;
+
+    g_mutex_unlock(mutex);
+}
+
+gboolean spice_usb_backend_device_isoch(SpiceUsbBackendDevice *dev)
+{
+    libusb_device *libdev = dev->libusb_device;
+    struct libusb_config_descriptor *conf_desc;
+    gboolean isoc_found = FALSE;
+    gint i, j, k;
+    int rc;
+
+    g_return_val_if_fail(libdev != NULL, 0);
+
+    rc = libusb_get_active_config_descriptor(libdev, &conf_desc);
+    if (rc) {
+        const char *desc = libusb_strerror(rc);
+        g_warning("can't get configuration descriptor, %s [%i]", desc, rc);
+        return FALSE;
+    }
+
+    for (i = 0; !isoc_found && i < conf_desc->bNumInterfaces; i++) {
+        for (j = 0; !isoc_found && j < conf_desc->interface[i].num_altsetting; j++) {
+            for (k = 0; !isoc_found && k < conf_desc->interface[i].altsetting[j].bNumEndpoints;k++) {
+                gint attributes = conf_desc->interface[i].altsetting[j].endpoint[k].bmAttributes;
+                gint type = attributes & LIBUSB_TRANSFER_TYPE_MASK;
+                if (type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS) {
+                    isoc_found = TRUE;
+                }
+            }
+        }
+    }
+
+    libusb_free_config_descriptor(conf_desc);
+    return isoc_found;
+}
+
+static gboolean fill_usb_info(SpiceUsbBackendDevice *bdev)
+{
+    UsbDeviceInformation *info = &bdev->device_info;
+
+    struct libusb_device_descriptor desc;
+    libusb_device *libdev = bdev->libusb_device;
+    libusb_get_device_descriptor(libdev, &desc);
+    info->bus = libusb_get_bus_number(libdev);
+    info->address = libusb_get_device_address(libdev);
+    if (info->address == 0xff || /* root hub (HCD) */
+        info->address <= 1 || /* root hub or bad address */
+        (desc.bDeviceClass == LIBUSB_CLASS_HUB) /*hub*/) {
+        return FALSE;
+    }
+
+    info->vid = desc.idVendor;
+    info->pid = desc.idProduct;
+    info->class = desc.bDeviceClass;
+    info->subclass = desc.bDeviceSubClass;
+    info->protocol = desc.bDeviceProtocol;
+
+    return TRUE;
+}
+
+static SpiceUsbBackendDevice *allocate_backend_device(libusb_device *libdev)
+{
+    SpiceUsbBackendDevice *dev = g_new0(SpiceUsbBackendDevice, 1);
+    dev->ref_count = 1;
+    dev->libusb_device = libdev;
+    if (!fill_usb_info(dev)) {
+        g_clear_pointer(&dev, g_free);
+    }
+    return dev;
+}
+
+static gboolean is_channel_ready(SpiceUsbredirChannel *channel)
+{
+    return spice_channel_get_state(SPICE_CHANNEL(channel)) == SPICE_CHANNEL_STATE_READY;
+}
+
+/* Note that this function must be re-entrant safe, as it can get called
+from both the main thread as well as from the usb event handling thread */
+static void usbredir_write_flush_callback(void *user_data)
+{
+    SpiceUsbBackendChannel *ch = user_data;
+    if (!ch->usbredirhost) {
+        /* just to be on the safe side */
+        return;
+    }
+    if (is_channel_ready(ch->user_data)) {
+        SPICE_DEBUG("%s ch %p -> usbredirhost", __FUNCTION__, ch);
+        usbredirhost_write_guest_data(ch->usbredirhost);
+    } else {
+        SPICE_DEBUG("%s ch %p (not ready)", __FUNCTION__, ch);
+    }
+}
+
+SpiceUsbBackend *spice_usb_backend_new(GError **error)
+{
+    int rc;
+    SpiceUsbBackend *be;
+    SPICE_DEBUG("%s >>", __FUNCTION__);
+    be = g_new0(SpiceUsbBackend, 1);
+    rc = libusb_init(&be->libusb_context);
+    if (rc < 0) {
+        const char *desc = libusb_strerror(rc);
+        g_warning("Error initializing LIBUSB support: %s [%i]", desc, rc);
+        g_set_error(error, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
+            "Error initializing LIBUSB support: %s [%i]", desc, rc);
+        g_free(be);
+        be = NULL;
+    } else {
+#ifdef G_OS_WIN32
+#if LIBUSB_API_VERSION >= 0x01000106
+        libusb_set_option(be->libusb_context, LIBUSB_OPTION_USE_USBDK);
+#endif
+#endif
+    }
+    SPICE_DEBUG("%s <<", __FUNCTION__);
+    return be;
+}
+
+gboolean spice_usb_backend_handle_events(SpiceUsbBackend *be)
+{
+    SPICE_DEBUG("%s >>", __FUNCTION__);
+    gboolean ok = FALSE;
+    if (be->libusb_context) {
+        int res = libusb_handle_events(be->libusb_context);
+        ok = res == 0;
+        if (res && res != LIBUSB_ERROR_INTERRUPTED) {
+            const char *desc = libusb_strerror(res);
+            g_warning("Error handling USB events: %s [%i]", desc, res);
+            ok = FALSE;
+        }
+    }
+    SPICE_DEBUG("%s << %d", __FUNCTION__, ok);
+    return ok;
+}
+
+static int LIBUSB_CALL hotplug_callback(libusb_context *ctx,
+                                        libusb_device *device,
+                                        libusb_hotplug_event event,
+                                        void *user_data)
+{
+    SpiceUsbBackend *be = (SpiceUsbBackend *)user_data;
+    if (be->hotplug_callback) {
+        SpiceUsbBackendDevice *dev;
+        gboolean val = event == LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED;
+        dev = allocate_backend_device(device);
+        if (dev) {
+            SPICE_DEBUG("created dev %p, usblib dev %p", dev, device);
+            libusb_ref_device(device);
+            be->hotplug_callback(be->hotplug_user_data, dev, val);
+            spice_usb_backend_device_unref(dev);
+        }
+    }
+    return 0;
+}
+
+void spice_usb_backend_deregister_hotplug(SpiceUsbBackend *be)
+{
+    g_return_if_fail(be != NULL);
+    if (be->hotplug_handle) {
+        libusb_hotplug_deregister_callback(be->libusb_context, be->hotplug_handle);
+        be->hotplug_handle = 0;
+    }
+    be->hotplug_callback = NULL;
+}
+
+gboolean spice_usb_backend_register_hotplug(SpiceUsbBackend *be,
+                                            void *user_data,
+                                            usb_hot_plug_callback proc)
+{
+    int rc;
+    g_return_val_if_fail(be != NULL, FALSE);
+
+    be->hotplug_callback = proc;
+    be->hotplug_user_data = user_data;
+    rc = libusb_hotplug_register_callback(be->libusb_context,
+        LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED | LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT,
+        LIBUSB_HOTPLUG_ENUMERATE, LIBUSB_HOTPLUG_MATCH_ANY,
+        LIBUSB_HOTPLUG_MATCH_ANY, LIBUSB_HOTPLUG_MATCH_ANY,
+        hotplug_callback, be, &be->hotplug_handle);
+    if (rc != LIBUSB_SUCCESS) {
+        const char *desc = libusb_strerror(rc);
+        g_warning("Error initializing USB hotplug support: %s [%i]", desc, rc);
+        be->hotplug_callback = NULL;
+        return FALSE;
+    }
+    return TRUE;
+}
+
+void spice_usb_backend_delete(SpiceUsbBackend *be)
+{
+    g_return_if_fail(be != NULL);
+    SPICE_DEBUG("%s >>", __FUNCTION__);
+    if (be->libusb_context) {
+        libusb_exit(be->libusb_context);
+    }
+    g_free(be);
+    SPICE_DEBUG("%s <<", __FUNCTION__);
+}
+
+SpiceUsbBackendDevice **spice_usb_backend_get_device_list(SpiceUsbBackend *be)
+{
+    LOUD_DEBUG("%s >>", __FUNCTION__);
+    libusb_device **devlist = NULL, **dev;
+    SpiceUsbBackendDevice *d, **list;
+
+    int n = 0, index;
+
+    if (be && be->libusb_context) {
+        libusb_get_device_list(be->libusb_context, &devlist);
+    }
+
+    /* add all the libusb device that not present in our list */
+    for (dev = devlist; dev && *dev; dev++) {
+        n++;
+    }
+
+    list = g_new0(SpiceUsbBackendDevice*, n + 1);
+
+    index = 0;
+
+    for (dev = devlist; dev && *dev; dev++) {
+        d = allocate_backend_device(*dev);
+        if (!d) {
+            libusb_unref_device(*dev);
+        } else {
+            SPICE_DEBUG("created dev %p, usblib dev %p", d, *dev);
+            list[index++] = d;
+        }
+    }
+
+    if (devlist) {
+        libusb_free_device_list(devlist, 0);
+    }
+
+    LOUD_DEBUG("%s <<", __FUNCTION__);
+    return list;
+}
+
+const UsbDeviceInformation* spice_usb_backend_device_get_info(SpiceUsbBackendDevice *dev)
+{
+    return &dev->device_info;
+}
+
+gconstpointer spice_usb_backend_device_get_libdev(SpiceUsbBackendDevice *dev)
+{
+    return dev->libusb_device;
+}
+
+void spice_usb_backend_free_device_list(SpiceUsbBackendDevice **devlist)
+{
+    LOUD_DEBUG("%s >>", __FUNCTION__);
+    SpiceUsbBackendDevice **dev;
+    for (dev = devlist; *dev; dev++) {
+        SpiceUsbBackendDevice *d = *dev;
+        spice_usb_backend_device_unref(d);
+    }
+    g_free(devlist);
+    LOUD_DEBUG("%s <<", __FUNCTION__);
+}
+
+SpiceUsbBackendDevice *spice_usb_backend_device_ref(SpiceUsbBackendDevice *dev)
+{
+    LOUD_DEBUG("%s >> %p", __FUNCTION__, dev);
+    g_atomic_int_inc(&dev->ref_count);
+    return dev;
+}
+
+void spice_usb_backend_device_unref(SpiceUsbBackendDevice *dev)
+{
+    LOUD_DEBUG("%s >> %p(%d)", __FUNCTION__, dev, dev->ref_count);
+    if (g_atomic_int_dec_and_test(&dev->ref_count)) {
+        libusb_unref_device(dev->libusb_device);
+        LOUD_DEBUG("%s freeing %p (libusb %p)", __FUNCTION__, dev, dev->libusb_device);
+        g_free(dev);
+    }
+}
+
+int spice_usb_backend_device_check_filter(
+    SpiceUsbBackendDevice *dev,
+    const struct usbredirfilter_rule *rules,
+    int count)
+{
+    return usbredirhost_check_device_filter(
+        rules, count, dev->libusb_device, 0);
+}
+
+static int usbredir_read_callback(void *user_data, uint8_t *data, int count)
+{
+    SpiceUsbBackendChannel *ch = user_data;
+
+    count = MIN(ch->read_buf_size, count);
+
+    if (count != 0) {
+        memcpy(data, ch->read_buf, count);
+    }
+
+    ch->read_buf_size -= count;
+    if (ch->read_buf_size) {
+        ch->read_buf += count;
+    }
+    else {
+        ch->read_buf = NULL;
+    }
+    SPICE_DEBUG("%s ch %p, %d bytes", __FUNCTION__, ch, count);
+
+    return count;
+}
+
+static const char *strip_usbredir_prefix(const char *msg)
+{
+    if (strncmp(msg, "usbredirhost: ", 14) == 0) {
+        msg += 14;
+    }
+    return msg;
+}
+
+static void channel_error(SpiceUsbBackendChannel *ch, const char *msg)
+{
+    if (!ch->error)
+        return;
+    g_set_error_literal(ch->error, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED, msg);
+    ch->error = NULL;
+}
+
+static void usbredir_log(void *user_data, int level, const char *msg)
+{
+    SpiceUsbBackendChannel *ch = (SpiceUsbBackendChannel *)user_data;
+    const char *stripped_msg = strip_usbredir_prefix(msg);
+    switch (level) {
+    case usbredirparser_error:
+        g_critical("%s", msg);
+        channel_error(ch, stripped_msg);
+        break;
+    case usbredirparser_warning:
+        g_warning("%s", msg);
+        channel_error(ch, stripped_msg);
+        break;
+    default:
+        break;
+    }
+}
+
+static int usbredir_write_callback(void *user_data, uint8_t *data, int count)
+{
+    SpiceUsbBackendChannel *ch = user_data;
+    int res;
+    SPICE_DEBUG("%s ch %p, %d bytes", __FUNCTION__, ch, count);
+    res = spice_usbredir_write_callback(ch->user_data, data, count);
+    return res;
+}
+
+static uint64_t usbredir_buffered_output_size_callback(void *user_data)
+{
+    SpiceUsbBackendChannel *ch = user_data;
+    return spice_channel_get_queue_size(SPICE_CHANNEL(ch->user_data));
+}
+
+int spice_usb_backend_read_guest_data(SpiceUsbBackendChannel *ch, uint8_t *data, int count)
+{
+    int res = 0;
+
+    g_return_val_if_fail(ch->read_buf == NULL, USB_REDIR_ERROR_READ_PARSE);
+
+    ch->read_buf = data;
+    ch->read_buf_size = count;
+    if (ch->usbredirhost) {
+        res = usbredirhost_read_guest_data(ch->usbredirhost);
+    } else {
+        res = USB_REDIR_ERROR_IO;
+    }
+    switch (res)
+    {
+    case usbredirhost_read_io_error:
+        res = USB_REDIR_ERROR_IO;
+        break;
+    case usbredirhost_read_parse_error:
+        res = USB_REDIR_ERROR_READ_PARSE;
+        break;
+    case usbredirhost_read_device_rejected:
+        res = USB_REDIR_ERROR_DEV_REJECTED;
+        break;
+    case usbredirhost_read_device_lost:
+        res = USB_REDIR_ERROR_DEV_LOST;
+        break;
+    }
+    SPICE_DEBUG("%s ch %p, %d bytes, res %d", __FUNCTION__, ch, count, res);
+
+    return res;
+}
+
+GError *spice_usb_backend_get_error_details(int error_code, gchar *desc)
+{
+    GError *err;
+    switch (error_code) {
+        case USB_REDIR_ERROR_READ_PARSE:
+            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
+                              _("usbredir protocol parse error for %s"), desc);
+            break;
+        case USB_REDIR_ERROR_DEV_REJECTED:
+            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_USB_DEVICE_REJECTED,
+                              _("%s rejected by host"), desc);
+            break;
+        case USB_REDIR_ERROR_DEV_LOST:
+            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_USB_DEVICE_LOST,
+                              _("%s disconnected (fatal IO error)"), desc);
+            break;
+        default:
+            err = g_error_new(SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
+                              _("Unknown error (%d) for %s"), error_code, desc);
+            }
+    return err;
+}
+
+void spice_usb_backend_return_write_data(SpiceUsbBackendChannel *ch, void *data)
+{
+    if (ch->usbredirhost) {
+        SPICE_DEBUG("%s ch %p", __FUNCTION__, ch);
+        usbredirhost_free_write_buffer(ch->usbredirhost, data);
+    } else {
+        SPICE_DEBUG("%s ch %p - NOBODY TO CALL", __FUNCTION__, ch);
+    }
+}
+
+gboolean spice_usb_backend_channel_attach(SpiceUsbBackendChannel *ch,
+                                          SpiceUsbBackendDevice *dev,
+                                          GError **error)
+{
+    SPICE_DEBUG("%s >> ch %p, dev %p (was attached %p)", __FUNCTION__, ch, dev, ch->attached);
+
+    g_return_val_if_fail(dev != NULL, FALSE);
+
+    libusb_device_handle *handle = NULL;
+    int rc = libusb_open(dev->libusb_device, &handle);
+    if (rc) {
+        const char *desc = libusb_strerror(rc);
+        g_set_error(error, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
+           "Error libusb_open: %s [%i]", desc, rc);
+        return FALSE;
+    }
+    ch->error = error;
+    rc = usbredirhost_set_device(ch->usbredirhost, handle);
+    if (rc) {
+        SPICE_DEBUG("%s ch %p, dev %p usbredirhost error %d", __FUNCTION__, ch, dev, rc);
+        ch->error = NULL;
+        return FALSE;
+    } else {
+        ch->attached = dev;
+        dev->attached_to = ch;
+    }
+    ch->error = NULL;
+    return TRUE;
+}
+
+void spice_usb_backend_channel_detach(SpiceUsbBackendChannel *ch)
+{
+    SPICE_DEBUG("%s >> ch %p, was attached %p", __FUNCTION__, ch, ch->attached);
+    if (!ch->attached) {
+        SPICE_DEBUG("%s: nothing to detach", __FUNCTION__);
+        return;
+    }
+    if (ch->usbredirhost) {
+        /* it will call libusb_close internally */
+        usbredirhost_set_device(ch->usbredirhost, NULL);
+    }
+    SPICE_DEBUG("%s ch %p, detach done", __FUNCTION__, ch);
+    ch->attached->attached_to = NULL;
+    ch->attached = NULL;
+}
+
+SpiceUsbBackendChannel *spice_usb_backend_channel_new(SpiceUsbBackend *be,
+                                                      void *user_data)
+{
+    SpiceUsbBackendChannel *ch;
+
+    g_return_val_if_fail(SPICE_IS_USBREDIR_CHANNEL(user_data), NULL);
+
+    ch = g_new0(SpiceUsbBackendChannel, 1);
+    SPICE_DEBUG("%s >>", __FUNCTION__);
+    ch->user_data = SPICE_USBREDIR_CHANNEL(user_data);
+    if (be->libusb_context) {
+        ch->usbredirhost = usbredirhost_open_full(
+            be->libusb_context,
+            NULL,
+            usbredir_log,
+            usbredir_read_callback,
+            usbredir_write_callback,
+            usbredir_write_flush_callback,
+            usbredir_alloc_lock,
+            usbredir_lock_lock,
+            usbredir_unlock_lock,
+            usbredir_free_lock,
+            ch, PACKAGE_STRING,
+            spice_util_get_debug() ? usbredirparser_debug : usbredirparser_warning,
+            usbredirhost_fl_write_cb_owns_buffer);
+        g_warn_if_fail(ch->usbredirhost != NULL);
+    }
+    if (ch->usbredirhost) {
+        usbredirhost_set_buffered_output_size_cb(ch->usbredirhost, usbredir_buffered_output_size_callback);
+    } else {
+        g_free(ch);
+        ch = NULL;
+    }
+
+    SPICE_DEBUG("%s << %p", __FUNCTION__, ch);
+    return ch;
+}
+
+void spice_usb_backend_channel_flush_writes(SpiceUsbBackendChannel *ch)
+{
+    SPICE_DEBUG("%s %p, host %p", __FUNCTION__, ch, ch->usbredirhost);
+    if (ch->usbredirhost) {
+        usbredirhost_write_guest_data(ch->usbredirhost);
+    }
+}
+
+void spice_usb_backend_channel_delete(SpiceUsbBackendChannel *ch)
+{
+    SPICE_DEBUG("%s >> %p", __FUNCTION__, ch);
+    if (!ch) {
+        return;
+    }
+    if (ch->usbredirhost) {
+        usbredirhost_close(ch->usbredirhost);
+    }
+
+    if (ch->rules) {
+        g_free(ch->rules);
+    }
+
+    g_free(ch);
+    SPICE_DEBUG("%s << %p", __FUNCTION__, ch);
+}
+
+void
+spice_usb_backend_channel_get_guest_filter(SpiceUsbBackendChannel *ch,
+                                           const struct usbredirfilter_rule **r,
+                                           int *count)
+{
+    int i;
+    *r = NULL;
+    *count = 0;
+    if (ch->usbredirhost) {
+        usbredirhost_get_guest_filter(ch->usbredirhost, r, count);
+    }
+    if (*r == NULL) {
+        *r = ch->rules;
+        *count = ch->rules_count;
+    }
+
+    SPICE_DEBUG("%s ch %p: %d filters", __FUNCTION__, ch, *count);
+
+    for (i = 0; i < *count; i++) {
+        const struct usbredirfilter_rule *ra = *r;
+        SPICE_DEBUG("%s class %d, %X:%X",
+            ra[i].allow ? "allowed" : "denied", ra[i].device_class,
+            (uint32_t)ra[i].vendor_id, (uint32_t)ra[i].product_id);
+    }
+}
+
+#endif /* USB_REDIR */
diff --git a/src/usb-backend.h b/src/usb-backend.h
new file mode 100644
index 00000000..9f2a97a6
--- /dev/null
+++ b/src/usb-backend.h
@@ -0,0 +1,102 @@ 
+/* -*- Mode: C; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/*
+    Copyright (C) 2018 Red Hat, Inc.
+
+    Red Hat Authors:
+    Yuri Benditovich<ybendito@redhat.com>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library 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
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __SPICE_USB_BACKEND_H__
+#define __SPICE_USB_BACKEND_H__
+
+#include <usbredirfilter.h>
+#include "usb-device-manager.h"
+
+G_BEGIN_DECLS
+
+typedef struct _SpiceUsbBackend SpiceUsbBackend;
+typedef struct _SpiceUsbBackendDevice SpiceUsbBackendDevice;
+typedef struct _SpiceUsbBackendChannel SpiceUsbBackendChannel;
+
+typedef struct UsbDeviceInformation
+{
+    uint16_t bus;
+    uint16_t address;
+    uint16_t vid;
+    uint16_t pid;
+    uint8_t class;
+    uint8_t subclass;
+    uint8_t protocol;
+} UsbDeviceInformation;
+
+typedef void(*usb_hot_plug_callback)(void *user_data, SpiceUsbBackendDevice *dev, gboolean added);
+
+enum {
+    USB_REDIR_ERROR_IO = -1,
+    USB_REDIR_ERROR_READ_PARSE = -2,
+    USB_REDIR_ERROR_DEV_REJECTED = -3,
+    USB_REDIR_ERROR_DEV_LOST = -4,
+};
+
+/* Spice USB backend API */
+/* sets error on failure */
+SpiceUsbBackend *spice_usb_backend_new(GError **error);
+void spice_usb_backend_delete(SpiceUsbBackend *context);
+
+/*
+returns newly-allocated null-terminated list of
+SpiceUsbBackendDevice pointers.
+The caller must call spice_usb_backend_free_device_list
+after it finishes list processing
+*/
+SpiceUsbBackendDevice **spice_usb_backend_get_device_list(SpiceUsbBackend *backend);
+void spice_usb_backend_free_device_list(SpiceUsbBackendDevice **devlist);
+gboolean spice_usb_backend_handle_events(SpiceUsbBackend *be);
+gboolean spice_usb_backend_register_hotplug(SpiceUsbBackend *be,
+                                            void *user_data,
+                                            usb_hot_plug_callback proc);
+void spice_usb_backend_deregister_hotplug(SpiceUsbBackend *be);
+
+/* Spice USB backend device API */
+SpiceUsbBackendDevice *spice_usb_backend_device_ref(SpiceUsbBackendDevice *dev);
+void spice_usb_backend_device_unref(SpiceUsbBackendDevice *dev);
+gconstpointer spice_usb_backend_device_get_libdev(SpiceUsbBackendDevice *dev);
+const UsbDeviceInformation* spice_usb_backend_device_get_info(SpiceUsbBackendDevice *dev);
+gboolean spice_usb_backend_device_isoch(SpiceUsbBackendDevice *dev);
+/* returns 0 if the device passes the filter */
+int spice_usb_backend_device_check_filter(SpiceUsbBackendDevice *dev,
+                                          const struct usbredirfilter_rule *rules, int count);
+
+/* Spice USB backend channel API */
+SpiceUsbBackendChannel *spice_usb_backend_channel_new(SpiceUsbBackend *context,
+                                                      void            *user_data);
+void spice_usb_backend_channel_delete(SpiceUsbBackendChannel *ch);
+/* returns 0 for success or error code */
+int spice_usb_backend_read_guest_data(SpiceUsbBackendChannel *ch, uint8_t *data, int count);
+GError *spice_usb_backend_get_error_details(int error_code, gchar *device_desc);
+gboolean spice_usb_backend_channel_attach(SpiceUsbBackendChannel *ch,
+                                          SpiceUsbBackendDevice *dev,
+                                          GError **error);
+void spice_usb_backend_channel_detach(SpiceUsbBackendChannel *ch);
+void spice_usb_backend_channel_flush_writes(SpiceUsbBackendChannel *ch);
+void spice_usb_backend_channel_get_guest_filter(SpiceUsbBackendChannel *ch,
+                                                const struct usbredirfilter_rule  **rules,
+                                                int *count);
+void spice_usb_backend_return_write_data(SpiceUsbBackendChannel *ch, void *data);
+
+G_END_DECLS
+
+#endif
diff --git a/src/usb-device-manager-priv.h b/src/usb-device-manager-priv.h
index 83884d7c..39aaf2f3 100644
--- a/src/usb-device-manager-priv.h
+++ b/src/usb-device-manager-priv.h
@@ -32,7 +32,6 @@  void spice_usb_device_manager_stop_event_listening(
     SpiceUsbDeviceManager *manager);
 
 #ifdef USE_USBREDIR
-#include <libusb.h>
 void spice_usb_device_manager_device_error(
     SpiceUsbDeviceManager *manager, SpiceUsbDevice *device, GError *err);
 
diff --git a/src/usb-device-manager.c b/src/usb-device-manager.c
index 9391d6ac..2bee55d1 100644
--- a/src/usb-device-manager.c
+++ b/src/usb-device-manager.c
@@ -25,15 +25,14 @@ 
 
 #ifdef USE_USBREDIR
 #include <errno.h>
-#include <libusb.h>
 
 #ifdef G_OS_WIN32
+#include <windows.h>
 #include "usbdk_api.h"
 #include "win-usb-dev.h"
 #endif
 
 #include "channel-usbredir-priv.h"
-#include "usbredirhost.h"
 #include "usbutil.h"
 #endif
 
@@ -94,7 +93,7 @@  struct _SpiceUsbDeviceManagerPrivate {
     gchar *auto_connect_filter;
     gchar *redirect_on_connect;
 #ifdef USE_USBREDIR
-    libusb_context *context;
+    SpiceUsbBackend *context;
     int event_listeners;
     GThread *event_thread;
     gint event_thread_run;
@@ -106,7 +105,6 @@  struct _SpiceUsbDeviceManagerPrivate {
     GUdevClient *udev;
 #else
     gboolean redirecting; /* Handled by GUdevClient in the gudev case */
-    libusb_hotplug_callback_handle hp_handle;
 #endif
 #ifdef G_OS_WIN32
     usbdk_api_wrapper     *usbdk_api;
@@ -136,7 +134,7 @@  typedef struct _SpiceUsbDeviceInfo {
     guint16 vid;
     guint16 pid;
     gboolean isochronous;
-    libusb_device *libdev;
+    SpiceUsbBackendDevice *bdev;
     gint    ref;
 } SpiceUsbDeviceInfo;
 
@@ -149,19 +147,18 @@  static void channel_event(SpiceChannel *channel, SpiceChannelEvent event,
                           gpointer user_data);
 #ifdef G_OS_WIN32
 static void spice_usb_device_manager_uevent_cb(GUdevClient     *client,
-                                               libusb_device   *udevice,
+                                               SpiceUsbBackendDevice *udevice,
                                                gboolean         add,
                                                gpointer         user_data);
 #else
-static int spice_usb_device_manager_hotplug_cb(libusb_context       *ctx,
-                                               libusb_device        *device,
-                                               libusb_hotplug_event  event,
-                                               void                 *data);
+static void spice_usb_device_manager_hotplug_cb(void *user_data,
+                                                SpiceUsbBackendDevice *dev,
+                                                gboolean added);
 #endif
 static void spice_usb_device_manager_check_redir_on_connect(
     SpiceUsbDeviceManager *self, SpiceChannel *channel);
 
-static SpiceUsbDeviceInfo *spice_usb_device_new(libusb_device *libdev);
+static SpiceUsbDeviceInfo *spice_usb_device_new(SpiceUsbBackendDevice *bdev);
 static SpiceUsbDevice *spice_usb_device_ref(SpiceUsbDevice *device);
 static void spice_usb_device_unref(SpiceUsbDevice *device);
 
@@ -170,12 +167,12 @@  static void _usbdk_hider_update(SpiceUsbDeviceManager *manager);
 static void _usbdk_hider_clear(SpiceUsbDeviceManager *manager);
 #endif
 
-static gboolean spice_usb_manager_device_equal_libdev(SpiceUsbDeviceManager *manager,
-                                                      SpiceUsbDevice *device,
-                                                      libusb_device *libdev);
-static libusb_device *
-spice_usb_device_manager_device_to_libdev(SpiceUsbDeviceManager *self,
-                                          SpiceUsbDevice *device);
+static gboolean spice_usb_manager_device_equal_bdev(SpiceUsbDeviceManager *manager,
+                                                    SpiceUsbDevice *device,
+                                                    SpiceUsbBackendDevice *bdev);
+static SpiceUsbBackendDevice *
+spice_usb_device_manager_device_to_bdev(SpiceUsbDeviceManager *self,
+                                        SpiceUsbDevice *device);
 
 static void
 _spice_usb_device_manager_connect_device_async(SpiceUsbDeviceManager *self,
@@ -277,14 +274,9 @@  static gboolean spice_usb_device_manager_initable_init(GInitable  *initable,
     GList *it;
 
 #ifndef G_OS_WIN32
-    int rc;
     /* Initialize libusb */
-    rc = libusb_init(&priv->context);
-    if (rc < 0) {
-        const char *desc = libusb_strerror(rc);
-        g_warning("Error initializing USB support: %s [%i]", desc, rc);
-        g_set_error(err, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
-                    "Error initializing USB support: %s [%i]", desc, rc);
+    priv->context = spice_usb_backend_new(err);
+    if (!priv->context) {
         return FALSE;
     }
 #endif
@@ -302,16 +294,8 @@  static gboolean spice_usb_device_manager_initable_init(GInitable  *initable,
     /* Do coldplug (detection of already connected devices) */
     g_udev_client_report_devices(priv->udev);
 #else
-    rc = libusb_hotplug_register_callback(priv->context,
-        LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED | LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT,
-        LIBUSB_HOTPLUG_ENUMERATE, LIBUSB_HOTPLUG_MATCH_ANY,
-        LIBUSB_HOTPLUG_MATCH_ANY, LIBUSB_HOTPLUG_MATCH_ANY,
-        spice_usb_device_manager_hotplug_cb, self, &priv->hp_handle);
-    if (rc < 0) {
-        const char *desc = libusb_strerror(rc);
-        g_warning("Error initializing USB hotplug support: %s [%i]", desc, rc);
-        g_set_error(err, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
-                  "Error initializing USB hotplug support: %s [%i]", desc, rc);
+    if (!spice_usb_backend_register_hotplug(priv->context, self,
+                                            spice_usb_device_manager_hotplug_cb)) {
         return FALSE;
     }
     spice_usb_device_manager_start_event_listening(self, NULL);
@@ -342,21 +326,17 @@  static void spice_usb_device_manager_dispose(GObject *gobject)
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
 
 #ifndef G_OS_WIN32
-    if (priv->hp_handle) {
-        spice_usb_device_manager_stop_event_listening(self);
-        if (g_atomic_int_get(&priv->event_thread_run)) {
-            /* Force termination of the event thread even if there were some
-             * mismatched spice_usb_device_manager_{start,stop}_event_listening
-             * calls. Otherwise, the usb event thread will be leaked, and will
-             * try to use the libusb context we destroy in finalize(), which would
-             * cause a crash */
-             g_warn_if_reached();
-             g_atomic_int_set(&priv->event_thread_run, FALSE);
-        }
-        /* This also wakes up the libusb_handle_events() in the event_thread */
-        libusb_hotplug_deregister_callback(priv->context, priv->hp_handle);
-        priv->hp_handle = 0;
+    spice_usb_device_manager_stop_event_listening(self);
+    if (g_atomic_int_get(&priv->event_thread_run)) {
+        /* Force termination of the event thread even if there were some
+         * mismatched spice_usb_device_manager_{start,stop}_event_listening
+         * calls. Otherwise, the usb event thread will be leaked, and will
+         * try to use the libusb context we destroy in finalize(), which would
+         * cause a crash */
+        g_warn_if_reached();
+        g_atomic_int_set(&priv->event_thread_run, FALSE);
     }
+    spice_usb_backend_deregister_hotplug(priv->context);
 #endif
     if (priv->event_thread) {
         g_warn_if_fail(g_atomic_int_get(&priv->event_thread_run) == FALSE);
@@ -386,7 +366,7 @@  static void spice_usb_device_manager_finalize(GObject *gobject)
     g_return_if_fail(priv->event_thread == NULL);
 #ifndef G_OS_WIN32
     if (priv->context)
-        libusb_exit(priv->context);
+        spice_usb_backend_delete(priv->context);
 #endif
     free(priv->auto_conn_filter_rules);
     free(priv->redirect_on_connect_rules);
@@ -709,37 +689,6 @@  static void spice_usb_device_manager_class_init(SpiceUsbDeviceManagerClass *klas
                      G_TYPE_ERROR);
 }
 
-#ifdef USE_USBREDIR
-
-/* ------------------------------------------------------------------ */
-/* gudev / libusb Helper functions                                    */
-
-static gboolean spice_usb_device_manager_get_device_descriptor(
-    libusb_device *libdev,
-    struct libusb_device_descriptor *desc)
-{
-    int errcode;
-    const gchar *errstr;
-
-    g_return_val_if_fail(libdev != NULL, FALSE);
-    g_return_val_if_fail(desc   != NULL, FALSE);
-
-    errcode = libusb_get_device_descriptor(libdev, desc);
-    if (errcode < 0) {
-        int bus, addr;
-
-        bus = libusb_get_bus_number(libdev);
-        addr = libusb_get_device_address(libdev);
-        errstr = libusb_strerror(errcode);
-        g_warning("cannot get device descriptor for (%p) %d.%d -- %s(%d)",
-                  libdev, bus, addr, errstr, errcode);
-        return FALSE;
-    }
-    return TRUE;
-}
-
-#endif // USE_USBREDIR
-
 /**
  * spice_usb_device_get_libusb_device:
  * @device: #SpiceUsbDevice to get the descriptor information of
@@ -758,32 +707,12 @@  spice_usb_device_get_libusb_device(const SpiceUsbDevice *device G_GNUC_UNUSED)
 
     g_return_val_if_fail(info != NULL, FALSE);
 
-    return info->libdev;
+    return spice_usb_backend_device_get_libdev(info->bdev);
 #endif
     return NULL;
 }
 
 #ifdef USE_USBREDIR
-static gboolean spice_usb_device_manager_get_libdev_vid_pid(
-    libusb_device *libdev, int *vid, int *pid)
-{
-    struct libusb_device_descriptor desc;
-
-    g_return_val_if_fail(libdev != NULL, FALSE);
-    g_return_val_if_fail(vid != NULL, FALSE);
-    g_return_val_if_fail(pid != NULL, FALSE);
-
-    *vid = *pid = 0;
-
-    if (!spice_usb_device_manager_get_device_descriptor(libdev, &desc)) {
-        return FALSE;
-    }
-    *vid = desc.idVendor;
-    *pid = desc.idProduct;
-
-    return TRUE;
-}
-
 /* ------------------------------------------------------------------ */
 /* callbacks                                                          */
 
@@ -899,31 +828,24 @@  spice_usb_device_manager_find_device(SpiceUsbDeviceManager *self,
 }
 
 static void spice_usb_device_manager_add_dev(SpiceUsbDeviceManager  *self,
-                                             libusb_device          *libdev)
+                                             SpiceUsbBackendDevice  *bdev)
 {
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
-    struct libusb_device_descriptor desc;
+    const UsbDeviceInformation *b_info = spice_usb_backend_device_get_info(bdev);
     SpiceUsbDevice *device;
 
-    if (!spice_usb_device_manager_get_device_descriptor(libdev, &desc))
-        return;
-
-    /* Skip hubs */
-    if (desc.bDeviceClass == LIBUSB_CLASS_HUB)
-        return;
-
     if (spice_usb_device_manager_find_device(self,
-                                             libusb_get_bus_number(libdev),
-                                             libusb_get_device_address(libdev))) {
+                                             b_info->bus,
+                                             b_info->address)) {
         SPICE_DEBUG("device not added %d:%d %04x:%04x",
-                    libusb_get_bus_number(libdev),
-                    libusb_get_device_address(libdev),
-                    desc.idVendor,
-                    desc.idProduct);
+                    b_info->bus,
+                    b_info->address,
+                    b_info->vid,
+                    b_info->pid);
         return;
     }
 
-    device = (SpiceUsbDevice*)spice_usb_device_new(libdev);
+    device = (SpiceUsbDevice*)spice_usb_device_new(bdev);
     if (!device)
         return;
 
@@ -935,10 +857,10 @@  static void spice_usb_device_manager_add_dev(SpiceUsbDeviceManager  *self,
         can_redirect = spice_usb_device_manager_can_redirect_device(
                                         self, device, NULL);
 
-        auto_ok = usbredirhost_check_device_filter(
+        auto_ok = spice_usb_backend_device_check_filter(
+                            bdev,
                             priv->auto_conn_filter_rules,
-                            priv->auto_conn_filter_rules_count,
-                            libdev, 0) == 0;
+                            priv->auto_conn_filter_rules_count) == 0;
 
         if (can_redirect && auto_ok)
             spice_usb_device_manager_connect_device_async(self,
@@ -955,15 +877,16 @@  static void spice_usb_device_manager_add_dev(SpiceUsbDeviceManager  *self,
 }
 
 static void spice_usb_device_manager_remove_dev(SpiceUsbDeviceManager *self,
-                                                guint bus, guint address)
+                                                SpiceUsbBackendDevice *bdev)
 {
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
     SpiceUsbDevice *device;
+    const UsbDeviceInformation *b_info = spice_usb_backend_device_get_info(bdev);
 
-    device = spice_usb_device_manager_find_device(self, bus, address);
+    device = spice_usb_device_manager_find_device(self, b_info->bus, b_info->address);
     if (!device) {
         g_warning("Could not find USB device to remove " DEV_ID_FMT,
-                  bus, address);
+                  b_info->bus, b_info->address);
         return;
     }
 
@@ -982,24 +905,22 @@  static void spice_usb_device_manager_remove_dev(SpiceUsbDeviceManager *self,
 
 #ifdef G_OS_WIN32
 static void spice_usb_device_manager_uevent_cb(GUdevClient     *client,
-                                               libusb_device   *dev,
+                                               SpiceUsbBackendDevice *bdev,
                                                gboolean         add,
                                                gpointer         user_data)
 {
     SpiceUsbDeviceManager *self = SPICE_USB_DEVICE_MANAGER(user_data);
 
     if (add)
-        spice_usb_device_manager_add_dev(self, dev);
+        spice_usb_device_manager_add_dev(self, bdev);
     else
-        spice_usb_device_manager_remove_dev(self,
-                                            libusb_get_bus_number(dev),
-                                            libusb_get_device_address(dev));
+        spice_usb_device_manager_remove_dev(self, bdev);
 }
 #else
 struct hotplug_idle_cb_args {
     SpiceUsbDeviceManager *self;
-    libusb_device *device;
-    libusb_hotplug_event event;
+    SpiceUsbBackendDevice *device;
+    gboolean               added;
 };
 
 static gboolean spice_usb_device_manager_hotplug_idle_cb(gpointer user_data)
@@ -1007,36 +928,29 @@  static gboolean spice_usb_device_manager_hotplug_idle_cb(gpointer user_data)
     struct hotplug_idle_cb_args *args = user_data;
     SpiceUsbDeviceManager *self = SPICE_USB_DEVICE_MANAGER(args->self);
 
-    switch (args->event) {
-    case LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED:
+    if (args->added)
         spice_usb_device_manager_add_dev(self, args->device);
-        break;
-    case LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT:
-        spice_usb_device_manager_remove_dev(self,
-                                    libusb_get_bus_number(args->device),
-                                    libusb_get_device_address(args->device));
-        break;
-    }
-    libusb_unref_device(args->device);
+    else
+        spice_usb_device_manager_remove_dev(self, args->device);
+
+    spice_usb_backend_device_unref(args->device);
     g_object_unref(self);
     g_free(args);
     return FALSE;
 }
 
 /* Can be called from both the main-thread as well as the event_thread */
-static int spice_usb_device_manager_hotplug_cb(libusb_context       *ctx,
-                                               libusb_device        *device,
-                                               libusb_hotplug_event  event,
-                                               void                 *user_data)
+static void spice_usb_device_manager_hotplug_cb(void *user_data,
+                                                SpiceUsbBackendDevice *dev,
+                                                gboolean added)
 {
     SpiceUsbDeviceManager *self = SPICE_USB_DEVICE_MANAGER(user_data);
     struct hotplug_idle_cb_args *args = g_malloc0(sizeof(*args));
 
     args->self = g_object_ref(self);
-    args->device = libusb_ref_device(device);
-    args->event = event;
+    args->device = spice_usb_backend_device_ref(dev);
+    args->added = added;
     g_idle_add(spice_usb_device_manager_hotplug_idle_cb, args);
-    return 0;
 }
 #endif // USE_USBREDIR
 
@@ -1063,13 +977,9 @@  static gpointer spice_usb_device_manager_usb_ev_thread(gpointer user_data)
 {
     SpiceUsbDeviceManager *self = SPICE_USB_DEVICE_MANAGER(user_data);
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
-    int rc;
 
     while (g_atomic_int_get(&priv->event_thread_run)) {
-        rc = libusb_handle_events(priv->context);
-        if (rc && rc != LIBUSB_ERROR_INTERRUPTED) {
-            const char *desc = libusb_strerror(rc);
-            g_warning("Error handling USB events: %s [%i]", desc, rc);
+        if (!spice_usb_backend_handle_events(priv->context)) {
             break;
         }
     }
@@ -1120,7 +1030,7 @@  static void spice_usb_device_manager_check_redir_on_connect(
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
     GTask *task;
     SpiceUsbDevice *device;
-    libusb_device *libdev;
+    SpiceUsbBackendDevice *bdev;
     guint i;
 
     if (priv->redirect_on_connect == NULL)
@@ -1132,11 +1042,11 @@  static void spice_usb_device_manager_check_redir_on_connect(
         if (spice_usb_device_manager_is_device_connected(self, device))
             continue;
 
-        libdev = spice_usb_device_manager_device_to_libdev(self, device);
-        if (usbredirhost_check_device_filter(
+        bdev = spice_usb_device_manager_device_to_bdev(self, device);
+        if (spice_usb_backend_device_check_filter(
+                            bdev,
                             priv->redirect_on_connect_rules,
-                            priv->redirect_on_connect_rules_count,
-                            libdev, 0) == 0) {
+                            priv->redirect_on_connect_rules_count) == 0) {
             /* Note: re-uses spice_usb_device_manager_connect_device_async's
                completion handling code! */
             task = g_task_new(self,
@@ -1146,14 +1056,14 @@  static void spice_usb_device_manager_check_redir_on_connect(
 
             spice_usbredir_channel_connect_device_async(
                                SPICE_USBREDIR_CHANNEL(channel),
-                               libdev, device, NULL,
+                               bdev, device, NULL,
                                spice_usb_device_manager_channel_connect_cb,
                                task);
-            libusb_unref_device(libdev);
+            spice_usb_backend_device_unref(bdev);
             return; /* We've taken the channel! */
         }
 
-        libusb_unref_device(libdev);
+        spice_usb_backend_device_unref(bdev);
     }
 }
 
@@ -1177,8 +1087,8 @@  static SpiceUsbredirChannel *spice_usb_device_manager_get_channel_for_dev(
     for (i = 0; i < priv->channels->len; i++) {
         SpiceUsbredirChannel *channel = g_ptr_array_index(priv->channels, i);
         spice_usbredir_channel_lock(channel);
-        libusb_device *libdev = spice_usbredir_channel_get_device(channel);
-        if (spice_usb_manager_device_equal_libdev(manager, device, libdev)) {
+        SpiceUsbBackendDevice *bdev = spice_usbredir_channel_get_device(channel);
+        if (spice_usb_manager_device_equal_bdev(manager, device, bdev)) {
             spice_usbredir_channel_unlock(channel);
             return channel;
         }
@@ -1235,9 +1145,9 @@  GPtrArray* spice_usb_device_manager_get_devices_with_filter(
         SpiceUsbDevice *device = g_ptr_array_index(priv->devices, i);
 
         if (rules) {
-            libusb_device *libdev =
-                spice_usb_device_manager_device_to_libdev(self, device);
-            if (usbredirhost_check_device_filter(rules, count, libdev, 0) != 0)
+            SpiceUsbBackendDevice *bdev =
+                spice_usb_device_manager_device_to_bdev(self, device);
+            if (spice_usb_backend_device_check_filter(bdev, rules, count) != 0)
                 continue;
         }
         g_ptr_array_add(devices_copy, spice_usb_device_ref(device));
@@ -1311,7 +1221,7 @@  _spice_usb_device_manager_connect_device_async(SpiceUsbDeviceManager *self,
     task = g_task_new(self, cancellable, callback, user_data);
 
     SpiceUsbDeviceManagerPrivate *priv = self->priv;
-    libusb_device *libdev;
+    SpiceUsbBackendDevice *bdev;
     guint i;
 
     if (spice_usb_device_manager_is_device_connected(self, device)) {
@@ -1327,14 +1237,14 @@  _spice_usb_device_manager_connect_device_async(SpiceUsbDeviceManager *self,
         if (spice_usbredir_channel_get_device(channel))
             continue; /* Skip already used channels */
 
-        libdev = spice_usb_device_manager_device_to_libdev(self, device);
+        bdev = spice_usb_device_manager_device_to_bdev(self, device);
         spice_usbredir_channel_connect_device_async(channel,
-                                 libdev,
+                                 bdev,
                                  device,
                                  cancellable,
                                  spice_usb_device_manager_channel_connect_cb,
                                  task);
-        libusb_unref_device(libdev);
+        spice_usb_backend_device_unref(bdev);
         return;
     }
 
@@ -1596,13 +1506,14 @@  spice_usb_device_manager_can_redirect_device(SpiceUsbDeviceManager  *self,
 
     if (guest_filter_rules) {
         gboolean filter_ok;
-        libusb_device *libdev;
-
-        libdev = spice_usb_device_manager_device_to_libdev(self, device);
-        filter_ok = (usbredirhost_check_device_filter(
-                            guest_filter_rules, guest_filter_rules_count,
-                            libdev, 0) == 0);
-        libusb_unref_device(libdev);
+        SpiceUsbBackendDevice *bdev;
+
+        bdev = spice_usb_device_manager_device_to_bdev(self, device);
+        filter_ok = (spice_usb_backend_device_check_filter(
+                            bdev,
+                            guest_filter_rules,
+                            guest_filter_rules_count) == 0);
+        spice_usb_backend_device_unref(bdev);
         if (!filter_ok) {
             g_set_error_literal(err, SPICE_CLIENT_ERROR, SPICE_CLIENT_ERROR_FAILED,
                                 _("Some USB devices are blocked by host policy"));
@@ -1696,60 +1607,27 @@  gchar *spice_usb_device_get_description(SpiceUsbDevice *device, const gchar *for
 
 
 #ifdef USE_USBREDIR
-static gboolean probe_isochronous_endpoint(libusb_device *libdev)
-{
-    struct libusb_config_descriptor *conf_desc;
-    gboolean isoc_found = FALSE;
-    gint i, j, k;
-
-    g_return_val_if_fail(libdev != NULL, FALSE);
-
-    if (libusb_get_active_config_descriptor(libdev, &conf_desc) != 0) {
-        g_return_val_if_reached(FALSE);
-    }
-
-    for (i = 0; !isoc_found && i < conf_desc->bNumInterfaces; i++) {
-        for (j = 0; !isoc_found && j < conf_desc->interface[i].num_altsetting; j++) {
-            for (k = 0; !isoc_found && k < conf_desc->interface[i].altsetting[j].bNumEndpoints;k++) {
-                gint attributes = conf_desc->interface[i].altsetting[j].endpoint[k].bmAttributes;
-                gint type = attributes & LIBUSB_TRANSFER_TYPE_MASK;
-                if (type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS)
-                    isoc_found = TRUE;
-            }
-        }
-    }
-
-    libusb_free_config_descriptor(conf_desc);
-    return isoc_found;
-}
-
 /*
  * SpiceUsbDeviceInfo
  */
-static SpiceUsbDeviceInfo *spice_usb_device_new(libusb_device *libdev)
+static SpiceUsbDeviceInfo *spice_usb_device_new(SpiceUsbBackendDevice *bdev)
 {
     SpiceUsbDeviceInfo *info;
-    int vid, pid;
-    guint8 bus, addr;
-
-    g_return_val_if_fail(libdev != NULL, NULL);
+    const UsbDeviceInformation *bdev_info;
 
-    bus = libusb_get_bus_number(libdev);
-    addr = libusb_get_device_address(libdev);
+    g_return_val_if_fail(bdev != NULL, NULL);
 
-    if (!spice_usb_device_manager_get_libdev_vid_pid(libdev, &vid, &pid)) {
-        return NULL;
-    }
+    bdev_info = spice_usb_backend_device_get_info(bdev);
 
     info = g_new0(SpiceUsbDeviceInfo, 1);
 
-    info->busnum  = bus;
-    info->devaddr = addr;
-    info->vid = vid;
-    info->pid = pid;
+    info->busnum  = bdev_info->bus;
+    info->devaddr = bdev_info->address;
+    info->vid = bdev_info->vid;
+    info->pid = bdev_info->pid;
     info->ref = 1;
-    info->isochronous = probe_isochronous_endpoint(libdev);
-    info->libdev = libusb_ref_device(libdev);
+    info->bdev = spice_usb_backend_device_ref(bdev);
+    info->isochronous = spice_usb_backend_device_isoch(bdev);
 
     return info;
 }
@@ -1885,35 +1763,35 @@  static void spice_usb_device_unref(SpiceUsbDevice *device)
 
     ref_count_is_0 = g_atomic_int_dec_and_test(&info->ref);
     if (ref_count_is_0) {
-        libusb_unref_device(info->libdev);
+        spice_usb_backend_device_unref(info->bdev);
         g_free(info);
     }
 }
 
 static gboolean
-spice_usb_manager_device_equal_libdev(SpiceUsbDeviceManager *manager,
-                                      SpiceUsbDevice *device,
-                                      libusb_device  *libdev)
+spice_usb_manager_device_equal_bdev(SpiceUsbDeviceManager *manager,
+                                    SpiceUsbDevice *device,
+                                    SpiceUsbBackendDevice *bdev)
 {
     SpiceUsbDeviceInfo *info = (SpiceUsbDeviceInfo *)device;
 
-    if ((device == NULL) || (libdev == NULL))
+    if ((device == NULL) || (bdev == NULL))
         return FALSE;
 
-    return info->libdev == libdev;
+    return info->bdev == bdev;
 }
 
 /*
  * Caller must libusb_unref_device the libusb_device returned by this function.
  * Returns a libusb_device, or NULL upon failure
  */
-static libusb_device *
-spice_usb_device_manager_device_to_libdev(SpiceUsbDeviceManager *self,
-                                          SpiceUsbDevice *device)
+static SpiceUsbBackendDevice *
+spice_usb_device_manager_device_to_bdev(SpiceUsbDeviceManager *self,
+                                        SpiceUsbDevice *device)
 {
     /* Simply return a ref to the cached libdev */
     SpiceUsbDeviceInfo *info = (SpiceUsbDeviceInfo *)device;
 
-    return libusb_ref_device(info->libdev);
+    return spice_usb_backend_device_ref(info->bdev);
 }
 #endif /* USE_USBREDIR */
diff --git a/src/win-usb-dev.c b/src/win-usb-dev.c
index b0274ddc..c2a51159 100644
--- a/src/win-usb-dev.c
+++ b/src/win-usb-dev.c
@@ -23,11 +23,9 @@ 
 #include "config.h"
 
 #include <windows.h>
-#include <libusb.h>
 #include "win-usb-dev.h"
 #include "spice-marshal.h"
 #include "spice-util.h"
-#include "usbutil.h"
 
 enum {
     PROP_0,
@@ -35,7 +33,7 @@  enum {
 };
 
 struct _GUdevClientPrivate {
-    libusb_context *ctx;
+    SpiceUsbBackend *ctx;
     GList *udev_list;
     HWND hwnd;
     gboolean redirecting;
@@ -68,9 +66,7 @@  static void g_udev_device_print_list(GList *l, const gchar *msg);
 #else
 static void g_udev_device_print_list(GList *l, const gchar *msg) {}
 #endif
-static void g_udev_device_print(libusb_device *dev, const gchar *msg);
-
-static gboolean g_udev_skip_search(libusb_device *dev);
+static void g_udev_device_print(SpiceUsbBackendDevice *dev, const gchar *msg);
 
 GQuark g_udev_client_error_quark(void)
 {
@@ -86,7 +82,7 @@  GUdevClient *g_udev_client_new(void)
     return singleton;
 }
 
-libusb_context *g_udev_client_get_context(GUdevClient *client)
+SpiceUsbBackend *g_udev_client_get_context(GUdevClient *client)
 {
     return client->priv->ctx;
 }
@@ -99,8 +95,7 @@  static ssize_t
 g_udev_client_list_devices(GUdevClient *self, GList **devs,
                            GError **err, const gchar *name)
 {
-    gssize rc;
-    libusb_device **lusb_list, **dev;
+    SpiceUsbBackendDevice **lusb_list, **dev;
     GUdevClientPrivate *priv;
     ssize_t n;
 
@@ -111,43 +106,33 @@  g_udev_client_list_devices(GUdevClient *self, GList **devs,
 
     g_return_val_if_fail(self->priv->ctx != NULL, -3);
 
-    rc = libusb_get_device_list(priv->ctx, &lusb_list);
-    if (rc < 0) {
-        const char *errstr = libusb_strerror(rc);
-        g_warning("%s: libusb_get_device_list failed - %s", name, errstr);
+    lusb_list = spice_usb_backend_get_device_list(priv->ctx);
+    if (!lusb_list) {
         g_set_error(err, G_UDEV_CLIENT_ERROR, G_UDEV_CLIENT_LIBUSB_FAILED,
-                    "%s: Error getting device list from libusb: %s [%"G_GSSIZE_FORMAT"]",
-                    name, errstr, rc);
+                    "%s: Error getting USB device list", name);
         return -4;
     }
 
     n = 0;
     for (dev = lusb_list; *dev; dev++) {
-        if (g_udev_skip_search(*dev)) {
-            continue;
-        }
-        *devs = g_list_prepend(*devs, libusb_ref_device(*dev));
+        *devs = g_list_prepend(*devs, spice_usb_backend_device_ref(*dev));
         n++;
     }
-    libusb_free_device_list(lusb_list, 1);
+    spice_usb_backend_free_device_list(lusb_list);
 
     return n;
 }
 
-static void unreference_libusb_device(gpointer data)
+static void unreference_backend_device(gpointer data)
 {
-    libusb_unref_device((libusb_device *)data);
+    spice_usb_backend_device_unref((SpiceUsbBackendDevice *)data);
 }
 
 static void g_udev_client_free_device_list(GList **devs)
 {
     g_return_if_fail(devs != NULL);
     if (*devs) {
-        /* the unreference_libusb_device method is required as
-         * libusb_unref_device calling convention differs from glib's
-         * see 558c967ec
-         */
-        g_list_free_full(*devs, unreference_libusb_device);
+        g_list_free_full(*devs, unreference_backend_device);
         *devs = NULL;
     }
 }
@@ -160,7 +145,6 @@  g_udev_client_initable_init(GInitable *initable, GCancellable *cancellable,
     GUdevClient *self;
     GUdevClientPrivate *priv;
     WNDCLASS wcls;
-    int rc;
 
     g_return_val_if_fail(G_UDEV_IS_CLIENT(initable), FALSE);
     g_return_val_if_fail(cancellable == NULL, FALSE);
@@ -168,14 +152,11 @@  g_udev_client_initable_init(GInitable *initable, GCancellable *cancellable,
     self = G_UDEV_CLIENT(initable);
     priv = self->priv;
 
-    rc = libusb_init(&priv->ctx);
-    if (rc < 0) {
-        const char *errstr = libusb_strerror(rc);
-        g_warning("Error initializing USB support: %s [%i]", errstr, rc);
-        g_set_error(err, G_UDEV_CLIENT_ERROR, G_UDEV_CLIENT_LIBUSB_FAILED,
-                    "Error initializing USB support: %s [%i]", errstr, rc);
+    priv->ctx = spice_usb_backend_new(err);
+    if (!priv->ctx) {
         return FALSE;
     }
+
 #ifdef G_OS_WIN32
 #if LIBUSB_API_VERSION >= 0x01000106
     libusb_set_option(priv->ctx, LIBUSB_OPTION_USE_USBDK);
@@ -248,9 +229,9 @@  static void g_udev_client_finalize(GObject *gobject)
     UnregisterClass(G_UDEV_CLIENT_WINCLASS_NAME, NULL);
     g_udev_client_free_device_list(&priv->udev_list);
 
-    /* free libusb context initializing by libusb_init() */
+    /* free backend context */
     g_warn_if_fail(priv->ctx != NULL);
-    libusb_exit(priv->ctx);
+    spice_usb_backend_delete(priv->ctx);
 
     /* Chain up to the parent class */
     if (G_OBJECT_CLASS(g_udev_client_parent_class)->finalize)
@@ -340,20 +321,18 @@  static void g_udev_client_class_init(GUdevClientClass *klass)
 }
 
 /* comparing bus:addr and vid:pid */
-static gint compare_libusb_devices(gconstpointer a, gconstpointer b)
+static gint compare_usb_devices(gconstpointer a, gconstpointer b)
 {
-    libusb_device *a_dev = (libusb_device *)a;
-    libusb_device *b_dev = (libusb_device *)b;
-    struct libusb_device_descriptor a_desc, b_desc;
+    const UsbDeviceInformation *a_info, *b_info;
     gboolean same_bus, same_addr, same_vid, same_pid;
+    a_info = spice_usb_backend_device_get_info((SpiceUsbBackendDevice *)a);
+    b_info = spice_usb_backend_device_get_info((SpiceUsbBackendDevice *)b);
 
-    libusb_get_device_descriptor(a_dev, &a_desc);
-    libusb_get_device_descriptor(b_dev, &b_desc);
 
-    same_bus = (libusb_get_bus_number(a_dev) == libusb_get_bus_number(b_dev));
-    same_addr = (libusb_get_device_address(a_dev) == libusb_get_device_address(b_dev));
-    same_vid = (a_desc.idVendor == b_desc.idVendor);
-    same_pid = (a_desc.idProduct == b_desc.idProduct);
+    same_bus = (a_info->bus == b_info->bus);
+    same_addr = (a_info->address == b_info->address);
+    same_vid = (a_info->vid == b_info->vid);
+    same_pid = (a_info->pid == b_info->pid);
 
     return (same_bus && same_addr && same_vid && same_pid) ? 0 : -1;
 }
@@ -363,12 +342,12 @@  static void update_device_list(GUdevClient *self, GList *new_device_list)
     GList *dev;
 
     for (dev = g_list_first(new_device_list); dev != NULL; dev = g_list_next(dev)) {
-        GList *found = g_list_find_custom(self->priv->udev_list, dev->data, compare_libusb_devices);
+        GList *found = g_list_find_custom(self->priv->udev_list, dev->data, compare_usb_devices);
         if (found != NULL) {
             /* keep old existing libusb_device in the new list, when
                usb-dev-manager will maintain its own list of libusb_device,
                these lists will be completely consistent */
-            libusb_device *temp = found->data;
+            SpiceUsbBackendDevice *temp = found->data;
             found->data = dev->data;
             dev->data = temp;
         }
@@ -386,7 +365,7 @@  static void notify_dev_state_change(GUdevClient *self,
     GList *dev;
 
     for (dev = g_list_first(old_list); dev != NULL; dev = g_list_next(dev)) {
-        GList *found = g_list_find_custom(new_list, dev->data, compare_libusb_devices);
+        GList *found = g_list_find_custom(new_list, dev->data, compare_usb_devices);
         if (found == NULL) {
             g_udev_device_print(dev->data, add ? "add" : "remove");
             g_signal_emit(self, signals[UEVENT_SIGNAL], 0, dev->data, add);
@@ -447,29 +426,11 @@  static void g_udev_device_print_list(GList *l, const gchar *msg)
 }
 #endif
 
-static void g_udev_device_print(libusb_device *dev, const gchar *msg)
+static void g_udev_device_print(SpiceUsbBackendDevice *dev, const gchar *msg)
 {
-    struct libusb_device_descriptor desc;
-
-    libusb_get_device_descriptor(dev, &desc);
+    const UsbDeviceInformation *info = spice_usb_backend_device_get_info(dev);
 
     SPICE_DEBUG("%s: %d.%d 0x%04x:0x%04x class %d", msg,
-                libusb_get_bus_number(dev),
-                libusb_get_device_address(dev),
-                desc.idVendor, desc.idProduct, desc.bDeviceClass);
-}
-
-static gboolean g_udev_skip_search(libusb_device *dev)
-{
-    gboolean skip;
-    uint8_t addr = libusb_get_device_address(dev);
-    struct libusb_device_descriptor desc;
-
-    libusb_get_device_descriptor(dev, &desc);
-
-    skip = ((addr == 0xff) ||  /* root hub (HCD) */
-            (addr == 1) || /* root hub addr */
-            (desc.bDeviceClass == LIBUSB_CLASS_HUB) || /* hub*/
-            (addr == 0)); /* bad address */
-    return skip;
+                info->bus, info->address,
+                info->vid, info->pid, info->class);
 }
diff --git a/src/win-usb-dev.h b/src/win-usb-dev.h
index b1c0e27f..fdfe73a3 100644
--- a/src/win-usb-dev.h
+++ b/src/win-usb-dev.h
@@ -23,6 +23,7 @@ 
 #define __WIN_USB_DEV_H__
 
 #include <gio/gio.h>
+#include "usb-backend.h"
 
 G_BEGIN_DECLS
 
@@ -51,12 +52,12 @@  struct _GUdevClientClass
     GObjectClass parent_class;
 
     /* signals */
-    void (*uevent)(GUdevClient *client, libusb_device *device, gboolean add);
+    void (*uevent)(GUdevClient *client, SpiceUsbBackendDevice *device, gboolean add);
 };
 
 GType g_udev_client_get_type(void) G_GNUC_CONST;
 GUdevClient *g_udev_client_new(void);
-libusb_context *g_udev_client_get_context(GUdevClient *client);
+SpiceUsbBackend *g_udev_client_get_context(GUdevClient *client);
 void g_udev_client_report_devices(GUdevClient *client);
 
 GQuark g_udev_client_error_quark(void);