Description: Implement stub backend for Hurd
Author: Petter Reinholdtsen <pere@hungry.com>

--- a/libusb/core.c
+++ b/libusb/core.c
@@ -48,6 +48,8 @@
 const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
 #elif defined(OS_DARWIN)
 const struct usbi_os_backend * const usbi_backend = &darwin_backend;
+#elif defined(OS_HURD)
+const struct usbi_os_backend * const usbi_backend = &hurd_backend;
 #elif defined(OS_OPENBSD)
 const struct usbi_os_backend * const usbi_backend = &openbsd_backend;
 #elif defined(OS_NETBSD)
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -533,7 +533,7 @@
 
 /* Internal abstraction for poll (needs struct usbi_transfer on Windows) */
 #if defined(OS_LINUX) || defined(OS_DARWIN) || defined(OS_OPENBSD) || defined(OS_NETBSD) ||\
-	defined(OS_HAIKU) || defined(OS_SUNOS)
+	defined(OS_HAIKU) || defined(OS_SUNOS) || defined(OS_HURD)
 #include <unistd.h>
 #include "os/poll_posix.h"
 #elif defined(OS_WINDOWS) || defined(OS_WINCE)
@@ -1136,6 +1136,7 @@
 
 extern const struct usbi_os_backend linux_usbfs_backend;
 extern const struct usbi_os_backend darwin_backend;
+extern const struct usbi_os_backend hurd_backend;
 extern const struct usbi_os_backend openbsd_backend;
 extern const struct usbi_os_backend netbsd_backend;
 extern const struct usbi_os_backend windows_backend;
--- /dev/null
+++ b/libusb/os/hurd_usb.c
@@ -0,0 +1,214 @@
+/*
+ * Copyright © 2016 Petter Reinholdtsen <pere@hungry.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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * Stup libusb implementation for GNU Hurd returning empty list of
+ * devices.  This allow programs to build on Hurd without USB support
+ * without having to update a lot of build dependencies.
+ */
+
+#include "libusbi.h"
+
+static int
+hurd_init(struct libusb_context *ctx)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_get_device_list(struct libusb_context * ctx,
+	struct discovered_devs **discdevs)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_open(struct libusb_device_handle *handle)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static void
+hurd_close(struct libusb_device_handle *handle)
+{
+	usbi_dbg(__FUNCTION__);
+}
+
+static int
+hurd_get_device_descriptor(struct libusb_device *dev, unsigned char *buf,
+    int *host_endian)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+int
+hurd_get_active_config_descriptor(struct libusb_device *dev,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+int
+hurd_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_get_configuration(struct libusb_device_handle *handle, int *config)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
+    int altsetting)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_reset_device(struct libusb_device_handle *handle)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_alloc_streams(struct libusb_device_handle *handle,
+		   uint32_t num_streams, unsigned char *endpoints, int num_endpoints)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static int
+hurd_free_streams(struct libusb_device_handle *handle,
+		  unsigned char *endpoints, int num_endpoints)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+static void
+hurd_destroy_device(struct libusb_device *dev)
+{
+	usbi_dbg(__FUNCTION__);
+}
+
+static int
+hurd_submit_transfer(struct usbi_transfer *itransfer)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+int
+hurd_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+hurd_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	usbi_dbg(__FUNCTION__);
+}
+
+int
+hurd_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	usbi_dbg(__FUNCTION__);
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+int
+hurd_clock_gettime(int clkid, struct timespec *tp)
+{
+	usbi_dbg("clock %d", clkid);
+
+	if (clkid == USBI_CLOCK_REALTIME)
+		return clock_gettime(CLOCK_REALTIME, tp);
+
+	if (clkid == USBI_CLOCK_MONOTONIC)
+		return clock_gettime(CLOCK_MONOTONIC, tp);
+
+	return (LIBUSB_ERROR_INVALID_PARAM);
+}
+
+const struct usbi_os_backend hurd_backend = {
+	.name = "Synchronous Hurd backend",
+	.caps = 0,
+	.init = hurd_init,
+	.get_device_list = hurd_get_device_list,
+	.open = hurd_open,
+	.close = hurd_close,
+	.get_device_descriptor = hurd_get_device_descriptor,
+	.get_active_config_descriptor = hurd_get_active_config_descriptor,
+	.get_config_descriptor = hurd_get_config_descriptor,
+	.set_configuration = hurd_set_configuration,
+	.claim_interface = hurd_claim_interface,
+	.release_interface = hurd_release_interface,
+	.set_interface_altsetting = hurd_set_interface_altsetting,
+	.clear_halt = hurd_clear_halt,
+	.reset_device = hurd_reset_device,
+	.alloc_streams = hurd_alloc_streams,
+	.free_streams = hurd_free_streams,
+	.submit_transfer = hurd_submit_transfer,
+	.cancel_transfer = hurd_cancel_transfer,
+	.clear_transfer_priv = hurd_clear_transfer_priv,
+	.clock_gettime = hurd_clock_gettime,
+};
--- a/configure.ac
+++ b/configure.ac
@@ -67,6 +67,11 @@
 	backend="darwin"
 	threads="posix"
 	;;
+*-gnu*)
+	AC_MSG_RESULT([Hurd])
+	backend="hurd"
+	threads="posix"
+	;;
 *-openbsd*)
 	AC_MSG_RESULT([OpenBSD])
 	backend="openbsd"
@@ -151,6 +156,14 @@
 		[AC_DEFINE([POLL_NFDS_TYPE],[unsigned int],[type of second poll() argument])],
 		[#include <poll.h>])
 	;;
+hurd)
+	AC_DEFINE(OS_HURD, 1, [Hurd backend])
+	AC_SUBST(OS_HURD)
+	THREAD_CFLAGS="-pthread"
+	LIBS="-pthread"
+	AC_CHECK_HEADERS([poll.h])
+	AC_DEFINE([POLL_NFDS_TYPE],[nfds_t],[type of second poll() argument])
+	;;
 openbsd)
 	AC_DEFINE(OS_OPENBSD, 1, [OpenBSD backend])
 	AC_SUBST(OS_OPENBSD)
@@ -204,6 +217,7 @@
 
 AM_CONDITIONAL(OS_LINUX, test "x$backend" = xlinux)
 AM_CONDITIONAL(OS_DARWIN, test "x$backend" = xdarwin)
+AM_CONDITIONAL(OS_HURD, test "x$backend" = xhurd)
 AM_CONDITIONAL(OS_OPENBSD, test "x$backend" = xopenbsd)
 AM_CONDITIONAL(OS_SUNOS, test "x$backend" = xsunos)
 AM_CONDITIONAL(OS_NETBSD, test "x$backend" = xnetbsd)
--- a/libusb/Makefile.am
+++ b/libusb/Makefile.am
@@ -20,6 +20,7 @@
 WINCE_USB_SRC = os/wince_usb.h os/wince_usb.c
 HAIKU_USB_SRC = os/haiku_usb.h os/haiku_usb_backend.cpp \
 		os/haiku_usb_raw.h os/haiku_usb_raw.cpp os/haiku_pollfs.cpp
+HURD_USB_SRC = os/hurd_usb.c
 
 EXTRA_DIST = $(POSIX_POLL_SRC) $(POSIX_THREADS_SRC) \
 	$(WINDOWS_POLL_SRC) $(WINDOWS_THREADS_SRC) \
@@ -62,6 +63,10 @@
 libusb_1_0_la_LIBADD = libusb_haiku.la
 endif
 
+if OS_HURD
+OS_SRC = $(HURD_USB_SRC)
+endif
+
 if OS_WINDOWS
 
 if USE_USBDK