Add Null POSIX backend

Add a simple null backend for POSIX platforms that reports no available
devices, and provides no capabilities. Make use of this new backend on
all the OSes without an existing backend, so libusb can be built even on
OSes without USB support.

5 files changed, 196 insertions, 4 deletions

diff --git a/configure.ac b/configure.ac
index da8a158..ddde325 100644
--- a/configure.ac
+++ b/configure.ac
@@ -100,7 +100,9 @@ case $host in
 	threads=posix
 	;;
 *)
-	AC_MSG_ERROR([unsupported operating system $host])
+	AC_MSG_RESULT([Null])
+	backend="null"
+	threads="posix"
 esac
 
 case $backend in
@@ -186,6 +188,14 @@ haiku)
 	AC_CHECK_HEADERS([poll.h])
 	AC_DEFINE([POLL_NFDS_TYPE],[nfds_t],[type of second poll() argument])
 	;;
+null)
+	AC_DEFINE(OS_NULL, 1, [Null backend])
+	AC_SUBST(OS_NULL)
+	THREAD_CFLAGS="-pthread"
+	LIBS="-pthread"
+	AC_CHECK_HEADERS([poll.h])
+	AC_DEFINE([POLL_NFDS_TYPE],[nfds_t],[type of second poll() argument])
+	;;
 esac
 
 AC_SUBST(LIBS)
@@ -197,6 +207,7 @@ AM_CONDITIONAL(OS_SUNOS, test "x$backend" = xsunos)
 AM_CONDITIONAL(OS_NETBSD, test "x$backend" = xnetbsd)
 AM_CONDITIONAL(OS_WINDOWS, test "x$backend" = xwindows)
 AM_CONDITIONAL(OS_HAIKU, test "x$backend" = xhaiku)
+AM_CONDITIONAL(OS_NULL, test "x$backend" = xnull)
 AM_CONDITIONAL(THREADS_POSIX, test "x$threads" = xposix)
 AM_CONDITIONAL(CREATE_IMPORT_LIB, test "x$create_import_lib" = xyes)
 AM_CONDITIONAL(USE_UDEV, test "x$enable_udev" = xyes)
diff --git a/libusb/Makefile.am b/libusb/Makefile.am
index e4da62e..466b633 100644
--- a/libusb/Makefile.am
+++ b/libusb/Makefile.am
@@ -22,13 +22,14 @@ WINDOWS_USB_SRC = libusb-1.0.def libusb-1.0.rc \
 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
+NULL_USB_SRC = os/null_usb.c
 
 EXTRA_DIST = $(POSIX_POLL_SRC) $(POSIX_THREADS_SRC) \
 	$(WINDOWS_POLL_SRC) $(WINDOWS_THREADS_SRC) \
 	$(LINUX_USBFS_SRC) $(DARWIN_USB_SRC) \
 	$(OPENBSD_USB_SRC) $(NETBSD_USB_SRC) \
 	$(WINDOWS_USB_SRC) $(WINCE_USB_SRC) \
-	$(HAIKU_USB_SRC) \
+	$(HAIKU_USB_SRC) $(NULL_USB_SRC) \
 	os/linux_udev.c os/linux_netlink.c
 
 if OS_LINUX
@@ -64,6 +65,10 @@ libusb_haiku_la_SOURCES = $(HAIKU_USB_SRC)
 libusb_1_0_la_LIBADD = libusb_haiku.la
 endif
 
+if OS_NULL
+OS_SRC = $(NULL_USB_SRC)
+endif
+
 if OS_WINDOWS
 OS_SRC = $(WINDOWS_USB_SRC)
 
diff --git a/libusb/libusbi.h b/libusb/libusbi.h
index 0a677bd..4cb6141 100644
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -575,7 +575,7 @@ int usbi_clear_event(struct libusb_context *ctx);
 
 /* 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_NULL)
 #include <unistd.h>
 #include "os/poll_posix.h"
 #elif defined(OS_WINDOWS) || defined(OS_WINCE)
diff --git a/libusb/os/null_usb.c b/libusb/os/null_usb.c
new file mode 100644
index 0000000..97fa0b8
--- /dev/null
+++ b/libusb/os/null_usb.c
@@ -0,0 +1,176 @@
+/*
+ * Copyright © 2019 Pino Toscano <toscano.pino@tiscali.it>
+ *
+ * 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
+ */
+
+#include "libusbi.h"
+
+static int
+null_get_device_list(struct libusb_context * ctx,
+	struct discovered_devs **discdevs)
+{
+	return LIBUSB_SUCCESS;
+}
+
+static int
+null_open(struct libusb_device_handle *handle)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static void
+null_close(struct libusb_device_handle *handle)
+{
+}
+
+static int
+null_get_device_descriptor(struct libusb_device *dev, unsigned char *buf,
+    int *host_endian)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_get_active_config_descriptor(struct libusb_device *dev,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
+    int altsetting)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_reset_device(struct libusb_device_handle *handle)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_submit_transfer(struct usbi_transfer *itransfer)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static void
+null_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+}
+
+static int
+null_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int
+null_clock_gettime(int clkid, struct timespec *tp)
+{
+	switch (clkid) {
+	case USBI_CLOCK_MONOTONIC:
+		return clock_gettime(CLOCK_REALTIME, tp);
+	case USBI_CLOCK_REALTIME:
+		return clock_gettime(CLOCK_REALTIME, tp);
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+const struct usbi_os_backend usbi_backend = {
+	.name = "Null backend",
+	.caps = 0,
+	.init = NULL,
+	.exit = NULL,
+	.set_option = NULL,
+	.get_device_list = null_get_device_list,
+	.hotplug_poll = NULL,
+	.wrap_sys_device = NULL,
+	.open = null_open,
+	.close = null_close,
+	.get_device_descriptor = null_get_device_descriptor,
+	.get_active_config_descriptor = null_get_active_config_descriptor,
+	.get_config_descriptor = null_get_config_descriptor,
+	.get_config_descriptor_by_value = NULL,
+	.get_configuration = NULL,
+	.set_configuration = null_set_configuration,
+	.claim_interface = null_claim_interface,
+	.release_interface = null_release_interface,
+	.set_interface_altsetting = null_set_interface_altsetting,
+	.clear_halt = null_clear_halt,
+	.reset_device = null_reset_device,
+	.alloc_streams = NULL,
+	.free_streams = NULL,
+	.dev_mem_alloc = NULL,
+	.dev_mem_free = NULL,
+	.kernel_driver_active = NULL,
+	.detach_kernel_driver = NULL,
+	.attach_kernel_driver = NULL,
+	.destroy_device = NULL,
+	.submit_transfer = null_submit_transfer,
+	.cancel_transfer = null_cancel_transfer,
+	.clear_transfer_priv = null_clear_transfer_priv,
+	.handle_events = NULL,
+	.handle_transfer_completion = null_handle_transfer_completion,
+	.clock_gettime = null_clock_gettime,
+#ifdef USBI_TIMERFD_AVAILABLE
+	.get_timerfd_clockid = NULL,
+#endif
+	.context_priv_size = 0,
+	.device_priv_size = 0,
+	.device_handle_priv_size = 0,
+	.transfer_priv_size = 0,
+};
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index adf20b4..4150474 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11414
+#define LIBUSB_NANO 11415