libosmocore libusb integration

Osmocom applications typically use libosmocore select.[ch] event loop
code as their main event dispatch mechanism.  When they want to deal
with libusb in a non-blocking/asynchronous way, they need to integrate
libusb into that select().

The new libosmousb is doing exactly that: Providing a shared utility
library for Osmocom programs that wish to use libusb.  This is useful
for example in simtrace2 host utilitie as well as osmo-e1d.

Change-Id: I656a1a38cbb5b1f3a9145d2869d3b4d0adefcae3
Closes: OS#4299

2 files changed, 158 insertions, 0 deletions

diff --git a/src/usb/Makefile.am b/src/usb/Makefile.am
new file mode 100644
index 00000000..bca39bfe
--- /dev/null
+++ b/src/usb/Makefile.am
@@ -0,0 +1,21 @@
+# This is _NOT_ the library release version, it's an API version.
+# Please read chapter "Library interface versions" of the libtool documentation
+# before making any modifications: https://www.gnu.org/software/libtool/manual/html_node/Versioning.html
+LIBVERSION=0:0:0
+
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)/include
+AM_CFLAGS = -fPIC -Wall $(LIBUSB_CFLAGS) $(TALLOC_CFLAGS)
+AM_LDFLAGS = $(COVERAGE_LDFLAGS)
+
+if ENABLE_LIBUSB
+
+lib_LTLIBRARIES = libosmousb.la
+
+libosmousb_la_SOURCES = osmo_libusb.c
+libosmosim_la_LDFLAGS = -version-info $(LIBVERSION)
+libosmosim_la_LIBADD = \
+	$(top_builddir)/src/libosmocore.la \
+	$(TALLOC_LIBS) \
+	$(LIBUSB_LIBS)
+
+endif
diff --git a/src/usb/osmo_libusb.c b/src/usb/osmo_libusb.c
new file mode 100644
index 00000000..fda95739
--- /dev/null
+++ b/src/usb/osmo_libusb.c
@@ -0,0 +1,137 @@
+/* libosmocore integration with libusb-1.0
+ *
+ * (C) 2019 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include <errno.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <poll.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/talloc.h>
+
+#include <libusb.h>
+
+/***********************************************************************
+ * logging integration
+ ***********************************************************************/
+
+#define DLUSB	DLINP
+
+#ifdef LIBUSB_LOG_CB_CONTEXT /* introduced in 1.0.23 */
+static const int usb2logl[] = {
+	[LIBUSB_LOG_LEVEL_NONE] = LOGL_FATAL,
+	[LIBUSB_LOG_LEVEL_ERROR] = LOGL_ERROR,
+	[LIBUSB_LOG_LEVEL_WARNING] = LOGL_NOTICE,
+	[LIBUSB_LOG_LEVEL_INFO] = LOGL_INFO,
+	[LIBUSB_LOG_LEVEL_DEBUG] = LOGL_DEBUG,
+};
+
+/* called by libusb if it wants to log something */
+static void libosmo_usb_log_cb(libusb_context *luctx, enum libusb_log_level level_usb, const char *str)
+{
+	int level = LOGL_NOTICE;
+
+	if (level_usb < ARRAY_SIZE(usb2logl))
+		level = usb2logl[level_usb];
+
+	LOGP(DLUSB, level, "%s", str);
+}
+#endif /* LIBUSB_LOG_CB_CONTEXT */
+
+/***********************************************************************
+ * select loop integration
+ ***********************************************************************/
+
+static int osmo_usb_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	libusb_context *luctx = ofd->data;
+
+	/* we assume that we're running Linux v2.6.27 with timerfd support here
+	 * and hence don't have to perform manual timeout handling.  See
+	 * "Notes on time-based events" at
+	 * http://libusb.sourceforge.net/api-1.0/group__libusb__poll.html */
+	struct timeval zero_tv = { 0, 0 };
+	libusb_handle_events_timeout(luctx, &zero_tv);
+
+	return 0;
+}
+
+/* called by libusb if it wants to add a file-descriptor */
+static void osmo_usb_added_cb(int fd, short events, void *user_data)
+{
+	struct osmo_fd *ofd = talloc_zero(OTC_GLOBAL, struct osmo_fd);
+	libusb_context *luctx = user_data;
+	unsigned int when = 0;
+
+	if (events & POLLIN)
+		when |= OSMO_FD_READ;
+	if (events & POLLOUT)
+		when |= OSMO_FD_WRITE;
+
+	osmo_fd_setup(ofd, fd, when, osmo_usb_fd_cb, luctx, 0);
+	osmo_fd_register(ofd);
+}
+
+/* called by libusb if it wants to remove a file-descriptor */
+static void osmo_usb_removed_cb(int fd, void *user_data)
+{
+	struct osmo_fd *ofd = osmo_fd_get_by_fd(fd);
+	if (!fd)
+		return;
+	osmo_fd_unregister(ofd);
+	talloc_free(ofd);
+}
+
+
+/***********************************************************************
+ * initialization
+ ***********************************************************************/
+
+int osmo_libusb_init(libusb_context **pluctx)
+{
+	libusb_context *luctx = NULL;
+	int rc;
+
+	rc = libusb_init(pluctx);
+	if (rc != 0)
+		return rc;
+
+	if (pluctx)
+		luctx = *pluctx;
+
+#ifdef LIBUSB_LOG_CB_CONTEXT /* introduced in 1.0.23 */
+	libusb_set_log_cb(luctx, &libosmo_usb_log_cb, LIBUSB_LOG_CB_CONTEXT);
+#endif
+
+	libusb_set_pollfd_notifiers(luctx, osmo_usb_added_cb, osmo_usb_removed_cb, luctx);
+
+	return 0;
+}
+
+void osmo_libusb_exit(libusb_context *luctx)
+{
+	/* we just assume libusb is cleaning up all the osmo_Fd's we've allocated */
+	libusb_exit(luctx);
+}