Add optional dbus support

As we might need dbus for inter-process-communication later, this adds a
very rudimentary dbus client integration for epoll-based loops.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

COPYING

@@ -40,6 +40,12 @@ licensed under the conditions of the LGPL-2.1 or later as published by the FSF:
 
 	Author: Rusty Russel <rusty@rustcorp.com.au>
 
+The dbus-loop code that allows using dbus in epoll loops easily is copied from
+the systemd-distribution and licensed under the conditions of the LGPL-2.1 or
+later as published by the FSF. It applies to external/dbus-loop.*
+
+	Copyright 2011 Lennart Poettering
+
 The vt.c source file is based on the VT handling of the wayland demo
 compositor:
 

Makefile.am

@@ -218,10 +218,18 @@ libeloop_la_SOURCES = \
 	src/eloop.h \
 	src/eloop.c
 
+if EV_HAVE_DBUS
+libeloop_la_SOURCES += \
+	external/dbus-loop.h \
+	external/dbus-loop.c
+endif
+
 libeloop_la_CPPFLAGS = \
-	$(AM_CPPFLAGS)
+	$(AM_CPPFLAGS) \
+	$(DBUS_CFLAGS)
 libeloop_la_LIBADD = \
-	libkmscon-static.la
+	libkmscon-static.la \
+	$(DBUS_LIBS)
 libeloop_la_LDFLAGS = \
 	-version-info 1:0:0
 

configure.ac

@@ -61,6 +61,9 @@ PKG_CHECK_MODULES([SYSTEMD], [libsystemd-login],
 PKG_CHECK_MODULES([UDEV], [libudev],
                   [have_udev=yes], [have_udev=no])
 
+PKG_CHECK_MODULES([DBUS], [dbus-1],
+                  [have_dbus=yes], [have_dbus=no])
+
 PKG_CHECK_MODULES([DRM], [libdrm],
                   [have_drm=yes], [have_drm=no])
 
@@ -212,6 +215,31 @@ else
         UDEV_LIBS=""
 fi
 
+#
+# DBus dependency
+# For IPC mechanisms we use DBus. Especially multi-seat enabled multi-session
+# capable applications need DBus to manage application and terminal switching.
+#
+
+dbus_enabled=no
+if test ! x$enable_dbus = xno ; then
+        if test x$have_dbus = xyes ; then
+                dbus_enabled=yes
+        elif test x$enable_dbus = xyes; then
+                AC_ERROR([dbus libraries not found])
+        fi
+fi
+
+if test x$dbus_enabled = xyes; then
+        AC_DEFINE([EV_HAVE_DBUS], [1],
+                  [Use dbus for IPC])
+else
+        DBUS_CFLAGS=""
+        DBUS_LIBS=""
+fi
+
+AM_CONDITIONAL([EV_HAVE_DBUS], [test x$dbus_enabled = xyes])
+
 #
 # Uterm fbdev backend
 # This checks whether the fbdev backend was requested and enables it then. There
@@ -330,6 +358,8 @@ AM_CONDITIONAL([UTERM_HAVE_XKBCOMMON], [test x$xkbcommon_enabled = xyes])
 
 AC_SUBST(SYSTEMD_CFLAGS)
 AC_SUBST(SYSTEMD_LIBS)
+AC_SUBST(DBUS_CFLAGS)
+AC_SUBST(DBUS_LIBS)
 AC_SUBST(DRM_CFLAGS)
 AC_SUBST(DRM_LIBS)
 AC_SUBST(EGL_CFLAGS)
@@ -364,6 +394,7 @@ AC_MSG_NOTICE([Build configuration:
 
 	      systemd: $systemd_enabled
 	         udev: $udev_enabled
+	         dbus: $dbus_enabled
 	    xkbcommon: $xkbcommon_enabled
 
 	libuterm video backends:

external/dbus-common.h

@@ -0,0 +1,84 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+
+#define new0(_x, _y) zero_alloc(sizeof(_x) * (_y))
+
+static void *zero_alloc(size_t s)
+{
+	void *mem = malloc(s);
+	if (mem)
+		memset(mem, 0, s);
+	return mem;
+}
+
+#define zero(_x) memset(&(_x), 0, sizeof(_x))
+#define PTR_TO_INT(_x) ((int) ((intptr_t) (_x)))
+#define INT_TO_PTR(u) ((void*) ((intptr_t) (u)))
+#define close_nointr_nofail(_x) close(_x)
+#define assert_se(_x) (void)(_x)
+#define USEC_PER_MSEC 1000ULL
+#define USEC_PER_SEC 1000000ULL
+#define NSEC_PER_USEC 1000ULL
+#define log_error(...)
+
+static struct timespec *timespec_store(struct timespec *ts, int64_t u)  {
+        assert(ts);
+        ts->tv_sec = (time_t) (u / USEC_PER_SEC);
+        ts->tv_nsec = (long int) ((u % USEC_PER_SEC) * NSEC_PER_USEC);
+        return ts;
+}
+
+uint32_t bus_flags_to_events(DBusWatch *bus_watch) {
+        unsigned flags;
+        uint32_t events = 0;
+
+        assert(bus_watch);
+
+        /* no watch flags for disabled watches */
+        if (!dbus_watch_get_enabled(bus_watch))
+                return 0;
+
+        flags = dbus_watch_get_flags(bus_watch);
+
+        if (flags & DBUS_WATCH_READABLE)
+                events |= EPOLLIN;
+        if (flags & DBUS_WATCH_WRITABLE)
+                events |= EPOLLOUT;
+
+        return events | EPOLLHUP | EPOLLERR;
+}
+
+unsigned bus_events_to_flags(uint32_t events) {
+        unsigned flags = 0;
+
+        if (events & EPOLLIN)
+                flags |= DBUS_WATCH_READABLE;
+        if (events & EPOLLOUT)
+                flags |= DBUS_WATCH_WRITABLE;
+        if (events & EPOLLHUP)
+                flags |= DBUS_WATCH_HANGUP;
+        if (events & EPOLLERR)
+                flags |= DBUS_WATCH_ERROR;
+
+        return flags;
+}

external/dbus-loop.c

@@ -0,0 +1,262 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdbool.h>
+#include <assert.h>
+#include <sys/epoll.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/timerfd.h>
+#include <unistd.h>
+
+#include "dbus-loop.h"
+#include "dbus-common.h"
+
+/* Minimal implementation of the dbus loop which integrates all dbus
+ * events into a single epoll fd which we can triviall integrate with
+ * other loops. Note that this is not used in the main systemd daemon
+ * since we run a more elaborate mainloop there. */
+
+typedef struct EpollData {
+        int fd;
+        void *object;
+        bool is_timeout:1;
+        bool fd_is_dupped:1;
+} EpollData;
+
+static dbus_bool_t add_watch(DBusWatch *watch, void *data) {
+        EpollData *e;
+        struct epoll_event ev;
+
+        assert(watch);
+
+        e = new0(EpollData, 1);
+        if (!e)
+                return FALSE;
+
+        e->fd = dbus_watch_get_unix_fd(watch);
+        e->object = watch;
+        e->is_timeout = false;
+
+        zero(ev);
+        ev.events = bus_flags_to_events(watch);
+        ev.data.ptr = e;
+
+        if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0) {
+
+                if (errno != EEXIST) {
+                        free(e);
+                        return FALSE;
+                }
+
+                /* Hmm, bloody D-Bus creates multiple watches on the
+                 * same fd. epoll() does not like that. As a dirty
+                 * hack we simply dup() the fd and hence get a second
+                 * one we can safely add to the epoll(). */
+
+                e->fd = dup(e->fd);
+                if (e->fd < 0) {
+                        free(e);
+                        return FALSE;
+                }
+
+                if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0) {
+                        close_nointr_nofail(e->fd);
+                        free(e);
+                        return FALSE;
+                }
+
+                e->fd_is_dupped = true;
+        }
+
+        dbus_watch_set_data(watch, e, NULL);
+
+        return TRUE;
+}
+
+static void remove_watch(DBusWatch *watch, void *data) {
+        EpollData *e;
+
+        assert(watch);
+
+        e = dbus_watch_get_data(watch);
+        if (!e)
+                return;
+
+        assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_DEL, e->fd, NULL) >= 0);
+
+        if (e->fd_is_dupped)
+                close_nointr_nofail(e->fd);
+
+        free(e);
+}
+
+static void toggle_watch(DBusWatch *watch, void *data) {
+        EpollData *e;
+        struct epoll_event ev;
+
+        assert(watch);
+
+        e = dbus_watch_get_data(watch);
+        if (!e)
+                return;
+
+        zero(ev);
+        ev.events = bus_flags_to_events(watch);
+        ev.data.ptr = e;
+
+        assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_MOD, e->fd, &ev) == 0);
+}
+
+static int timeout_arm(EpollData *e) {
+        struct itimerspec its;
+
+        assert(e);
+        assert(e->is_timeout);
+
+        zero(its);
+
+        if (dbus_timeout_get_enabled(e->object)) {
+                timespec_store(&its.it_value, dbus_timeout_get_interval(e->object) * USEC_PER_MSEC);
+                its.it_interval = its.it_value;
+        }
+
+        if (timerfd_settime(e->fd, 0, &its, NULL) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static dbus_bool_t add_timeout(DBusTimeout *timeout, void *data) {
+        EpollData *e;
+        struct epoll_event ev;
+
+        assert(timeout);
+
+        e = new0(EpollData, 1);
+        if (!e)
+                return FALSE;
+
+        e->fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC);
+        if (e->fd < 0)
+                goto fail;
+
+        e->object = timeout;
+        e->is_timeout = true;
+
+        if (timeout_arm(e) < 0)
+                goto fail;
+
+        zero(ev);
+        ev.events = EPOLLIN;
+        ev.data.ptr = e;
+
+        if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0)
+                goto fail;
+
+        dbus_timeout_set_data(timeout, e, NULL);
+
+        return TRUE;
+
+fail:
+        if (e->fd >= 0)
+                close_nointr_nofail(e->fd);
+
+        free(e);
+        return FALSE;
+}
+
+static void remove_timeout(DBusTimeout *timeout, void *data) {
+        EpollData *e;
+
+        assert(timeout);
+
+        e = dbus_timeout_get_data(timeout);
+        if (!e)
+                return;
+
+        assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_DEL, e->fd, NULL) >= 0);
+        close_nointr_nofail(e->fd);
+        free(e);
+}
+
+static void toggle_timeout(DBusTimeout *timeout, void *data) {
+        EpollData *e;
+        int r;
+
+        assert(timeout);
+
+        e = dbus_timeout_get_data(timeout);
+        if (!e)
+                return;
+
+        r = timeout_arm(e);
+        if (r < 0)
+                log_error("Failed to rearm timer: %s", strerror(-r));
+}
+
+int bus_loop_open(DBusConnection *c) {
+        int fd;
+
+        assert(c);
+
+        fd = epoll_create1(EPOLL_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        if (!dbus_connection_set_watch_functions(c, add_watch, remove_watch, toggle_watch, INT_TO_PTR(fd), NULL) ||
+            !dbus_connection_set_timeout_functions(c, add_timeout, remove_timeout, toggle_timeout, INT_TO_PTR(fd), NULL)) {
+                close_nointr_nofail(fd);
+                return -ENOMEM;
+        }
+
+        return fd;
+}
+
+int bus_loop_dispatch(int fd) {
+        int n;
+        struct epoll_event event;
+        EpollData *d;
+
+        assert(fd >= 0);
+
+        zero(event);
+
+        n = epoll_wait(fd, &event, 1, 0);
+        if (n < 0)
+                return errno == EAGAIN || errno == EINTR ? 0 : -errno;
+
+        assert_se(d = event.data.ptr);
+
+        if (d->is_timeout) {
+                DBusTimeout *t = d->object;
+
+                if (dbus_timeout_get_enabled(t))
+                        dbus_timeout_handle(t);
+        } else {
+                DBusWatch *w = d->object;
+
+                if (dbus_watch_get_enabled(w))
+                        dbus_watch_handle(w, bus_events_to_flags(event.events));
+        }
+
+        return 0;
+}

external/dbus-loop.h

@@ -0,0 +1,30 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#ifndef foodbusloophfoo
+#define foodbusloophfoo
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <dbus/dbus.h>
+
+int bus_loop_open(DBusConnection *c);
+int bus_loop_dispatch(int fd);
+
+#endif