Initial udev service discovery plugin

This implements device discovery with libudev, which is part of the udev
source package (and hence available in any recent Linux distribution).
Both cold and hot plugging (w.r.t. VLC) are implemented.

TODO:
 * V4L1 devices (currently V4L2 is assumed)
 * other subsystems (linux-dvb -> DVB, block -> discs)
 * item removal on unplug
 * better item name and category for non-USB devices

configure.ac

@@ -4561,6 +4561,10 @@ dnl
 dnl  HAL services discovery
 PKG_ENABLE_MODULES_VLC([HAL], [], [hal >= 0.5.0], [Linux HAL services discovery], [auto])
 
+dnl
+dnl  libudev services discovery
+PKG_ENABLE_MODULES_VLC([UDEV], [], [libudev], [Linux udev services discovery], [auto])
+
 dnl
 dnl MTP devices services discovery
 PKG_ENABLE_MODULES_VLC([MTP], [], [libmtp >= 0.3.0],[MTP devices support],[auto])

modules/services_discovery/Modules.am

@@ -7,3 +7,4 @@ SOURCES_bonjour = bonjour.c
 SOURCES_podcast = podcast.c
 SOURCES_mtp = mtp.c
 SOURCES_mediadirs = mediadirs.c
+SOURCES_udev = udev.c

modules/services_discovery/udev.c

+/**
+ * @file udev.c
+ * @brief List of multimedia devices for VLC media player
+ */
+/*****************************************************************************
+ * Copyright © 2009 Rémi Denis-Courmont
+ *
+ * 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 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 St, Fifth Floor, Boston, MA  02110-1301  USA
+ ****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <libudev.h>
+#include <vlc_common.h>
+#include <vlc_services_discovery.h>
+#include <vlc_plugin.h>
+#include <poll.h>
+#include <errno.h>
+
+static int  Open (vlc_object_t *);
+static void Close (vlc_object_t *);
+
+/*
+ * Module descriptor
+ */
+vlc_module_begin ()
+    set_shortname (N_("Devices"))
+    set_description (N_("Capture devices"))
+    set_category (CAT_PLAYLIST)
+    set_subcategory (SUBCAT_PLAYLIST_SD)
+    set_capability ("services_discovery", 0)
+    set_callbacks (Open, Close)
+
+    add_shortcut ("udev")
+vlc_module_end ()
+
+struct services_discovery_sys_t
+{
+    struct udev_monitor *monitor;
+    vlc_thread_t         thread;
+};
+
+static void *Run (void *);
+static void HandleDevice (services_discovery_t *, struct udev_device *, bool);
+
+/**
+ * Probes and initializes.
+ */
+static int Open (vlc_object_t *obj)
+{
+    const char subsys[] = "video4linux";
+    services_discovery_t *sd = (services_discovery_t *)obj;
+    services_discovery_sys_t *p_sys = malloc (sizeof (*p_sys));
+
+    if (p_sys == NULL)
+        return VLC_ENOMEM;
+    sd->p_sys = p_sys;
+
+    struct udev_monitor *mon = NULL;
+    struct udev *udev = udev_new ();
+    if (udev == NULL)
+        goto error;
+
+    mon = udev_monitor_new_from_netlink (udev, "udev");
+    if (mon == NULL
+     || udev_monitor_filter_add_match_subsystem_devtype (mon, subsys, NULL))
+        goto error;
+    p_sys->monitor = mon;
+
+    /* Enumerate existing devices */
+    struct udev_enumerate *devenum = udev_enumerate_new (udev);
+    if (devenum == NULL)
+        goto error;
+    if (udev_enumerate_add_match_subsystem (devenum, subsys))
+    {
+        udev_enumerate_unref (devenum);
+        goto error;
+    }
+
+    udev_monitor_enable_receiving (mon);
+    /* Note that we enumerate _after_ monitoring is enabled so that we do not
+     * loose device events occuring while we are enumerating. We could still
+     * loose events if the Netlink socket receive buffer overflows. */
+    udev_enumerate_scan_devices (devenum);
+    struct udev_list_entry *devlist = udev_enumerate_get_list_entry (devenum);
+    struct udev_list_entry *deventry;
+    udev_list_entry_foreach (deventry, devlist)
+    {
+        const char *path = udev_list_entry_get_name (deventry);
+        struct udev_device *dev = udev_device_new_from_syspath (udev, path);
+        HandleDevice (sd, dev, true);
+        udev_device_unref (dev);
+    }
+    udev_enumerate_unref (devenum);
+
+    if (vlc_clone (&p_sys->thread, Run, sd, VLC_THREAD_PRIORITY_LOW))
+        goto error;
+    return VLC_SUCCESS;
+
+error:
+    if (mon != NULL)
+        udev_monitor_unref (mon);
+    if (udev != NULL)
+        udev_unref (udev);
+    free (p_sys);
+    return VLC_EGENERIC;
+}
+
+
+/**
+ * Releases resources
+ */
+static void Close (vlc_object_t *obj)
+{
+    services_discovery_t *sd = (services_discovery_t *)obj;
+    services_discovery_sys_t *p_sys = sd->p_sys;
+    struct udev *udev = udev_monitor_get_udev (p_sys->monitor);
+
+    vlc_cancel (p_sys->thread);
+    vlc_join (p_sys->thread, NULL);
+    udev_monitor_unref (p_sys->monitor);
+    udev_unref (udev);
+    free (p_sys);
+}
+
+
+static void *Run (void *data)
+{
+    services_discovery_t *sd = data;
+    services_discovery_sys_t *p_sys = sd->p_sys;
+    struct udev_monitor *mon = p_sys->monitor;
+
+    int fd = udev_monitor_get_fd (mon);
+    struct pollfd ufd = { .fd = fd, .events = POLLIN, };
+
+    for (;;)
+    {
+        while (poll (&ufd, 1, -1) == -1)
+            if (errno != EINTR)
+                break;
+
+        struct udev_device *dev = udev_monitor_receive_device (mon);
+        if (dev == NULL)
+            continue;
+
+        /* FIXME: handle change, offline, online */
+        if (!strcmp (udev_device_get_action (dev), "add"))
+            HandleDevice (sd, dev, true);
+        else if (!strcmp (udev_device_get_action (dev), "remove"))
+            HandleDevice (sd, dev, false);
+
+        //udev_device_unref (dev);
+    }
+    return NULL;
+}
+
+static int hex (char c)
+{
+    if (c >= '0' && c <= '9')
+        return c - '0';
+    if (c >= 'A' && c <= 'F')
+        return c + 10 - 'A';
+    if (c >= 'a' && c <= 'f')
+        return c + 10 - 'a';
+    return -1;
+}
+
+static char *decode (const char *enc)
+{
+    char *ret = enc ? strdup (enc) : NULL;
+    if (ret == NULL)
+        return NULL;
+
+    char *out = ret;
+    for (const char *in = ret; *in; out++)
+    {
+        int h1, h2;
+
+        if ((in[0] == '\\') && (in[1] == 'x')
+         && ((h1 = hex (in[2])) != -1)
+         && ((h2 = hex (in[3])) != -1))
+        {
+            *out = (h1 << 4) | h2;
+            in += 4;
+        }
+        else
+        {
+            *out = *in;
+            in++;
+        }
+    }
+    *out = 0;
+    return ret;
+}
+
+static char *decode_property (struct udev_device *dev, const char *name)
+{
+    return decode (udev_device_get_property_value (dev, name));
+}
+
+static void HandleDevice (services_discovery_t *sd, struct udev_device *dev,
+                          bool add)
+{
+    //services_discovery_sys_t *p_sys = sd->p_sys;
+    if (!add)
+    {
+        msg_Err (sd, "FIXME: removing device not implemented!");
+        return;
+    }
+
+    const char *scheme = "v4l2"; /* FIXME: V4L v1 */
+    const char *node = udev_device_get_devnode (dev);
+    char *vnd = decode_property (dev, "ID_VENDOR_ENC");
+    char *name = decode_property (dev, "ID_MODEL_ENC");
+
+    char *mrl;
+    if (asprintf (&mrl, "%s://%s", scheme, node) == -1)
+        return;
+
+    /* FIXME: check for duplicates (race between monitor starting to receive
+     * and initial enumeration). */
+    input_item_t *item;
+    item = input_item_NewWithType (VLC_OBJECT (sd), mrl,
+                                   name ? name : "Unnamed",
+                                   0, NULL, 0, -1, ITEM_TYPE_CARD);
+    msg_Dbg (sd, "adding %s", mrl);
+    free (name);
+    free (mrl);
+
+    if (item != NULL)
+    {
+        services_discovery_AddItem (sd, item, vnd ? vnd : "Generic");
+        vlc_gc_decref (item);
+    }
+    free (vnd);
+}