[PATCH] D-BUS patch for udev-008

Attached is a patch against udev-008 to send out a D-BUS message when a
device node is added or removed.

Using D-BUS lingo, udev acquires the org.kernel.udev service and sends
out a NodeCreated or NodeDeleted signal on the
org.kernel.udev.NodeMonitor interface. Each signal carries two
parameters: the node in question and the corresponding sysfs path.

[Note: the D-BUS concepts of service, interface, object can be a bit
confusing at first glance]

An example program listening for these messages looks like this

#!/usr/bin/python

import dbus
import gtk

def udev_signal_received(dbus_iface, member, service, object_path, message):
    [filename, sysfs_path] = message.get_args_list()
    if member=='NodeCreated':
        print 'Node %s created for %s'%(filename, sysfs_path)
    elif member=='NodeDeleted':
        print 'Node %s deleted for %s'%(filename, sysfs_path)

def main():
    bus = dbus.Bus(dbus.Bus.TYPE_SYSTEM)
    bus.add_signal_receiver(udev_signal_received,
                            'org.kernel.udev.NodeMonitor',  # interface
                            'org.kernel.udev',              # service
                            '/org/kernel/udev/NodeMonitor') # object

    gtk.mainloop()

if __name__ == '__main__':
    main()

and this is the output when hot-plugging some usb-storage.

[david@laptop udev-008]$ ~/node_monitor.py
Node /udev/sda created for /block/sda
Node /udev/sda1 created for /block/sda/sda1
Node /udev/sda1 deleted for /block/sda/sda1
Node /udev/sda deleted for /block/sda

The patch requires D-BUS 0.20 or later while the python example program
requires D-BUS from CVS as I only recently applied a patch against the
python bindings.

1 files changed, 42 insertions, 0 deletions

diff --git a/udev-add.c b/udev-add.c
index ddf432bbc7..174331fade 100644
--- a/udev-add.c
+++ b/udev-add.c
@@ -100,6 +100,42 @@ static int create_path(char *file)
 	return 0;
 }
 
+#ifdef USE_DBUS
+/** Send out a signal that a device node is created
+ *
+ *  @param  dev                 udevice object
+ *  @param  path                Sysfs path of device
+ */
+static void sysbus_send_create(struct udevice *dev, const char *path)
+{
+        char filename[255];
+        DBusMessage* message;
+        DBusMessageIter iter;
+
+        if (sysbus_connection == NULL)
+                return;
+
+        strncpy(filename, udev_root, sizeof(filename));
+        strncat(filename, dev->name, sizeof(filename));
+
+        /* object, interface, member */
+        message = dbus_message_new_signal("/org/kernel/udev/NodeMonitor", 
+                                          "org.kernel.udev.NodeMonitor",
+                                          "NodeCreated");
+        
+        dbus_message_iter_init(message, &iter);
+        dbus_message_iter_append_string(&iter, filename);
+        dbus_message_iter_append_string(&iter, path);
+
+        if ( !dbus_connection_send(sysbus_connection, message, NULL) )
+                dbg("error sending d-bus signal");
+
+        dbus_message_unref(message);
+        
+        dbus_connection_flush(sysbus_connection);
+}
+#endif /* USE_DBUS */
+
 /*
  * we possibly want to add some symlinks here
  * only numeric owner/group id's are supported
@@ -323,6 +359,12 @@ int udev_add_device(char *path, char *subsystem)
 	dbg("name='%s'", dev.name);
 	retval = create_node(&dev);
 
+#ifdef USE_DBUS
+        if (retval == 0) {
+                sysbus_send_create(&dev, path);
+        }
+#endif /* USE_DBUS */
+
 exit:
 	if (class_dev)
 		sysfs_close_class_device(class_dev);