[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, 41 insertions, 0 deletions

diff --git a/udev-remove.c b/udev-remove.c
index d42ed4be78..307b907c88 100644
--- a/udev-remove.c
+++ b/udev-remove.c
@@ -100,6 +100,42 @@ static int delete_node(struct udevice *dev)
 	return retval;
 }
 
+#ifdef USE_DBUS
+/** Send out a signal that a device node is deleted
+ *
+ *  @param  name                Name of the device node, e.g. /udev/sda1
+ *  @param  path                Sysfs path of device
+ */
+static void sysbus_send_remove(const char* name, const char *path)
+{
+        char filename[255];
+        DBusMessage* message;
+        DBusMessageIter iter;
+
+        if (sysbus_connection == NULL)
+                return;
+
+        strncpy(filename, udev_root, sizeof(filename));
+        strncat(filename, name, sizeof(filename));
+
+        /* object, interface, member */
+        message = dbus_message_new_signal("/org/kernel/udev/NodeMonitor", 
+                                          "org.kernel.udev.NodeMonitor",
+                                          "NodeDeleted");
+        
+        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 */
+
 /*
  * Look up the sysfs path in the database to see if we have named this device
  * something different from the kernel name.  If we have, us it.  If not, use
@@ -122,5 +158,10 @@ int udev_remove_device(char *path, char *subsystem)
 
 	dbg("name is '%s'", dev->name);
 	udevdb_delete_dev(path);
+
+#ifdef USE_DBUS
+	sysbus_send_remove(name, device);
+#endif /* USE_DBUS */
+  
 	return delete_node(dev);
 }