Our current scheme for managing the lifetimes of interfaces based on
their embedded struct device doesn't work.
As things stand:
usb_parse_configuration() calls device_initialize() for
every interface in every configuration, at the time the
USB device is first created.
usb_set_configuration() calls device_add() for each
interface in the configuration being activated.
It also calls usb_disable_device(), which in turn calls
device_del() for each interface in the configuration
being deactivated.
Finally, usb_release_dev() first calls usb_disable_device()
and then usb_destroy_configuration(), which in turn calls
put_device() for every interface in every configuration.
Here's the problem: So long as the interface's embedded struct device has
a nonzero refcount (which it does until usb_destroy_configuration), it
will hold a reference to its parent usb_device. Consequently
usb_release_dev() is never called, because the usb_device's refcount
never goes to 0!
The only solution I can see is to go back to the way things used to be.
Don't use device_initialize() and put_device(). Instead call
device_register() and device_unregister() for each interface when its
configuration is activated and deactivated.
The problem with this is that we might end up re-registering an interface
while someone still holds a reference to an old incarnation. That is, we
register an interface for config #1, someone grabs a reference to it, we
then switch to config #2 and deregister the interface, then we switch back
to config #1 and try to register it again, but there's still that
outstanding reference. To rule out this possibility, when deactivating a
configuration we must wait until all the interfaces in that config have
been released.
Comments or complaints, anyone?
Alan Stern
--- 2.6/drivers/usb/core/config.c.orig Tue Dec 16 16:41:44 2003
+++ 2.6/drivers/usb/core/config.c Thu Dec 18 15:11:36 2003
@@ -70,13 +70,10 @@
return buffer - buffer0;
}
-static void usb_release_intf(struct device *dev)
+static void usb_free_intf(struct usb_interface *intf)
{
- struct usb_interface *intf;
int j;
- intf = to_usb_interface(dev);
-
if (intf->altsetting) {
for (j = 0; j < intf->num_altsetting; j++) {
struct usb_host_interface *as = &intf->altsetting[j];
@@ -303,8 +300,6 @@
return -ENOMEM;
}
memset(interface, 0, sizeof(struct usb_interface));
- interface->dev.release = usb_release_intf;
- device_initialize(&interface->dev);
interface->num_altsetting = nalts[i];
if (interface->num_altsetting > USB_MAXALTSETTING) {
@@ -395,7 +390,7 @@
struct usb_interface *ifp = cf->interface[i];
if (ifp)
- put_device(&ifp->dev);
+ usb_free_intf(ifp);
}
}
kfree(dev->config);
--- 2.6/drivers/usb/core/message.c.orig Mon Dec 15 12:02:38 2003
+++ 2.6/drivers/usb/core/message.c Thu Dec 18 15:14:04 2003
@@ -804,12 +804,16 @@
if (dev->actconfig) {
for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
struct usb_interface *interface;
+ struct completion intf_completion;
/* remove this interface */
interface = dev->actconfig->interface[i];
dev_dbg (&dev->dev, "unregistering interface %s\n",
interface->dev.bus_id);
- device_del(&interface->dev);
+ init_completion (&intf_completion);
+ interface->dev.complete = &intf_completion;
+ device_unregister (&interface->dev);
+ wait_for_completion (&intf_completion);
}
dev->actconfig = 0;
if (dev->state == USB_STATE_CONFIGURED)
@@ -1135,7 +1139,7 @@
"registering %s (config #%d, interface %d)\n",
intf->dev.bus_id, configuration,
desc->bInterfaceNumber);
- device_add (&intf->dev);
+ device_register (&intf->dev);
usb_create_driverfs_intf_files (intf);
}
}
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