On Thu, 11 Aug 2005, Greg KH wrote:
> > Well, there's still a little bit to discuss. Pat mentioned that in
> > general, the remove method is supposed to handle children. Presumably
> > this applies to the usb_generic driver. Should it try to unconfigure a
> > USB device (thus deleting the interfaces) when it is unbound? Or am I
> > going overboard here, considering that usb_generic is pretty much a
> > do-nothing placeholder?
>
> It is a "placeholder" but an important one (it wouldn't work without
> it...) I hadn't thought about unbinding that "driver" before, I guess
> if it's not too much trouble we should also support that kind of
> unbinding. That would allow people to test "disconnect" without ever
> removing a device, much like the "fakephp" driver allows you to do this
> for pci devices.
I'm not quite sure what you mean. Unbinding usb_generic wouldn't be quite
like a disconnect, because it would leave the usb_device intact. But it
would be like a disconnect in that the interfaces with their associated
drivers would go away. However, people can accomplish the same thing
right now by writing '0' to /sys/device/.../bConfigurationValue (unless
the device perversely has a configuration 0).
Is the patch below what you had in mind? To tell the truth, I'm not sure
that it's needed at all. The usb_generic "driver" doesn't serve any
purpose other than to mark USB devices (as opposed to interfaces) and to
provide suspend/resume methods.
As for supporting this kind of unbinding... as things stand we have no
choice. There's currently no way to prevent the sysfs unbind attribute
from doing its thing. I wonder if we wouldn't be better off finding a way
for a driver to indicate that it should never be unbound, until the device
is removed.
If you like the patch, I'll resend it with a real Changelog message.
Alan Stern
Index: usb-2.6/drivers/usb/core/usb.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/usb.c
+++ usb-2.6/drivers/usb/core/usb.c
@@ -65,6 +65,16 @@ static int generic_probe (struct device
}
static int generic_remove (struct device *dev)
{
+ struct usb_device *udev = to_usb_device(dev);
+
+ /* if this is only an unbind, not a physical disconnect, then
+ * unconfigure the device */
+ if (udev->state == USB_STATE_CONFIGURED)
+ usb_set_configuration(udev, 0);
+
+ /* in case the call failed or the device was suspended */
+ if (udev->state >= USB_STATE_CONFIGURED)
+ usb_disable_device(udev, 0);
return 0;
}
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