On Mon, Jul 9, 2012 at 7:15 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > What I see is that usb_gadget_disconnect() does tell the UDC driver to
> > stop activity on the port, but that only happens after
> > composite_disconnect() was called. Can you confirm that the order of
> > the calls in usb_gadget_remove_driver() is correct?
>
> They might need to be changed. It does seems like a bad idea to tell
> the gadget driver that a disconnect occurred before the host knows
> about it.
>
> If you change the order of those two calls, does that make your posted
> patch unnecessary?
Yes, that works too. Here is the change:
-- 8< --
From: Kevin Cernekee <cernekee@xxxxxxxxx>
usb_gadget_remove_driver() runs through a four-step sequence to shut down
the gadget driver. For the case of a composite gadget + at91 UDC, this
would look like:
udc->driver->disconnect(udc->gadget); // composite_disconnect()
usb_gadget_disconnect(udc->gadget); // at91_pullup(gadget, 0)
udc->driver->unbind(udc->gadget); // composite_unbind()
usb_gadget_udc_stop(udc->gadget, udc->driver); // at91_stop()
The UDC driver can receive SETUP packets from the host up until the
point when usb_gadget_disconnect() returns. On rare occasions, the
gadget driver may see this sequence:
udc->driver->disconnect(udc->gadget); // composite_disconnect()
udc->driver->setup(udc->gadget, &ctrl); // composite_setup()
udc->driver->unbind(udc->gadget); // composite_unbind()
Some gadget drivers, such as composite, assume this will never happen
and crash as a result.
The fix is to quiesce the UDC hardware (via usb_gadget_disconnect)
before running the gadget driver through the disconnect/unbind sequence.
Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxx>
---
drivers/usb/gadget/udc-core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
index e5e44f8..bae243c 100644
--- a/drivers/usb/gadget/udc-core.c
+++ b/drivers/usb/gadget/udc-core.c
@@ -262,8 +262,8 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
if (udc_is_newstyle(udc)) {
- udc->driver->disconnect(udc->gadget);
usb_gadget_disconnect(udc->gadget);
+ udc->driver->disconnect(udc->gadget);
udc->driver->unbind(udc->gadget);
usb_gadget_udc_stop(udc->gadget, udc->driver);
} else {
--
1.7.11.1
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