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xhci: free the correct ring

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gcc warns about what first looks like a reference to an uninitialized
variable:

drivers/usb/host/xhci-ring.c: In function 'handle_cmd_completion':
drivers/usb/host/xhci-ring.c:753:4: error: 'ep_ring' may be used uninitialized in this function [-Werror=maybe-uninitialized]
    xhci_unmap_td_bounce_buffer(xhci, ep_ring, cur_td);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/usb/host/xhci-ring.c:647:20: note: 'ep_ring' was declared here
  struct xhci_ring *ep_ring;
                    ^~~~~~~

It's clear to see that the list_empty() check means it can never be
uninitialized, however it still looks wrong:

When ep->cancelled_td_list contains more than one entry, the
ep_ring variable will point to the ring that was retrieved
from the last urb, and we have to look it up again in the
second loop instead, which fixes the behavior and gets rid of the
warning too.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: f9c589e142d0 ("xhci: TD-fragment, align the unsplittable case with a bounce buffer")
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Arnd Bergmann 2016-06-30 14:26:17 +02:00 committed by Greg Kroah-Hartman
parent 463c4683cf
commit f76a28a69a
1 changed files with 1 additions and 0 deletions
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drivers/usb/host/xhci-ring.c
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@ -749,6 +749,7 @@ remove_finished_td:
/* Doesn't matter what we pass for status, since the core will
* just overwrite it (because the URB has been unlinked).
*/
ep_ring = xhci_urb_to_transfer_ring(xhci, cur_td->urb);
if (ep_ring && cur_td->bounce_seg)
xhci_unmap_td_bounce_buffer(xhci, ep_ring, cur_td);
xhci_giveback_urb_in_irq(xhci, cur_td, 0);