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    Subject[PATCH 3.16.y-ckt 087/165] xhci: fix reporting of 0-sized URBs in control endpoint
    Date
    3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Aleksander Morgado <aleksander@aleksander.es>

    commit 45ba2154d12fc43b70312198ec47085f10be801a upstream.

    When a control transfer has a short data stage, the xHCI controller generates
    two transfer events: a COMP_SHORT_TX event that specifies the untransferred
    amount, and a COMP_SUCCESS event. But when the data stage is not short, only the
    COMP_SUCCESS event occurs. Therefore, xhci-hcd must set urb->actual_length to
    urb->transfer_buffer_length while processing the COMP_SUCCESS event, unless
    urb->actual_length was set already by a previous COMP_SHORT_TX event.

    The driver checks this by seeing whether urb->actual_length == 0, but this alone
    is the wrong test, as it is entirely possible for a short transfer to have an
    urb->actual_length = 0.

    This patch changes the xhci driver to rely on a new td->urb_length_set flag,
    which is set to true when a COMP_SHORT_TX event is received and the URB length
    updated at that stage.

    This fixes a bug which affected the HSO plugin, which relies on URBs with
    urb->actual_length == 0 to halt re-submitting the RX URB in the control
    endpoint.

    Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
    Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/usb/host/xhci-ring.c | 10 ++++++++--
    drivers/usb/host/xhci.h | 3 +++
    2 files changed, 11 insertions(+), 2 deletions(-)

    diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
    index 17df04a2d18b..5e4e1d1d7de7 100644
    --- a/drivers/usb/host/xhci-ring.c
    +++ b/drivers/usb/host/xhci-ring.c
    @@ -1981,7 +1981,7 @@ static int process_ctrl_td(struct xhci_hcd *xhci, struct xhci_td *td,
    if (event_trb != ep_ring->dequeue) {
    /* The event was for the status stage */
    if (event_trb == td->last_trb) {
    - if (td->urb->actual_length != 0) {
    + if (td->urb_length_set) {
    /* Don't overwrite a previously set error code
    */
    if ((*status == -EINPROGRESS || *status == 0) &&
    @@ -1995,7 +1995,13 @@ static int process_ctrl_td(struct xhci_hcd *xhci, struct xhci_td *td,
    td->urb->transfer_buffer_length;
    }
    } else {
    - /* Maybe the event was for the data stage? */
    + /*
    + * Maybe the event was for the data stage? If so, update
    + * already the actual_length of the URB and flag it as
    + * set, so that it is not overwritten in the event for
    + * the last TRB.
    + */
    + td->urb_length_set = true;
    td->urb->actual_length =
    td->urb->transfer_buffer_length -
    EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));
    diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
    index c57261affada..5b6a8ddda5cb 100644
    --- a/drivers/usb/host/xhci.h
    +++ b/drivers/usb/host/xhci.h
    @@ -1,3 +1,4 @@
    +
    /*
    * xHCI host controller driver
    *
    @@ -1289,6 +1290,8 @@ struct xhci_td {
    struct xhci_segment *start_seg;
    union xhci_trb *first_trb;
    union xhci_trb *last_trb;
    + /* actual_length of the URB has already been set */
    + bool urb_length_set;
    };

    /* xHCI command default timeout value */

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