Hello. On 02/22/2015 12:56 AM, Aleksander Morgado wrote:
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 not only on the urb->actual_length, but also on the ep_ring->last_td_was_short flag, which is set to true when a COMP_SHORT_TX event is received.
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@xxxxxxxxxxxxx> --- drivers/usb/host/xhci-ring.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 88da8d6..6b050f1 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c
[...]
@@ -2484,6 +2480,14 @@ static int handle_tx_event(struct xhci_hcd *xhci, ret = process_bulk_intr_td(xhci, td, event_trb, event, ep, &status); + /* Flag whether the just processed TRB was short. Do it after + * processing, so that the processor methods can also use this + * flag. */
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