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 <[email protected]>
---
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. */
The preferred multi-line comment style is this:
/*
* bla
* bla
*/
[...]
WBR, Sergei
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