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xhci: fix reporting of 0-sized URBs in control endpoint 

commit 45ba2154d1 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>
This commit is contained in:
Aleksander Morgado 2015-03-06 17:14:21 +02:00 committed by Greg Kroah-Hartman
parent 7f5d322892
commit 8ddb858381
2 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/usb/host/xhci-ring.c
View File

@ -2133,7 +2133,7 @@ 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) &&
@ -2147,7 +2147,13 @@ 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));

3
drivers/usb/host/xhci.h
View File

@ -1,3 +1,4 @@
/*
* xHCI host controller driver
*
@ -1290,6 +1291,8 @@ 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 */