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@xxxxxxxxxxxxx>
---
Hey Mathias,
This v5 of the patch takes into account the possibility of needing to return
-EREMOTEIO if URB_SHORT_NOT_OK was requested in the transfer flags.
With this change we no longer check for having a value in urb->actual_length,
instead we just use the new flag and therefore we treat in the same way all
cases where we got a SHORT_TX event (including those were the transfer was 0).
Also changed the length of the comment lines to avoid going off 80chars per
line.
Let me know what you think.
---
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 88da8d6..73485fa 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1946,7 +1946,7 @@ 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) &&
@@ -1960,7 +1960,13 @@ 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 9745147..bd868aa 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1,3 +1,4 @@
+
/*
* xHCI host controller driver
*
@@ -1288,6 +1289,8 @@ 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 */
--
2.3.1
--
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