Re: [PATCH 1/2] xhci: fix reporting of 0-sized URBs in control endpoint

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Hello.

On 03/06/2015 06:14 PM, Mathias Nyman wrote:

From: Aleksander Morgado <aleksander@xxxxxxxxxxxxx>

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.

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Aleksander Morgado <aleksander@xxxxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>

[...]

diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 3b97f05..d066393 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1,3 +1,4 @@
+
  /*
   * xHCI host controller driver
   *

   Hm, I thought you've dropped this new line...

WBR, Sergei

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