[PATCH] usb: xhci: Remove skip_isoc_td()

[Michal Pecio <michal.pecio@gmail.com>]

This function is pointless because usb_submit_urb() initializes all
isoc frame descriptors to -EXDEV and 0 length so that HCDs don't need
to do anything with transfers which were never executed.

Other HCDs rely on this (e.g. EHCI itd_complete()), so we can too.
This gets rid of a potentially dangereous function which could corrupt
memory if we weren't super careful to only call it on isoc URBs.

Also, set status to 0 rather than any random status determined by the
later TD which caused skipping. This status will be ignored anyway.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 26 +++++---------------------
 1 file changed, 5 insertions(+), 21 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index b8568a069897..a6c2f2373849 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2497,26 +2497,6 @@ static void process_isoc_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 	finish_td(xhci, ep, ep_ring, td, trb_comp_code);
 }
 
-static void skip_isoc_td(struct xhci_hcd *xhci, struct xhci_td *td,
-			 struct xhci_virt_ep *ep, int status)
-{
-	struct urb_priv *urb_priv;
-	struct usb_iso_packet_descriptor *frame;
-	int idx;
-
-	urb_priv = td->urb->hcpriv;
-	idx = urb_priv->num_tds_done;
-	frame = &td->urb->iso_frame_desc[idx];
-
-	/* The transfer is partly done. */
-	frame->status = -EXDEV;
-
-	/* calc actual length */
-	frame->actual_length = 0;
-
-	xhci_dequeue_td(xhci, td, ep->ring, status);
-}
-
 /*
  * Process bulk and interrupt tds, update urb status and actual_length.
  */
@@ -2860,7 +2840,11 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 				if (trb_comp_code == COMP_STOPPED_LENGTH_INVALID)
 					return 0;
 
-				skip_isoc_td(xhci, td, ep, status);
+				/*
+				 * TD was missed, skip it. Core already initialized frame->status
+				 * to -EXDEV and frame->actual_length to 0, nothing more to do.
+				 */
+				xhci_dequeue_td(xhci, td, ep_ring, 0);
 
 				if (!list_empty(&ep_ring->td_list)) {
 					if (ring_xrun_event) {
-- 
2.48.1