[PATCH] USB: URB_ASYNC_UNLINK flag removed from the kernel

29 July 2005, Cambridge, MA:

This afternoon Alan Stern submitted a patch to remove the URB_ASYNC_UNLINK
flag from the Linux kernel.  Mr. Stern explained, "This flag is a relic
from an earlier, less-well-designed system.  For over a year it hasn't
been used for anything other than printing warning messages."

An anonymous spokesman for the Linux kernel development community
commented, "This is exactly the sort of thing we see happening all the
time.  As the kernel evolves, support for old techniques and old code can
be jettisoned and replaced by newer, better approaches.  Proprietary
operating systems do not have the freedom or flexibility to change so
quickly."

Mr. Stern, a staff member at Harvard University's Rowland Institute who
works on Linux only as a hobby, noted that the patch (labelled as548) did
not update two files, keyspan.c and option.c, in the USB drivers' "serial"
subdirectory.  "Those files need more extensive changes," he remarked.
"They examine the status field of several URBs at times when they're not
supposed to.  That will need to be fixed before the URB_ASYNC_UNLINK flag
is removed."

Greg Kroah-Hartman, the kernel maintainer responsible for overseeing all
of Linux's USB drivers, did not respond to our inquiries or return our
calls.  His only comment was "Applied, thanks."

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index e428751..c1ba530 100644
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -96,8 +96,8 @@
  * or before the URB_ACTIVE bit was set.  If so, it's essential to cancel
  * the URB if it hasn't been cancelled already (i.e., if the URB_ACTIVE bit
  * is still set).  Either way, the function must then wait for the URB to
- * finish.  Note that because the URB_ASYNC_UNLINK flag is set, the URB can
- * still be in progress even after a call to usb_unlink_urb() returns.
+ * finish.  Note that the URB can still be in progress even after a call to
+ * usb_unlink_urb() returns.
  *
  * The idea is that (1) once the ABORTING or DISCONNECTING bit is set,
  * either the stop_transport() function or the submitting function
@@ -158,8 +158,7 @@ static int usb_stor_msg_common(struct us_data *us, int timeout)
 	 * hasn't been mapped for DMA.  Yes, this is clunky, but it's
 	 * easier than always having the caller tell us whether the
 	 * transfer buffer has already been mapped. */
-	us->current_urb->transfer_flags =
-			URB_ASYNC_UNLINK | URB_NO_SETUP_DMA_MAP;
+	us->current_urb->transfer_flags = URB_NO_SETUP_DMA_MAP;
 	if (us->current_urb->transfer_buffer == us->iobuf)
 		us->current_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 	us->current_urb->transfer_dma = us->iobuf_dma;