[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, 1 insertions, 8 deletions

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 434e351..4dbe580 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -616,7 +616,6 @@ extern int usb_disabled(void);
 #define URB_ISO_ASAP		0x0002	/* iso-only, urb->start_frame ignored */
 #define URB_NO_TRANSFER_DMA_MAP	0x0004	/* urb->transfer_dma valid on submit */
 #define URB_NO_SETUP_DMA_MAP	0x0008	/* urb->setup_dma valid on submit */
-#define URB_ASYNC_UNLINK	0x0010	/* usb_unlink_urb() returns asap */
 #define URB_NO_FSBR		0x0020	/* UHCI-specific */
 #define URB_ZERO_PACKET		0x0040	/* Finish bulk OUTs with short packet */
 #define URB_NO_INTERRUPT	0x0080	/* HINT: no non-error interrupt needed */
@@ -724,13 +723,7 @@ typedef void (*usb_complete_t)(struct urb *, struct pt_regs *);
  * Initialization:
  *
  * All URBs submitted must initialize the dev, pipe, transfer_flags (may be
- * zero), and complete fields.
- * The URB_ASYNC_UNLINK transfer flag affects later invocations of
- * the usb_unlink_urb() routine.  Note: Failure to set URB_ASYNC_UNLINK
- * with usb_unlink_urb() is deprecated.  For synchronous unlinks use
- * usb_kill_urb() instead.
- *
- * All URBs must also initialize 
+ * zero), and complete fields.  All URBs must also initialize
  * transfer_buffer and transfer_buffer_length.  They may provide the
  * URB_SHORT_NOT_OK transfer flag, indicating that short reads are
  * to be treated as errors; that flag is invalid for write requests.