[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>
diff --git a/drivers/net/irda/irda-usb.c b/drivers/net/irda/irda-usb.c
index 46e0022..6c766fd 100644
--- a/drivers/net/irda/irda-usb.c
+++ b/drivers/net/irda/irda-usb.c
@@ -267,7 +267,7 @@
frame, IRDA_USB_SPEED_MTU,
speed_bulk_callback, self);
urb->transfer_buffer_length = USB_IRDA_HEADER;
- urb->transfer_flags = URB_ASYNC_UNLINK;
+ urb->transfer_flags = 0;
/* Irq disabled -> GFP_ATOMIC */
if ((ret = usb_submit_urb(urb, GFP_ATOMIC))) {
@@ -401,15 +401,12 @@
skb->data, IRDA_SKB_MAX_MTU,
write_bulk_callback, skb);
urb->transfer_buffer_length = skb->len;
- /* Note : unlink *must* be Asynchronous because of the code in
- * irda_usb_net_timeout() -> call in irq - Jean II */
- urb->transfer_flags = URB_ASYNC_UNLINK;
/* This flag (URB_ZERO_PACKET) indicates that what we send is not
* a continuous stream of data but separate packets.
* In this case, the USB layer will insert an empty USB frame (TD)
* after each of our packets that is exact multiple of the frame size.
* This is how the dongle will detect the end of packet - Jean II */
- urb->transfer_flags |= URB_ZERO_PACKET;
+ urb->transfer_flags = URB_ZERO_PACKET;
/* Generate min turn time. FIXME: can we do better than this? */
/* Trying to a turnaround time at this level is trying to measure
@@ -630,8 +627,6 @@
* in completion handler, because urb->status will
* be -ENOENT. We will fix that at the next watchdog,
* leaving more time to USB to recover...
- * Also, we are in interrupt, so we need to have
- * URB_ASYNC_UNLINK to work properly...
* Jean II */
done = 1;
break;
@@ -1008,9 +1003,7 @@
}
}
/* Cancel Tx and speed URB - need to be synchronous to avoid races */
- self->tx_urb->transfer_flags &= ~URB_ASYNC_UNLINK;
usb_kill_urb(self->tx_urb);
- self->speed_urb->transfer_flags &= ~URB_ASYNC_UNLINK;
usb_kill_urb(self->speed_urb);
/* Stop and remove instance of IrLAP */
@@ -1521,9 +1514,7 @@
usb_kill_urb(self->rx_urb[i]);
/* Cancel Tx and speed URB.
* Toggle flags to make sure it's synchronous. */
- self->tx_urb->transfer_flags &= ~URB_ASYNC_UNLINK;
usb_kill_urb(self->tx_urb);
- self->speed_urb->transfer_flags &= ~URB_ASYNC_UNLINK;
usb_kill_urb(self->speed_urb);
}