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From: Weongyo Jeong <weongyo@FreeBSD.org>
Date: Sat, 13 Nov 2010 21:37:19 +0000 (UTC)
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Subject: svn commit: r215262 - user/weongyo/usb/sys/dev/usb
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Author: weongyo
Date: Sat Nov 13 21:37:18 2010
New Revision: 215262
URL: http://svn.freebsd.org/changeset/base/215262

Log:
  Only try to tap the USB packet if the waiting descriptors exist.

Modified:
  user/weongyo/usb/sys/dev/usb/usb_pf.c

Modified: user/weongyo/usb/sys/dev/usb/usb_pf.c
==============================================================================
--- user/weongyo/usb/sys/dev/usb/usb_pf.c	Sat Nov 13 21:17:53 2010	(r215261)
+++ user/weongyo/usb/sys/dev/usb/usb_pf.c	Sat Nov 13 21:37:18 2010	(r215262)
@@ -1678,9 +1678,11 @@ usbpf_xfertap(struct usb_xfer *xfer, int
 	char *buf, *ptr, *end;
 
 	/*
-	 * XXX check first whether there are any descriptors waiting.  If no
-	 * we don't need to handle this xfer.
+	 * NB: usbpf_uifd_cnt isn't protected by USBPFIF_LOCK() because it's
+	 * not harmful.
 	 */
+	if (usbpf_uifd_cnt == 0)
+		return
 
 	/*
 	 * XXX TODO