Core structure and functions to support a feed-forward clock within the kernel.

Implement ffcounter, a monotonically increasing cumulative counter on top of the
active timecounter. Provide low-level functions to read the ffcounter and
convert it to absolute time or a time interval in seconds using the current
ffclock estimates, which track the drift of the oscillator. Add a ring of
fftimehands to track passing of time on each kernel tick and pick up updates of
ffclock estimates.

Committed on behalf of Julien Ridoux and Darryl Veitch from the University of
Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward
Clock Synchronization Algorithms" project.

For more information, see http://www.synclab.org/radclock/

Submitted by:	Julien Ridoux (jridoux at unimelb edu au)

1 files changed, 42 insertions, 0 deletions

diff --git a/sys/sys/_ffcounter.h b/sys/sys/_ffcounter.h
new file mode 100644
index 000000000000..0d5864a7f34e
--- /dev/null
+++ b/sys/sys/_ffcounter.h
@@ -0,0 +1,42 @@
+/*-
+ * Copyright (c) 2011 The University of Melbourne
+ * All rights reserved.
+ *
+ * This software was developed by Julien Ridoux at the University of Melbourne
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS__FFCOUNTER_H_
+#define _SYS__FFCOUNTER_H_
+
+/*
+ * The feed-forward clock counter. The fundamental element of a feed-forward
+ * clock is a wide monotonically increasing counter that accumulates at the same
+ * rate as the selected timecounter.
+ */
+typedef uint64_t ffcounter;
+
+#endif /* _SYS__FFCOUNTER_H_ */