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LinuxPPS: core support

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This patch adds the kernel side of the PPS support currently named
"LinuxPPS".

PPS means "pulse per second" and a PPS source is just a device which
provides a high precision signal each second so that an application can
use it to adjust system clock time.

Common use is the combination of the NTPD as userland program with a GPS
receiver as PPS source to obtain a wallclock-time with sub-millisecond
synchronisation to UTC.

To obtain this goal the userland programs shoud use the PPS API
specification (RFC 2783 - Pulse-Per-Second API for UNIX-like Operating
Systems, Version 1.0) which in part is implemented by this patch.  It
provides a set of chars devices, one per PPS source, which can be used to
get the time signal.  The RFC's functions can be implemented by accessing
to these char devices.

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rodolfo Giometti
2009-06-17 16:28:37 -07:00
committed by Linus Torvalds
parent 8820f27ad9
commit eae9d2ba0c
14 changed files with 1249 additions and 0 deletions
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Documentation/ABI/testing/sysfs-pps Normal file
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What: /sys/class/pps/
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ directory will contain files and
directories that will provide a unified interface to
the PPS sources.
What: /sys/class/pps/ppsX/
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/ directory is related to X-th
PPS source into the system. Each directory will
contain files to manage and control its PPS source.
What: /sys/class/pps/ppsX/assert
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/assert file reports the assert events
and the assert sequence number of the X-th source in the form:
<secs>.<nsec>#<sequence>
If the source has no assert events the content of this file
is empty.
What: /sys/class/pps/ppsX/clear
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/clear file reports the clear events
and the clear sequence number of the X-th source in the form:
<secs>.<nsec>#<sequence>
If the source has no clear events the content of this file
is empty.
What: /sys/class/pps/ppsX/mode
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/mode file reports the functioning
mode of the X-th source in hexadecimal encoding.
Please, refer to linux/include/linux/pps.h for further
info.
What: /sys/class/pps/ppsX/echo
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/echo file reports if the X-th does
or does not support an "echo" function.
What: /sys/class/pps/ppsX/name
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/name file reports the name of the
X-th source.
What: /sys/class/pps/ppsX/path
Date: February 2008
Contact: Rodolfo Giometti <giometti@linux.it>
Description:
The /sys/class/pps/ppsX/path file reports the path name of
the device connected with the X-th source.
If the source is not connected with any device the content
of this file is empty.