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authorRodolfo Giometti <giometti@linux.it>2009-06-17 16:28:37 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-18 13:04:04 -0700
commiteae9d2ba0cfc27a2ad9765f23efb98fb80d80234 (patch)
treef4be40ca528b2f23f97fa9cb6ebe91b8d6696d5b /Documentation/ABI/testing/sysfs-pps
parent8820f27ad9a5ad2a62cdcdf425d7921c31831800 (diff)
downloadop-kernel-dev-eae9d2ba0cfc27a2ad9765f23efb98fb80d80234.zip
op-kernel-dev-eae9d2ba0cfc27a2ad9765f23efb98fb80d80234.tar.gz
LinuxPPS: core support
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>
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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.
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