eae9d2ba0c
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>
2.1 KiB
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.