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>
diff --git a/Documentation/ABI/testing/sysfs-pps b/Documentation/ABI/testing/sysfs-pps
new file mode 100644
index 0000000..25028c7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps
@@ -0,0 +1,73 @@
+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.