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>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 000000000000..cc2eb8edb514
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+        tristate "PPS support"
+        depends on EXPERIMENTAL
+        ---help---
+          PPS (Pulse Per Second) is a special pulse provided by some GPS
+          antennae. Userland can use it to get a high-precision time
+          reference.
+
+          Some antennae's PPS signals are connected with the CD (Carrier
+          Detect) pin of the serial line they use to communicate with the
+          host. In this case use the SERIAL_LINE client support.
+
+          Some antennae's PPS signals are connected with some special host
+          inputs so you have to enable the corresponding client support.
+
+          To compile this driver as a module, choose M here: the module
+          will be called pps_core.ko.
+
+config PPS_DEBUG
+        bool "PPS debugging messages"
+        depends on PPS
+        help
+          Say Y here if you want the PPS support to produce a bunch of debug
+          messages to the system log.  Select this if you are having a
+          problem with PPS support and want to see more of what is going on.
+
+endmenu