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