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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>
123 lines
3.8 KiB
C
123 lines
3.8 KiB
C
/*
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* PPS API header
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*
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* Copyright (C) 2005-2009 Rodolfo Giometti <giometti@linux.it>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _PPS_H_
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#define _PPS_H_
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#define PPS_VERSION "5.3.6"
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#define PPS_MAX_SOURCES 16 /* should be enough... */
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/* Implementation note: the logical states ``assert'' and ``clear''
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* are implemented in terms of the chip register, i.e. ``assert''
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* means the bit is set. */
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/*
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* 3.2 New data structures
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*/
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#define PPS_API_VERS_1 1
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#define PPS_API_VERS PPS_API_VERS_1 /* we use API version 1 */
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#define PPS_MAX_NAME_LEN 32
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/* 32-bit vs. 64-bit compatibility.
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*
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* 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
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* architectures it's 8 bytes. On i386, there will be no padding between the
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* two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
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* pps_kparams. But on most platforms there will be padding to ensure correct
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* alignment.
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*
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* The simple fix is probably to add an explicit padding.
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* [David Woodhouse]
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*/
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struct pps_ktime {
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__s64 sec;
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__s32 nsec;
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__u32 flags;
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};
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#define PPS_TIME_INVALID (1<<0) /* used to specify timeout==NULL */
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struct pps_kinfo {
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__u32 assert_sequence; /* seq. num. of assert event */
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__u32 clear_sequence; /* seq. num. of clear event */
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struct pps_ktime assert_tu; /* time of assert event */
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struct pps_ktime clear_tu; /* time of clear event */
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int current_mode; /* current mode bits */
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};
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struct pps_kparams {
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int api_version; /* API version # */
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int mode; /* mode bits */
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struct pps_ktime assert_off_tu; /* offset compensation for assert */
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struct pps_ktime clear_off_tu; /* offset compensation for clear */
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};
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/*
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* 3.3 Mode bit definitions
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*/
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/* Device/implementation parameters */
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#define PPS_CAPTUREASSERT 0x01 /* capture assert events */
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#define PPS_CAPTURECLEAR 0x02 /* capture clear events */
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#define PPS_CAPTUREBOTH 0x03 /* capture assert and clear events */
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#define PPS_OFFSETASSERT 0x10 /* apply compensation for assert ev. */
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#define PPS_OFFSETCLEAR 0x20 /* apply compensation for clear ev. */
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#define PPS_CANWAIT 0x100 /* can we wait for an event? */
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#define PPS_CANPOLL 0x200 /* bit reserved for future use */
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/* Kernel actions */
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#define PPS_ECHOASSERT 0x40 /* feed back assert event to output */
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#define PPS_ECHOCLEAR 0x80 /* feed back clear event to output */
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/* Timestamp formats */
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#define PPS_TSFMT_TSPEC 0x1000 /* select timespec format */
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#define PPS_TSFMT_NTPFP 0x2000 /* select NTP format */
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/*
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* 3.4.4 New functions: disciplining the kernel timebase
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*/
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/* Kernel consumers */
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#define PPS_KC_HARDPPS 0 /* hardpps() (or equivalent) */
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#define PPS_KC_HARDPPS_PLL 1 /* hardpps() constrained to
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use a phase-locked loop */
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#define PPS_KC_HARDPPS_FLL 2 /* hardpps() constrained to
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use a frequency-locked loop */
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/*
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* Here begins the implementation-specific part!
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*/
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struct pps_fdata {
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struct pps_kinfo info;
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struct pps_ktime timeout;
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};
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#include <linux/ioctl.h>
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#define PPS_GETPARAMS _IOR('p', 0xa1, struct pps_kparams *)
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#define PPS_SETPARAMS _IOW('p', 0xa2, struct pps_kparams *)
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#define PPS_GETCAP _IOR('p', 0xa3, int *)
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#define PPS_FETCH _IOWR('p', 0xa4, struct pps_fdata *)
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#endif /* _PPS_H_ */
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