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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>
90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
/*
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* PPS API kernel header
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*
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* Copyright (C) 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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#include <linux/pps.h>
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#include <linux/cdev.h>
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#include <linux/device.h>
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#include <linux/time.h>
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/*
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* Global defines
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*/
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/* The specific PPS source info */
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struct pps_source_info {
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char name[PPS_MAX_NAME_LEN]; /* simbolic name */
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char path[PPS_MAX_NAME_LEN]; /* path of connected device */
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int mode; /* PPS's allowed mode */
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void (*echo)(int source, int event, void *data); /* PPS echo function */
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struct module *owner;
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struct device *dev;
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};
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/* The main struct */
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struct pps_device {
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struct pps_source_info info; /* PSS source info */
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struct pps_kparams params; /* PPS's current params */
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__u32 assert_sequence; /* PPS' assert event seq # */
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__u32 clear_sequence; /* PPS' clear event seq # */
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struct pps_ktime assert_tu;
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struct pps_ktime clear_tu;
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int current_mode; /* PPS mode at event time */
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int go; /* PPS event is arrived? */
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wait_queue_head_t queue; /* PPS event queue */
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unsigned int id; /* PPS source unique ID */
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struct cdev cdev;
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struct device *dev;
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int devno;
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struct fasync_struct *async_queue; /* fasync method */
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spinlock_t lock;
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atomic_t usage; /* usage count */
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};
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/*
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* Global variables
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*/
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extern spinlock_t pps_idr_lock;
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extern struct idr pps_idr;
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extern struct timespec pps_irq_ts[];
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extern struct device_attribute pps_attrs[];
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/*
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* Exported functions
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*/
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struct pps_device *pps_get_source(int source);
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extern void pps_put_source(struct pps_device *pps);
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extern int pps_register_source(struct pps_source_info *info,
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int default_params);
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extern void pps_unregister_source(int source);
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extern int pps_register_cdev(struct pps_device *pps);
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extern void pps_unregister_cdev(struct pps_device *pps);
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extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);
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