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LinuxPPS: core support

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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>
This commit is contained in:
Rodolfo Giometti 2009-06-17 16:28:37 -07:00 • committed by Linus Torvalds
parent 8820f27ad9
commit eae9d2ba0c
14 changed files with 1249 additions and 0 deletions
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1
include/linux/Kbuild
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@ -308,6 +308,7 @@ unifdef-y += pmu.h
unifdef-y += poll.h
unifdef-y += ppp_defs.h
unifdef-y += ppp-comp.h
unifdef-y += pps.h
unifdef-y += ptrace.h
unifdef-y += quota.h
unifdef-y += random.h

122
include/linux/pps.h Normal file
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@ -0,0 +1,122 @@
/*
* PPS API header
*
* Copyright (C) 2005-2009 Rodolfo Giometti <giometti@linux.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef _PPS_H_
#define _PPS_H_
#define PPS_VERSION "5.3.6"
#define PPS_MAX_SOURCES 16 /* should be enough... */
/* Implementation note: the logical states ``assert'' and ``clear''
* are implemented in terms of the chip register, i.e. ``assert''
* means the bit is set. */
/*
* 3.2 New data structures
*/
#define PPS_API_VERS_1 1
#define PPS_API_VERS PPS_API_VERS_1 /* we use API version 1 */
#define PPS_MAX_NAME_LEN 32
/* 32-bit vs. 64-bit compatibility.
*
* 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
* architectures it's 8 bytes. On i386, there will be no padding between the
* two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
* pps_kparams. But on most platforms there will be padding to ensure correct
* alignment.
*
* The simple fix is probably to add an explicit padding.
* [David Woodhouse]
*/
struct pps_ktime {
__s64 sec;
__s32 nsec;
__u32 flags;
};
#define PPS_TIME_INVALID (1<<0) /* used to specify timeout==NULL */
struct pps_kinfo {
__u32 assert_sequence; /* seq. num. of assert event */
__u32 clear_sequence; /* seq. num. of clear event */
struct pps_ktime assert_tu; /* time of assert event */
struct pps_ktime clear_tu; /* time of clear event */
int current_mode; /* current mode bits */
};
struct pps_kparams {
int api_version; /* API version # */
int mode; /* mode bits */
struct pps_ktime assert_off_tu; /* offset compensation for assert */
struct pps_ktime clear_off_tu; /* offset compensation for clear */
};
/*
* 3.3 Mode bit definitions
*/
/* Device/implementation parameters */
#define PPS_CAPTUREASSERT 0x01 /* capture assert events */
#define PPS_CAPTURECLEAR 0x02 /* capture clear events */
#define PPS_CAPTUREBOTH 0x03 /* capture assert and clear events */
#define PPS_OFFSETASSERT 0x10 /* apply compensation for assert ev. */
#define PPS_OFFSETCLEAR 0x20 /* apply compensation for clear ev. */
#define PPS_CANWAIT 0x100 /* can we wait for an event? */
#define PPS_CANPOLL 0x200 /* bit reserved for future use */
/* Kernel actions */
#define PPS_ECHOASSERT 0x40 /* feed back assert event to output */
#define PPS_ECHOCLEAR 0x80 /* feed back clear event to output */
/* Timestamp formats */
#define PPS_TSFMT_TSPEC 0x1000 /* select timespec format */
#define PPS_TSFMT_NTPFP 0x2000 /* select NTP format */
/*
* 3.4.4 New functions: disciplining the kernel timebase
*/
/* Kernel consumers */
#define PPS_KC_HARDPPS 0 /* hardpps() (or equivalent) */
#define PPS_KC_HARDPPS_PLL 1 /* hardpps() constrained to
use a phase-locked loop */
#define PPS_KC_HARDPPS_FLL 2 /* hardpps() constrained to
use a frequency-locked loop */
/*
* Here begins the implementation-specific part!
*/
struct pps_fdata {
struct pps_kinfo info;
struct pps_ktime timeout;
};
#include <linux/ioctl.h>
#define PPS_GETPARAMS _IOR('p', 0xa1, struct pps_kparams *)
#define PPS_SETPARAMS _IOW('p', 0xa2, struct pps_kparams *)
#define PPS_GETCAP _IOR('p', 0xa3, int *)
#define PPS_FETCH _IOWR('p', 0xa4, struct pps_fdata *)
#endif /* _PPS_H_ */

89
include/linux/pps_kernel.h Normal file
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@ -0,0 +1,89 @@
/*
* PPS API kernel header
*
* Copyright (C) 2009 Rodolfo Giometti <giometti@linux.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/pps.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/time.h>
/*
* Global defines
*/
/* The specific PPS source info */
struct pps_source_info {
char name[PPS_MAX_NAME_LEN]; /* simbolic name */
char path[PPS_MAX_NAME_LEN]; /* path of connected device */
int mode; /* PPS's allowed mode */
void (*echo)(int source, int event, void *data); /* PPS echo function */
struct module *owner;
struct device *dev;
};
/* The main struct */
struct pps_device {
struct pps_source_info info; /* PSS source info */
struct pps_kparams params; /* PPS's current params */
__u32 assert_sequence; /* PPS' assert event seq # */
__u32 clear_sequence; /* PPS' clear event seq # */
struct pps_ktime assert_tu;
struct pps_ktime clear_tu;
int current_mode; /* PPS mode at event time */
int go; /* PPS event is arrived? */
wait_queue_head_t queue; /* PPS event queue */
unsigned int id; /* PPS source unique ID */
struct cdev cdev;
struct device *dev;
int devno;
struct fasync_struct *async_queue; /* fasync method */
spinlock_t lock;
atomic_t usage; /* usage count */
};
/*
* Global variables
*/
extern spinlock_t pps_idr_lock;
extern struct idr pps_idr;
extern struct timespec pps_irq_ts[];
extern struct device_attribute pps_attrs[];
/*
* Exported functions
*/
struct pps_device *pps_get_source(int source);
extern void pps_put_source(struct pps_device *pps);
extern int pps_register_source(struct pps_source_info *info,
int default_params);
extern void pps_unregister_source(int source);
extern int pps_register_cdev(struct pps_device *pps);
extern void pps_unregister_cdev(struct pps_device *pps);
extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);