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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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329
drivers/pps/kapi.c Normal file
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@@ -0,0 +1,329 @@
/*
* kernel API
*
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/fs.h>
#include <linux/pps_kernel.h>
/*
* Global variables
*/
DEFINE_SPINLOCK(pps_idr_lock);
DEFINE_IDR(pps_idr);
/*
* Local functions
*/
static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
{
ts->nsec += offset->nsec;
while (ts->nsec >= NSEC_PER_SEC) {
ts->nsec -= NSEC_PER_SEC;
ts->sec++;
}
while (ts->nsec < 0) {
ts->nsec += NSEC_PER_SEC;
ts->sec--;
}
ts->sec += offset->sec;
}
/*
* Exported functions
*/
/* pps_get_source - find a PPS source
* @source: the PPS source ID.
*
* This function is used to find an already registered PPS source into the
* system.
*
* The function returns NULL if found nothing, otherwise it returns a pointer
* to the PPS source data struct (the refcounter is incremented by 1).
*/
struct pps_device *pps_get_source(int source)
{
struct pps_device *pps;
unsigned long flags;
spin_lock_irqsave(&pps_idr_lock, flags);
pps = idr_find(&pps_idr, source);
if (pps != NULL)
atomic_inc(&pps->usage);
spin_unlock_irqrestore(&pps_idr_lock, flags);
return pps;
}
/* pps_put_source - free the PPS source data
* @pps: a pointer to the PPS source.
*
* This function is used to free a PPS data struct if its refcount is 0.
*/
void pps_put_source(struct pps_device *pps)
{
unsigned long flags;
spin_lock_irqsave(&pps_idr_lock, flags);
BUG_ON(atomic_read(&pps->usage) == 0);
if (!atomic_dec_and_test(&pps->usage)) {
pps = NULL;
goto exit;
}
/* No more reference to the PPS source. We can safely remove the
* PPS data struct.
*/
idr_remove(&pps_idr, pps->id);
exit:
spin_unlock_irqrestore(&pps_idr_lock, flags);
kfree(pps);
}
/* pps_register_source - add a PPS source in the system
* @info: the PPS info struct
* @default_params: the default PPS parameters of the new source
*
* This function is used to add a new PPS source in the system. The new
* source is described by info's fields and it will have, as default PPS
* parameters, the ones specified into default_params.
*
* The function returns, in case of success, the PPS source ID.
*/
int pps_register_source(struct pps_source_info *info, int default_params)
{
struct pps_device *pps;
int id;
int err;
/* Sanity checks */
if ((info->mode & default_params) != default_params) {
printk(KERN_ERR "pps: %s: unsupported default parameters\n",
info->name);
err = -EINVAL;
goto pps_register_source_exit;
}
if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
info->echo == NULL) {
printk(KERN_ERR "pps: %s: echo function is not defined\n",
info->name);
err = -EINVAL;
goto pps_register_source_exit;
}
if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
printk(KERN_ERR "pps: %s: unspecified time format\n",
info->name);
err = -EINVAL;
goto pps_register_source_exit;
}
/* Allocate memory for the new PPS source struct */
pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
if (pps == NULL) {
err = -ENOMEM;
goto pps_register_source_exit;
}
/* These initializations must be done before calling idr_get_new()
* in order to avoid reces into pps_event().
*/
pps->params.api_version = PPS_API_VERS;
pps->params.mode = default_params;
pps->info = *info;
init_waitqueue_head(&pps->queue);
spin_lock_init(&pps->lock);
atomic_set(&pps->usage, 1);
/* Get new ID for the new PPS source */
if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
err = -ENOMEM;
goto kfree_pps;
}
spin_lock_irq(&pps_idr_lock);
/* Now really allocate the PPS source.
* After idr_get_new() calling the new source will be freely available
* into the kernel.
*/
err = idr_get_new(&pps_idr, pps, &id);
if (err < 0) {
spin_unlock_irq(&pps_idr_lock);
goto kfree_pps;
}
id = id & MAX_ID_MASK;
if (id >= PPS_MAX_SOURCES) {
spin_unlock_irq(&pps_idr_lock);
printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
info->name);
err = -EBUSY;
goto free_idr;
}
pps->id = id;
spin_unlock_irq(&pps_idr_lock);
/* Create the char device */
err = pps_register_cdev(pps);
if (err < 0) {
printk(KERN_ERR "pps: %s: unable to create char device\n",
info->name);
goto free_idr;
}
pr_info("new PPS source %s at ID %d\n", info->name, id);
return id;
free_idr:
spin_lock_irq(&pps_idr_lock);
idr_remove(&pps_idr, id);
spin_unlock_irq(&pps_idr_lock);
kfree_pps:
kfree(pps);
pps_register_source_exit:
printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
return err;
}
EXPORT_SYMBOL(pps_register_source);
/* pps_unregister_source - remove a PPS source from the system
* @source: the PPS source ID
*
* This function is used to remove a previously registered PPS source from
* the system.
*/
void pps_unregister_source(int source)
{
struct pps_device *pps;
spin_lock_irq(&pps_idr_lock);
pps = idr_find(&pps_idr, source);
if (!pps) {
BUG();
spin_unlock_irq(&pps_idr_lock);
return;
}
spin_unlock_irq(&pps_idr_lock);
pps_unregister_cdev(pps);
pps_put_source(pps);
}
EXPORT_SYMBOL(pps_unregister_source);
/* pps_event - register a PPS event into the system
* @source: the PPS source ID
* @ts: the event timestamp
* @event: the event type
* @data: userdef pointer
*
* This function is used by each PPS client in order to register a new
* PPS event into the system (it's usually called inside an IRQ handler).
*
* If an echo function is associated with the PPS source it will be called
* as:
* pps->info.echo(source, event, data);
*/
void pps_event(int source, struct pps_ktime *ts, int event, void *data)
{
struct pps_device *pps;
unsigned long flags;
if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
event, source);
return;
}
pps = pps_get_source(source);
if (!pps)
return;
pr_debug("PPS event on source %d at %llu.%06u\n",
pps->id, (unsigned long long) ts->sec, ts->nsec);
spin_lock_irqsave(&pps->lock, flags);
/* Must call the echo function? */
if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
pps->info.echo(source, event, data);
/* Check the event */
pps->current_mode = pps->params.mode;
if (event & PPS_CAPTUREASSERT) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETASSERT)
pps_add_offset(ts, &pps->params.assert_off_tu);
/* Save the time stamp */
pps->assert_tu = *ts;
pps->assert_sequence++;
pr_debug("capture assert seq #%u for source %d\n",
pps->assert_sequence, source);
}
if (event & PPS_CAPTURECLEAR) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETCLEAR)
pps_add_offset(ts, &pps->params.clear_off_tu);
/* Save the time stamp */
pps->clear_tu = *ts;
pps->clear_sequence++;
pr_debug("capture clear seq #%u for source %d\n",
pps->clear_sequence, source);
}
pps->go = ~0;
wake_up_interruptible(&pps->queue);
kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
spin_unlock_irqrestore(&pps->lock, flags);
/* Now we can release the PPS source for (possible) deregistration */
pps_put_source(pps);
}
EXPORT_SYMBOL(pps_event);