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