![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>
313 lines
7 KiB
C
313 lines
7 KiB
C
/*
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* PPS core file
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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/uaccess.h>
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#include <linux/idr.h>
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#include <linux/cdev.h>
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#include <linux/poll.h>
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#include <linux/pps_kernel.h>
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/*
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* Local variables
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*/
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static dev_t pps_devt;
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static struct class *pps_class;
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/*
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* Char device methods
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*/
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static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
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{
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struct pps_device *pps = file->private_data;
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poll_wait(file, &pps->queue, wait);
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return POLLIN | POLLRDNORM;
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}
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static int pps_cdev_fasync(int fd, struct file *file, int on)
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{
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struct pps_device *pps = file->private_data;
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return fasync_helper(fd, file, on, &pps->async_queue);
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}
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static long pps_cdev_ioctl(struct file *file,
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unsigned int cmd, unsigned long arg)
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{
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struct pps_device *pps = file->private_data;
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struct pps_kparams params;
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struct pps_fdata fdata;
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unsigned long ticks;
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void __user *uarg = (void __user *) arg;
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int __user *iuarg = (int __user *) arg;
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int err;
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switch (cmd) {
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case PPS_GETPARAMS:
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pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
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/* Return current parameters */
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err = copy_to_user(uarg, &pps->params,
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sizeof(struct pps_kparams));
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if (err)
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return -EFAULT;
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break;
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case PPS_SETPARAMS:
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pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
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/* Check the capabilities */
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if (!capable(CAP_SYS_TIME))
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return -EPERM;
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err = copy_from_user(¶ms, uarg, sizeof(struct pps_kparams));
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if (err)
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return -EFAULT;
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if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
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pr_debug("capture mode unspecified (%x)\n",
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params.mode);
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return -EINVAL;
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}
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/* Check for supported capabilities */
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if ((params.mode & ~pps->info.mode) != 0) {
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pr_debug("unsupported capabilities (%x)\n",
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params.mode);
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return -EINVAL;
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}
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spin_lock_irq(&pps->lock);
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/* Save the new parameters */
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pps->params = params;
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/* Restore the read only parameters */
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if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
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/* section 3.3 of RFC 2783 interpreted */
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pr_debug("time format unspecified (%x)\n",
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params.mode);
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pps->params.mode |= PPS_TSFMT_TSPEC;
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}
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if (pps->info.mode & PPS_CANWAIT)
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pps->params.mode |= PPS_CANWAIT;
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pps->params.api_version = PPS_API_VERS;
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spin_unlock_irq(&pps->lock);
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break;
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case PPS_GETCAP:
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pr_debug("PPS_GETCAP: source %d\n", pps->id);
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err = put_user(pps->info.mode, iuarg);
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if (err)
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return -EFAULT;
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break;
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case PPS_FETCH:
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pr_debug("PPS_FETCH: source %d\n", pps->id);
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err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
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if (err)
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return -EFAULT;
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pps->go = 0;
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/* Manage the timeout */
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if (fdata.timeout.flags & PPS_TIME_INVALID)
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err = wait_event_interruptible(pps->queue, pps->go);
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else {
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pr_debug("timeout %lld.%09d\n",
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(long long) fdata.timeout.sec,
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fdata.timeout.nsec);
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ticks = fdata.timeout.sec * HZ;
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ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
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if (ticks != 0) {
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err = wait_event_interruptible_timeout(
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pps->queue, pps->go, ticks);
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if (err == 0)
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return -ETIMEDOUT;
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}
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}
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/* Check for pending signals */
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if (err == -ERESTARTSYS) {
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pr_debug("pending signal caught\n");
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return -EINTR;
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}
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/* Return the fetched timestamp */
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spin_lock_irq(&pps->lock);
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fdata.info.assert_sequence = pps->assert_sequence;
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fdata.info.clear_sequence = pps->clear_sequence;
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fdata.info.assert_tu = pps->assert_tu;
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fdata.info.clear_tu = pps->clear_tu;
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fdata.info.current_mode = pps->current_mode;
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spin_unlock_irq(&pps->lock);
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err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
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if (err)
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return -EFAULT;
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break;
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default:
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return -ENOTTY;
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break;
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}
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return 0;
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}
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static int pps_cdev_open(struct inode *inode, struct file *file)
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{
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struct pps_device *pps = container_of(inode->i_cdev,
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struct pps_device, cdev);
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int found;
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found = pps_get_source(pps->id) != 0;
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if (!found)
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return -ENODEV;
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file->private_data = pps;
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return 0;
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}
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static int pps_cdev_release(struct inode *inode, struct file *file)
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{
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struct pps_device *pps = file->private_data;
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/* Free the PPS source and wake up (possible) deregistration */
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pps_put_source(pps);
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return 0;
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}
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/*
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* Char device stuff
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*/
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static const struct file_operations pps_cdev_fops = {
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.owner = THIS_MODULE,
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.llseek = no_llseek,
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.poll = pps_cdev_poll,
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.fasync = pps_cdev_fasync,
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.unlocked_ioctl = pps_cdev_ioctl,
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.open = pps_cdev_open,
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.release = pps_cdev_release,
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};
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int pps_register_cdev(struct pps_device *pps)
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{
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int err;
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pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
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cdev_init(&pps->cdev, &pps_cdev_fops);
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pps->cdev.owner = pps->info.owner;
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err = cdev_add(&pps->cdev, pps->devno, 1);
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if (err) {
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printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
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pps->info.name, MAJOR(pps_devt), pps->id);
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return err;
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}
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pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
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"pps%d", pps->id);
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if (err)
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goto del_cdev;
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dev_set_drvdata(pps->dev, pps);
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pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
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MAJOR(pps_devt), pps->id);
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return 0;
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del_cdev:
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cdev_del(&pps->cdev);
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return err;
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}
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void pps_unregister_cdev(struct pps_device *pps)
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{
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device_destroy(pps_class, pps->devno);
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cdev_del(&pps->cdev);
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}
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/*
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* Module stuff
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*/
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static void __exit pps_exit(void)
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{
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class_destroy(pps_class);
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unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
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}
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static int __init pps_init(void)
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{
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int err;
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pps_class = class_create(THIS_MODULE, "pps");
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if (!pps_class) {
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printk(KERN_ERR "pps: failed to allocate class\n");
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return -ENOMEM;
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}
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pps_class->dev_attrs = pps_attrs;
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err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
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if (err < 0) {
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printk(KERN_ERR "pps: failed to allocate char device region\n");
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goto remove_class;
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}
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pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
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pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
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"<giometti@linux.it>\n", PPS_VERSION);
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return 0;
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remove_class:
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class_destroy(pps_class);
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return err;
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}
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subsys_initcall(pps_init);
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module_exit(pps_exit);
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MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
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MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
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MODULE_LICENSE("GPL");
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