LinuxPPS: core support

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>

1 files changed, 312 insertions, 0 deletions

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
new file mode 100644
index 000000000000..ac8cc8cea1e3
--- /dev/null
+++ b/drivers/pps/pps.c
@@ -0,0 +1,312 @@
+/*
+ * PPS core file
+ *
+ *
+ * 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/uaccess.h>
+#include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Local variables
+ */
+
+static dev_t pps_devt;
+static struct class *pps_class;
+
+/*
+ * Char device methods
+ */
+
+static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
+{
+        struct pps_device *pps = file->private_data;
+
+        poll_wait(file, &pps->queue, wait);
+
+        return POLLIN | POLLRDNORM;
+}
+
+static int pps_cdev_fasync(int fd, struct file *file, int on)
+{
+        struct pps_device *pps = file->private_data;
+        return fasync_helper(fd, file, on, &pps->async_queue);
+}
+
+static long pps_cdev_ioctl(struct file *file,
+                unsigned int cmd, unsigned long arg)
+{
+        struct pps_device *pps = file->private_data;
+        struct pps_kparams params;
+        struct pps_fdata fdata;
+        unsigned long ticks;
+        void __user *uarg = (void __user *) arg;
+        int __user *iuarg = (int __user *) arg;
+        int err;
+
+        switch (cmd) {
+        case PPS_GETPARAMS:
+                pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
+
+                /* Return current parameters */
+                err = copy_to_user(uarg, &pps->params,
+                                                sizeof(struct pps_kparams));
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        case PPS_SETPARAMS:
+                pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
+
+                /* Check the capabilities */
+                if (!capable(CAP_SYS_TIME))
+                        return -EPERM;
+
+                err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
+                if (err)
+                        return -EFAULT;
+                if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
+                        pr_debug("capture mode unspecified (%x)\n",
+                                                                params.mode);
+                        return -EINVAL;
+                }
+
+                /* Check for supported capabilities */
+                if ((params.mode & ~pps->info.mode) != 0) {
+                        pr_debug("unsupported capabilities (%x)\n",
+                                                                params.mode);
+                        return -EINVAL;
+                }
+
+                spin_lock_irq(&pps->lock);
+
+                /* Save the new parameters */
+                pps->params = params;
+
+                /* Restore the read only parameters */
+                if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+                        /* section 3.3 of RFC 2783 interpreted */
+                        pr_debug("time format unspecified (%x)\n",
+                                                                params.mode);
+                        pps->params.mode |= PPS_TSFMT_TSPEC;
+                }
+                if (pps->info.mode & PPS_CANWAIT)
+                        pps->params.mode |= PPS_CANWAIT;
+                pps->params.api_version = PPS_API_VERS;
+
+                spin_unlock_irq(&pps->lock);
+
+                break;
+
+        case PPS_GETCAP:
+                pr_debug("PPS_GETCAP: source %d\n", pps->id);
+
+                err = put_user(pps->info.mode, iuarg);
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        case PPS_FETCH:
+                pr_debug("PPS_FETCH: source %d\n", pps->id);
+
+                err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
+                if (err)
+                        return -EFAULT;
+
+                pps->go = 0;
+
+                /* Manage the timeout */
+                if (fdata.timeout.flags & PPS_TIME_INVALID)
+                        err = wait_event_interruptible(pps->queue, pps->go);
+                else {
+                        pr_debug("timeout %lld.%09d\n",
+                                        (long long) fdata.timeout.sec,
+                                        fdata.timeout.nsec);
+                        ticks = fdata.timeout.sec * HZ;
+                        ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
+
+                        if (ticks != 0) {
+                                err = wait_event_interruptible_timeout(
+                                                pps->queue, pps->go, ticks);
+                                if (err == 0)
+                                        return -ETIMEDOUT;
+                        }
+                }
+
+                /* Check for pending signals */
+                if (err == -ERESTARTSYS) {
+                        pr_debug("pending signal caught\n");
+                        return -EINTR;
+                }
+
+                /* Return the fetched timestamp */
+                spin_lock_irq(&pps->lock);
+
+                fdata.info.assert_sequence = pps->assert_sequence;
+                fdata.info.clear_sequence = pps->clear_sequence;
+                fdata.info.assert_tu = pps->assert_tu;
+                fdata.info.clear_tu = pps->clear_tu;
+                fdata.info.current_mode = pps->current_mode;
+
+                spin_unlock_irq(&pps->lock);
+
+                err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        default:
+                return -ENOTTY;
+                break;
+        }
+
+        return 0;
+}
+
+static int pps_cdev_open(struct inode *inode, struct file *file)
+{
+        struct pps_device *pps = container_of(inode->i_cdev,
+                                                struct pps_device, cdev);
+        int found;
+
+        found = pps_get_source(pps->id) != 0;
+        if (!found)
+                return -ENODEV;
+
+        file->private_data = pps;
+
+        return 0;
+}
+
+static int pps_cdev_release(struct inode *inode, struct file *file)
+{
+        struct pps_device *pps = file->private_data;
+
+        /* Free the PPS source and wake up (possible) deregistration */
+        pps_put_source(pps);
+
+        return 0;
+}
+
+/*
+ * Char device stuff
+ */
+
+static const struct file_operations pps_cdev_fops = {
+        .owner          = THIS_MODULE,
+        .llseek         = no_llseek,
+        .poll           = pps_cdev_poll,
+        .fasync         = pps_cdev_fasync,
+        .unlocked_ioctl = pps_cdev_ioctl,
+        .open           = pps_cdev_open,
+        .release        = pps_cdev_release,
+};
+
+int pps_register_cdev(struct pps_device *pps)
+{
+        int err;
+
+        pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
+        cdev_init(&pps->cdev, &pps_cdev_fops);
+        pps->cdev.owner = pps->info.owner;
+
+        err = cdev_add(&pps->cdev, pps->devno, 1);
+        if (err) {
+                printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
+                                pps->info.name, MAJOR(pps_devt), pps->id);
+                return err;
+        }
+        pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
+                                                        "pps%d", pps->id);
+        if (err)
+                goto del_cdev;
+        dev_set_drvdata(pps->dev, pps);
+
+        pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
+                        MAJOR(pps_devt), pps->id);
+
+        return 0;
+
+del_cdev:
+        cdev_del(&pps->cdev);
+
+        return err;
+}
+
+void pps_unregister_cdev(struct pps_device *pps)
+{
+        device_destroy(pps_class, pps->devno);
+        cdev_del(&pps->cdev);
+}
+
+/*
+ * Module stuff
+ */
+
+static void __exit pps_exit(void)
+{
+        class_destroy(pps_class);
+        unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+}
+
+static int __init pps_init(void)
+{
+        int err;
+
+        pps_class = class_create(THIS_MODULE, "pps");
+        if (!pps_class) {
+                printk(KERN_ERR "pps: failed to allocate class\n");
+                return -ENOMEM;
+        }
+        pps_class->dev_attrs = pps_attrs;
+
+        err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
+        if (err < 0) {
+                printk(KERN_ERR "pps: failed to allocate char device region\n");
+                goto remove_class;
+        }
+
+        pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
+        pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
+                "<giometti@linux.it>\n", PPS_VERSION);
+
+        return 0;
+
+remove_class:
+        class_destroy(pps_class);
+
+        return err;
+}
+
+subsys_initcall(pps_init);
+module_exit(pps_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
+MODULE_LICENSE("GPL");