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>

5 files changed, 780 insertions, 0 deletions

diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 000000000000..cc2eb8edb514
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+	tristate "PPS support"
+	depends on EXPERIMENTAL
+	---help---
+	  PPS (Pulse Per Second) is a special pulse provided by some GPS
+	  antennae. Userland can use it to get a high-precision time
+	  reference.
+
+	  Some antennae's PPS signals are connected with the CD (Carrier
+	  Detect) pin of the serial line they use to communicate with the
+	  host. In this case use the SERIAL_LINE client support.
+
+	  Some antennae's PPS signals are connected with some special host
+	  inputs so you have to enable the corresponding client support.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pps_core.ko.
+
+config PPS_DEBUG
+	bool "PPS debugging messages"
+	depends on PPS
+	help
+	  Say Y here if you want the PPS support to produce a bunch of debug
+	  messages to the system log.  Select this if you are having a
+	  problem with PPS support and want to see more of what is going on.
+
+endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
new file mode 100644
index 000000000000..19ea582f431d
--- /dev/null
+++ b/drivers/pps/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for the PPS core.
+#
+
+pps_core-y			:= pps.o kapi.o sysfs.o
+obj-$(CONFIG_PPS)		:= pps_core.o
+
+ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 000000000000..35a0b192d768
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -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);
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");
diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 000000000000..ef0978c71eee
--- /dev/null
+++ b/drivers/pps/sysfs.c
@@ -0,0 +1,98 @@
+/*
+ * PPS sysfs support
+ *
+ *
+ * Copyright (C) 2007-2009   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/device.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Attribute functions
+ */
+
+static ssize_t pps_show_assert(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	if (!(pps->info.mode & PPS_CAPTUREASSERT))
+		return 0;
+
+	return sprintf(buf, "%lld.%09d#%d\n",
+			(long long) pps->assert_tu.sec, pps->assert_tu.nsec,
+			pps->assert_sequence);
+}
+
+static ssize_t pps_show_clear(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	if (!(pps->info.mode & PPS_CAPTURECLEAR))
+		return 0;
+
+	return sprintf(buf, "%lld.%09d#%d\n",
+			(long long) pps->clear_tu.sec, pps->clear_tu.nsec,
+			pps->clear_sequence);
+}
+
+static ssize_t pps_show_mode(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%4x\n", pps->info.mode);
+}
+
+static ssize_t pps_show_echo(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", !!pps->info.echo);
+}
+
+static ssize_t pps_show_name(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%s\n", pps->info.name);
+}
+
+static ssize_t pps_show_path(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pps_device *pps = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%s\n", pps->info.path);
+}
+
+struct device_attribute pps_attrs[] = {
+	__ATTR(assert, S_IRUGO, pps_show_assert, NULL),
+	__ATTR(clear, S_IRUGO, pps_show_clear, NULL),
+	__ATTR(mode, S_IRUGO, pps_show_mode, NULL),
+	__ATTR(echo, S_IRUGO, pps_show_echo, NULL),
+	__ATTR(name, S_IRUGO, pps_show_name, NULL),
+	__ATTR(path, S_IRUGO, pps_show_path, NULL),
+	__ATTR_NULL,
+};