ptp: Added a brand new class driver for ptp clocks.

This patch adds an infrastructure for hardware clocks that implement
IEEE 1588, the Precision Time Protocol (PTP). A class driver offers a
registration method to particular hardware clock drivers. Each clock is
presented as a standard POSIX clock.

The ancillary clock features are exposed in two different ways, via
the sysfs and by a character device.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: John Stultz <john.stultz@linaro.org>

6 files changed, 860 insertions, 0 deletions

diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
new file mode 100644
index 000000000000..70d4bb1cbdab
--- /dev/null
+++ b/drivers/ptp/Kconfig
@@ -0,0 +1,30 @@
+#
+# PTP clock support configuration
+#
+
+menu "PTP clock support"
+
+comment "Enable Device Drivers -> PPS to see the PTP clock options."
+        depends on PPS=n
+
+config PTP_1588_CLOCK
+        tristate "PTP clock support"
+        depends on EXPERIMENTAL
+        depends on PPS
+        help
+          The IEEE 1588 standard defines a method to precisely
+          synchronize distributed clocks over Ethernet networks. The
+          standard defines a Precision Time Protocol (PTP), which can
+          be used to achieve synchronization within a few dozen
+          microseconds. In addition, with the help of special hardware
+          time stamping units, it can be possible to achieve
+          synchronization to within a few hundred nanoseconds.
+
+          This driver adds support for PTP clocks as character
+          devices. If you want to use a PTP clock, then you should
+          also enable at least one clock driver as well.
+
+          To compile this driver as a module, choose M here: the module
+          will be called ptp.
+
+endmenu
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
new file mode 100644
index 000000000000..480e2afdc999
--- /dev/null
+++ b/drivers/ptp/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for PTP 1588 clock support.
+#
+
+ptp-y                                   := ptp_clock.o ptp_chardev.o ptp_sysfs.o
+obj-$(CONFIG_PTP_1588_CLOCK)            += ptp.o
diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
new file mode 100644
index 000000000000..a8d03aeb4051
--- /dev/null
+++ b/drivers/ptp/ptp_chardev.c
@@ -0,0 +1,159 @@
+/*
+ * PTP 1588 clock support - character device implementation.
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ *
+ *  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/module.h>
+#include <linux/posix-clock.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+
+#include "ptp_private.h"
+
+int ptp_open(struct posix_clock *pc, fmode_t fmode)
+{
+        return 0;
+}
+
+long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
+{
+        struct ptp_clock_caps caps;
+        struct ptp_clock_request req;
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+        struct ptp_clock_info *ops = ptp->info;
+        int enable, err = 0;
+
+        switch (cmd) {
+
+        case PTP_CLOCK_GETCAPS:
+                memset(&caps, 0, sizeof(caps));
+                caps.max_adj = ptp->info->max_adj;
+                caps.n_alarm = ptp->info->n_alarm;
+                caps.n_ext_ts = ptp->info->n_ext_ts;
+                caps.n_per_out = ptp->info->n_per_out;
+                caps.pps = ptp->info->pps;
+                err = copy_to_user((void __user *)arg, &caps, sizeof(caps));
+                break;
+
+        case PTP_EXTTS_REQUEST:
+                if (copy_from_user(&req.extts, (void __user *)arg,
+                                   sizeof(req.extts))) {
+                        err = -EFAULT;
+                        break;
+                }
+                if (req.extts.index >= ops->n_ext_ts) {
+                        err = -EINVAL;
+                        break;
+                }
+                req.type = PTP_CLK_REQ_EXTTS;
+                enable = req.extts.flags & PTP_ENABLE_FEATURE ? 1 : 0;
+                err = ops->enable(ops, &req, enable);
+                break;
+
+        case PTP_PEROUT_REQUEST:
+                if (copy_from_user(&req.perout, (void __user *)arg,
+                                   sizeof(req.perout))) {
+                        err = -EFAULT;
+                        break;
+                }
+                if (req.perout.index >= ops->n_per_out) {
+                        err = -EINVAL;
+                        break;
+                }
+                req.type = PTP_CLK_REQ_PEROUT;
+                enable = req.perout.period.sec || req.perout.period.nsec;
+                err = ops->enable(ops, &req, enable);
+                break;
+
+        case PTP_ENABLE_PPS:
+                if (!capable(CAP_SYS_TIME))
+                        return -EPERM;
+                req.type = PTP_CLK_REQ_PPS;
+                enable = arg ? 1 : 0;
+                err = ops->enable(ops, &req, enable);
+                break;
+
+        default:
+                err = -ENOTTY;
+                break;
+        }
+        return err;
+}
+
+unsigned int ptp_poll(struct posix_clock *pc, struct file *fp, poll_table *wait)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+
+        poll_wait(fp, &ptp->tsev_wq, wait);
+
+        return queue_cnt(&ptp->tsevq) ? POLLIN : 0;
+}
+
+ssize_t ptp_read(struct posix_clock *pc,
+                 uint rdflags, char __user *buf, size_t cnt)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+        struct timestamp_event_queue *queue = &ptp->tsevq;
+        struct ptp_extts_event event[PTP_BUF_TIMESTAMPS];
+        unsigned long flags;
+        size_t qcnt, i;
+
+        if (cnt % sizeof(struct ptp_extts_event) != 0)
+                return -EINVAL;
+
+        if (cnt > sizeof(event))
+                cnt = sizeof(event);
+
+        cnt = cnt / sizeof(struct ptp_extts_event);
+
+        if (mutex_lock_interruptible(&ptp->tsevq_mux))
+                return -ERESTARTSYS;
+
+        if (wait_event_interruptible(ptp->tsev_wq,
+                                     ptp->defunct || queue_cnt(queue))) {
+                mutex_unlock(&ptp->tsevq_mux);
+                return -ERESTARTSYS;
+        }
+
+        if (ptp->defunct)
+                return -ENODEV;
+
+        spin_lock_irqsave(&queue->lock, flags);
+
+        qcnt = queue_cnt(queue);
+
+        if (cnt > qcnt)
+                cnt = qcnt;
+
+        for (i = 0; i < cnt; i++) {
+                event[i] = queue->buf[queue->head];
+                queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS;
+        }
+
+        spin_unlock_irqrestore(&queue->lock, flags);
+
+        cnt = cnt * sizeof(struct ptp_extts_event);
+
+        mutex_unlock(&ptp->tsevq_mux);
+
+        if (copy_to_user(buf, event, cnt)) {
+                mutex_unlock(&ptp->tsevq_mux);
+                return -EFAULT;
+        }
+
+        return cnt;
+}
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
new file mode 100644
index 000000000000..cf3f9997546d
--- /dev/null
+++ b/drivers/ptp/ptp_clock.c
@@ -0,0 +1,343 @@
+/*
+ * PTP 1588 clock support
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ *
+ *  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/bitops.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/posix-clock.h>
+#include <linux/pps_kernel.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+
+#include "ptp_private.h"
+
+#define PTP_MAX_ALARMS 4
+#define PTP_MAX_CLOCKS 8
+#define PTP_PPS_DEFAULTS (PPS_CAPTUREASSERT | PPS_OFFSETASSERT)
+#define PTP_PPS_EVENT PPS_CAPTUREASSERT
+#define PTP_PPS_MODE (PTP_PPS_DEFAULTS | PPS_CANWAIT | PPS_TSFMT_TSPEC)
+
+/* private globals */
+
+static dev_t ptp_devt;
+static struct class *ptp_class;
+
+static DECLARE_BITMAP(ptp_clocks_map, PTP_MAX_CLOCKS);
+static DEFINE_MUTEX(ptp_clocks_mutex); /* protects 'ptp_clocks_map' */
+
+/* time stamp event queue operations */
+
+static inline int queue_free(struct timestamp_event_queue *q)
+{
+        return PTP_MAX_TIMESTAMPS - queue_cnt(q) - 1;
+}
+
+static void enqueue_external_timestamp(struct timestamp_event_queue *queue,
+                                       struct ptp_clock_event *src)
+{
+        struct ptp_extts_event *dst;
+        unsigned long flags;
+        s64 seconds;
+        u32 remainder;
+
+        seconds = div_u64_rem(src->timestamp, 1000000000, &remainder);
+
+        spin_lock_irqsave(&queue->lock, flags);
+
+        dst = &queue->buf[queue->tail];
+        dst->index = src->index;
+        dst->t.sec = seconds;
+        dst->t.nsec = remainder;
+
+        if (!queue_free(queue))
+                queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS;
+
+        queue->tail = (queue->tail + 1) % PTP_MAX_TIMESTAMPS;
+
+        spin_unlock_irqrestore(&queue->lock, flags);
+}
+
+static s32 scaled_ppm_to_ppb(long ppm)
+{
+        /*
+         * The 'freq' field in the 'struct timex' is in parts per
+         * million, but with a 16 bit binary fractional field.
+         *
+         * We want to calculate
+         *
+         *    ppb = scaled_ppm * 1000 / 2^16
+         *
+         * which simplifies to
+         *
+         *    ppb = scaled_ppm * 125 / 2^13
+         */
+        s64 ppb = 1 + ppm;
+        ppb *= 125;
+        ppb >>= 13;
+        return (s32) ppb;
+}
+
+/* posix clock implementation */
+
+static int ptp_clock_getres(struct posix_clock *pc, struct timespec *tp)
+{
+        return 1; /* always round timer functions to one nanosecond */
+}
+
+static int ptp_clock_settime(struct posix_clock *pc, const struct timespec *tp)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+        return ptp->info->settime(ptp->info, tp);
+}
+
+static int ptp_clock_gettime(struct posix_clock *pc, struct timespec *tp)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+        return ptp->info->gettime(ptp->info, tp);
+}
+
+static int ptp_clock_adjtime(struct posix_clock *pc, struct timex *tx)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+        struct ptp_clock_info *ops;
+        int err = -EOPNOTSUPP;
+
+        ops = ptp->info;
+
+        if (tx->modes & ADJ_SETOFFSET) {
+                struct timespec ts;
+                ktime_t kt;
+                s64 delta;
+
+                ts.tv_sec  = tx->time.tv_sec;
+                ts.tv_nsec = tx->time.tv_usec;
+
+                if (!(tx->modes & ADJ_NANO))
+                        ts.tv_nsec *= 1000;
+
+                if ((unsigned long) ts.tv_nsec >= NSEC_PER_SEC)
+                        return -EINVAL;
+
+                kt = timespec_to_ktime(ts);
+                delta = ktime_to_ns(kt);
+                err = ops->adjtime(ops, delta);
+
+        } else if (tx->modes & ADJ_FREQUENCY) {
+
+                err = ops->adjfreq(ops, scaled_ppm_to_ppb(tx->freq));
+        }
+
+        return err;
+}
+
+static struct posix_clock_operations ptp_clock_ops = {
+        .owner          = THIS_MODULE,
+        .clock_adjtime  = ptp_clock_adjtime,
+        .clock_gettime  = ptp_clock_gettime,
+        .clock_getres   = ptp_clock_getres,
+        .clock_settime  = ptp_clock_settime,
+        .ioctl          = ptp_ioctl,
+        .open           = ptp_open,
+        .poll           = ptp_poll,
+        .read           = ptp_read,
+};
+
+static void delete_ptp_clock(struct posix_clock *pc)
+{
+        struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+
+        mutex_destroy(&ptp->tsevq_mux);
+
+        /* Remove the clock from the bit map. */
+        mutex_lock(&ptp_clocks_mutex);
+        clear_bit(ptp->index, ptp_clocks_map);
+        mutex_unlock(&ptp_clocks_mutex);
+
+        kfree(ptp);
+}
+
+/* public interface */
+
+struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info)
+{
+        struct ptp_clock *ptp;
+        int err = 0, index, major = MAJOR(ptp_devt);
+
+        if (info->n_alarm > PTP_MAX_ALARMS)
+                return ERR_PTR(-EINVAL);
+
+        /* Find a free clock slot and reserve it. */
+        err = -EBUSY;
+        mutex_lock(&ptp_clocks_mutex);
+        index = find_first_zero_bit(ptp_clocks_map, PTP_MAX_CLOCKS);
+        if (index < PTP_MAX_CLOCKS)
+                set_bit(index, ptp_clocks_map);
+        else
+                goto no_slot;
+
+        /* Initialize a clock structure. */
+        err = -ENOMEM;
+        ptp = kzalloc(sizeof(struct ptp_clock), GFP_KERNEL);
+        if (ptp == NULL)
+                goto no_memory;
+
+        ptp->clock.ops = ptp_clock_ops;
+        ptp->clock.release = delete_ptp_clock;
+        ptp->info = info;
+        ptp->devid = MKDEV(major, index);
+        ptp->index = index;
+        spin_lock_init(&ptp->tsevq.lock);
+        mutex_init(&ptp->tsevq_mux);
+        init_waitqueue_head(&ptp->tsev_wq);
+
+        /* Create a new device in our class. */
+        ptp->dev = device_create(ptp_class, NULL, ptp->devid, ptp,
+                                 "ptp%d", ptp->index);
+        if (IS_ERR(ptp->dev))
+                goto no_device;
+
+        dev_set_drvdata(ptp->dev, ptp);
+
+        err = ptp_populate_sysfs(ptp);
+        if (err)
+                goto no_sysfs;
+
+        /* Register a new PPS source. */
+        if (info->pps) {
+                struct pps_source_info pps;
+                memset(&pps, 0, sizeof(pps));
+                snprintf(pps.name, PPS_MAX_NAME_LEN, "ptp%d", index);
+                pps.mode = PTP_PPS_MODE;
+                pps.owner = info->owner;
+                ptp->pps_source = pps_register_source(&pps, PTP_PPS_DEFAULTS);
+                if (!ptp->pps_source) {
+                        pr_err("failed to register pps source\n");
+                        goto no_pps;
+                }
+        }
+
+        /* Create a posix clock. */
+        err = posix_clock_register(&ptp->clock, ptp->devid);
+        if (err) {
+                pr_err("failed to create posix clock\n");
+                goto no_clock;
+        }
+
+        mutex_unlock(&ptp_clocks_mutex);
+        return ptp;
+
+no_clock:
+        if (ptp->pps_source)
+                pps_unregister_source(ptp->pps_source);
+no_pps:
+        ptp_cleanup_sysfs(ptp);
+no_sysfs:
+        device_destroy(ptp_class, ptp->devid);
+no_device:
+        mutex_destroy(&ptp->tsevq_mux);
+        kfree(ptp);
+no_memory:
+        clear_bit(index, ptp_clocks_map);
+no_slot:
+        mutex_unlock(&ptp_clocks_mutex);
+        return ERR_PTR(err);
+}
+EXPORT_SYMBOL(ptp_clock_register);
+
+int ptp_clock_unregister(struct ptp_clock *ptp)
+{
+        ptp->defunct = 1;
+        wake_up_interruptible(&ptp->tsev_wq);
+
+        /* Release the clock's resources. */
+        if (ptp->pps_source)
+                pps_unregister_source(ptp->pps_source);
+        ptp_cleanup_sysfs(ptp);
+        device_destroy(ptp_class, ptp->devid);
+
+        posix_clock_unregister(&ptp->clock);
+        return 0;
+}
+EXPORT_SYMBOL(ptp_clock_unregister);
+
+void ptp_clock_event(struct ptp_clock *ptp, struct ptp_clock_event *event)
+{
+        struct pps_event_time evt;
+
+        switch (event->type) {
+
+        case PTP_CLOCK_ALARM:
+                break;
+
+        case PTP_CLOCK_EXTTS:
+                enqueue_external_timestamp(&ptp->tsevq, event);
+                wake_up_interruptible(&ptp->tsev_wq);
+                break;
+
+        case PTP_CLOCK_PPS:
+                pps_get_ts(&evt);
+                pps_event(ptp->pps_source, &evt, PTP_PPS_EVENT, NULL);
+                break;
+        }
+}
+EXPORT_SYMBOL(ptp_clock_event);
+
+/* module operations */
+
+static void __exit ptp_exit(void)
+{
+        class_destroy(ptp_class);
+        unregister_chrdev_region(ptp_devt, PTP_MAX_CLOCKS);
+}
+
+static int __init ptp_init(void)
+{
+        int err;
+
+        ptp_class = class_create(THIS_MODULE, "ptp");
+        if (IS_ERR(ptp_class)) {
+                pr_err("ptp: failed to allocate class\n");
+                return PTR_ERR(ptp_class);
+        }
+
+        err = alloc_chrdev_region(&ptp_devt, 0, PTP_MAX_CLOCKS, "ptp");
+        if (err < 0) {
+                pr_err("ptp: failed to allocate device region\n");
+                goto no_region;
+        }
+
+        ptp_class->dev_attrs = ptp_dev_attrs;
+        pr_info("PTP clock support registered\n");
+        return 0;
+
+no_region:
+        class_destroy(ptp_class);
+        return err;
+}
+
+subsys_initcall(ptp_init);
+module_exit(ptp_exit);
+
+MODULE_AUTHOR("Richard Cochran <richard.cochran@omicron.at>");
+MODULE_DESCRIPTION("PTP clocks support");
+MODULE_LICENSE("GPL");
diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
new file mode 100644
index 000000000000..4d5b5082c3b1
--- /dev/null
+++ b/drivers/ptp/ptp_private.h
@@ -0,0 +1,92 @@
+/*
+ * PTP 1588 clock support - private declarations for the core module.
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ *
+ *  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.
+ */
+#ifndef _PTP_PRIVATE_H_
+#define _PTP_PRIVATE_H_
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/posix-clock.h>
+#include <linux/ptp_clock.h>
+#include <linux/ptp_clock_kernel.h>
+#include <linux/time.h>
+
+#define PTP_MAX_TIMESTAMPS 128
+#define PTP_BUF_TIMESTAMPS 30
+
+struct timestamp_event_queue {
+        struct ptp_extts_event buf[PTP_MAX_TIMESTAMPS];
+        int head;
+        int tail;
+        spinlock_t lock;
+};
+
+struct ptp_clock {
+        struct posix_clock clock;
+        struct device *dev;
+        struct ptp_clock_info *info;
+        dev_t devid;
+        int index; /* index into clocks.map */
+        struct pps_device *pps_source;
+        struct timestamp_event_queue tsevq; /* simple fifo for time stamps */
+        struct mutex tsevq_mux; /* one process at a time reading the fifo */
+        wait_queue_head_t tsev_wq;
+        int defunct; /* tells readers to go away when clock is being removed */
+};
+
+/*
+ * The function queue_cnt() is safe for readers to call without
+ * holding q->lock. Readers use this function to verify that the queue
+ * is nonempty before proceeding with a dequeue operation. The fact
+ * that a writer might concurrently increment the tail does not
+ * matter, since the queue remains nonempty nonetheless.
+ */
+static inline int queue_cnt(struct timestamp_event_queue *q)
+{
+        int cnt = q->tail - q->head;
+        return cnt < 0 ? PTP_MAX_TIMESTAMPS + cnt : cnt;
+}
+
+/*
+ * see ptp_chardev.c
+ */
+
+long ptp_ioctl(struct posix_clock *pc,
+               unsigned int cmd, unsigned long arg);
+
+int ptp_open(struct posix_clock *pc, fmode_t fmode);
+
+ssize_t ptp_read(struct posix_clock *pc,
+                 uint flags, char __user *buf, size_t cnt);
+
+uint ptp_poll(struct posix_clock *pc,
+              struct file *fp, poll_table *wait);
+
+/*
+ * see ptp_sysfs.c
+ */
+
+extern struct device_attribute ptp_dev_attrs[];
+
+int ptp_cleanup_sysfs(struct ptp_clock *ptp);
+
+int ptp_populate_sysfs(struct ptp_clock *ptp);
+
+#endif
diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
new file mode 100644
index 000000000000..2f93926ac976
--- /dev/null
+++ b/drivers/ptp/ptp_sysfs.c
@@ -0,0 +1,230 @@
+/*
+ * PTP 1588 clock support - sysfs interface.
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ *
+ *  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/capability.h>
+
+#include "ptp_private.h"
+
+static ssize_t clock_name_show(struct device *dev,
+                               struct device_attribute *attr, char *page)
+{
+        struct ptp_clock *ptp = dev_get_drvdata(dev);
+        return snprintf(page, PAGE_SIZE-1, "%s\n", ptp->info->name);
+}
+
+#define PTP_SHOW_INT(name)                                              \
+static ssize_t name##_show(struct device *dev,                          \
+                           struct device_attribute *attr, char *page)   \
+{                                                                       \
+        struct ptp_clock *ptp = dev_get_drvdata(dev);                   \
+        return snprintf(page, PAGE_SIZE-1, "%d\n", ptp->info->name);    \
+}
+
+PTP_SHOW_INT(max_adj);
+PTP_SHOW_INT(n_alarm);
+PTP_SHOW_INT(n_ext_ts);
+PTP_SHOW_INT(n_per_out);
+PTP_SHOW_INT(pps);
+
+#define PTP_RO_ATTR(_var, _name) {                              \
+        .attr   = { .name = __stringify(_name), .mode = 0444 }, \
+        .show   = _var##_show,                                  \
+}
+
+struct device_attribute ptp_dev_attrs[] = {
+        PTP_RO_ATTR(clock_name, clock_name),
+        PTP_RO_ATTR(max_adj,    max_adjustment),
+        PTP_RO_ATTR(n_alarm,    n_alarms),
+        PTP_RO_ATTR(n_ext_ts,   n_external_timestamps),
+        PTP_RO_ATTR(n_per_out,  n_periodic_outputs),
+        PTP_RO_ATTR(pps,        pps_available),
+        __ATTR_NULL,
+};
+
+static ssize_t extts_enable_store(struct device *dev,
+                                  struct device_attribute *attr,
+                                  const char *buf, size_t count)
+{
+        struct ptp_clock *ptp = dev_get_drvdata(dev);
+        struct ptp_clock_info *ops = ptp->info;
+        struct ptp_clock_request req = { .type = PTP_CLK_REQ_EXTTS };
+        int cnt, enable;
+        int err = -EINVAL;
+
+        cnt = sscanf(buf, "%u %d", &req.extts.index, &enable);
+        if (cnt != 2)
+                goto out;
+        if (req.extts.index >= ops->n_ext_ts)
+                goto out;
+
+        err = ops->enable(ops, &req, enable ? 1 : 0);
+        if (err)
+                goto out;
+
+        return count;
+out:
+        return err;
+}
+
+static ssize_t extts_fifo_show(struct device *dev,
+                               struct device_attribute *attr, char *page)
+{
+        struct ptp_clock *ptp = dev_get_drvdata(dev);
+        struct timestamp_event_queue *queue = &ptp->tsevq;
+        struct ptp_extts_event event;
+        unsigned long flags;
+        size_t qcnt;
+        int cnt = 0;
+
+        memset(&event, 0, sizeof(event));
+
+        if (mutex_lock_interruptible(&ptp->tsevq_mux))
+                return -ERESTARTSYS;
+
+        spin_lock_irqsave(&queue->lock, flags);
+        qcnt = queue_cnt(queue);
+        if (qcnt) {
+                event = queue->buf[queue->head];
+                queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS;
+        }
+        spin_unlock_irqrestore(&queue->lock, flags);
+
+        if (!qcnt)
+                goto out;
+
+        cnt = snprintf(page, PAGE_SIZE, "%u %lld %u\n",
+                       event.index, event.t.sec, event.t.nsec);
+out:
+        mutex_unlock(&ptp->tsevq_mux);
+        return cnt;
+}
+
+static ssize_t period_store(struct device *dev,
+                            struct device_attribute *attr,
+                            const char *buf, size_t count)
+{
+        struct ptp_clock *ptp = dev_get_drvdata(dev);
+        struct ptp_clock_info *ops = ptp->info;
+        struct ptp_clock_request req = { .type = PTP_CLK_REQ_PEROUT };
+        int cnt, enable, err = -EINVAL;
+
+        cnt = sscanf(buf, "%u %lld %u %lld %u", &req.perout.index,
+                     &req.perout.start.sec, &req.perout.start.nsec,
+                     &req.perout.period.sec, &req.perout.period.nsec);
+        if (cnt != 5)
+                goto out;
+        if (req.perout.index >= ops->n_per_out)
+                goto out;
+
+        enable = req.perout.period.sec || req.perout.period.nsec;
+        err = ops->enable(ops, &req, enable);
+        if (err)
+                goto out;
+
+        return count;
+out:
+        return err;
+}
+
+static ssize_t pps_enable_store(struct device *dev,
+                                struct device_attribute *attr,
+                                const char *buf, size_t count)
+{
+        struct ptp_clock *ptp = dev_get_drvdata(dev);
+        struct ptp_clock_info *ops = ptp->info;
+        struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
+        int cnt, enable;
+        int err = -EINVAL;
+
+        if (!capable(CAP_SYS_TIME))
+                return -EPERM;
+
+        cnt = sscanf(buf, "%d", &enable);
+        if (cnt != 1)
+                goto out;
+
+        err = ops->enable(ops, &req, enable ? 1 : 0);
+        if (err)
+                goto out;
+
+        return count;
+out:
+        return err;
+}
+
+static DEVICE_ATTR(extts_enable, 0220, NULL, extts_enable_store);
+static DEVICE_ATTR(fifo,         0444, extts_fifo_show, NULL);
+static DEVICE_ATTR(period,       0220, NULL, period_store);
+static DEVICE_ATTR(pps_enable,   0220, NULL, pps_enable_store);
+
+int ptp_cleanup_sysfs(struct ptp_clock *ptp)
+{
+        struct device *dev = ptp->dev;
+        struct ptp_clock_info *info = ptp->info;
+
+        if (info->n_ext_ts) {
+                device_remove_file(dev, &dev_attr_extts_enable);
+                device_remove_file(dev, &dev_attr_fifo);
+        }
+        if (info->n_per_out)
+                device_remove_file(dev, &dev_attr_period);
+
+        if (info->pps)
+                device_remove_file(dev, &dev_attr_pps_enable);
+
+        return 0;
+}
+
+int ptp_populate_sysfs(struct ptp_clock *ptp)
+{
+        struct device *dev = ptp->dev;
+        struct ptp_clock_info *info = ptp->info;
+        int err;
+
+        if (info->n_ext_ts) {
+                err = device_create_file(dev, &dev_attr_extts_enable);
+                if (err)
+                        goto out1;
+                err = device_create_file(dev, &dev_attr_fifo);
+                if (err)
+                        goto out2;
+        }
+        if (info->n_per_out) {
+                err = device_create_file(dev, &dev_attr_period);
+                if (err)
+                        goto out3;
+        }
+        if (info->pps) {
+                err = device_create_file(dev, &dev_attr_pps_enable);
+                if (err)
+                        goto out4;
+        }
+        return 0;
+out4:
+        if (info->n_per_out)
+                device_remove_file(dev, &dev_attr_period);
+out3:
+        if (info->n_ext_ts)
+                device_remove_file(dev, &dev_attr_fifo);
+out2:
+        if (info->n_ext_ts)
+                device_remove_file(dev, &dev_attr_extts_enable);
+out1:
+        return err;
+}