1 files changed, 646 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
new file mode 100644
index 000000000..dc23cd708
--- /dev/null
+++ b/drivers/ptp/ptp_chardev.c
@@ -0,0 +1,646 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PTP 1588 clock support - character device implementation.
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ */
+#include <linux/compat.h>
+#include <linux/module.h>
+#include <linux/posix-clock.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/timekeeping.h>
+#include <linux/debugfs.h>
+
+#include <linux/nospec.h>
+
+#include "ptp_private.h"
+
+static int ptp_disable_pinfunc(struct ptp_clock_info *ops,
+			       enum ptp_pin_function func, unsigned int chan)
+{
+	struct ptp_clock_request rq;
+	int err = 0;
+
+	memset(&rq, 0, sizeof(rq));
+
+	switch (func) {
+	case PTP_PF_NONE:
+		break;
+	case PTP_PF_EXTTS:
+		rq.type = PTP_CLK_REQ_EXTTS;
+		rq.extts.index = chan;
+		err = ops->enable(ops, &rq, 0);
+		break;
+	case PTP_PF_PEROUT:
+		rq.type = PTP_CLK_REQ_PEROUT;
+		rq.perout.index = chan;
+		err = ops->enable(ops, &rq, 0);
+		break;
+	case PTP_PF_PHYSYNC:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return err;
+}
+
+void ptp_disable_all_events(struct ptp_clock *ptp)
+{
+	struct ptp_clock_info *info = ptp->info;
+	unsigned int i;
+
+	mutex_lock(&ptp->pincfg_mux);
+	/* Disable any pins that may raise EXTTS events */
+	for (i = 0; i < info->n_pins; i++)
+		if (info->pin_config[i].func == PTP_PF_EXTTS)
+			ptp_disable_pinfunc(info, info->pin_config[i].func,
+					    info->pin_config[i].chan);
+
+	/* Disable the PPS event if the driver has PPS support */
+	if (info->pps) {
+		struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
+		info->enable(info, &req, 0);
+	}
+	mutex_unlock(&ptp->pincfg_mux);
+}
+
+int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
+		    enum ptp_pin_function func, unsigned int chan)
+{
+	struct ptp_clock_info *info = ptp->info;
+	struct ptp_pin_desc *pin1 = NULL, *pin2 = &info->pin_config[pin];
+	unsigned int i;
+
+	/* Check to see if any other pin previously had this function. */
+	for (i = 0; i < info->n_pins; i++) {
+		if (info->pin_config[i].func == func &&
+		    info->pin_config[i].chan == chan) {
+			pin1 = &info->pin_config[i];
+			break;
+		}
+	}
+	if (pin1 && i == pin)
+		return 0;
+
+	/* Check the desired function and channel. */
+	switch (func) {
+	case PTP_PF_NONE:
+		break;
+	case PTP_PF_EXTTS:
+		if (chan >= info->n_ext_ts)
+			return -EINVAL;
+		break;
+	case PTP_PF_PEROUT:
+		if (chan >= info->n_per_out)
+			return -EINVAL;
+		break;
+	case PTP_PF_PHYSYNC:
+		if (chan != 0)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (info->verify(info, pin, func, chan)) {
+		pr_err("driver cannot use function %u and channel %u on pin %u\n",
+		       func, chan, pin);
+		return -EOPNOTSUPP;
+	}
+
+	/* Disable whichever pin was previously assigned to this function and
+	 * channel.
+	 */
+	if (pin1) {
+		ptp_disable_pinfunc(info, func, chan);
+		pin1->func = PTP_PF_NONE;
+		pin1->chan = 0;
+	}
+
+	/* Disable whatever function was previously assigned to the requested
+	 * pin.
+	 */
+	ptp_disable_pinfunc(info, pin2->func, pin2->chan);
+	pin2->func = func;
+	pin2->chan = chan;
+
+	return 0;
+}
+
+int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
+{
+	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
+	struct timestamp_event_queue *queue;
+	char debugfsname[32];
+
+	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
+	if (!queue)
+		return -EINVAL;
+	queue->mask = bitmap_alloc(PTP_MAX_CHANNELS, GFP_KERNEL);
+	if (!queue->mask) {
+		kfree(queue);
+		return -EINVAL;
+	}
+	bitmap_set(queue->mask, 0, PTP_MAX_CHANNELS);
+	spin_lock_init(&queue->lock);
+	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
+		list_add_tail(&queue->qlist, &ptp->tsevqs);
+	pccontext->private_clkdata = queue;
+
+	/* Debugfs contents */
+	sprintf(debugfsname, "0x%p", queue);
+	queue->debugfs_instance =
+		debugfs_create_dir(debugfsname, ptp->debugfs_root);
+	queue->dfs_bitmap.array = (u32 *)queue->mask;
+	queue->dfs_bitmap.n_elements =
+		DIV_ROUND_UP(PTP_MAX_CHANNELS, BITS_PER_BYTE * sizeof(u32));
+	debugfs_create_u32_array("mask", 0444, queue->debugfs_instance,
+				 &queue->dfs_bitmap);
+
+	return 0;
+}
+
+int ptp_release(struct posix_clock_context *pccontext)
+{
+	struct timestamp_event_queue *queue = pccontext->private_clkdata;
+	struct ptp_clock *ptp =
+		container_of(pccontext->clk, struct ptp_clock, clock);
+
+	debugfs_remove(queue->debugfs_instance);
+	pccontext->private_clkdata = NULL;
+	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
+		list_del(&queue->qlist);
+	bitmap_free(queue->mask);
+	kfree(queue);
+	return 0;
+}
+
+static long ptp_clock_getcaps(struct ptp_clock *ptp, void __user *arg)
+{
+	struct ptp_clock_caps caps = {
+		.max_adj		= ptp->info->max_adj,
+		.n_alarm		= ptp->info->n_alarm,
+		.n_ext_ts		= ptp->info->n_ext_ts,
+		.n_per_out		= ptp->info->n_per_out,
+		.pps			= ptp->info->pps,
+		.n_pins			= ptp->info->n_pins,
+		.cross_timestamping	= ptp->info->getcrosststamp != NULL,
+		.adjust_phase		= ptp->info->adjphase != NULL &&
+					  ptp->info->getmaxphase != NULL,
+	};
+
+	if (caps.adjust_phase)
+		caps.max_phase_adj = ptp->info->getmaxphase(ptp->info);
+
+	return copy_to_user(arg, &caps, sizeof(caps)) ? -EFAULT : 0;
+}
+
+static long ptp_extts_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
+{
+	struct ptp_clock_request req = { .type = PTP_CLK_REQ_EXTTS };
+	struct ptp_clock_info *ops = ptp->info;
+	unsigned int supported_extts_flags;
+
+	if (copy_from_user(&req.extts, arg, sizeof(req.extts)))
+		return -EFAULT;
+
+	if (cmd == PTP_EXTTS_REQUEST2) {
+		/* Tell the drivers to check the flags carefully. */
+		req.extts.flags |= PTP_STRICT_FLAGS;
+		/* Make sure no reserved bit is set. */
+		if ((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
+		    req.extts.rsv[0] || req.extts.rsv[1])
+			return -EINVAL;
+
+		/* Ensure one of the rising/falling edge bits is set. */
+		if ((req.extts.flags & PTP_ENABLE_FEATURE) &&
+		    (req.extts.flags & PTP_EXTTS_EDGES) == 0)
+			return -EINVAL;
+	} else {
+		req.extts.flags &= PTP_EXTTS_V1_VALID_FLAGS;
+		memset(req.extts.rsv, 0, sizeof(req.extts.rsv));
+	}
+
+	if (req.extts.index >= ops->n_ext_ts)
+		return -EINVAL;
+
+	supported_extts_flags = ptp->info->supported_extts_flags;
+	/* The PTP_ENABLE_FEATURE flag is always supported. */
+	supported_extts_flags |= PTP_ENABLE_FEATURE;
+	/* If the driver does not support strictly checking flags, the
+	 * PTP_RISING_EDGE and PTP_FALLING_EDGE flags are merely hints
+	 * which are not enforced.
+	 */
+	if (!(supported_extts_flags & PTP_STRICT_FLAGS))
+		supported_extts_flags |= PTP_EXTTS_EDGES;
+	/* Reject unsupported flags */
+	if (req.extts.flags & ~supported_extts_flags)
+		return -EOPNOTSUPP;
+
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
+		return ops->enable(ops, &req, req.extts.flags & PTP_ENABLE_FEATURE ? 1 : 0);
+}
+
+static long ptp_perout_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
+{
+	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PEROUT };
+	struct ptp_perout_request *perout = &req.perout;
+	struct ptp_clock_info *ops = ptp->info;
+
+	if (copy_from_user(perout, arg, sizeof(*perout)))
+		return -EFAULT;
+
+	if (cmd == PTP_PEROUT_REQUEST2) {
+		if (perout->flags & ~PTP_PEROUT_VALID_FLAGS)
+			return -EINVAL;
+
+		/*
+		 * The "on" field has undefined meaning if
+		 * PTP_PEROUT_DUTY_CYCLE isn't set, we must still treat it
+		 * as reserved, which must be set to zero.
+		 */
+		if (!(perout->flags & PTP_PEROUT_DUTY_CYCLE) &&
+		    !mem_is_zero(perout->rsv, sizeof(perout->rsv)))
+			return -EINVAL;
+
+		if (perout->flags & PTP_PEROUT_DUTY_CYCLE) {
+			/* The duty cycle must be subunitary. */
+			if (perout->on.sec > perout->period.sec ||
+			    (perout->on.sec == perout->period.sec &&
+			     perout->on.nsec > perout->period.nsec))
+				return -ERANGE;
+		}
+
+		if (perout->flags & PTP_PEROUT_PHASE) {
+			/*
+			 * The phase should be specified modulo the period,
+			 * therefore anything equal or larger than 1 period
+			 * is invalid.
+			 */
+			if (perout->phase.sec > perout->period.sec ||
+			    (perout->phase.sec == perout->period.sec &&
+			     perout->phase.nsec >= perout->period.nsec))
+				return -ERANGE;
+		}
+	} else {
+		perout->flags &= PTP_PEROUT_V1_VALID_FLAGS;
+		memset(perout->rsv, 0, sizeof(perout->rsv));
+	}
+
+	if (perout->index >= ops->n_per_out)
+		return -EINVAL;
+	if (perout->flags & ~ops->supported_perout_flags)
+		return -EOPNOTSUPP;
+
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
+		return ops->enable(ops, &req, perout->period.sec || perout->period.nsec);
+}
+
+static long ptp_enable_pps(struct ptp_clock *ptp, bool enable)
+{
+	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
+	struct ptp_clock_info *ops = ptp->info;
+
+	if (!capable(CAP_SYS_TIME))
+		return -EPERM;
+
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
+		return ops->enable(ops, &req, enable);
+}
+
+typedef int (*ptp_crosststamp_fn)(struct ptp_clock_info *,
+				  struct system_device_crosststamp *);
+
+static long ptp_sys_offset_precise(struct ptp_clock *ptp, void __user *arg,
+				   ptp_crosststamp_fn crosststamp_fn)
+{
+	struct system_device_crosststamp xtstamp = { .clock_id = CLOCK_REALTIME };
+	struct ptp_sys_offset_precise precise_offset;
+	struct timespec64 ts;
+	int err;
+
+	if (!crosststamp_fn)
+		return -EOPNOTSUPP;
+
+	err = crosststamp_fn(ptp->info, &xtstamp);
+	if (err)
+		return err;
+
+	memset(&precise_offset, 0, sizeof(precise_offset));
+	ts = ktime_to_timespec64(xtstamp.device);
+	precise_offset.device.sec = ts.tv_sec;
+	precise_offset.device.nsec = ts.tv_nsec;
+	ts = ktime_to_timespec64(xtstamp.sys_systime);
+	precise_offset.sys_realtime.sec = ts.tv_sec;
+	precise_offset.sys_realtime.nsec = ts.tv_nsec;
+	ts = ktime_to_timespec64(xtstamp.sys_monoraw);
+	precise_offset.sys_monoraw.sec = ts.tv_sec;
+	precise_offset.sys_monoraw.nsec = ts.tv_nsec;
+
+	return copy_to_user(arg, &precise_offset, sizeof(precise_offset)) ? -EFAULT : 0;
+}
+
+typedef int (*ptp_gettimex_fn)(struct ptp_clock_info *,
+			       struct timespec64 *,
+			       struct ptp_system_timestamp *);
+
+static long ptp_sys_offset_extended(struct ptp_clock *ptp, void __user *arg,
+				    ptp_gettimex_fn gettimex_fn)
+{
+	struct ptp_sys_offset_extended *extoff __free(kfree) = NULL;
+	struct ptp_system_timestamp sts;
+
+	if (!gettimex_fn)
+		return -EOPNOTSUPP;
+
+	extoff = memdup_user(arg, sizeof(*extoff));
+	if (IS_ERR(extoff))
+		return PTR_ERR(extoff);
+
+	if (extoff->n_samples > PTP_MAX_SAMPLES || extoff->rsv[0] || extoff->rsv[1])
+		return -EINVAL;
+
+	switch (extoff->clockid) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_RAW:
+		break;
+	case CLOCK_AUX ... CLOCK_AUX_LAST:
+		if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
+			break;
+		fallthrough;
+	default:
+		return -EINVAL;
+	}
+
+	sts.clockid = extoff->clockid;
+	for (unsigned int i = 0; i < extoff->n_samples; i++) {
+		struct timespec64 ts;
+		int err;
+
+		err = gettimex_fn(ptp->info, &ts, &sts);
+		if (err)
+			return err;
+
+		/* Filter out disabled or unavailable clocks */
+		if (!sts.pre_sts.valid || !sts.post_sts.valid)
+			return -EINVAL;
+
+		extoff->ts[i][1].sec = ts.tv_sec;
+		extoff->ts[i][1].nsec = ts.tv_nsec;
+
+		ts = ktime_to_timespec64(sts.pre_sts.systime);
+		extoff->ts[i][0].sec = ts.tv_sec;
+		extoff->ts[i][0].nsec = ts.tv_nsec;
+
+		ts = ktime_to_timespec64(sts.post_sts.systime);
+		extoff->ts[i][2].sec = ts.tv_sec;
+		extoff->ts[i][2].nsec = ts.tv_nsec;
+	}
+
+	return copy_to_user(arg, extoff, sizeof(*extoff)) ? -EFAULT : 0;
+}
+
+static long ptp_sys_offset(struct ptp_clock *ptp, void __user *arg)
+{
+	struct ptp_sys_offset *sysoff __free(kfree) = NULL;
+	struct ptp_clock_time *pct;
+	struct timespec64 ts;
+
+	sysoff = memdup_user(arg, sizeof(*sysoff));
+	if (IS_ERR(sysoff))
+		return PTR_ERR(sysoff);
+
+	if (sysoff->n_samples > PTP_MAX_SAMPLES)
+		return -EINVAL;
+
+	pct = &sysoff->ts[0];
+	for (unsigned int i = 0; i < sysoff->n_samples; i++) {
+		struct ptp_clock_info *ops = ptp->info;
+		int err;
+
+		ktime_get_real_ts64(&ts);
+		pct->sec = ts.tv_sec;
+		pct->nsec = ts.tv_nsec;
+		pct++;
+		if (ops->gettimex64)
+			err = ops->gettimex64(ops, &ts, NULL);
+		else
+			err = ops->gettime64(ops, &ts);
+		if (err)
+			return err;
+		pct->sec = ts.tv_sec;
+		pct->nsec = ts.tv_nsec;
+		pct++;
+	}
+	ktime_get_real_ts64(&ts);
+	pct->sec = ts.tv_sec;
+	pct->nsec = ts.tv_nsec;
+
+	return copy_to_user(arg, sysoff, sizeof(*sysoff)) ? -EFAULT : 0;
+}
+
+static long ptp_pin_getfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
+{
+	struct ptp_clock_info *ops = ptp->info;
+	struct ptp_pin_desc pd;
+
+	if (copy_from_user(&pd, arg, sizeof(pd)))
+		return -EFAULT;
+
+	if (cmd == PTP_PIN_GETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
+		return -EINVAL;
+
+	if (pd.index >= ops->n_pins)
+		return -EINVAL;
+
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
+		pd = ops->pin_config[array_index_nospec(pd.index, ops->n_pins)];
+
+	return copy_to_user(arg, &pd, sizeof(pd)) ? -EFAULT : 0;
+}
+
+static long ptp_pin_setfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
+{
+	struct ptp_clock_info *ops = ptp->info;
+	struct ptp_pin_desc pd;
+	unsigned int pin_index;
+
+	if (copy_from_user(&pd, arg, sizeof(pd)))
+		return -EFAULT;
+
+	if (cmd == PTP_PIN_SETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
+		return -EINVAL;
+
+	if (pd.index >= ops->n_pins)
+		return -EINVAL;
+
+	pin_index = array_index_nospec(pd.index, ops->n_pins);
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
+		return ptp_set_pinfunc(ptp, pin_index, pd.func, pd.chan);
+}
+
+static long ptp_mask_clear_all(struct timestamp_event_queue *tsevq)
+{
+	bitmap_clear(tsevq->mask, 0, PTP_MAX_CHANNELS);
+	return 0;
+}
+
+static long ptp_mask_en_single(struct timestamp_event_queue *tsevq, void __user *arg)
+{
+	unsigned int channel;
+
+	if (copy_from_user(&channel, arg, sizeof(channel)))
+		return -EFAULT;
+	if (channel >= PTP_MAX_CHANNELS)
+		return -EFAULT;
+	set_bit(channel, tsevq->mask);
+	return 0;
+}
+
+long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
+	       unsigned long arg)
+{
+	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
+	void __user *argptr;
+
+	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
+		arg = (unsigned long)compat_ptr(arg);
+	argptr = (void __force __user *)arg;
+
+	switch (cmd) {
+	case PTP_CLOCK_GETCAPS:
+	case PTP_CLOCK_GETCAPS2:
+		return ptp_clock_getcaps(ptp, argptr);
+
+	case PTP_EXTTS_REQUEST:
+	case PTP_EXTTS_REQUEST2:
+		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
+			return -EACCES;
+		return ptp_extts_request(ptp, cmd, argptr);
+
+	case PTP_PEROUT_REQUEST:
+	case PTP_PEROUT_REQUEST2:
+		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
+			return -EACCES;
+		return ptp_perout_request(ptp, cmd, argptr);
+
+	case PTP_ENABLE_PPS:
+	case PTP_ENABLE_PPS2:
+		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
+			return -EACCES;
+		return ptp_enable_pps(ptp, !!arg);
+
+	case PTP_SYS_OFFSET_PRECISE:
+	case PTP_SYS_OFFSET_PRECISE2:
+		return ptp_sys_offset_precise(ptp, argptr,
+					      ptp->info->getcrosststamp);
+
+	case PTP_SYS_OFFSET_EXTENDED:
+	case PTP_SYS_OFFSET_EXTENDED2:
+		return ptp_sys_offset_extended(ptp, argptr,
+					       ptp->info->gettimex64);
+
+	case PTP_SYS_OFFSET:
+	case PTP_SYS_OFFSET2:
+		return ptp_sys_offset(ptp, argptr);
+
+	case PTP_PIN_GETFUNC:
+	case PTP_PIN_GETFUNC2:
+		return ptp_pin_getfunc(ptp, cmd, argptr);
+
+	case PTP_PIN_SETFUNC:
+	case PTP_PIN_SETFUNC2:
+		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
+			return -EACCES;
+		return ptp_pin_setfunc(ptp, cmd, argptr);
+
+	case PTP_MASK_CLEAR_ALL:
+		return ptp_mask_clear_all(pccontext->private_clkdata);
+
+	case PTP_MASK_EN_SINGLE:
+		return ptp_mask_en_single(pccontext->private_clkdata, argptr);
+
+	case PTP_SYS_OFFSET_PRECISE_CYCLES:
+		if (!ptp->has_cycles)
+			return -EOPNOTSUPP;
+		return ptp_sys_offset_precise(ptp, argptr,
+					      ptp->info->getcrosscycles);
+
+	case PTP_SYS_OFFSET_EXTENDED_CYCLES:
+		if (!ptp->has_cycles)
+			return -EOPNOTSUPP;
+		return ptp_sys_offset_extended(ptp, argptr,
+					       ptp->info->getcyclesx64);
+	default:
+		return -ENOTTY;
+	}
+}
+
+__poll_t ptp_poll(struct posix_clock_context *pccontext, struct file *fp,
+		  poll_table *wait)
+{
+	struct ptp_clock *ptp =
+		container_of(pccontext->clk, struct ptp_clock, clock);
+	struct timestamp_event_queue *queue;
+
+	queue = pccontext->private_clkdata;
+	if (!queue)
+		return EPOLLERR;
+
+	poll_wait(fp, &ptp->tsev_wq, wait);
+
+	return queue_cnt(queue) ? EPOLLIN : 0;
+}
+
+#define EXTTS_BUFSIZE (PTP_BUF_TIMESTAMPS * sizeof(struct ptp_extts_event))
+
+ssize_t ptp_read(struct posix_clock_context *pccontext, uint rdflags,
+		 char __user *buf, size_t cnt)
+{
+	struct ptp_clock *ptp =	container_of(pccontext->clk, struct ptp_clock, clock);
+	struct timestamp_event_queue *queue;
+	struct ptp_extts_event *event;
+	ssize_t result;
+
+	queue = pccontext->private_clkdata;
+	if (!queue)
+		return -EINVAL;
+
+	if (cnt % sizeof(*event) != 0)
+		return -EINVAL;
+
+	if (cnt > EXTTS_BUFSIZE)
+		cnt = EXTTS_BUFSIZE;
+
+	if (wait_event_interruptible(ptp->tsev_wq, ptp->defunct || queue_cnt(queue)))
+		return -ERESTARTSYS;
+
+	if (ptp->defunct)
+		return -ENODEV;
+
+	event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
+	if (!event)
+		return -ENOMEM;
+
+	scoped_guard(spinlock_irq, &queue->lock) {
+		size_t qcnt = min((size_t)queue_cnt(queue), cnt / sizeof(*event));
+
+		for (size_t i = 0; i < qcnt; i++) {
+			event[i] = queue->buf[queue->head];
+			/* Paired with READ_ONCE() in queue_cnt() */
+			WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS);
+		}
+		cnt = qcnt * sizeof(*event);
+	}
+
+	result = cnt;
+	if (copy_to_user(buf, event, cnt))
+		result = -EFAULT;
+
+	kfree(event);
+	return result;
+}