ptp_chardev.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * PTP 1588 clock support - character device implementation.
  4 *
  5 * Copyright (C) 2010 OMICRON electronics GmbH
  6 */
  7#include <linux/compat.h>
  8#include <linux/module.h>
  9#include <linux/posix-clock.h>
 10#include <linux/poll.h>
 11#include <linux/sched.h>
 12#include <linux/slab.h>
 13#include <linux/timekeeping.h>
 14#include <linux/debugfs.h>
 15
 16#include <linux/nospec.h>
 17
 18#include "ptp_private.h"
 19
 20static int ptp_disable_pinfunc(struct ptp_clock_info *ops,
 21			       enum ptp_pin_function func, unsigned int chan)
 22{
 23	struct ptp_clock_request rq;
 24	int err = 0;
 25
 26	memset(&rq, 0, sizeof(rq));
 27
 28	switch (func) {
 29	case PTP_PF_NONE:
 30		break;
 31	case PTP_PF_EXTTS:
 32		rq.type = PTP_CLK_REQ_EXTTS;
 33		rq.extts.index = chan;
 34		err = ops->enable(ops, &rq, 0);
 35		break;
 36	case PTP_PF_PEROUT:
 37		rq.type = PTP_CLK_REQ_PEROUT;
 38		rq.perout.index = chan;
 39		err = ops->enable(ops, &rq, 0);
 40		break;
 41	case PTP_PF_PHYSYNC:
 42		break;
 43	default:
 44		return -EINVAL;
 45	}
 46
 47	return err;
 48}
 49
 50void ptp_disable_all_events(struct ptp_clock *ptp)
 51{
 52	struct ptp_clock_info *info = ptp->info;
 53	unsigned int i;
 54
 55	mutex_lock(&ptp->pincfg_mux);
 56	/* Disable any pins that may raise EXTTS events */
 57	for (i = 0; i < info->n_pins; i++)
 58		if (info->pin_config[i].func == PTP_PF_EXTTS)
 59			ptp_disable_pinfunc(info, info->pin_config[i].func,
 60					    info->pin_config[i].chan);
 61
 62	/* Disable the PPS event if the driver has PPS support */
 63	if (info->pps) {
 64		struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
 65		info->enable(info, &req, 0);
 66	}
 67	mutex_unlock(&ptp->pincfg_mux);
 68}
 69
 70int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
 71		    enum ptp_pin_function func, unsigned int chan)
 72{
 73	struct ptp_clock_info *info = ptp->info;
 74	struct ptp_pin_desc *pin1 = NULL, *pin2 = &info->pin_config[pin];
 75	unsigned int i;
 76
 77	/* Check to see if any other pin previously had this function. */
 78	for (i = 0; i < info->n_pins; i++) {
 79		if (info->pin_config[i].func == func &&
 80		    info->pin_config[i].chan == chan) {
 81			pin1 = &info->pin_config[i];
 82			break;
 83		}
 84	}
 85	if (pin1 && i == pin)
 86		return 0;
 87
 88	/* Check the desired function and channel. */
 89	switch (func) {
 90	case PTP_PF_NONE:
 91		break;
 92	case PTP_PF_EXTTS:
 93		if (chan >= info->n_ext_ts)
 94			return -EINVAL;
 95		break;
 96	case PTP_PF_PEROUT:
 97		if (chan >= info->n_per_out)
 98			return -EINVAL;
 99		break;
100	case PTP_PF_PHYSYNC:
101		if (chan != 0)
102			return -EINVAL;
103		break;
104	default:
105		return -EINVAL;
106	}
107
108	if (info->verify(info, pin, func, chan)) {
109		pr_err("driver cannot use function %u and channel %u on pin %u\n",
110		       func, chan, pin);
111		return -EOPNOTSUPP;
112	}
113
114	/* Disable whichever pin was previously assigned to this function and
115	 * channel.
116	 */
117	if (pin1) {
118		ptp_disable_pinfunc(info, func, chan);
119		pin1->func = PTP_PF_NONE;
120		pin1->chan = 0;
121	}
122
123	/* Disable whatever function was previously assigned to the requested
124	 * pin.
125	 */
126	ptp_disable_pinfunc(info, pin2->func, pin2->chan);
127	pin2->func = func;
128	pin2->chan = chan;
129
130	return 0;
131}
132
133int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
134{
135	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
136	struct timestamp_event_queue *queue;
137	char debugfsname[32];
138
139	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
140	if (!queue)
141		return -EINVAL;
142	queue->mask = bitmap_alloc(PTP_MAX_CHANNELS, GFP_KERNEL);
143	if (!queue->mask) {
144		kfree(queue);
145		return -EINVAL;
146	}
147	bitmap_set(queue->mask, 0, PTP_MAX_CHANNELS);
148	spin_lock_init(&queue->lock);
149	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
150		list_add_tail(&queue->qlist, &ptp->tsevqs);
151	pccontext->private_clkdata = queue;
152
153	/* Debugfs contents */
154	sprintf(debugfsname, "0x%p", queue);
155	queue->debugfs_instance =
156		debugfs_create_dir(debugfsname, ptp->debugfs_root);
157	queue->dfs_bitmap.array = (u32 *)queue->mask;
158	queue->dfs_bitmap.n_elements =
159		DIV_ROUND_UP(PTP_MAX_CHANNELS, BITS_PER_BYTE * sizeof(u32));
160	debugfs_create_u32_array("mask", 0444, queue->debugfs_instance,
161				 &queue->dfs_bitmap);
162
163	return 0;
164}
165
166int ptp_release(struct posix_clock_context *pccontext)
167{
168	struct timestamp_event_queue *queue = pccontext->private_clkdata;
169	struct ptp_clock *ptp =
170		container_of(pccontext->clk, struct ptp_clock, clock);
171
172	debugfs_remove(queue->debugfs_instance);
173	pccontext->private_clkdata = NULL;
174	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
175		list_del(&queue->qlist);
176	bitmap_free(queue->mask);
177	kfree(queue);
178	return 0;
179}
180
181static long ptp_clock_getcaps(struct ptp_clock *ptp, void __user *arg)
182{
183	struct ptp_clock_caps caps = {
184		.max_adj		= ptp->info->max_adj,
185		.n_alarm		= ptp->info->n_alarm,
186		.n_ext_ts		= ptp->info->n_ext_ts,
187		.n_per_out		= ptp->info->n_per_out,
188		.pps			= ptp->info->pps,
189		.n_pins			= ptp->info->n_pins,
190		.cross_timestamping	= ptp->info->getcrosststamp != NULL,
191		.adjust_phase		= ptp->info->adjphase != NULL &&
192					  ptp->info->getmaxphase != NULL,
193	};
194
195	if (caps.adjust_phase)
196		caps.max_phase_adj = ptp->info->getmaxphase(ptp->info);
197
198	return copy_to_user(arg, &caps, sizeof(caps)) ? -EFAULT : 0;
199}
200
201static long ptp_extts_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
202{
203	struct ptp_clock_request req = { .type = PTP_CLK_REQ_EXTTS };
204	struct ptp_clock_info *ops = ptp->info;
205	unsigned int supported_extts_flags;
206
207	if (copy_from_user(&req.extts, arg, sizeof(req.extts)))
208		return -EFAULT;
209
210	if (cmd == PTP_EXTTS_REQUEST2) {
211		/* Tell the drivers to check the flags carefully. */
212		req.extts.flags |= PTP_STRICT_FLAGS;
213		/* Make sure no reserved bit is set. */
214		if ((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
215		    req.extts.rsv[0] || req.extts.rsv[1])
216			return -EINVAL;
217
218		/* Ensure one of the rising/falling edge bits is set. */
219		if ((req.extts.flags & PTP_ENABLE_FEATURE) &&
220		    (req.extts.flags & PTP_EXTTS_EDGES) == 0)
221			return -EINVAL;
222	} else {
223		req.extts.flags &= PTP_EXTTS_V1_VALID_FLAGS;
224		memset(req.extts.rsv, 0, sizeof(req.extts.rsv));
225	}
226
227	if (req.extts.index >= ops->n_ext_ts)
228		return -EINVAL;
229
230	supported_extts_flags = ptp->info->supported_extts_flags;
231	/* The PTP_ENABLE_FEATURE flag is always supported. */
232	supported_extts_flags |= PTP_ENABLE_FEATURE;
233	/* If the driver does not support strictly checking flags, the
234	 * PTP_RISING_EDGE and PTP_FALLING_EDGE flags are merely hints
235	 * which are not enforced.
236	 */
237	if (!(supported_extts_flags & PTP_STRICT_FLAGS))
238		supported_extts_flags |= PTP_EXTTS_EDGES;
239	/* Reject unsupported flags */
240	if (req.extts.flags & ~supported_extts_flags)
241		return -EOPNOTSUPP;
242
243	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
244		return ops->enable(ops, &req, req.extts.flags & PTP_ENABLE_FEATURE ? 1 : 0);
245}
246
247static long ptp_perout_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
248{
249	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PEROUT };
250	struct ptp_perout_request *perout = &req.perout;
251	struct ptp_clock_info *ops = ptp->info;
252
253	if (copy_from_user(perout, arg, sizeof(*perout)))
254		return -EFAULT;
255
256	if (cmd == PTP_PEROUT_REQUEST2) {
257		if (perout->flags & ~PTP_PEROUT_VALID_FLAGS)
258			return -EINVAL;
259
260		/*
261		 * The "on" field has undefined meaning if
262		 * PTP_PEROUT_DUTY_CYCLE isn't set, we must still treat it
263		 * as reserved, which must be set to zero.
264		 */
265		if (!(perout->flags & PTP_PEROUT_DUTY_CYCLE) &&
266		    !mem_is_zero(perout->rsv, sizeof(perout->rsv)))
267			return -EINVAL;
268
269		if (perout->flags & PTP_PEROUT_DUTY_CYCLE) {
270			/* The duty cycle must be subunitary. */
271			if (perout->on.sec > perout->period.sec ||
272			    (perout->on.sec == perout->period.sec &&
273			     perout->on.nsec > perout->period.nsec))
274				return -ERANGE;
275		}
276
277		if (perout->flags & PTP_PEROUT_PHASE) {
278			/*
279			 * The phase should be specified modulo the period,
280			 * therefore anything equal or larger than 1 period
281			 * is invalid.
282			 */
283			if (perout->phase.sec > perout->period.sec ||
284			    (perout->phase.sec == perout->period.sec &&
285			     perout->phase.nsec >= perout->period.nsec))
286				return -ERANGE;
287		}
288	} else {
289		perout->flags &= PTP_PEROUT_V1_VALID_FLAGS;
290		memset(perout->rsv, 0, sizeof(perout->rsv));
291	}
292
293	if (perout->index >= ops->n_per_out)
294		return -EINVAL;
295	if (perout->flags & ~ops->supported_perout_flags)
296		return -EOPNOTSUPP;
297
298	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
299		return ops->enable(ops, &req, perout->period.sec || perout->period.nsec);
300}
301
302static long ptp_enable_pps(struct ptp_clock *ptp, bool enable)
303{
304	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
305	struct ptp_clock_info *ops = ptp->info;
306
307	if (!capable(CAP_SYS_TIME))
308		return -EPERM;
309
310	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
311		return ops->enable(ops, &req, enable);
312}
313
314typedef int (*ptp_crosststamp_fn)(struct ptp_clock_info *,
315				  struct system_device_crosststamp *);
316
317static long ptp_sys_offset_precise(struct ptp_clock *ptp, void __user *arg,
318				   ptp_crosststamp_fn crosststamp_fn)
319{
320	struct ptp_sys_offset_precise precise_offset;
321	struct system_device_crosststamp xtstamp;
322	struct timespec64 ts;
323	int err;
324
325	if (!crosststamp_fn)
326		return -EOPNOTSUPP;
327
328	err = crosststamp_fn(ptp->info, &xtstamp);
329	if (err)
330		return err;
331
332	memset(&precise_offset, 0, sizeof(precise_offset));
333	ts = ktime_to_timespec64(xtstamp.device);
334	precise_offset.device.sec = ts.tv_sec;
335	precise_offset.device.nsec = ts.tv_nsec;
336	ts = ktime_to_timespec64(xtstamp.sys_realtime);
337	precise_offset.sys_realtime.sec = ts.tv_sec;
338	precise_offset.sys_realtime.nsec = ts.tv_nsec;
339	ts = ktime_to_timespec64(xtstamp.sys_monoraw);
340	precise_offset.sys_monoraw.sec = ts.tv_sec;
341	precise_offset.sys_monoraw.nsec = ts.tv_nsec;
342
343	return copy_to_user(arg, &precise_offset, sizeof(precise_offset)) ? -EFAULT : 0;
344}
345
346typedef int (*ptp_gettimex_fn)(struct ptp_clock_info *,
347			       struct timespec64 *,
348			       struct ptp_system_timestamp *);
349
350static long ptp_sys_offset_extended(struct ptp_clock *ptp, void __user *arg,
351				    ptp_gettimex_fn gettimex_fn)
352{
353	struct ptp_sys_offset_extended *extoff __free(kfree) = NULL;
354	struct ptp_system_timestamp sts;
355
356	if (!gettimex_fn)
357		return -EOPNOTSUPP;
358
359	extoff = memdup_user(arg, sizeof(*extoff));
360	if (IS_ERR(extoff))
361		return PTR_ERR(extoff);
362
363	if (extoff->n_samples > PTP_MAX_SAMPLES || extoff->rsv[0] || extoff->rsv[1])
364		return -EINVAL;
365
366	switch (extoff->clockid) {
367	case CLOCK_REALTIME:
368	case CLOCK_MONOTONIC:
369	case CLOCK_MONOTONIC_RAW:
370		break;
371	case CLOCK_AUX ... CLOCK_AUX_LAST:
372		if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
373			break;
374		fallthrough;
375	default:
376		return -EINVAL;
377	}
378
379	sts.clockid = extoff->clockid;
380	for (unsigned int i = 0; i < extoff->n_samples; i++) {
381		struct timespec64 ts;
382		int err;
383
384		err = gettimex_fn(ptp->info, &ts, &sts);
385		if (err)
386			return err;
387
388		/* Filter out disabled or unavailable clocks */
389		if (sts.pre_ts.tv_sec < 0 || sts.post_ts.tv_sec < 0)
390			return -EINVAL;
391
392		extoff->ts[i][0].sec = sts.pre_ts.tv_sec;
393		extoff->ts[i][0].nsec = sts.pre_ts.tv_nsec;
394		extoff->ts[i][1].sec = ts.tv_sec;
395		extoff->ts[i][1].nsec = ts.tv_nsec;
396		extoff->ts[i][2].sec = sts.post_ts.tv_sec;
397		extoff->ts[i][2].nsec = sts.post_ts.tv_nsec;
398	}
399
400	return copy_to_user(arg, extoff, sizeof(*extoff)) ? -EFAULT : 0;
401}
402
403static long ptp_sys_offset(struct ptp_clock *ptp, void __user *arg)
404{
405	struct ptp_sys_offset *sysoff __free(kfree) = NULL;
406	struct ptp_clock_time *pct;
407	struct timespec64 ts;
408
409	sysoff = memdup_user(arg, sizeof(*sysoff));
410	if (IS_ERR(sysoff))
411		return PTR_ERR(sysoff);
412
413	if (sysoff->n_samples > PTP_MAX_SAMPLES)
414		return -EINVAL;
415
416	pct = &sysoff->ts[0];
417	for (unsigned int i = 0; i < sysoff->n_samples; i++) {
418		struct ptp_clock_info *ops = ptp->info;
419		int err;
420
421		ktime_get_real_ts64(&ts);
422		pct->sec = ts.tv_sec;
423		pct->nsec = ts.tv_nsec;
424		pct++;
425		if (ops->gettimex64)
426			err = ops->gettimex64(ops, &ts, NULL);
427		else
428			err = ops->gettime64(ops, &ts);
429		if (err)
430			return err;
431		pct->sec = ts.tv_sec;
432		pct->nsec = ts.tv_nsec;
433		pct++;
434	}
435	ktime_get_real_ts64(&ts);
436	pct->sec = ts.tv_sec;
437	pct->nsec = ts.tv_nsec;
438
439	return copy_to_user(arg, sysoff, sizeof(*sysoff)) ? -EFAULT : 0;
440}
441
442static long ptp_pin_getfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
443{
444	struct ptp_clock_info *ops = ptp->info;
445	struct ptp_pin_desc pd;
446
447	if (copy_from_user(&pd, arg, sizeof(pd)))
448		return -EFAULT;
449
450	if (cmd == PTP_PIN_GETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
451		return -EINVAL;
452
453	if (pd.index >= ops->n_pins)
454		return -EINVAL;
455
456	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
457		pd = ops->pin_config[array_index_nospec(pd.index, ops->n_pins)];
458
459	return copy_to_user(arg, &pd, sizeof(pd)) ? -EFAULT : 0;
460}
461
462static long ptp_pin_setfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
463{
464	struct ptp_clock_info *ops = ptp->info;
465	struct ptp_pin_desc pd;
466	unsigned int pin_index;
467
468	if (copy_from_user(&pd, arg, sizeof(pd)))
469		return -EFAULT;
470
471	if (cmd == PTP_PIN_SETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
472		return -EINVAL;
473
474	if (pd.index >= ops->n_pins)
475		return -EINVAL;
476
477	pin_index = array_index_nospec(pd.index, ops->n_pins);
478	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
479		return ptp_set_pinfunc(ptp, pin_index, pd.func, pd.chan);
480}
481
482static long ptp_mask_clear_all(struct timestamp_event_queue *tsevq)
483{
484	bitmap_clear(tsevq->mask, 0, PTP_MAX_CHANNELS);
485	return 0;
486}
487
488static long ptp_mask_en_single(struct timestamp_event_queue *tsevq, void __user *arg)
489{
490	unsigned int channel;
491
492	if (copy_from_user(&channel, arg, sizeof(channel)))
493		return -EFAULT;
494	if (channel >= PTP_MAX_CHANNELS)
495		return -EFAULT;
496	set_bit(channel, tsevq->mask);
497	return 0;
498}
499
500long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
501	       unsigned long arg)
502{
503	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
504	void __user *argptr;
505
506	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
507		arg = (unsigned long)compat_ptr(arg);
508	argptr = (void __force __user *)arg;
509
510	switch (cmd) {
511	case PTP_CLOCK_GETCAPS:
512	case PTP_CLOCK_GETCAPS2:
513		return ptp_clock_getcaps(ptp, argptr);
514
515	case PTP_EXTTS_REQUEST:
516	case PTP_EXTTS_REQUEST2:
517		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
518			return -EACCES;
519		return ptp_extts_request(ptp, cmd, argptr);
520
521	case PTP_PEROUT_REQUEST:
522	case PTP_PEROUT_REQUEST2:
523		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
524			return -EACCES;
525		return ptp_perout_request(ptp, cmd, argptr);
526
527	case PTP_ENABLE_PPS:
528	case PTP_ENABLE_PPS2:
529		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
530			return -EACCES;
531		return ptp_enable_pps(ptp, !!arg);
532
533	case PTP_SYS_OFFSET_PRECISE:
534	case PTP_SYS_OFFSET_PRECISE2:
535		return ptp_sys_offset_precise(ptp, argptr,
536					      ptp->info->getcrosststamp);
537
538	case PTP_SYS_OFFSET_EXTENDED:
539	case PTP_SYS_OFFSET_EXTENDED2:
540		return ptp_sys_offset_extended(ptp, argptr,
541					       ptp->info->gettimex64);
542
543	case PTP_SYS_OFFSET:
544	case PTP_SYS_OFFSET2:
545		return ptp_sys_offset(ptp, argptr);
546
547	case PTP_PIN_GETFUNC:
548	case PTP_PIN_GETFUNC2:
549		return ptp_pin_getfunc(ptp, cmd, argptr);
550
551	case PTP_PIN_SETFUNC:
552	case PTP_PIN_SETFUNC2:
553		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
554			return -EACCES;
555		return ptp_pin_setfunc(ptp, cmd, argptr);
556
557	case PTP_MASK_CLEAR_ALL:
558		return ptp_mask_clear_all(pccontext->private_clkdata);
559
560	case PTP_MASK_EN_SINGLE:
561		return ptp_mask_en_single(pccontext->private_clkdata, argptr);
562
563	case PTP_SYS_OFFSET_PRECISE_CYCLES:
564		if (!ptp->has_cycles)
565			return -EOPNOTSUPP;
566		return ptp_sys_offset_precise(ptp, argptr,
567					      ptp->info->getcrosscycles);
568
569	case PTP_SYS_OFFSET_EXTENDED_CYCLES:
570		if (!ptp->has_cycles)
571			return -EOPNOTSUPP;
572		return ptp_sys_offset_extended(ptp, argptr,
573					       ptp->info->getcyclesx64);
574	default:
575		return -ENOTTY;
576	}
577}
578
579__poll_t ptp_poll(struct posix_clock_context *pccontext, struct file *fp,
580		  poll_table *wait)
581{
582	struct ptp_clock *ptp =
583		container_of(pccontext->clk, struct ptp_clock, clock);
584	struct timestamp_event_queue *queue;
585
586	queue = pccontext->private_clkdata;
587	if (!queue)
588		return EPOLLERR;
589
590	poll_wait(fp, &ptp->tsev_wq, wait);
591
592	return queue_cnt(queue) ? EPOLLIN : 0;
593}
594
595#define EXTTS_BUFSIZE (PTP_BUF_TIMESTAMPS * sizeof(struct ptp_extts_event))
596
597ssize_t ptp_read(struct posix_clock_context *pccontext, uint rdflags,
598		 char __user *buf, size_t cnt)
599{
600	struct ptp_clock *ptp =	container_of(pccontext->clk, struct ptp_clock, clock);
601	struct timestamp_event_queue *queue;
602	struct ptp_extts_event *event;
603	ssize_t result;
604
605	queue = pccontext->private_clkdata;
606	if (!queue)
607		return -EINVAL;
608
609	if (cnt % sizeof(*event) != 0)
610		return -EINVAL;
611
612	if (cnt > EXTTS_BUFSIZE)
613		cnt = EXTTS_BUFSIZE;
614
615	if (wait_event_interruptible(ptp->tsev_wq, ptp->defunct || queue_cnt(queue)))
616		return -ERESTARTSYS;
617
618	if (ptp->defunct)
619		return -ENODEV;
620
621	event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
622	if (!event)
623		return -ENOMEM;
624
625	scoped_guard(spinlock_irq, &queue->lock) {
626		size_t qcnt = min((size_t)queue_cnt(queue), cnt / sizeof(*event));
627
628		for (size_t i = 0; i < qcnt; i++) {
629			event[i] = queue->buf[queue->head];
630			/* Paired with READ_ONCE() in queue_cnt() */
631			WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS);
632		}
633		cnt = qcnt * sizeof(*event);
634	}
635
636	result = cnt;
637	if (copy_to_user(buf, event, cnt))
638		result = -EFAULT;
639
640	kfree(event);
641	return result;
642}