xref: /linux/drivers/ptp/ptp_chardev.c (revision fc3a2810412c163b5df1b377d332e048860f45db)
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 
20 static 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 
50 int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
51 		    enum ptp_pin_function func, unsigned int chan)
52 {
53 	struct ptp_clock_info *info = ptp->info;
54 	struct ptp_pin_desc *pin1 = NULL, *pin2 = &info->pin_config[pin];
55 	unsigned int i;
56 
57 	/* Check to see if any other pin previously had this function. */
58 	for (i = 0; i < info->n_pins; i++) {
59 		if (info->pin_config[i].func == func &&
60 		    info->pin_config[i].chan == chan) {
61 			pin1 = &info->pin_config[i];
62 			break;
63 		}
64 	}
65 	if (pin1 && i == pin)
66 		return 0;
67 
68 	/* Check the desired function and channel. */
69 	switch (func) {
70 	case PTP_PF_NONE:
71 		break;
72 	case PTP_PF_EXTTS:
73 		if (chan >= info->n_ext_ts)
74 			return -EINVAL;
75 		break;
76 	case PTP_PF_PEROUT:
77 		if (chan >= info->n_per_out)
78 			return -EINVAL;
79 		break;
80 	case PTP_PF_PHYSYNC:
81 		if (chan != 0)
82 			return -EINVAL;
83 		break;
84 	default:
85 		return -EINVAL;
86 	}
87 
88 	if (info->verify(info, pin, func, chan)) {
89 		pr_err("driver cannot use function %u and channel %u on pin %u\n",
90 		       func, chan, pin);
91 		return -EOPNOTSUPP;
92 	}
93 
94 	/* Disable whatever function was previously assigned. */
95 	if (pin1) {
96 		ptp_disable_pinfunc(info, func, chan);
97 		pin1->func = PTP_PF_NONE;
98 		pin1->chan = 0;
99 	}
100 	ptp_disable_pinfunc(info, pin2->func, pin2->chan);
101 	pin2->func = func;
102 	pin2->chan = chan;
103 
104 	return 0;
105 }
106 
107 int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
108 {
109 	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
110 	struct timestamp_event_queue *queue;
111 	char debugfsname[32];
112 
113 	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
114 	if (!queue)
115 		return -EINVAL;
116 	queue->mask = bitmap_alloc(PTP_MAX_CHANNELS, GFP_KERNEL);
117 	if (!queue->mask) {
118 		kfree(queue);
119 		return -EINVAL;
120 	}
121 	bitmap_set(queue->mask, 0, PTP_MAX_CHANNELS);
122 	spin_lock_init(&queue->lock);
123 	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
124 		list_add_tail(&queue->qlist, &ptp->tsevqs);
125 	pccontext->private_clkdata = queue;
126 
127 	/* Debugfs contents */
128 	sprintf(debugfsname, "0x%p", queue);
129 	queue->debugfs_instance =
130 		debugfs_create_dir(debugfsname, ptp->debugfs_root);
131 	queue->dfs_bitmap.array = (u32 *)queue->mask;
132 	queue->dfs_bitmap.n_elements =
133 		DIV_ROUND_UP(PTP_MAX_CHANNELS, BITS_PER_BYTE * sizeof(u32));
134 	debugfs_create_u32_array("mask", 0444, queue->debugfs_instance,
135 				 &queue->dfs_bitmap);
136 
137 	return 0;
138 }
139 
140 int ptp_release(struct posix_clock_context *pccontext)
141 {
142 	struct timestamp_event_queue *queue = pccontext->private_clkdata;
143 	struct ptp_clock *ptp =
144 		container_of(pccontext->clk, struct ptp_clock, clock);
145 
146 	debugfs_remove(queue->debugfs_instance);
147 	pccontext->private_clkdata = NULL;
148 	scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
149 		list_del(&queue->qlist);
150 	bitmap_free(queue->mask);
151 	kfree(queue);
152 	return 0;
153 }
154 
155 static long ptp_clock_getcaps(struct ptp_clock *ptp, void __user *arg)
156 {
157 	struct ptp_clock_caps caps = {
158 		.max_adj		= ptp->info->max_adj,
159 		.n_alarm		= ptp->info->n_alarm,
160 		.n_ext_ts		= ptp->info->n_ext_ts,
161 		.n_per_out		= ptp->info->n_per_out,
162 		.pps			= ptp->info->pps,
163 		.n_pins			= ptp->info->n_pins,
164 		.cross_timestamping	= ptp->info->getcrosststamp != NULL,
165 		.adjust_phase		= ptp->info->adjphase != NULL &&
166 					  ptp->info->getmaxphase != NULL,
167 	};
168 
169 	if (caps.adjust_phase)
170 		caps.max_phase_adj = ptp->info->getmaxphase(ptp->info);
171 
172 	return copy_to_user(arg, &caps, sizeof(caps)) ? -EFAULT : 0;
173 }
174 
175 static long ptp_extts_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
176 {
177 	struct ptp_clock_request req = { .type = PTP_CLK_REQ_EXTTS };
178 	struct ptp_clock_info *ops = ptp->info;
179 	unsigned int supported_extts_flags;
180 
181 	if (copy_from_user(&req.extts, arg, sizeof(req.extts)))
182 		return -EFAULT;
183 
184 	if (cmd == PTP_EXTTS_REQUEST2) {
185 		/* Tell the drivers to check the flags carefully. */
186 		req.extts.flags |= PTP_STRICT_FLAGS;
187 		/* Make sure no reserved bit is set. */
188 		if ((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
189 		    req.extts.rsv[0] || req.extts.rsv[1])
190 			return -EINVAL;
191 
192 		/* Ensure one of the rising/falling edge bits is set. */
193 		if ((req.extts.flags & PTP_ENABLE_FEATURE) &&
194 		    (req.extts.flags & PTP_EXTTS_EDGES) == 0)
195 			return -EINVAL;
196 	} else {
197 		req.extts.flags &= PTP_EXTTS_V1_VALID_FLAGS;
198 		memset(req.extts.rsv, 0, sizeof(req.extts.rsv));
199 	}
200 
201 	if (req.extts.index >= ops->n_ext_ts)
202 		return -EINVAL;
203 
204 	supported_extts_flags = ptp->info->supported_extts_flags;
205 	/* The PTP_ENABLE_FEATURE flag is always supported. */
206 	supported_extts_flags |= PTP_ENABLE_FEATURE;
207 	/* If the driver does not support strictly checking flags, the
208 	 * PTP_RISING_EDGE and PTP_FALLING_EDGE flags are merely hints
209 	 * which are not enforced.
210 	 */
211 	if (!(supported_extts_flags & PTP_STRICT_FLAGS))
212 		supported_extts_flags |= PTP_EXTTS_EDGES;
213 	/* Reject unsupported flags */
214 	if (req.extts.flags & ~supported_extts_flags)
215 		return -EOPNOTSUPP;
216 
217 	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
218 		return ops->enable(ops, &req, req.extts.flags & PTP_ENABLE_FEATURE ? 1 : 0);
219 }
220 
221 static long ptp_perout_request(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
222 {
223 	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PEROUT };
224 	struct ptp_perout_request *perout = &req.perout;
225 	struct ptp_clock_info *ops = ptp->info;
226 
227 	if (copy_from_user(perout, arg, sizeof(*perout)))
228 		return -EFAULT;
229 
230 	if (cmd == PTP_PEROUT_REQUEST2) {
231 		if (perout->flags & ~PTP_PEROUT_VALID_FLAGS)
232 			return -EINVAL;
233 
234 		/*
235 		 * The "on" field has undefined meaning if
236 		 * PTP_PEROUT_DUTY_CYCLE isn't set, we must still treat it
237 		 * as reserved, which must be set to zero.
238 		 */
239 		if (!(perout->flags & PTP_PEROUT_DUTY_CYCLE) &&
240 		    !mem_is_zero(perout->rsv, sizeof(perout->rsv)))
241 			return -EINVAL;
242 
243 		if (perout->flags & PTP_PEROUT_DUTY_CYCLE) {
244 			/* The duty cycle must be subunitary. */
245 			if (perout->on.sec > perout->period.sec ||
246 			    (perout->on.sec == perout->period.sec &&
247 			     perout->on.nsec > perout->period.nsec))
248 				return -ERANGE;
249 		}
250 
251 		if (perout->flags & PTP_PEROUT_PHASE) {
252 			/*
253 			 * The phase should be specified modulo the period,
254 			 * therefore anything equal or larger than 1 period
255 			 * is invalid.
256 			 */
257 			if (perout->phase.sec > perout->period.sec ||
258 			    (perout->phase.sec == perout->period.sec &&
259 			     perout->phase.nsec >= perout->period.nsec))
260 				return -ERANGE;
261 		}
262 	} else {
263 		perout->flags &= PTP_PEROUT_V1_VALID_FLAGS;
264 		memset(perout->rsv, 0, sizeof(perout->rsv));
265 	}
266 
267 	if (perout->index >= ops->n_per_out)
268 		return -EINVAL;
269 	if (perout->flags & ~ops->supported_perout_flags)
270 		return -EOPNOTSUPP;
271 
272 	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
273 		return ops->enable(ops, &req, perout->period.sec || perout->period.nsec);
274 }
275 
276 static long ptp_enable_pps(struct ptp_clock *ptp, bool enable)
277 {
278 	struct ptp_clock_request req = { .type = PTP_CLK_REQ_PPS };
279 	struct ptp_clock_info *ops = ptp->info;
280 
281 	if (!capable(CAP_SYS_TIME))
282 		return -EPERM;
283 
284 	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
285 		return ops->enable(ops, &req, enable);
286 }
287 
288 typedef int (*ptp_crosststamp_fn)(struct ptp_clock_info *,
289 				  struct system_device_crosststamp *);
290 
291 static long ptp_sys_offset_precise(struct ptp_clock *ptp, void __user *arg,
292 				   ptp_crosststamp_fn crosststamp_fn)
293 {
294 	struct ptp_sys_offset_precise precise_offset;
295 	struct system_device_crosststamp xtstamp;
296 	struct timespec64 ts;
297 	int err;
298 
299 	if (!crosststamp_fn)
300 		return -EOPNOTSUPP;
301 
302 	err = crosststamp_fn(ptp->info, &xtstamp);
303 	if (err)
304 		return err;
305 
306 	memset(&precise_offset, 0, sizeof(precise_offset));
307 	ts = ktime_to_timespec64(xtstamp.device);
308 	precise_offset.device.sec = ts.tv_sec;
309 	precise_offset.device.nsec = ts.tv_nsec;
310 	ts = ktime_to_timespec64(xtstamp.sys_realtime);
311 	precise_offset.sys_realtime.sec = ts.tv_sec;
312 	precise_offset.sys_realtime.nsec = ts.tv_nsec;
313 	ts = ktime_to_timespec64(xtstamp.sys_monoraw);
314 	precise_offset.sys_monoraw.sec = ts.tv_sec;
315 	precise_offset.sys_monoraw.nsec = ts.tv_nsec;
316 
317 	return copy_to_user(arg, &precise_offset, sizeof(precise_offset)) ? -EFAULT : 0;
318 }
319 
320 typedef int (*ptp_gettimex_fn)(struct ptp_clock_info *,
321 			       struct timespec64 *,
322 			       struct ptp_system_timestamp *);
323 
324 static long ptp_sys_offset_extended(struct ptp_clock *ptp, void __user *arg,
325 				    ptp_gettimex_fn gettimex_fn)
326 {
327 	struct ptp_sys_offset_extended *extoff __free(kfree) = NULL;
328 	struct ptp_system_timestamp sts;
329 
330 	if (!gettimex_fn)
331 		return -EOPNOTSUPP;
332 
333 	extoff = memdup_user(arg, sizeof(*extoff));
334 	if (IS_ERR(extoff))
335 		return PTR_ERR(extoff);
336 
337 	if (extoff->n_samples > PTP_MAX_SAMPLES || extoff->rsv[0] || extoff->rsv[1])
338 		return -EINVAL;
339 
340 	switch (extoff->clockid) {
341 	case CLOCK_REALTIME:
342 	case CLOCK_MONOTONIC:
343 	case CLOCK_MONOTONIC_RAW:
344 		break;
345 	case CLOCK_AUX ... CLOCK_AUX_LAST:
346 		if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
347 			break;
348 		fallthrough;
349 	default:
350 		return -EINVAL;
351 	}
352 
353 	sts.clockid = extoff->clockid;
354 	for (unsigned int i = 0; i < extoff->n_samples; i++) {
355 		struct timespec64 ts;
356 		int err;
357 
358 		err = gettimex_fn(ptp->info, &ts, &sts);
359 		if (err)
360 			return err;
361 
362 		/* Filter out disabled or unavailable clocks */
363 		if (sts.pre_ts.tv_sec < 0 || sts.post_ts.tv_sec < 0)
364 			return -EINVAL;
365 
366 		extoff->ts[i][0].sec = sts.pre_ts.tv_sec;
367 		extoff->ts[i][0].nsec = sts.pre_ts.tv_nsec;
368 		extoff->ts[i][1].sec = ts.tv_sec;
369 		extoff->ts[i][1].nsec = ts.tv_nsec;
370 		extoff->ts[i][2].sec = sts.post_ts.tv_sec;
371 		extoff->ts[i][2].nsec = sts.post_ts.tv_nsec;
372 	}
373 
374 	return copy_to_user(arg, extoff, sizeof(*extoff)) ? -EFAULT : 0;
375 }
376 
377 static long ptp_sys_offset(struct ptp_clock *ptp, void __user *arg)
378 {
379 	struct ptp_sys_offset *sysoff __free(kfree) = NULL;
380 	struct ptp_clock_time *pct;
381 	struct timespec64 ts;
382 
383 	sysoff = memdup_user(arg, sizeof(*sysoff));
384 	if (IS_ERR(sysoff))
385 		return PTR_ERR(sysoff);
386 
387 	if (sysoff->n_samples > PTP_MAX_SAMPLES)
388 		return -EINVAL;
389 
390 	pct = &sysoff->ts[0];
391 	for (unsigned int i = 0; i < sysoff->n_samples; i++) {
392 		struct ptp_clock_info *ops = ptp->info;
393 		int err;
394 
395 		ktime_get_real_ts64(&ts);
396 		pct->sec = ts.tv_sec;
397 		pct->nsec = ts.tv_nsec;
398 		pct++;
399 		if (ops->gettimex64)
400 			err = ops->gettimex64(ops, &ts, NULL);
401 		else
402 			err = ops->gettime64(ops, &ts);
403 		if (err)
404 			return err;
405 		pct->sec = ts.tv_sec;
406 		pct->nsec = ts.tv_nsec;
407 		pct++;
408 	}
409 	ktime_get_real_ts64(&ts);
410 	pct->sec = ts.tv_sec;
411 	pct->nsec = ts.tv_nsec;
412 
413 	return copy_to_user(arg, sysoff, sizeof(*sysoff)) ? -EFAULT : 0;
414 }
415 
416 static long ptp_pin_getfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
417 {
418 	struct ptp_clock_info *ops = ptp->info;
419 	struct ptp_pin_desc pd;
420 
421 	if (copy_from_user(&pd, arg, sizeof(pd)))
422 		return -EFAULT;
423 
424 	if (cmd == PTP_PIN_GETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
425 		return -EINVAL;
426 
427 	if (pd.index >= ops->n_pins)
428 		return -EINVAL;
429 
430 	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
431 		pd = ops->pin_config[array_index_nospec(pd.index, ops->n_pins)];
432 
433 	return copy_to_user(arg, &pd, sizeof(pd)) ? -EFAULT : 0;
434 }
435 
436 static long ptp_pin_setfunc(struct ptp_clock *ptp, unsigned int cmd, void __user *arg)
437 {
438 	struct ptp_clock_info *ops = ptp->info;
439 	struct ptp_pin_desc pd;
440 	unsigned int pin_index;
441 
442 	if (copy_from_user(&pd, arg, sizeof(pd)))
443 		return -EFAULT;
444 
445 	if (cmd == PTP_PIN_SETFUNC2 && !mem_is_zero(pd.rsv, sizeof(pd.rsv)))
446 		return -EINVAL;
447 
448 	if (pd.index >= ops->n_pins)
449 		return -EINVAL;
450 
451 	pin_index = array_index_nospec(pd.index, ops->n_pins);
452 	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &ptp->pincfg_mux)
453 		return ptp_set_pinfunc(ptp, pin_index, pd.func, pd.chan);
454 }
455 
456 static long ptp_mask_clear_all(struct timestamp_event_queue *tsevq)
457 {
458 	bitmap_clear(tsevq->mask, 0, PTP_MAX_CHANNELS);
459 	return 0;
460 }
461 
462 static long ptp_mask_en_single(struct timestamp_event_queue *tsevq, void __user *arg)
463 {
464 	unsigned int channel;
465 
466 	if (copy_from_user(&channel, arg, sizeof(channel)))
467 		return -EFAULT;
468 	if (channel >= PTP_MAX_CHANNELS)
469 		return -EFAULT;
470 	set_bit(channel, tsevq->mask);
471 	return 0;
472 }
473 
474 long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
475 	       unsigned long arg)
476 {
477 	struct ptp_clock *ptp = container_of(pccontext->clk, struct ptp_clock, clock);
478 	void __user *argptr;
479 
480 	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
481 		arg = (unsigned long)compat_ptr(arg);
482 	argptr = (void __force __user *)arg;
483 
484 	switch (cmd) {
485 	case PTP_CLOCK_GETCAPS:
486 	case PTP_CLOCK_GETCAPS2:
487 		return ptp_clock_getcaps(ptp, argptr);
488 
489 	case PTP_EXTTS_REQUEST:
490 	case PTP_EXTTS_REQUEST2:
491 		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
492 			return -EACCES;
493 		return ptp_extts_request(ptp, cmd, argptr);
494 
495 	case PTP_PEROUT_REQUEST:
496 	case PTP_PEROUT_REQUEST2:
497 		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
498 			return -EACCES;
499 		return ptp_perout_request(ptp, cmd, argptr);
500 
501 	case PTP_ENABLE_PPS:
502 	case PTP_ENABLE_PPS2:
503 		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
504 			return -EACCES;
505 		return ptp_enable_pps(ptp, !!arg);
506 
507 	case PTP_SYS_OFFSET_PRECISE:
508 	case PTP_SYS_OFFSET_PRECISE2:
509 		return ptp_sys_offset_precise(ptp, argptr,
510 					      ptp->info->getcrosststamp);
511 
512 	case PTP_SYS_OFFSET_EXTENDED:
513 	case PTP_SYS_OFFSET_EXTENDED2:
514 		return ptp_sys_offset_extended(ptp, argptr,
515 					       ptp->info->gettimex64);
516 
517 	case PTP_SYS_OFFSET:
518 	case PTP_SYS_OFFSET2:
519 		return ptp_sys_offset(ptp, argptr);
520 
521 	case PTP_PIN_GETFUNC:
522 	case PTP_PIN_GETFUNC2:
523 		return ptp_pin_getfunc(ptp, cmd, argptr);
524 
525 	case PTP_PIN_SETFUNC:
526 	case PTP_PIN_SETFUNC2:
527 		if ((pccontext->fp->f_mode & FMODE_WRITE) == 0)
528 			return -EACCES;
529 		return ptp_pin_setfunc(ptp, cmd, argptr);
530 
531 	case PTP_MASK_CLEAR_ALL:
532 		return ptp_mask_clear_all(pccontext->private_clkdata);
533 
534 	case PTP_MASK_EN_SINGLE:
535 		return ptp_mask_en_single(pccontext->private_clkdata, argptr);
536 
537 	case PTP_SYS_OFFSET_PRECISE_CYCLES:
538 		return ptp_sys_offset_precise(ptp, argptr,
539 					      ptp->info->getcrosscycles);
540 
541 	case PTP_SYS_OFFSET_EXTENDED_CYCLES:
542 		return ptp_sys_offset_extended(ptp, argptr,
543 					       ptp->info->getcyclesx64);
544 	default:
545 		return -ENOTTY;
546 	}
547 }
548 
549 __poll_t ptp_poll(struct posix_clock_context *pccontext, struct file *fp,
550 		  poll_table *wait)
551 {
552 	struct ptp_clock *ptp =
553 		container_of(pccontext->clk, struct ptp_clock, clock);
554 	struct timestamp_event_queue *queue;
555 
556 	queue = pccontext->private_clkdata;
557 	if (!queue)
558 		return EPOLLERR;
559 
560 	poll_wait(fp, &ptp->tsev_wq, wait);
561 
562 	return queue_cnt(queue) ? EPOLLIN : 0;
563 }
564 
565 #define EXTTS_BUFSIZE (PTP_BUF_TIMESTAMPS * sizeof(struct ptp_extts_event))
566 
567 ssize_t ptp_read(struct posix_clock_context *pccontext, uint rdflags,
568 		 char __user *buf, size_t cnt)
569 {
570 	struct ptp_clock *ptp =	container_of(pccontext->clk, struct ptp_clock, clock);
571 	struct timestamp_event_queue *queue;
572 	struct ptp_extts_event *event;
573 	ssize_t result;
574 
575 	queue = pccontext->private_clkdata;
576 	if (!queue)
577 		return -EINVAL;
578 
579 	if (cnt % sizeof(*event) != 0)
580 		return -EINVAL;
581 
582 	if (cnt > EXTTS_BUFSIZE)
583 		cnt = EXTTS_BUFSIZE;
584 
585 	if (wait_event_interruptible(ptp->tsev_wq, ptp->defunct || queue_cnt(queue)))
586 		return -ERESTARTSYS;
587 
588 	if (ptp->defunct)
589 		return -ENODEV;
590 
591 	event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
592 	if (!event)
593 		return -ENOMEM;
594 
595 	scoped_guard(spinlock_irq, &queue->lock) {
596 		size_t qcnt = min((size_t)queue_cnt(queue), cnt / sizeof(*event));
597 
598 		for (size_t i = 0; i < qcnt; i++) {
599 			event[i] = queue->buf[queue->head];
600 			/* Paired with READ_ONCE() in queue_cnt() */
601 			WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS);
602 		}
603 		cnt = qcnt * sizeof(*event);
604 	}
605 
606 	result = cnt;
607 	if (copy_to_user(buf, event, cnt))
608 		result = -EFAULT;
609 
610 	kfree(event);
611 	return result;
612 }
613