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(ops: info, func: info->pin_config[i].func,
60 chan: 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(lock: &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(ops: 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(ops: info, func: pin2->func, chan: 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(objp: queue);
145 return -EINVAL;
146 }
147 bitmap_set(map: queue->mask, start: 0, PTP_MAX_CHANNELS);
148 spin_lock_init(&queue->lock);
149 scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
150 list_add_tail(new: &queue->qlist, head: &ptp->tsevqs);
151 pccontext->private_clkdata = queue;
152
153 /* Debugfs contents */
154 sprintf(buf: debugfsname, fmt: "0x%p", queue);
155 queue->debugfs_instance =
156 debugfs_create_dir(name: debugfsname, parent: 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(name: "mask", mode: 0444, parent: queue->debugfs_instance,
161 array: &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(dentry: queue->debugfs_instance);
173 pccontext->private_clkdata = NULL;
174 scoped_guard(spinlock_irq, &ptp->tsevqs_lock)
175 list_del(entry: &queue->qlist);
176 bitmap_free(bitmap: queue->mask);
177 kfree(objp: 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(to: arg, from: &caps, n: 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(to: &req.extts, from: arg, n: 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(to: perout, from: arg, n: 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(s: perout->rsv, n: 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(to: arg, from: &precise_offset, n: 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(ptr: extoff))
361 return PTR_ERR(ptr: 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(to: arg, from: extoff, n: 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(ptr: sysoff))
411 return PTR_ERR(ptr: 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(tv: &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(tv: &ts);
436 pct->sec = ts.tv_sec;
437 pct->nsec = ts.tv_nsec;
438
439 return copy_to_user(to: arg, from: sysoff, n: 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(to: &pd, from: arg, n: sizeof(pd)))
448 return -EFAULT;
449
450 if (cmd == PTP_PIN_GETFUNC2 && !mem_is_zero(s: pd.rsv, n: 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(to: arg, from: &pd, n: 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(to: &pd, from: arg, n: sizeof(pd)))
469 return -EFAULT;
470
471 if (cmd == PTP_PIN_SETFUNC2 && !mem_is_zero(s: pd.rsv, n: 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: pin_index, func: pd.func, chan: pd.chan);
480}
481
482static long ptp_mask_clear_all(struct timestamp_event_queue *tsevq)
483{
484 bitmap_clear(map: tsevq->mask, start: 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(to: &channel, from: arg, n: sizeof(channel)))
493 return -EFAULT;
494 if (channel >= PTP_MAX_CHANNELS)
495 return -EFAULT;
496 set_bit(nr: channel, addr: 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(uptr: 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, arg: 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, arg: 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, arg: 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, enable: !!arg);
532
533 case PTP_SYS_OFFSET_PRECISE:
534 case PTP_SYS_OFFSET_PRECISE2:
535 return ptp_sys_offset_precise(ptp, arg: argptr,
536 crosststamp_fn: ptp->info->getcrosststamp);
537
538 case PTP_SYS_OFFSET_EXTENDED:
539 case PTP_SYS_OFFSET_EXTENDED2:
540 return ptp_sys_offset_extended(ptp, arg: argptr,
541 gettimex_fn: ptp->info->gettimex64);
542
543 case PTP_SYS_OFFSET:
544 case PTP_SYS_OFFSET2:
545 return ptp_sys_offset(ptp, arg: argptr);
546
547 case PTP_PIN_GETFUNC:
548 case PTP_PIN_GETFUNC2:
549 return ptp_pin_getfunc(ptp, cmd, arg: 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, arg: argptr);
556
557 case PTP_MASK_CLEAR_ALL:
558 return ptp_mask_clear_all(tsevq: pccontext->private_clkdata);
559
560 case PTP_MASK_EN_SINGLE:
561 return ptp_mask_en_single(tsevq: pccontext->private_clkdata, arg: argptr);
562
563 case PTP_SYS_OFFSET_PRECISE_CYCLES:
564 if (!ptp->has_cycles)
565 return -EOPNOTSUPP;
566 return ptp_sys_offset_precise(ptp, arg: argptr,
567 crosststamp_fn: 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, arg: argptr,
573 gettimex_fn: 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(filp: fp, wait_address: &ptp->tsev_wq, p: wait);
591
592 return queue_cnt(q: 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(to: buf, from: event, n: cnt))
638 result = -EFAULT;
639
640 kfree(objp: event);
641 return result;
642}
643

source code of linux/drivers/ptp/ptp_chardev.c