Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
/*
 * NFC hardware simulation driver
 * Copyright (c) 2013, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.
 *
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/nfc.h>
#include <net/nfc/nfc.h>

#define DEV_ERR(_dev, fmt, args...) nfc_err(&_dev->nfc_dev->dev, \
						"%s: " fmt, __func__, ## args)

#define DEV_DBG(_dev, fmt, args...) dev_dbg(&_dev->nfc_dev->dev, \
						"%s: " fmt, __func__, ## args)

#define NFCSIM_VERSION "0.1"

#define NFCSIM_POLL_NONE	0
#define NFCSIM_POLL_INITIATOR	1
#define NFCSIM_POLL_TARGET	2
#define NFCSIM_POLL_DUAL	(NFCSIM_POLL_INITIATOR | NFCSIM_POLL_TARGET)

struct nfcsim {
	struct nfc_dev *nfc_dev;

	struct mutex lock;

	struct delayed_work recv_work;

	struct sk_buff *clone_skb;

	struct delayed_work poll_work;
	u8 polling_mode;
	u8 curr_polling_mode;

	u8 shutting_down;

	u8 up;

	u8 initiator;

	data_exchange_cb_t cb;
	void *cb_context;

	struct nfcsim *peer_dev;
};

static struct nfcsim *dev0;
static struct nfcsim *dev1;

static struct workqueue_struct *wq;

static void nfcsim_cleanup_dev(struct nfcsim *dev, u8 shutdown)
{
	DEV_DBG(dev, "shutdown=%d\n", shutdown);

	mutex_lock(&dev->lock);

	dev->polling_mode = NFCSIM_POLL_NONE;
	dev->shutting_down = shutdown;
	dev->cb = NULL;
	dev_kfree_skb(dev->clone_skb);
	dev->clone_skb = NULL;

	mutex_unlock(&dev->lock);

	cancel_delayed_work_sync(&dev->poll_work);
	cancel_delayed_work_sync(&dev->recv_work);
}

static int nfcsim_target_found(struct nfcsim *dev)
{
	struct nfc_target nfc_tgt;

	DEV_DBG(dev, "\n");

	memset(&nfc_tgt, 0, sizeof(struct nfc_target));

	nfc_tgt.supported_protocols = NFC_PROTO_NFC_DEP_MASK;
	nfc_targets_found(dev->nfc_dev, &nfc_tgt, 1);

	return 0;
}

static int nfcsim_dev_up(struct nfc_dev *nfc_dev)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "\n");

	mutex_lock(&dev->lock);

	dev->up = 1;

	mutex_unlock(&dev->lock);

	return 0;
}

static int nfcsim_dev_down(struct nfc_dev *nfc_dev)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "\n");

	mutex_lock(&dev->lock);

	dev->up = 0;

	mutex_unlock(&dev->lock);

	return 0;
}

static int nfcsim_dep_link_up(struct nfc_dev *nfc_dev,
			      struct nfc_target *target,
			      u8 comm_mode, u8 *gb, size_t gb_len)
{
	int rc;
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);
	struct nfcsim *peer = dev->peer_dev;
	u8 *remote_gb;
	size_t remote_gb_len;

	DEV_DBG(dev, "target_idx: %d, comm_mode: %d\n", target->idx, comm_mode);

	mutex_lock(&peer->lock);

	nfc_tm_activated(peer->nfc_dev, NFC_PROTO_NFC_DEP_MASK,
			 NFC_COMM_ACTIVE, gb, gb_len);

	remote_gb = nfc_get_local_general_bytes(peer->nfc_dev, &remote_gb_len);
	if (!remote_gb) {
		DEV_ERR(peer, "Can't get remote general bytes\n");

		mutex_unlock(&peer->lock);
		return -EINVAL;
	}

	mutex_unlock(&peer->lock);

	mutex_lock(&dev->lock);

	rc = nfc_set_remote_general_bytes(nfc_dev, remote_gb, remote_gb_len);
	if (rc) {
		DEV_ERR(dev, "Can't set remote general bytes\n");
		mutex_unlock(&dev->lock);
		return rc;
	}

	rc = nfc_dep_link_is_up(nfc_dev, target->idx, NFC_COMM_ACTIVE,
				NFC_RF_INITIATOR);

	mutex_unlock(&dev->lock);

	return rc;
}

static int nfcsim_dep_link_down(struct nfc_dev *nfc_dev)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "\n");

	nfcsim_cleanup_dev(dev, 0);

	return 0;
}

static int nfcsim_start_poll(struct nfc_dev *nfc_dev,
			     u32 im_protocols, u32 tm_protocols)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);
	int rc;

	mutex_lock(&dev->lock);

	if (dev->polling_mode != NFCSIM_POLL_NONE) {
		DEV_ERR(dev, "Already in polling mode\n");
		rc = -EBUSY;
		goto exit;
	}

	if (im_protocols & NFC_PROTO_NFC_DEP_MASK)
		dev->polling_mode |= NFCSIM_POLL_INITIATOR;

	if (tm_protocols & NFC_PROTO_NFC_DEP_MASK)
		dev->polling_mode |= NFCSIM_POLL_TARGET;

	if (dev->polling_mode == NFCSIM_POLL_NONE) {
		DEV_ERR(dev, "Unsupported polling mode\n");
		rc = -EINVAL;
		goto exit;
	}

	dev->initiator = 0;
	dev->curr_polling_mode = NFCSIM_POLL_NONE;

	queue_delayed_work(wq, &dev->poll_work, 0);

	DEV_DBG(dev, "Start polling: im: 0x%X, tm: 0x%X\n", im_protocols,
		tm_protocols);

	rc = 0;
exit:
	mutex_unlock(&dev->lock);

	return rc;
}

static void nfcsim_stop_poll(struct nfc_dev *nfc_dev)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "Stop poll\n");

	mutex_lock(&dev->lock);

	dev->polling_mode = NFCSIM_POLL_NONE;

	mutex_unlock(&dev->lock);

	cancel_delayed_work_sync(&dev->poll_work);
}

static int nfcsim_activate_target(struct nfc_dev *nfc_dev,
				  struct nfc_target *target, u32 protocol)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "\n");

	return -ENOTSUPP;
}

static void nfcsim_deactivate_target(struct nfc_dev *nfc_dev,
				     struct nfc_target *target)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);

	DEV_DBG(dev, "\n");
}

static void nfcsim_wq_recv(struct work_struct *work)
{
	struct nfcsim *dev = container_of(work, struct nfcsim,
					  recv_work.work);

	mutex_lock(&dev->lock);

	if (dev->shutting_down || !dev->up || !dev->clone_skb) {
		dev_kfree_skb(dev->clone_skb);
		goto exit;
	}

	if (dev->initiator) {
		if (!dev->cb) {
			DEV_ERR(dev, "Null recv callback\n");
			dev_kfree_skb(dev->clone_skb);
			goto exit;
		}

		dev->cb(dev->cb_context, dev->clone_skb, 0);
		dev->cb = NULL;
	} else {
		nfc_tm_data_received(dev->nfc_dev, dev->clone_skb);
	}

exit:
	dev->clone_skb = NULL;

	mutex_unlock(&dev->lock);
}

static int nfcsim_tx(struct nfc_dev *nfc_dev, struct nfc_target *target,
		     struct sk_buff *skb, data_exchange_cb_t cb,
		     void *cb_context)
{
	struct nfcsim *dev = nfc_get_drvdata(nfc_dev);
	struct nfcsim *peer = dev->peer_dev;
	int err;

	mutex_lock(&dev->lock);

	if (dev->shutting_down || !dev->up) {
		mutex_unlock(&dev->lock);
		err = -ENODEV;
		goto exit;
	}

	dev->cb = cb;
	dev->cb_context = cb_context;

	mutex_unlock(&dev->lock);

	mutex_lock(&peer->lock);

	peer->clone_skb = skb_clone(skb, GFP_KERNEL);

	if (!peer->clone_skb) {
		DEV_ERR(dev, "skb_clone failed\n");
		mutex_unlock(&peer->lock);
		err = -ENOMEM;
		goto exit;
	}

	/* This simulates an arbitrary transmission delay between the 2 devices.
	 * If packet transmission occurs immediately between them, we have a
	 * non-stop flow of several tens of thousands SYMM packets per second
	 * and a burning cpu.
	 *
	 * TODO: Add support for a sysfs entry to control this delay.
	 */
	queue_delayed_work(wq, &peer->recv_work, msecs_to_jiffies(5));

	mutex_unlock(&peer->lock);

	err = 0;
exit:
	dev_kfree_skb(skb);

	return err;
}

static int nfcsim_im_transceive(struct nfc_dev *nfc_dev,
				struct nfc_target *target, struct sk_buff *skb,
				data_exchange_cb_t cb, void *cb_context)
{
	return nfcsim_tx(nfc_dev, target, skb, cb, cb_context);
}

static int nfcsim_tm_send(struct nfc_dev *nfc_dev, struct sk_buff *skb)
{
	return nfcsim_tx(nfc_dev, NULL, skb, NULL, NULL);
}

static struct nfc_ops nfcsim_nfc_ops = {
	.dev_up = nfcsim_dev_up,
	.dev_down = nfcsim_dev_down,
	.dep_link_up = nfcsim_dep_link_up,
	.dep_link_down = nfcsim_dep_link_down,
	.start_poll = nfcsim_start_poll,
	.stop_poll = nfcsim_stop_poll,
	.activate_target = nfcsim_activate_target,
	.deactivate_target = nfcsim_deactivate_target,
	.im_transceive = nfcsim_im_transceive,
	.tm_send = nfcsim_tm_send,
};

static void nfcsim_set_polling_mode(struct nfcsim *dev)
{
	if (dev->polling_mode == NFCSIM_POLL_NONE) {
		dev->curr_polling_mode = NFCSIM_POLL_NONE;
		return;
	}

	if (dev->curr_polling_mode == NFCSIM_POLL_NONE) {
		if (dev->polling_mode & NFCSIM_POLL_INITIATOR)
			dev->curr_polling_mode = NFCSIM_POLL_INITIATOR;
		else
			dev->curr_polling_mode = NFCSIM_POLL_TARGET;

		return;
	}

	if (dev->polling_mode == NFCSIM_POLL_DUAL) {
		if (dev->curr_polling_mode == NFCSIM_POLL_TARGET)
			dev->curr_polling_mode = NFCSIM_POLL_INITIATOR;
		else
			dev->curr_polling_mode = NFCSIM_POLL_TARGET;
	}
}

static void nfcsim_wq_poll(struct work_struct *work)
{
	struct nfcsim *dev = container_of(work, struct nfcsim, poll_work.work);
	struct nfcsim *peer = dev->peer_dev;

	/* These work items run on an ordered workqueue and are therefore
	 * serialized. So we can take both mutexes without being dead locked.
	 */
	mutex_lock(&dev->lock);
	mutex_lock(&peer->lock);

	nfcsim_set_polling_mode(dev);

	if (dev->curr_polling_mode == NFCSIM_POLL_NONE) {
		DEV_DBG(dev, "Not polling\n");
		goto unlock;
	}

	DEV_DBG(dev, "Polling as %s",
		dev->curr_polling_mode == NFCSIM_POLL_INITIATOR ?
		"initiator\n" : "target\n");

	if (dev->curr_polling_mode == NFCSIM_POLL_TARGET)
		goto sched_work;

	if (peer->curr_polling_mode == NFCSIM_POLL_TARGET) {
		peer->polling_mode = NFCSIM_POLL_NONE;
		dev->polling_mode = NFCSIM_POLL_NONE;

		dev->initiator = 1;

		nfcsim_target_found(dev);

		goto unlock;
	}

sched_work:
	/* This defines the delay for an initiator to check if the other device
	 * is polling in target mode.
	 * If the device starts in dual mode polling, it switches between
	 * initiator and target at every round.
	 * Because the wq is ordered and only 1 work item is executed at a time,
	 * we'll always have one device polling as initiator and the other as
	 * target at some point, even if both are started in dual mode.
	 */
	queue_delayed_work(wq, &dev->poll_work, msecs_to_jiffies(200));

unlock:
	mutex_unlock(&peer->lock);
	mutex_unlock(&dev->lock);
}

static struct nfcsim *nfcsim_init_dev(void)
{
	struct nfcsim *dev;
	int rc = -ENOMEM;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (dev == NULL)
		return ERR_PTR(-ENOMEM);

	mutex_init(&dev->lock);

	INIT_DELAYED_WORK(&dev->recv_work, nfcsim_wq_recv);
	INIT_DELAYED_WORK(&dev->poll_work, nfcsim_wq_poll);

	dev->nfc_dev = nfc_allocate_device(&nfcsim_nfc_ops,
					   NFC_PROTO_NFC_DEP_MASK,
					   0, 0);
	if (!dev->nfc_dev)
		goto error;

	nfc_set_drvdata(dev->nfc_dev, dev);

	rc = nfc_register_device(dev->nfc_dev);
	if (rc)
		goto free_nfc_dev;

	return dev;

free_nfc_dev:
	nfc_free_device(dev->nfc_dev);

error:
	kfree(dev);

	return ERR_PTR(rc);
}

static void nfcsim_free_device(struct nfcsim *dev)
{
	nfc_unregister_device(dev->nfc_dev);

	nfc_free_device(dev->nfc_dev);

	kfree(dev);
}

static int __init nfcsim_init(void)
{
	int rc;

	/* We need an ordered wq to ensure that poll_work items are executed
	 * one at a time.
	 */
	wq = alloc_ordered_workqueue("nfcsim", 0);
	if (!wq) {
		rc = -ENOMEM;
		goto exit;
	}

	dev0 = nfcsim_init_dev();
	if (IS_ERR(dev0)) {
		rc = PTR_ERR(dev0);
		goto exit;
	}

	dev1 = nfcsim_init_dev();
	if (IS_ERR(dev1)) {
		kfree(dev0);

		rc = PTR_ERR(dev1);
		goto exit;
	}

	dev0->peer_dev = dev1;
	dev1->peer_dev = dev0;

	pr_debug("NFCsim " NFCSIM_VERSION " initialized\n");

	rc = 0;
exit:
	if (rc)
		pr_err("Failed to initialize nfcsim driver (%d)\n",
		       rc);

	return rc;
}

static void __exit nfcsim_exit(void)
{
	nfcsim_cleanup_dev(dev0, 1);
	nfcsim_cleanup_dev(dev1, 1);

	nfcsim_free_device(dev0);
	nfcsim_free_device(dev1);

	destroy_workqueue(wq);
}

module_init(nfcsim_init);
module_exit(nfcsim_exit);

MODULE_DESCRIPTION("NFCSim driver ver " NFCSIM_VERSION);
MODULE_VERSION(NFCSIM_VERSION);
MODULE_LICENSE("GPL");