aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/net/can/usb/peak_usb/pcan_usb_core.c
blob: 0b7766b715fd22a26adaecb6491e69bef7d2798b (plain)
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
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
// SPDX-License-Identifier: GPL-2.0-only
/*
 * CAN driver for PEAK System USB adapters
 * Derived from the PCAN project file driver/src/pcan_usb_core.c
 *
 * Copyright (C) 2003-2010 PEAK System-Technik GmbH
 * Copyright (C) 2010-2012 Stephane Grosjean <s.grosjean@peak-system.com>
 *
 * Many thanks to Klaus Hitschler <klaus.hitschler@gmx.de>
 */
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/usb.h>

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include "pcan_usb_core.h"

MODULE_AUTHOR("Stephane Grosjean <s.grosjean@peak-system.com>");
MODULE_DESCRIPTION("CAN driver for PEAK-System USB adapters");
MODULE_LICENSE("GPL v2");

/* Table of devices that work with this driver */
static struct usb_device_id peak_usb_table[] = {
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USB_PRODUCT_ID)},
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USBPRO_PRODUCT_ID)},
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USBFD_PRODUCT_ID)},
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USBPROFD_PRODUCT_ID)},
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USBCHIP_PRODUCT_ID)},
	{USB_DEVICE(PCAN_USB_VENDOR_ID, PCAN_USBX6_PRODUCT_ID)},
	{} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, peak_usb_table);

/* List of supported PCAN-USB adapters (NULL terminated list) */
static const struct peak_usb_adapter *const peak_usb_adapters_list[] = {
	&pcan_usb,
	&pcan_usb_pro,
	&pcan_usb_fd,
	&pcan_usb_pro_fd,
	&pcan_usb_chip,
	&pcan_usb_x6,
};

/*
 * dump memory
 */
#define DUMP_WIDTH	16
void pcan_dump_mem(char *prompt, void *p, int l)
{
	pr_info("%s dumping %s (%d bytes):\n",
		PCAN_USB_DRIVER_NAME, prompt ? prompt : "memory", l);
	print_hex_dump(KERN_INFO, PCAN_USB_DRIVER_NAME " ", DUMP_PREFIX_NONE,
		       DUMP_WIDTH, 1, p, l, false);
}

/*
 * initialize a time_ref object with usb adapter own settings
 */
void peak_usb_init_time_ref(struct peak_time_ref *time_ref,
			    const struct peak_usb_adapter *adapter)
{
	if (time_ref) {
		memset(time_ref, 0, sizeof(struct peak_time_ref));
		time_ref->adapter = adapter;
	}
}

/*
 * sometimes, another now may be  more recent than current one...
 */
void peak_usb_update_ts_now(struct peak_time_ref *time_ref, u32 ts_now)
{
	time_ref->ts_dev_2 = ts_now;

	/* should wait at least two passes before computing */
	if (ktime_to_ns(time_ref->tv_host) > 0) {
		u32 delta_ts = time_ref->ts_dev_2 - time_ref->ts_dev_1;

		if (time_ref->ts_dev_2 < time_ref->ts_dev_1)
			delta_ts &= (1 << time_ref->adapter->ts_used_bits) - 1;

		time_ref->ts_total += delta_ts;
	}
}

/*
 * register device timestamp as now
 */
void peak_usb_set_ts_now(struct peak_time_ref *time_ref, u32 ts_now)
{
	if (ktime_to_ns(time_ref->tv_host_0) == 0) {
		/* use monotonic clock to correctly compute further deltas */
		time_ref->tv_host_0 = ktime_get();
		time_ref->tv_host = ktime_set(0, 0);
	} else {
		/*
		 * delta_us should not be >= 2^32 => delta should be < 4294s
		 * handle 32-bits wrapping here: if count of s. reaches 4200,
		 * reset counters and change time base
		 */
		if (ktime_to_ns(time_ref->tv_host)) {
			ktime_t delta = ktime_sub(time_ref->tv_host,
						  time_ref->tv_host_0);
			if (ktime_to_ns(delta) > (4200ull * NSEC_PER_SEC)) {
				time_ref->tv_host_0 = time_ref->tv_host;
				time_ref->ts_total = 0;
			}
		}

		time_ref->tv_host = ktime_get();
		time_ref->tick_count++;
	}

	time_ref->ts_dev_1 = time_ref->ts_dev_2;
	peak_usb_update_ts_now(time_ref, ts_now);
}

/*
 * compute time according to current ts and time_ref data
 */
void peak_usb_get_ts_time(struct peak_time_ref *time_ref, u32 ts, ktime_t *time)
{
	/* protect from getting time before setting now */
	if (ktime_to_ns(time_ref->tv_host)) {
		u64 delta_us;

		delta_us = ts - time_ref->ts_dev_2;
		if (ts < time_ref->ts_dev_2)
			delta_us &= (1 << time_ref->adapter->ts_used_bits) - 1;

		delta_us += time_ref->ts_total;

		delta_us *= time_ref->adapter->us_per_ts_scale;
		delta_us >>= time_ref->adapter->us_per_ts_shift;

		*time = ktime_add_us(time_ref->tv_host_0, delta_us);
	} else {
		*time = ktime_get();
	}
}

/*
 * post received skb after having set any hw timestamp
 */
int peak_usb_netif_rx(struct sk_buff *skb,
		      struct peak_time_ref *time_ref, u32 ts_low)
{
	struct skb_shared_hwtstamps *hwts = skb_hwtstamps(skb);

	peak_usb_get_ts_time(time_ref, ts_low, &hwts->hwtstamp);

	return netif_rx(skb);
}

/*
 * callback for bulk Rx urb
 */
static void peak_usb_read_bulk_callback(struct urb *urb)
{
	struct peak_usb_device *dev = urb->context;
	struct net_device *netdev;
	int err;

	netdev = dev->netdev;

	if (!netif_device_present(netdev))
		return;

	/* check reception status */
	switch (urb->status) {
	case 0:
		/* success */
		break;

	case -EILSEQ:
	case -ENOENT:
	case -ECONNRESET:
	case -ESHUTDOWN:
		return;

	default:
		if (net_ratelimit())
			netdev_err(netdev,
				   "Rx urb aborted (%d)\n", urb->status);
		goto resubmit_urb;
	}

	/* protect from any incoming empty msgs */
	if ((urb->actual_length > 0) && (dev->adapter->dev_decode_buf)) {
		/* handle these kinds of msgs only if _start callback called */
		if (dev->state & PCAN_USB_STATE_STARTED) {
			err = dev->adapter->dev_decode_buf(dev, urb);
			if (err)
				pcan_dump_mem("received usb message",
					      urb->transfer_buffer,
					      urb->transfer_buffer_length);
		}
	}

resubmit_urb:
	usb_fill_bulk_urb(urb, dev->udev,
		usb_rcvbulkpipe(dev->udev, dev->ep_msg_in),
		urb->transfer_buffer, dev->adapter->rx_buffer_size,
		peak_usb_read_bulk_callback, dev);

	usb_anchor_urb(urb, &dev->rx_submitted);
	err = usb_submit_urb(urb, GFP_ATOMIC);
	if (!err)
		return;

	usb_unanchor_urb(urb);

	if (err == -ENODEV)
		netif_device_detach(netdev);
	else
		netdev_err(netdev, "failed resubmitting read bulk urb: %d\n",
			   err);
}

/*
 * callback for bulk Tx urb
 */
static void peak_usb_write_bulk_callback(struct urb *urb)
{
	struct peak_tx_urb_context *context = urb->context;
	struct peak_usb_device *dev;
	struct net_device *netdev;

	BUG_ON(!context);

	dev = context->dev;
	netdev = dev->netdev;

	atomic_dec(&dev->active_tx_urbs);

	if (!netif_device_present(netdev))
		return;

	/* check tx status */
	switch (urb->status) {
	case 0:
		/* transmission complete */
		netdev->stats.tx_packets++;
		netdev->stats.tx_bytes += context->data_len;

		/* prevent tx timeout */
		netif_trans_update(netdev);
		break;

	default:
		if (net_ratelimit())
			netdev_err(netdev, "Tx urb aborted (%d)\n",
				   urb->status);
	case -EPROTO:
	case -ENOENT:
	case -ECONNRESET:
	case -ESHUTDOWN:

		break;
	}

	/* should always release echo skb and corresponding context */
	can_get_echo_skb(netdev, context->echo_index);
	context->echo_index = PCAN_USB_MAX_TX_URBS;

	/* do wakeup tx queue in case of success only */
	if (!urb->status)
		netif_wake_queue(netdev);
}

/*
 * called by netdev to send one skb on the CAN interface.
 */
static netdev_tx_t peak_usb_ndo_start_xmit(struct sk_buff *skb,
					   struct net_device *netdev)
{
	struct peak_usb_device *dev = netdev_priv(netdev);
	struct peak_tx_urb_context *context = NULL;
	struct net_device_stats *stats = &netdev->stats;
	struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
	struct urb *urb;
	u8 *obuf;
	int i, err;
	size_t size = dev->adapter->tx_buffer_size;

	if (can_dropped_invalid_skb(netdev, skb))
		return NETDEV_TX_OK;

	for (i = 0; i < PCAN_USB_MAX_TX_URBS; i++)
		if (dev->tx_contexts[i].echo_index == PCAN_USB_MAX_TX_URBS) {
			context = dev->tx_contexts + i;
			break;
		}

	if (!context) {
		/* should not occur except during restart */
		return NETDEV_TX_BUSY;
	}

	urb = context->urb;
	obuf = urb->transfer_buffer;

	err = dev->adapter->dev_encode_msg(dev, skb, obuf, &size);
	if (err) {
		if (net_ratelimit())
			netdev_err(netdev, "packet dropped\n");
		dev_kfree_skb(skb);
		stats->tx_dropped++;
		return NETDEV_TX_OK;
	}

	context->echo_index = i;

	/* Note: this works with CANFD frames too */
	context->data_len = cfd->len;

	usb_anchor_urb(urb, &dev->tx_submitted);

	can_put_echo_skb(skb, netdev, context->echo_index);

	atomic_inc(&dev->active_tx_urbs);

	err = usb_submit_urb(urb, GFP_ATOMIC);
	if (err) {
		can_free_echo_skb(netdev, context->echo_index);

		usb_unanchor_urb(urb);

		/* this context is not used in fact */
		context->echo_index = PCAN_USB_MAX_TX_URBS;

		atomic_dec(&dev->active_tx_urbs);

		switch (err) {
		case -ENODEV:
			netif_device_detach(netdev);
			break;
		default:
			netdev_warn(netdev, "tx urb submitting failed err=%d\n",
				    err);
			/* fall through */
		case -ENOENT:
			/* cable unplugged */
			stats->tx_dropped++;
		}
	} else {
		netif_trans_update(netdev);

		/* slow down tx path */
		if (atomic_read(&dev->active_tx_urbs) >= PCAN_USB_MAX_TX_URBS)
			netif_stop_queue(netdev);
	}

	return NETDEV_TX_OK;
}

/*
 * start the CAN interface.
 * Rx and Tx urbs are allocated here. Rx urbs are submitted here.
 */
static int peak_usb_start(struct peak_usb_device *dev)
{
	struct net_device *netdev = dev->netdev;
	int err, i;

	for (i = 0; i < PCAN_USB_MAX_RX_URBS; i++) {
		struct urb *urb;
		u8 *buf;

		/* create a URB, and a buffer for it, to receive usb messages */
		urb = usb_alloc_urb(0, GFP_KERNEL);
		if (!urb) {
			err = -ENOMEM;
			break;
		}

		buf = kmalloc(dev->adapter->rx_buffer_size, GFP_KERNEL);
		if (!buf) {
			usb_free_urb(urb);
			err = -ENOMEM;
			break;
		}

		usb_fill_bulk_urb(urb, dev->udev,
			usb_rcvbulkpipe(dev->udev, dev->ep_msg_in),
			buf, dev->adapter->rx_buffer_size,
			peak_usb_read_bulk_callback, dev);

		/* ask last usb_free_urb() to also kfree() transfer_buffer */
		urb->transfer_flags |= URB_FREE_BUFFER;
		usb_anchor_urb(urb, &dev->rx_submitted);

		err = usb_submit_urb(urb, GFP_KERNEL);
		if (err) {
			if (err == -ENODEV)
				netif_device_detach(dev->netdev);

			usb_unanchor_urb(urb);
			kfree(buf);
			usb_free_urb(urb);
			break;
		}

		/* drop reference, USB core will take care of freeing it */
		usb_free_urb(urb);
	}

	/* did we submit any URBs? Warn if we was not able to submit all urbs */
	if (i < PCAN_USB_MAX_RX_URBS) {
		if (i == 0) {
			netdev_err(netdev, "couldn't setup any rx URB\n");
			return err;
		}

		netdev_warn(netdev, "rx performance may be slow\n");
	}

	/* pre-alloc tx buffers and corresponding urbs */
	for (i = 0; i < PCAN_USB_MAX_TX_URBS; i++) {
		struct peak_tx_urb_context *context;
		struct urb *urb;
		u8 *buf;

		/* create a URB and a buffer for it, to transmit usb messages */
		urb = usb_alloc_urb(0, GFP_KERNEL);
		if (!urb) {
			err = -ENOMEM;
			break;
		}

		buf = kmalloc(dev->adapter->tx_buffer_size, GFP_KERNEL);
		if (!buf) {
			usb_free_urb(urb);
			err = -ENOMEM;
			break;
		}

		context = dev->tx_contexts + i;
		context->dev = dev;
		context->urb = urb;

		usb_fill_bulk_urb(urb, dev->udev,
			usb_sndbulkpipe(dev->udev, dev->ep_msg_out),
			buf, dev->adapter->tx_buffer_size,
			peak_usb_write_bulk_callback, context);

		/* ask last usb_free_urb() to also kfree() transfer_buffer */
		urb->transfer_flags |= URB_FREE_BUFFER;
	}

	/* warn if we were not able to allocate enough tx contexts */
	if (i < PCAN_USB_MAX_TX_URBS) {
		if (i == 0) {
			netdev_err(netdev, "couldn't setup any tx URB\n");
			goto err_tx;
		}

		netdev_warn(netdev, "tx performance may be slow\n");
	}

	if (dev->adapter->dev_start) {
		err = dev->adapter->dev_start(dev);
		if (err)
			goto err_adapter;
	}

	dev->state |= PCAN_USB_STATE_STARTED;

	/* can set bus on now */
	if (dev->adapter->dev_set_bus) {
		err = dev->adapter->dev_set_bus(dev, 1);
		if (err)
			goto err_adapter;
	}

	dev->can.state = CAN_STATE_ERROR_ACTIVE;

	return 0;

err_adapter:
	if (err == -ENODEV)
		netif_device_detach(dev->netdev);

	netdev_warn(netdev, "couldn't submit control: %d\n", err);

	for (i = 0; i < PCAN_USB_MAX_TX_URBS; i++) {
		usb_free_urb(dev->tx_contexts[i].urb);
		dev->tx_contexts[i].urb = NULL;
	}
err_tx:
	usb_kill_anchored_urbs(&dev->rx_submitted);

	return err;
}

/*
 * called by netdev to open the corresponding CAN interface.
 */
static int peak_usb_ndo_open(struct net_device *netdev)
{
	struct peak_usb_device *dev = netdev_priv(netdev);
	int err;

	/* common open */
	err = open_candev(netdev);
	if (err)
		return err;

	/* finally start device */
	err = peak_usb_start(dev);
	if (err) {
		netdev_err(netdev, "couldn't start device: %d\n", err);
		close_candev(netdev);
		return err;
	}

	netif_start_queue(netdev);

	return 0;
}

/*
 * unlink in-flight Rx and Tx urbs and free their memory.
 */
static void peak_usb_unlink_all_urbs(struct peak_usb_device *dev)
{
	int i;

	/* free all Rx (submitted) urbs */
	usb_kill_anchored_urbs(&dev->rx_submitted);

	/* free unsubmitted Tx urbs first */
	for (i = 0; i < PCAN_USB_MAX_TX_URBS; i++) {
		struct urb *urb = dev->tx_contexts[i].urb;

		if (!urb ||
		    dev->tx_contexts[i].echo_index != PCAN_USB_MAX_TX_URBS) {
			/*
			 * this urb is already released or always submitted,
			 * let usb core free by itself
			 */
			continue;
		}

		usb_free_urb(urb);
		dev->tx_contexts[i].urb = NULL;
	}

	/* then free all submitted Tx urbs */
	usb_kill_anchored_urbs(&dev->tx_submitted);
	atomic_set(&dev->active_tx_urbs, 0);
}

/*
 * called by netdev to close the corresponding CAN interface.
 */
static int peak_usb_ndo_stop(struct net_device *netdev)
{
	struct peak_usb_device *dev = netdev_priv(netdev);

	dev->state &= ~PCAN_USB_STATE_STARTED;
	netif_stop_queue(netdev);

	close_candev(netdev);

	dev->can.state = CAN_STATE_STOPPED;

	/* unlink all pending urbs and free used memory */
	peak_usb_unlink_all_urbs(dev);

	if (dev->adapter->dev_stop)
		dev->adapter->dev_stop(dev);

	/* can set bus off now */
	if (dev->adapter->dev_set_bus) {
		int err = dev->adapter->dev_set_bus(dev, 0);
		if (err)
			return err;
	}

	return 0;
}

/*
 * handle end of waiting for the device to reset
 */
void peak_usb_restart_complete(struct peak_usb_device *dev)
{
	/* finally MUST update can state */
	dev->can.state = CAN_STATE_ERROR_ACTIVE;

	/* netdev queue can be awaken now */
	netif_wake_queue(dev->netdev);
}

void peak_usb_async_complete(struct urb *urb)
{
	kfree(urb->transfer_buffer);
	usb_free_urb(urb);
}

/*
 * device (auto-)restart mechanism runs in a timer context =>
 * MUST handle restart with asynchronous usb transfers
 */
static int peak_usb_restart(struct peak_usb_device *dev)
{
	struct urb *urb;
	int err;
	u8 *buf;

	/*
	 * if device doesn't define any asynchronous restart handler, simply
	 * wake the netdev queue up
	 */
	if (!dev->adapter->dev_restart_async) {
		peak_usb_restart_complete(dev);
		return 0;
	}

	/* first allocate a urb to handle the asynchronous steps */
	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb)
		return -ENOMEM;

	/* also allocate enough space for the commands to send */
	buf = kmalloc(PCAN_USB_MAX_CMD_LEN, GFP_ATOMIC);
	if (!buf) {
		usb_free_urb(urb);
		return -ENOMEM;
	}

	/* call the device specific handler for the restart */
	err = dev->adapter->dev_restart_async(dev, urb, buf);
	if (!err)
		return 0;

	kfree(buf);
	usb_free_urb(urb);

	return err;
}

/*
 * candev callback used to change CAN mode.
 * Warning: this is called from a timer context!
 */
static int peak_usb_set_mode(struct net_device *netdev, enum can_mode mode)
{
	struct peak_usb_device *dev = netdev_priv(netdev);
	int err = 0;

	switch (mode) {
	case CAN_MODE_START:
		err = peak_usb_restart(dev);
		if (err)
			netdev_err(netdev, "couldn't start device (err %d)\n",
				   err);
		break;

	default:
		return -EOPNOTSUPP;
	}

	return err;
}

/*
 * candev callback used to set device nominal/arbitration bitrate.
 */
static int peak_usb_set_bittiming(struct net_device *netdev)
{
	struct peak_usb_device *dev = netdev_priv(netdev);
	const struct peak_usb_adapter *pa = dev->adapter;

	if (pa->dev_set_bittiming) {
		struct can_bittiming *bt = &dev->can.bittiming;
		int err = pa->dev_set_bittiming(dev, bt);

		if (err)
			netdev_info(netdev, "couldn't set bitrate (err %d)\n",
				    err);
		return err;
	}

	return 0;
}

/*
 * candev callback used to set device data bitrate.
 */
static int peak_usb_set_data_bittiming(struct net_device *netdev)
{
	struct peak_usb_device *dev = netdev_priv(netdev);
	const struct peak_usb_adapter *pa = dev->adapter;

	if (pa->dev_set_data_bittiming) {
		struct can_bittiming *bt = &dev->can.data_bittiming;
		int err = pa->dev_set_data_bittiming(dev, bt);

		if (err)
			netdev_info(netdev,
				    "couldn't set data bitrate (err %d)\n",
				    err);

		return err;
	}

	return 0;
}

static const struct net_device_ops peak_usb_netdev_ops = {
	.ndo_open = peak_usb_ndo_open,
	.ndo_stop = peak_usb_ndo_stop,
	.ndo_start_xmit = peak_usb_ndo_start_xmit,
	.ndo_change_mtu = can_change_mtu,
};

/*
 * create one device which is attached to CAN controller #ctrl_idx of the
 * usb adapter.
 */
static int peak_usb_create_dev(const struct peak_usb_adapter *peak_usb_adapter,
			       struct usb_interface *intf, int ctrl_idx)
{
	struct usb_device *usb_dev = interface_to_usbdev(intf);
	int sizeof_candev = peak_usb_adapter->sizeof_dev_private;
	struct peak_usb_device *dev;
	struct net_device *netdev;
	int i, err;
	u16 tmp16;

	if (sizeof_candev < sizeof(struct peak_usb_device))
		sizeof_candev = sizeof(struct peak_usb_device);

	netdev = alloc_candev(sizeof_candev, PCAN_USB_MAX_TX_URBS);
	if (!netdev) {
		dev_err(&intf->dev, "%s: couldn't alloc candev\n",
			PCAN_USB_DRIVER_NAME);
		return -ENOMEM;
	}

	dev = netdev_priv(netdev);

	/* allocate a buffer large enough to send commands */
	dev->cmd_buf = kzalloc(PCAN_USB_MAX_CMD_LEN, GFP_KERNEL);
	if (!dev->cmd_buf) {
		err = -ENOMEM;
		goto lbl_free_candev;
	}

	dev->udev = usb_dev;
	dev->netdev = netdev;
	dev->adapter = peak_usb_adapter;
	dev->ctrl_idx = ctrl_idx;
	dev->state = PCAN_USB_STATE_CONNECTED;

	dev->ep_msg_in = peak_usb_adapter->ep_msg_in;
	dev->ep_msg_out = peak_usb_adapter->ep_msg_out[ctrl_idx];

	dev->can.clock = peak_usb_adapter->clock;
	dev->can.bittiming_const = peak_usb_adapter->bittiming_const;
	dev->can.do_set_bittiming = peak_usb_set_bittiming;
	dev->can.data_bittiming_const = peak_usb_adapter->data_bittiming_const;
	dev->can.do_set_data_bittiming = peak_usb_set_data_bittiming;
	dev->can.do_set_mode = peak_usb_set_mode;
	dev->can.do_get_berr_counter = peak_usb_adapter->do_get_berr_counter;
	dev->can.ctrlmode_supported = peak_usb_adapter->ctrlmode_supported;

	netdev->netdev_ops = &peak_usb_netdev_ops;

	netdev->flags |= IFF_ECHO; /* we support local echo */

	init_usb_anchor(&dev->rx_submitted);

	init_usb_anchor(&dev->tx_submitted);
	atomic_set(&dev->active_tx_urbs, 0);

	for (i = 0; i < PCAN_USB_MAX_TX_URBS; i++)
		dev->tx_contexts[i].echo_index = PCAN_USB_MAX_TX_URBS;

	dev->prev_siblings = usb_get_intfdata(intf);
	usb_set_intfdata(intf, dev);

	SET_NETDEV_DEV(netdev, &intf->dev);
	netdev->dev_id = ctrl_idx;

	err = register_candev(netdev);
	if (err) {
		dev_err(&intf->dev, "couldn't register CAN device: %d\n", err);
		goto lbl_restore_intf_data;
	}

	if (dev->prev_siblings)
		(dev->prev_siblings)->next_siblings = dev;

	/* keep hw revision into the netdevice */
	tmp16 = le16_to_cpu(usb_dev->descriptor.bcdDevice);
	dev->device_rev = tmp16 >> 8;

	if (dev->adapter->dev_init) {
		err = dev->adapter->dev_init(dev);
		if (err)
			goto lbl_unregister_candev;
	}

	/* set bus off */
	if (dev->adapter->dev_set_bus) {
		err = dev->adapter->dev_set_bus(dev, 0);
		if (err)
			goto lbl_unregister_candev;
	}

	/* get device number early */
	if (dev->adapter->dev_get_device_id)
		dev->adapter->dev_get_device_id(dev, &dev->device_number);

	netdev_info(netdev, "attached to %s channel %u (device %u)\n",
			peak_usb_adapter->name, ctrl_idx, dev->device_number);

	return 0;

lbl_unregister_candev:
	unregister_candev(netdev);

lbl_restore_intf_data:
	usb_set_intfdata(intf, dev->prev_siblings);
	kfree(dev->cmd_buf);

lbl_free_candev:
	free_candev(netdev);

	return err;
}

/*
 * called by the usb core when the device is unplugged from the system
 */
static void peak_usb_disconnect(struct usb_interface *intf)
{
	struct peak_usb_device *dev;
	struct peak_usb_device *dev_prev_siblings;

	/* unregister as many netdev devices as siblings */
	for (dev = usb_get_intfdata(intf); dev; dev = dev_prev_siblings) {
		struct net_device *netdev = dev->netdev;
		char name[IFNAMSIZ];

		dev_prev_siblings = dev->prev_siblings;
		dev->state &= ~PCAN_USB_STATE_CONNECTED;
		strlcpy(name, netdev->name, IFNAMSIZ);

		unregister_netdev(netdev);

		kfree(dev->cmd_buf);
		dev->next_siblings = NULL;
		if (dev->adapter->dev_free)
			dev->adapter->dev_free(dev);

		free_candev(netdev);
		dev_info(&intf->dev, "%s removed\n", name);
	}

	usb_set_intfdata(intf, NULL);
}

/*
 * probe function for new PEAK-System devices
 */
static int peak_usb_probe(struct usb_interface *intf,
			  const struct usb_device_id *id)
{
	struct usb_device *usb_dev = interface_to_usbdev(intf);
	const u16 usb_id_product = le16_to_cpu(usb_dev->descriptor.idProduct);
	const struct peak_usb_adapter *peak_usb_adapter = NULL;
	int i, err = -ENOMEM;

	/* get corresponding PCAN-USB adapter */
	for (i = 0; i < ARRAY_SIZE(peak_usb_adapters_list); i++)
		if (peak_usb_adapters_list[i]->device_id == usb_id_product) {
			peak_usb_adapter = peak_usb_adapters_list[i];
			break;
		}

	if (!peak_usb_adapter) {
		/* should never come except device_id bad usage in this file */
		pr_err("%s: didn't find device id. 0x%x in devices list\n",
			PCAN_USB_DRIVER_NAME, usb_id_product);
		return -ENODEV;
	}

	/* got corresponding adapter: check if it handles current interface */
	if (peak_usb_adapter->intf_probe) {
		err = peak_usb_adapter->intf_probe(intf);
		if (err)
			return err;
	}

	for (i = 0; i < peak_usb_adapter->ctrl_count; i++) {
		err = peak_usb_create_dev(peak_usb_adapter, intf, i);
		if (err) {
			/* deregister already created devices */
			peak_usb_disconnect(intf);
			break;
		}
	}

	return err;
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver peak_usb_driver = {
	.name = PCAN_USB_DRIVER_NAME,
	.disconnect = peak_usb_disconnect,
	.probe = peak_usb_probe,
	.id_table = peak_usb_table,
};

static int __init peak_usb_init(void)
{
	int err;

	/* register this driver with the USB subsystem */
	err = usb_register(&peak_usb_driver);
	if (err)
		pr_err("%s: usb_register failed (err %d)\n",
			PCAN_USB_DRIVER_NAME, err);

	return err;
}

static int peak_usb_do_device_exit(struct device *d, void *arg)
{
	struct usb_interface *intf = to_usb_interface(d);
	struct peak_usb_device *dev;

	/* stop as many netdev devices as siblings */
	for (dev = usb_get_intfdata(intf); dev; dev = dev->prev_siblings) {
		struct net_device *netdev = dev->netdev;

		if (netif_device_present(netdev))
			if (dev->adapter->dev_exit)
				dev->adapter->dev_exit(dev);
	}

	return 0;
}

static void __exit peak_usb_exit(void)
{
	int err;

	/* last chance do send any synchronous commands here */
	err = driver_for_each_device(&peak_usb_driver.drvwrap.driver, NULL,
				     NULL, peak_usb_do_device_exit);
	if (err)
		pr_err("%s: failed to stop all can devices (err %d)\n",
			PCAN_USB_DRIVER_NAME, err);

	/* deregister this driver with the USB subsystem */
	usb_deregister(&peak_usb_driver);

	pr_info("%s: PCAN-USB interfaces driver unloaded\n",
		PCAN_USB_DRIVER_NAME);
}

module_init(peak_usb_init);
module_exit(peak_usb_exit);