summaryrefslogtreecommitdiff
path: root/drivers/net/can/usb/ems_usb.c
blob: 0a37af4a3fa40e3ed9a859f586646283b9c7e97a (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
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
// SPDX-License-Identifier: GPL-2.0-only
/*
 * CAN driver for EMS Dr. Thomas Wuensche CPC-USB/ARM7
 *
 * Copyright (C) 2004-2009 EMS Dr. Thomas Wuensche
 */
#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>

MODULE_AUTHOR("Sebastian Haas <haas@ems-wuensche.com>");
MODULE_DESCRIPTION("CAN driver for EMS Dr. Thomas Wuensche CAN/USB interfaces");
MODULE_LICENSE("GPL v2");

/* Control-Values for CPC_Control() Command Subject Selection */
#define CONTR_CAN_MESSAGE 0x04
#define CONTR_CAN_STATE   0x0C
#define CONTR_BUS_ERROR   0x1C

/* Control Command Actions */
#define CONTR_CONT_OFF 0
#define CONTR_CONT_ON  1
#define CONTR_ONCE     2

/* Messages from CPC to PC */
#define CPC_MSG_TYPE_CAN_FRAME       1  /* CAN data frame */
#define CPC_MSG_TYPE_RTR_FRAME       8  /* CAN remote frame */
#define CPC_MSG_TYPE_CAN_PARAMS      12 /* Actual CAN parameters */
#define CPC_MSG_TYPE_CAN_STATE       14 /* CAN state message */
#define CPC_MSG_TYPE_EXT_CAN_FRAME   16 /* Extended CAN data frame */
#define CPC_MSG_TYPE_EXT_RTR_FRAME   17 /* Extended remote frame */
#define CPC_MSG_TYPE_CONTROL         19 /* change interface behavior */
#define CPC_MSG_TYPE_CONFIRM         20 /* command processed confirmation */
#define CPC_MSG_TYPE_OVERRUN         21 /* overrun events */
#define CPC_MSG_TYPE_CAN_FRAME_ERROR 23 /* detected bus errors */
#define CPC_MSG_TYPE_ERR_COUNTER     25 /* RX/TX error counter */

/* Messages from the PC to the CPC interface  */
#define CPC_CMD_TYPE_CAN_FRAME     1   /* CAN data frame */
#define CPC_CMD_TYPE_CONTROL       3   /* control of interface behavior */
#define CPC_CMD_TYPE_CAN_PARAMS    6   /* set CAN parameters */
#define CPC_CMD_TYPE_RTR_FRAME     13  /* CAN remote frame */
#define CPC_CMD_TYPE_CAN_STATE     14  /* CAN state message */
#define CPC_CMD_TYPE_EXT_CAN_FRAME 15  /* Extended CAN data frame */
#define CPC_CMD_TYPE_EXT_RTR_FRAME 16  /* Extended CAN remote frame */
#define CPC_CMD_TYPE_CAN_EXIT      200 /* exit the CAN */

#define CPC_CMD_TYPE_INQ_ERR_COUNTER 25 /* request the CAN error counters */
#define CPC_CMD_TYPE_CLEAR_MSG_QUEUE 8  /* clear CPC_MSG queue */
#define CPC_CMD_TYPE_CLEAR_CMD_QUEUE 28 /* clear CPC_CMD queue */

#define CPC_CC_TYPE_SJA1000 2 /* Philips basic CAN controller */

#define CPC_CAN_ECODE_ERRFRAME 0x01 /* Ecode type */

/* Overrun types */
#define CPC_OVR_EVENT_CAN       0x01
#define CPC_OVR_EVENT_CANSTATE  0x02
#define CPC_OVR_EVENT_BUSERROR  0x04

/*
 * If the CAN controller lost a message we indicate it with the highest bit
 * set in the count field.
 */
#define CPC_OVR_HW 0x80

/* Size of the "struct ems_cpc_msg" without the union */
#define CPC_MSG_HEADER_LEN   11
#define CPC_CAN_MSG_MIN_SIZE 5

/* Define these values to match your devices */
#define USB_CPCUSB_VENDOR_ID 0x12D6

#define USB_CPCUSB_ARM7_PRODUCT_ID 0x0444

/* Mode register NXP LPC2119/SJA1000 CAN Controller */
#define SJA1000_MOD_NORMAL 0x00
#define SJA1000_MOD_RM     0x01

/* ECC register NXP LPC2119/SJA1000 CAN Controller */
#define SJA1000_ECC_SEG   0x1F
#define SJA1000_ECC_DIR   0x20
#define SJA1000_ECC_ERR   0x06
#define SJA1000_ECC_BIT   0x00
#define SJA1000_ECC_FORM  0x40
#define SJA1000_ECC_STUFF 0x80
#define SJA1000_ECC_MASK  0xc0

/* Status register content */
#define SJA1000_SR_BS 0x80
#define SJA1000_SR_ES 0x40

#define SJA1000_DEFAULT_OUTPUT_CONTROL 0xDA

/*
 * The device actually uses a 16MHz clock to generate the CAN clock
 * but it expects SJA1000 bit settings based on 8MHz (is internally
 * converted).
 */
#define EMS_USB_ARM7_CLOCK 8000000

#define CPC_TX_QUEUE_TRIGGER_LOW	25
#define CPC_TX_QUEUE_TRIGGER_HIGH	35

/*
 * CAN-Message representation in a CPC_MSG. Message object type is
 * CPC_MSG_TYPE_CAN_FRAME or CPC_MSG_TYPE_RTR_FRAME or
 * CPC_MSG_TYPE_EXT_CAN_FRAME or CPC_MSG_TYPE_EXT_RTR_FRAME.
 */
struct cpc_can_msg {
	__le32 id;
	u8 length;
	u8 msg[8];
};

/* Representation of the CAN parameters for the SJA1000 controller */
struct cpc_sja1000_params {
	u8 mode;
	u8 acc_code0;
	u8 acc_code1;
	u8 acc_code2;
	u8 acc_code3;
	u8 acc_mask0;
	u8 acc_mask1;
	u8 acc_mask2;
	u8 acc_mask3;
	u8 btr0;
	u8 btr1;
	u8 outp_contr;
};

/* CAN params message representation */
struct cpc_can_params {
	u8 cc_type;

	/* Will support M16C CAN controller in the future */
	union {
		struct cpc_sja1000_params sja1000;
	} cc_params;
};

/* Structure for confirmed message handling */
struct cpc_confirm {
	u8 error; /* error code */
};

/* Structure for overrun conditions */
struct cpc_overrun {
	u8 event;
	u8 count;
};

/* SJA1000 CAN errors (compatible to NXP LPC2119) */
struct cpc_sja1000_can_error {
	u8 ecc;
	u8 rxerr;
	u8 txerr;
};

/* structure for CAN error conditions */
struct cpc_can_error {
	u8 ecode;

	struct {
		u8 cc_type;

		/* Other controllers may also provide error code capture regs */
		union {
			struct cpc_sja1000_can_error sja1000;
		} regs;
	} cc;
};

/*
 * Structure containing RX/TX error counter. This structure is used to request
 * the values of the CAN controllers TX and RX error counter.
 */
struct cpc_can_err_counter {
	u8 rx;
	u8 tx;
};

/* Main message type used between library and application */
struct __packed ems_cpc_msg {
	u8 type;	/* type of message */
	u8 length;	/* length of data within union 'msg' */
	u8 msgid;	/* confirmation handle */
	__le32 ts_sec;	/* timestamp in seconds */
	__le32 ts_nsec;	/* timestamp in nano seconds */

	union {
		u8 generic[64];
		struct cpc_can_msg can_msg;
		struct cpc_can_params can_params;
		struct cpc_confirm confirmation;
		struct cpc_overrun overrun;
		struct cpc_can_error error;
		struct cpc_can_err_counter err_counter;
		u8 can_state;
	} msg;
};

/*
 * Table of devices that work with this driver
 * NOTE: This driver supports only CPC-USB/ARM7 (LPC2119) yet.
 */
static struct usb_device_id ems_usb_table[] = {
	{USB_DEVICE(USB_CPCUSB_VENDOR_ID, USB_CPCUSB_ARM7_PRODUCT_ID)},
	{} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, ems_usb_table);

#define RX_BUFFER_SIZE      64
#define CPC_HEADER_SIZE     4
#define INTR_IN_BUFFER_SIZE 4

#define MAX_RX_URBS 10
#define MAX_TX_URBS 10

struct ems_usb;

struct ems_tx_urb_context {
	struct ems_usb *dev;

	u32 echo_index;
	u8 dlc;
};

struct ems_usb {
	struct can_priv can; /* must be the first member */

	struct sk_buff *echo_skb[MAX_TX_URBS];

	struct usb_device *udev;
	struct net_device *netdev;

	atomic_t active_tx_urbs;
	struct usb_anchor tx_submitted;
	struct ems_tx_urb_context tx_contexts[MAX_TX_URBS];

	struct usb_anchor rx_submitted;

	struct urb *intr_urb;

	u8 *tx_msg_buffer;

	u8 *intr_in_buffer;
	unsigned int free_slots; /* remember number of available slots */

	struct ems_cpc_msg active_params; /* active controller parameters */
};

static void ems_usb_read_interrupt_callback(struct urb *urb)
{
	struct ems_usb *dev = urb->context;
	struct net_device *netdev = dev->netdev;
	int err;

	if (!netif_device_present(netdev))
		return;

	switch (urb->status) {
	case 0:
		dev->free_slots = dev->intr_in_buffer[1];
		if (dev->free_slots > CPC_TX_QUEUE_TRIGGER_HIGH &&
		    netif_queue_stopped(netdev))
			netif_wake_queue(netdev);
		break;

	case -ECONNRESET: /* unlink */
	case -ENOENT:
	case -EPIPE:
	case -EPROTO:
	case -ESHUTDOWN:
		return;

	default:
		netdev_info(netdev, "Rx interrupt aborted %d\n", urb->status);
		break;
	}

	err = usb_submit_urb(urb, GFP_ATOMIC);

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

static void ems_usb_rx_can_msg(struct ems_usb *dev, struct ems_cpc_msg *msg)
{
	struct can_frame *cf;
	struct sk_buff *skb;
	int i;
	struct net_device_stats *stats = &dev->netdev->stats;

	skb = alloc_can_skb(dev->netdev, &cf);
	if (skb == NULL)
		return;

	cf->can_id = le32_to_cpu(msg->msg.can_msg.id);
	cf->len = can_cc_dlc2len(msg->msg.can_msg.length & 0xF);

	if (msg->type == CPC_MSG_TYPE_EXT_CAN_FRAME ||
	    msg->type == CPC_MSG_TYPE_EXT_RTR_FRAME)
		cf->can_id |= CAN_EFF_FLAG;

	if (msg->type == CPC_MSG_TYPE_RTR_FRAME ||
	    msg->type == CPC_MSG_TYPE_EXT_RTR_FRAME) {
		cf->can_id |= CAN_RTR_FLAG;
	} else {
		for (i = 0; i < cf->len; i++)
			cf->data[i] = msg->msg.can_msg.msg[i];
	}

	stats->rx_packets++;
	stats->rx_bytes += cf->len;
	netif_rx(skb);
}

static void ems_usb_rx_err(struct ems_usb *dev, struct ems_cpc_msg *msg)
{
	struct can_frame *cf;
	struct sk_buff *skb;
	struct net_device_stats *stats = &dev->netdev->stats;

	skb = alloc_can_err_skb(dev->netdev, &cf);
	if (skb == NULL)
		return;

	if (msg->type == CPC_MSG_TYPE_CAN_STATE) {
		u8 state = msg->msg.can_state;

		if (state & SJA1000_SR_BS) {
			dev->can.state = CAN_STATE_BUS_OFF;
			cf->can_id |= CAN_ERR_BUSOFF;

			dev->can.can_stats.bus_off++;
			can_bus_off(dev->netdev);
		} else if (state & SJA1000_SR_ES) {
			dev->can.state = CAN_STATE_ERROR_WARNING;
			dev->can.can_stats.error_warning++;
		} else {
			dev->can.state = CAN_STATE_ERROR_ACTIVE;
			dev->can.can_stats.error_passive++;
		}
	} else if (msg->type == CPC_MSG_TYPE_CAN_FRAME_ERROR) {
		u8 ecc = msg->msg.error.cc.regs.sja1000.ecc;
		u8 txerr = msg->msg.error.cc.regs.sja1000.txerr;
		u8 rxerr = msg->msg.error.cc.regs.sja1000.rxerr;

		/* bus error interrupt */
		dev->can.can_stats.bus_error++;
		stats->rx_errors++;

		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;

		switch (ecc & SJA1000_ECC_MASK) {
		case SJA1000_ECC_BIT:
			cf->data[2] |= CAN_ERR_PROT_BIT;
			break;
		case SJA1000_ECC_FORM:
			cf->data[2] |= CAN_ERR_PROT_FORM;
			break;
		case SJA1000_ECC_STUFF:
			cf->data[2] |= CAN_ERR_PROT_STUFF;
			break;
		default:
			cf->data[3] = ecc & SJA1000_ECC_SEG;
			break;
		}

		/* Error occurred during transmission? */
		if ((ecc & SJA1000_ECC_DIR) == 0)
			cf->data[2] |= CAN_ERR_PROT_TX;

		if (dev->can.state == CAN_STATE_ERROR_WARNING ||
		    dev->can.state == CAN_STATE_ERROR_PASSIVE) {
			cf->can_id |= CAN_ERR_CRTL;
			cf->data[1] = (txerr > rxerr) ?
			    CAN_ERR_CRTL_TX_PASSIVE : CAN_ERR_CRTL_RX_PASSIVE;
		}
	} else if (msg->type == CPC_MSG_TYPE_OVERRUN) {
		cf->can_id |= CAN_ERR_CRTL;
		cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;

		stats->rx_over_errors++;
		stats->rx_errors++;
	}

	stats->rx_packets++;
	stats->rx_bytes += cf->len;
	netif_rx(skb);
}

/*
 * callback for bulk IN urb
 */
static void ems_usb_read_bulk_callback(struct urb *urb)
{
	struct ems_usb *dev = urb->context;
	struct net_device *netdev;
	int retval;

	netdev = dev->netdev;

	if (!netif_device_present(netdev))
		return;

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

	case -ENOENT:
		return;

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

	if (urb->actual_length > CPC_HEADER_SIZE) {
		struct ems_cpc_msg *msg;
		u8 *ibuf = urb->transfer_buffer;
		u8 msg_count, start;

		msg_count = ibuf[0] & ~0x80;

		start = CPC_HEADER_SIZE;

		while (msg_count) {
			msg = (struct ems_cpc_msg *)&ibuf[start];

			switch (msg->type) {
			case CPC_MSG_TYPE_CAN_STATE:
				/* Process CAN state changes */
				ems_usb_rx_err(dev, msg);
				break;

			case CPC_MSG_TYPE_CAN_FRAME:
			case CPC_MSG_TYPE_EXT_CAN_FRAME:
			case CPC_MSG_TYPE_RTR_FRAME:
			case CPC_MSG_TYPE_EXT_RTR_FRAME:
				ems_usb_rx_can_msg(dev, msg);
				break;

			case CPC_MSG_TYPE_CAN_FRAME_ERROR:
				/* Process errorframe */
				ems_usb_rx_err(dev, msg);
				break;

			case CPC_MSG_TYPE_OVERRUN:
				/* Message lost while receiving */
				ems_usb_rx_err(dev, msg);
				break;
			}

			start += CPC_MSG_HEADER_LEN + msg->length;
			msg_count--;

			if (start > urb->transfer_buffer_length) {
				netdev_err(netdev, "format error\n");
				break;
			}
		}
	}

resubmit_urb:
	usb_fill_bulk_urb(urb, dev->udev, usb_rcvbulkpipe(dev->udev, 2),
			  urb->transfer_buffer, RX_BUFFER_SIZE,
			  ems_usb_read_bulk_callback, dev);

	retval = usb_submit_urb(urb, GFP_ATOMIC);

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

/*
 * callback for bulk IN urb
 */
static void ems_usb_write_bulk_callback(struct urb *urb)
{
	struct ems_tx_urb_context *context = urb->context;
	struct ems_usb *dev;
	struct net_device *netdev;

	BUG_ON(!context);

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

	/* free up our allocated buffer */
	usb_free_coherent(urb->dev, urb->transfer_buffer_length,
			  urb->transfer_buffer, urb->transfer_dma);

	atomic_dec(&dev->active_tx_urbs);

	if (!netif_device_present(netdev))
		return;

	if (urb->status)
		netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);

	netif_trans_update(netdev);

	/* transmission complete interrupt */
	netdev->stats.tx_packets++;
	netdev->stats.tx_bytes += context->dlc;

	can_get_echo_skb(netdev, context->echo_index, NULL);

	/* Release context */
	context->echo_index = MAX_TX_URBS;

}

/*
 * Send the given CPC command synchronously
 */
static int ems_usb_command_msg(struct ems_usb *dev, struct ems_cpc_msg *msg)
{
	int actual_length;

	/* Copy payload */
	memcpy(&dev->tx_msg_buffer[CPC_HEADER_SIZE], msg,
	       msg->length + CPC_MSG_HEADER_LEN);

	/* Clear header */
	memset(&dev->tx_msg_buffer[0], 0, CPC_HEADER_SIZE);

	return usb_bulk_msg(dev->udev, usb_sndbulkpipe(dev->udev, 2),
			    &dev->tx_msg_buffer[0],
			    msg->length + CPC_MSG_HEADER_LEN + CPC_HEADER_SIZE,
			    &actual_length, 1000);
}

/*
 * Change CAN controllers' mode register
 */
static int ems_usb_write_mode(struct ems_usb *dev, u8 mode)
{
	dev->active_params.msg.can_params.cc_params.sja1000.mode = mode;

	return ems_usb_command_msg(dev, &dev->active_params);
}

/*
 * Send a CPC_Control command to change behaviour when interface receives a CAN
 * message, bus error or CAN state changed notifications.
 */
static int ems_usb_control_cmd(struct ems_usb *dev, u8 val)
{
	struct ems_cpc_msg cmd;

	cmd.type = CPC_CMD_TYPE_CONTROL;
	cmd.length = CPC_MSG_HEADER_LEN + 1;

	cmd.msgid = 0;

	cmd.msg.generic[0] = val;

	return ems_usb_command_msg(dev, &cmd);
}

/*
 * Start interface
 */
static int ems_usb_start(struct ems_usb *dev)
{
	struct net_device *netdev = dev->netdev;
	int err, i;

	dev->intr_in_buffer[0] = 0;
	dev->free_slots = 50; /* initial size */

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

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

		buf = usb_alloc_coherent(dev->udev, RX_BUFFER_SIZE, GFP_KERNEL,
					 &urb->transfer_dma);
		if (!buf) {
			netdev_err(netdev, "No memory left for USB buffer\n");
			usb_free_urb(urb);
			err = -ENOMEM;
			break;
		}

		usb_fill_bulk_urb(urb, dev->udev, usb_rcvbulkpipe(dev->udev, 2),
				  buf, RX_BUFFER_SIZE,
				  ems_usb_read_bulk_callback, dev);
		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
		usb_anchor_urb(urb, &dev->rx_submitted);

		err = usb_submit_urb(urb, GFP_KERNEL);
		if (err) {
			usb_unanchor_urb(urb);
			usb_free_coherent(dev->udev, RX_BUFFER_SIZE, buf,
					  urb->transfer_dma);
			usb_free_urb(urb);
			break;
		}

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

	/* Did we submit any URBs */
	if (i == 0) {
		netdev_warn(netdev, "couldn't setup read URBs\n");
		return err;
	}

	/* Warn if we've couldn't transmit all the URBs */
	if (i < MAX_RX_URBS)
		netdev_warn(netdev, "rx performance may be slow\n");

	/* Setup and start interrupt URB */
	usb_fill_int_urb(dev->intr_urb, dev->udev,
			 usb_rcvintpipe(dev->udev, 1),
			 dev->intr_in_buffer,
			 INTR_IN_BUFFER_SIZE,
			 ems_usb_read_interrupt_callback, dev, 1);

	err = usb_submit_urb(dev->intr_urb, GFP_KERNEL);
	if (err) {
		netdev_warn(netdev, "intr URB submit failed: %d\n", err);

		return err;
	}

	/* CPC-USB will transfer received message to host */
	err = ems_usb_control_cmd(dev, CONTR_CAN_MESSAGE | CONTR_CONT_ON);
	if (err)
		goto failed;

	/* CPC-USB will transfer CAN state changes to host */
	err = ems_usb_control_cmd(dev, CONTR_CAN_STATE | CONTR_CONT_ON);
	if (err)
		goto failed;

	/* CPC-USB will transfer bus errors to host */
	err = ems_usb_control_cmd(dev, CONTR_BUS_ERROR | CONTR_CONT_ON);
	if (err)
		goto failed;

	err = ems_usb_write_mode(dev, SJA1000_MOD_NORMAL);
	if (err)
		goto failed;

	dev->can.state = CAN_STATE_ERROR_ACTIVE;

	return 0;

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

	return err;
}

static void unlink_all_urbs(struct ems_usb *dev)
{
	int i;

	usb_unlink_urb(dev->intr_urb);

	usb_kill_anchored_urbs(&dev->rx_submitted);

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

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

static int ems_usb_open(struct net_device *netdev)
{
	struct ems_usb *dev = netdev_priv(netdev);
	int err;

	err = ems_usb_write_mode(dev, SJA1000_MOD_RM);
	if (err)
		return err;

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

	/* finally start device */
	err = ems_usb_start(dev);
	if (err) {
		if (err == -ENODEV)
			netif_device_detach(dev->netdev);

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

		close_candev(netdev);

		return err;
	}


	netif_start_queue(netdev);

	return 0;
}

static netdev_tx_t ems_usb_start_xmit(struct sk_buff *skb, struct net_device *netdev)
{
	struct ems_usb *dev = netdev_priv(netdev);
	struct ems_tx_urb_context *context = NULL;
	struct net_device_stats *stats = &netdev->stats;
	struct can_frame *cf = (struct can_frame *)skb->data;
	struct ems_cpc_msg *msg;
	struct urb *urb;
	u8 *buf;
	int i, err;
	size_t size = CPC_HEADER_SIZE + CPC_MSG_HEADER_LEN
			+ sizeof(struct cpc_can_msg);

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

	/* create a URB, and a buffer for it, and copy the data to the URB */
	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb)
		goto nomem;

	buf = usb_alloc_coherent(dev->udev, size, GFP_ATOMIC, &urb->transfer_dma);
	if (!buf) {
		netdev_err(netdev, "No memory left for USB buffer\n");
		usb_free_urb(urb);
		goto nomem;
	}

	msg = (struct ems_cpc_msg *)&buf[CPC_HEADER_SIZE];

	msg->msg.can_msg.id = cpu_to_le32(cf->can_id & CAN_ERR_MASK);
	msg->msg.can_msg.length = cf->len;

	if (cf->can_id & CAN_RTR_FLAG) {
		msg->type = cf->can_id & CAN_EFF_FLAG ?
			CPC_CMD_TYPE_EXT_RTR_FRAME : CPC_CMD_TYPE_RTR_FRAME;

		msg->length = CPC_CAN_MSG_MIN_SIZE;
	} else {
		msg->type = cf->can_id & CAN_EFF_FLAG ?
			CPC_CMD_TYPE_EXT_CAN_FRAME : CPC_CMD_TYPE_CAN_FRAME;

		for (i = 0; i < cf->len; i++)
			msg->msg.can_msg.msg[i] = cf->data[i];

		msg->length = CPC_CAN_MSG_MIN_SIZE + cf->len;
	}

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

	/*
	 * May never happen! When this happens we'd more URBs in flight as
	 * allowed (MAX_TX_URBS).
	 */
	if (!context) {
		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
		usb_free_urb(urb);

		netdev_warn(netdev, "couldn't find free context\n");

		return NETDEV_TX_BUSY;
	}

	context->dev = dev;
	context->echo_index = i;
	context->dlc = cf->len;

	usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 2), buf,
			  size, ems_usb_write_bulk_callback, context);
	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
	usb_anchor_urb(urb, &dev->tx_submitted);

	can_put_echo_skb(skb, netdev, context->echo_index, 0);

	atomic_inc(&dev->active_tx_urbs);

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

		usb_unanchor_urb(urb);
		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
		dev_kfree_skb(skb);

		atomic_dec(&dev->active_tx_urbs);

		if (err == -ENODEV) {
			netif_device_detach(netdev);
		} else {
			netdev_warn(netdev, "failed tx_urb %d\n", err);

			stats->tx_dropped++;
		}
	} else {
		netif_trans_update(netdev);

		/* Slow down tx path */
		if (atomic_read(&dev->active_tx_urbs) >= MAX_TX_URBS ||
		    dev->free_slots < CPC_TX_QUEUE_TRIGGER_LOW) {
			netif_stop_queue(netdev);
		}
	}

	/*
	 * Release our reference to this URB, the USB core will eventually free
	 * it entirely.
	 */
	usb_free_urb(urb);

	return NETDEV_TX_OK;

nomem:
	dev_kfree_skb(skb);
	stats->tx_dropped++;

	return NETDEV_TX_OK;
}

static int ems_usb_close(struct net_device *netdev)
{
	struct ems_usb *dev = netdev_priv(netdev);

	/* Stop polling */
	unlink_all_urbs(dev);

	netif_stop_queue(netdev);

	/* Set CAN controller to reset mode */
	if (ems_usb_write_mode(dev, SJA1000_MOD_RM))
		netdev_warn(netdev, "couldn't stop device");

	close_candev(netdev);

	return 0;
}

static const struct net_device_ops ems_usb_netdev_ops = {
	.ndo_open = ems_usb_open,
	.ndo_stop = ems_usb_close,
	.ndo_start_xmit = ems_usb_start_xmit,
	.ndo_change_mtu = can_change_mtu,
};

static const struct can_bittiming_const ems_usb_bittiming_const = {
	.name = "ems_usb",
	.tseg1_min = 1,
	.tseg1_max = 16,
	.tseg2_min = 1,
	.tseg2_max = 8,
	.sjw_max = 4,
	.brp_min = 1,
	.brp_max = 64,
	.brp_inc = 1,
};

static int ems_usb_set_mode(struct net_device *netdev, enum can_mode mode)
{
	struct ems_usb *dev = netdev_priv(netdev);

	switch (mode) {
	case CAN_MODE_START:
		if (ems_usb_write_mode(dev, SJA1000_MOD_NORMAL))
			netdev_warn(netdev, "couldn't start device");

		if (netif_queue_stopped(netdev))
			netif_wake_queue(netdev);
		break;

	default:
		return -EOPNOTSUPP;
	}

	return 0;
}

static int ems_usb_set_bittiming(struct net_device *netdev)
{
	struct ems_usb *dev = netdev_priv(netdev);
	struct can_bittiming *bt = &dev->can.bittiming;
	u8 btr0, btr1;

	btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
	btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
		(((bt->phase_seg2 - 1) & 0x7) << 4);
	if (dev->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
		btr1 |= 0x80;

	netdev_info(netdev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);

	dev->active_params.msg.can_params.cc_params.sja1000.btr0 = btr0;
	dev->active_params.msg.can_params.cc_params.sja1000.btr1 = btr1;

	return ems_usb_command_msg(dev, &dev->active_params);
}

static void init_params_sja1000(struct ems_cpc_msg *msg)
{
	struct cpc_sja1000_params *sja1000 =
		&msg->msg.can_params.cc_params.sja1000;

	msg->type = CPC_CMD_TYPE_CAN_PARAMS;
	msg->length = sizeof(struct cpc_can_params);
	msg->msgid = 0;

	msg->msg.can_params.cc_type = CPC_CC_TYPE_SJA1000;

	/* Acceptance filter open */
	sja1000->acc_code0 = 0x00;
	sja1000->acc_code1 = 0x00;
	sja1000->acc_code2 = 0x00;
	sja1000->acc_code3 = 0x00;

	/* Acceptance filter open */
	sja1000->acc_mask0 = 0xFF;
	sja1000->acc_mask1 = 0xFF;
	sja1000->acc_mask2 = 0xFF;
	sja1000->acc_mask3 = 0xFF;

	sja1000->btr0 = 0;
	sja1000->btr1 = 0;

	sja1000->outp_contr = SJA1000_DEFAULT_OUTPUT_CONTROL;
	sja1000->mode = SJA1000_MOD_RM;
}

/*
 * probe function for new CPC-USB devices
 */
static int ems_usb_probe(struct usb_interface *intf,
			 const struct usb_device_id *id)
{
	struct net_device *netdev;
	struct ems_usb *dev;
	int i, err = -ENOMEM;

	netdev = alloc_candev(sizeof(struct ems_usb), MAX_TX_URBS);
	if (!netdev) {
		dev_err(&intf->dev, "ems_usb: Couldn't alloc candev\n");
		return -ENOMEM;
	}

	dev = netdev_priv(netdev);

	dev->udev = interface_to_usbdev(intf);
	dev->netdev = netdev;

	dev->can.state = CAN_STATE_STOPPED;
	dev->can.clock.freq = EMS_USB_ARM7_CLOCK;
	dev->can.bittiming_const = &ems_usb_bittiming_const;
	dev->can.do_set_bittiming = ems_usb_set_bittiming;
	dev->can.do_set_mode = ems_usb_set_mode;
	dev->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;

	netdev->netdev_ops = &ems_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 < MAX_TX_URBS; i++)
		dev->tx_contexts[i].echo_index = MAX_TX_URBS;

	dev->intr_urb = usb_alloc_urb(0, GFP_KERNEL);
	if (!dev->intr_urb)
		goto cleanup_candev;

	dev->intr_in_buffer = kzalloc(INTR_IN_BUFFER_SIZE, GFP_KERNEL);
	if (!dev->intr_in_buffer)
		goto cleanup_intr_urb;

	dev->tx_msg_buffer = kzalloc(CPC_HEADER_SIZE +
				     sizeof(struct ems_cpc_msg), GFP_KERNEL);
	if (!dev->tx_msg_buffer)
		goto cleanup_intr_in_buffer;

	usb_set_intfdata(intf, dev);

	SET_NETDEV_DEV(netdev, &intf->dev);

	init_params_sja1000(&dev->active_params);

	err = ems_usb_command_msg(dev, &dev->active_params);
	if (err) {
		netdev_err(netdev, "couldn't initialize controller: %d\n", err);
		goto cleanup_tx_msg_buffer;
	}

	err = register_candev(netdev);
	if (err) {
		netdev_err(netdev, "couldn't register CAN device: %d\n", err);
		goto cleanup_tx_msg_buffer;
	}

	return 0;

cleanup_tx_msg_buffer:
	kfree(dev->tx_msg_buffer);

cleanup_intr_in_buffer:
	kfree(dev->intr_in_buffer);

cleanup_intr_urb:
	usb_free_urb(dev->intr_urb);

cleanup_candev:
	free_candev(netdev);

	return err;
}

/*
 * called by the usb core when the device is removed from the system
 */
static void ems_usb_disconnect(struct usb_interface *intf)
{
	struct ems_usb *dev = usb_get_intfdata(intf);

	usb_set_intfdata(intf, NULL);

	if (dev) {
		unregister_netdev(dev->netdev);

		unlink_all_urbs(dev);

		usb_free_urb(dev->intr_urb);

		kfree(dev->intr_in_buffer);
		kfree(dev->tx_msg_buffer);

		free_candev(dev->netdev);
	}
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver ems_usb_driver = {
	.name = "ems_usb",
	.probe = ems_usb_probe,
	.disconnect = ems_usb_disconnect,
	.id_table = ems_usb_table,
};

module_usb_driver(ems_usb_driver);