summaryrefslogtreecommitdiff
path: root/drivers/net/can/usb/gs_usb.c
blob: 77e3cc06a30c8cb970b6afef41352a15716c9331 (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
/* CAN driver for Geschwister Schneider USB/CAN devices
 * and bytewerk.org candleLight USB CAN interfaces.
 *
 * Copyright (C) 2013-2016 Geschwister Schneider Technologie-,
 * Entwicklungs- und Vertriebs UG (Haftungsbeschränkt).
 * Copyright (C) 2016 Hubert Denkmair
 *
 * Many thanks to all socketcan devs!
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published
 * by the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that 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/init.h>
#include <linux/signal.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>

/* Device specific constants */
#define USB_GSUSB_1_VENDOR_ID      0x1d50
#define USB_GSUSB_1_PRODUCT_ID     0x606f

#define USB_CANDLELIGHT_VENDOR_ID  0x1209
#define USB_CANDLELIGHT_PRODUCT_ID 0x2323

#define GSUSB_ENDPOINT_IN          1
#define GSUSB_ENDPOINT_OUT         2

/* Device specific constants */
enum gs_usb_breq {
	GS_USB_BREQ_HOST_FORMAT = 0,
	GS_USB_BREQ_BITTIMING,
	GS_USB_BREQ_MODE,
	GS_USB_BREQ_BERR,
	GS_USB_BREQ_BT_CONST,
	GS_USB_BREQ_DEVICE_CONFIG,
	GS_USB_BREQ_TIMESTAMP,
	GS_USB_BREQ_IDENTIFY,
};

enum gs_can_mode {
	/* reset a channel. turns it off */
	GS_CAN_MODE_RESET = 0,
	/* starts a channel */
	GS_CAN_MODE_START
};

enum gs_can_state {
	GS_CAN_STATE_ERROR_ACTIVE = 0,
	GS_CAN_STATE_ERROR_WARNING,
	GS_CAN_STATE_ERROR_PASSIVE,
	GS_CAN_STATE_BUS_OFF,
	GS_CAN_STATE_STOPPED,
	GS_CAN_STATE_SLEEPING
};

enum gs_can_identify_mode {
	GS_CAN_IDENTIFY_OFF = 0,
	GS_CAN_IDENTIFY_ON
};

/* data types passed between host and device */
struct gs_host_config {
	u32 byte_order;
} __packed;
/* All data exchanged between host and device is exchanged in host byte order,
 * thanks to the struct gs_host_config byte_order member, which is sent first
 * to indicate the desired byte order.
 */

struct gs_device_config {
	u8 reserved1;
	u8 reserved2;
	u8 reserved3;
	u8 icount;
	u32 sw_version;
	u32 hw_version;
} __packed;

#define GS_CAN_MODE_NORMAL               0
#define GS_CAN_MODE_LISTEN_ONLY          BIT(0)
#define GS_CAN_MODE_LOOP_BACK            BIT(1)
#define GS_CAN_MODE_TRIPLE_SAMPLE        BIT(2)
#define GS_CAN_MODE_ONE_SHOT             BIT(3)

struct gs_device_mode {
	u32 mode;
	u32 flags;
} __packed;

struct gs_device_state {
	u32 state;
	u32 rxerr;
	u32 txerr;
} __packed;

struct gs_device_bittiming {
	u32 prop_seg;
	u32 phase_seg1;
	u32 phase_seg2;
	u32 sjw;
	u32 brp;
} __packed;

struct gs_identify_mode {
	u32 mode;
} __packed;

#define GS_CAN_FEATURE_LISTEN_ONLY      BIT(0)
#define GS_CAN_FEATURE_LOOP_BACK        BIT(1)
#define GS_CAN_FEATURE_TRIPLE_SAMPLE    BIT(2)
#define GS_CAN_FEATURE_ONE_SHOT         BIT(3)
#define GS_CAN_FEATURE_HW_TIMESTAMP     BIT(4)
#define GS_CAN_FEATURE_IDENTIFY         BIT(5)

struct gs_device_bt_const {
	u32 feature;
	u32 fclk_can;
	u32 tseg1_min;
	u32 tseg1_max;
	u32 tseg2_min;
	u32 tseg2_max;
	u32 sjw_max;
	u32 brp_min;
	u32 brp_max;
	u32 brp_inc;
} __packed;

#define GS_CAN_FLAG_OVERFLOW 1

struct gs_host_frame {
	u32 echo_id;
	u32 can_id;

	u8 can_dlc;
	u8 channel;
	u8 flags;
	u8 reserved;

	u8 data[8];
} __packed;
/* The GS USB devices make use of the same flags and masks as in
 * linux/can.h and linux/can/error.h, and no additional mapping is necessary.
 */

/* Only send a max of GS_MAX_TX_URBS frames per channel at a time. */
#define GS_MAX_TX_URBS 10
/* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
#define GS_MAX_RX_URBS 30
/* Maximum number of interfaces the driver supports per device.
 * Current hardware only supports 2 interfaces. The future may vary.
 */
#define GS_MAX_INTF 2

struct gs_tx_context {
	struct gs_can *dev;
	unsigned int echo_id;
};

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

	struct gs_usb *parent;

	struct net_device *netdev;
	struct usb_device *udev;
	struct usb_interface *iface;

	struct can_bittiming_const bt_const;
	unsigned int channel;	/* channel number */

	/* This lock prevents a race condition between xmit and receive. */
	spinlock_t tx_ctx_lock;
	struct gs_tx_context tx_context[GS_MAX_TX_URBS];

	struct usb_anchor tx_submitted;
	atomic_t active_tx_urbs;
};

/* usb interface struct */
struct gs_usb {
	struct gs_can *canch[GS_MAX_INTF];
	struct usb_anchor rx_submitted;
	atomic_t active_channels;
	struct usb_device *udev;
};

/* 'allocate' a tx context.
 * returns a valid tx context or NULL if there is no space.
 */
static struct gs_tx_context *gs_alloc_tx_context(struct gs_can *dev)
{
	int i = 0;
	unsigned long flags;

	spin_lock_irqsave(&dev->tx_ctx_lock, flags);

	for (; i < GS_MAX_TX_URBS; i++) {
		if (dev->tx_context[i].echo_id == GS_MAX_TX_URBS) {
			dev->tx_context[i].echo_id = i;
			spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
			return &dev->tx_context[i];
		}
	}

	spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
	return NULL;
}

/* releases a tx context
 */
static void gs_free_tx_context(struct gs_tx_context *txc)
{
	txc->echo_id = GS_MAX_TX_URBS;
}

/* Get a tx context by id.
 */
static struct gs_tx_context *gs_get_tx_context(struct gs_can *dev,
					       unsigned int id)
{
	unsigned long flags;

	if (id < GS_MAX_TX_URBS) {
		spin_lock_irqsave(&dev->tx_ctx_lock, flags);
		if (dev->tx_context[id].echo_id == id) {
			spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
			return &dev->tx_context[id];
		}
		spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
	}
	return NULL;
}

static int gs_cmd_reset(struct gs_usb *gsusb, struct gs_can *gsdev)
{
	struct gs_device_mode *dm;
	struct usb_interface *intf = gsdev->iface;
	int rc;

	dm = kzalloc(sizeof(*dm), GFP_KERNEL);
	if (!dm)
		return -ENOMEM;

	dm->mode = GS_CAN_MODE_RESET;

	rc = usb_control_msg(interface_to_usbdev(intf),
			     usb_sndctrlpipe(interface_to_usbdev(intf), 0),
			     GS_USB_BREQ_MODE,
			     USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
			     gsdev->channel,
			     0,
			     dm,
			     sizeof(*dm),
			     1000);

	return rc;
}

static void gs_update_state(struct gs_can *dev, struct can_frame *cf)
{
	struct can_device_stats *can_stats = &dev->can.can_stats;

	if (cf->can_id & CAN_ERR_RESTARTED) {
		dev->can.state = CAN_STATE_ERROR_ACTIVE;
		can_stats->restarts++;
	} else if (cf->can_id & CAN_ERR_BUSOFF) {
		dev->can.state = CAN_STATE_BUS_OFF;
		can_stats->bus_off++;
	} else if (cf->can_id & CAN_ERR_CRTL) {
		if ((cf->data[1] & CAN_ERR_CRTL_TX_WARNING) ||
		    (cf->data[1] & CAN_ERR_CRTL_RX_WARNING)) {
			dev->can.state = CAN_STATE_ERROR_WARNING;
			can_stats->error_warning++;
		} else if ((cf->data[1] & CAN_ERR_CRTL_TX_PASSIVE) ||
			   (cf->data[1] & CAN_ERR_CRTL_RX_PASSIVE)) {
			dev->can.state = CAN_STATE_ERROR_PASSIVE;
			can_stats->error_passive++;
		} else {
			dev->can.state = CAN_STATE_ERROR_ACTIVE;
		}
	}
}

static void gs_usb_receive_bulk_callback(struct urb *urb)
{
	struct gs_usb *usbcan = urb->context;
	struct gs_can *dev;
	struct net_device *netdev;
	int rc;
	struct net_device_stats *stats;
	struct gs_host_frame *hf = urb->transfer_buffer;
	struct gs_tx_context *txc;
	struct can_frame *cf;
	struct sk_buff *skb;

	BUG_ON(!usbcan);

	switch (urb->status) {
	case 0: /* success */
		break;
	case -ENOENT:
	case -ESHUTDOWN:
		return;
	default:
		/* do not resubmit aborted urbs. eg: when device goes down */
		return;
	}

	/* device reports out of range channel id */
	if (hf->channel >= GS_MAX_INTF)
		goto resubmit_urb;

	dev = usbcan->canch[hf->channel];

	netdev = dev->netdev;
	stats = &netdev->stats;

	if (!netif_device_present(netdev))
		return;

	if (hf->echo_id == -1) { /* normal rx */
		skb = alloc_can_skb(dev->netdev, &cf);
		if (!skb)
			return;

		cf->can_id = hf->can_id;

		cf->can_dlc = get_can_dlc(hf->can_dlc);
		memcpy(cf->data, hf->data, 8);

		/* ERROR frames tell us information about the controller */
		if (hf->can_id & CAN_ERR_FLAG)
			gs_update_state(dev, cf);

		netdev->stats.rx_packets++;
		netdev->stats.rx_bytes += hf->can_dlc;

		netif_rx(skb);
	} else { /* echo_id == hf->echo_id */
		if (hf->echo_id >= GS_MAX_TX_URBS) {
			netdev_err(netdev,
				   "Unexpected out of range echo id %d\n",
				   hf->echo_id);
			goto resubmit_urb;
		}

		netdev->stats.tx_packets++;
		netdev->stats.tx_bytes += hf->can_dlc;

		txc = gs_get_tx_context(dev, hf->echo_id);

		/* bad devices send bad echo_ids. */
		if (!txc) {
			netdev_err(netdev,
				   "Unexpected unused echo id %d\n",
				   hf->echo_id);
			goto resubmit_urb;
		}

		can_get_echo_skb(netdev, hf->echo_id);

		gs_free_tx_context(txc);

		netif_wake_queue(netdev);
	}

	if (hf->flags & GS_CAN_FLAG_OVERFLOW) {
		skb = alloc_can_err_skb(netdev, &cf);
		if (!skb)
			goto resubmit_urb;

		cf->can_id |= CAN_ERR_CRTL;
		cf->can_dlc = CAN_ERR_DLC;
		cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
		stats->rx_over_errors++;
		stats->rx_errors++;
		netif_rx(skb);
	}

 resubmit_urb:
	usb_fill_bulk_urb(urb,
			  usbcan->udev,
			  usb_rcvbulkpipe(usbcan->udev, GSUSB_ENDPOINT_IN),
			  hf,
			  sizeof(struct gs_host_frame),
			  gs_usb_receive_bulk_callback,
			  usbcan
			  );

	rc = usb_submit_urb(urb, GFP_ATOMIC);

	/* USB failure take down all interfaces */
	if (rc == -ENODEV) {
		for (rc = 0; rc < GS_MAX_INTF; rc++) {
			if (usbcan->canch[rc])
				netif_device_detach(usbcan->canch[rc]->netdev);
		}
	}
}

static int gs_usb_set_bittiming(struct net_device *netdev)
{
	struct gs_can *dev = netdev_priv(netdev);
	struct can_bittiming *bt = &dev->can.bittiming;
	struct usb_interface *intf = dev->iface;
	int rc;
	struct gs_device_bittiming *dbt;

	dbt = kmalloc(sizeof(*dbt), GFP_KERNEL);
	if (!dbt)
		return -ENOMEM;

	dbt->prop_seg = bt->prop_seg;
	dbt->phase_seg1 = bt->phase_seg1;
	dbt->phase_seg2 = bt->phase_seg2;
	dbt->sjw = bt->sjw;
	dbt->brp = bt->brp;

	/* request bit timings */
	rc = usb_control_msg(interface_to_usbdev(intf),
			     usb_sndctrlpipe(interface_to_usbdev(intf), 0),
			     GS_USB_BREQ_BITTIMING,
			     USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
			     dev->channel,
			     0,
			     dbt,
			     sizeof(*dbt),
			     1000);

	kfree(dbt);

	if (rc < 0)
		dev_err(netdev->dev.parent, "Couldn't set bittimings (err=%d)",
			rc);

	return rc;
}

static void gs_usb_xmit_callback(struct urb *urb)
{
	struct gs_tx_context *txc = urb->context;
	struct gs_can *dev = txc->dev;
	struct net_device *netdev = dev->netdev;

	if (urb->status)
		netdev_info(netdev, "usb xmit fail %d\n", txc->echo_id);

	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 (netif_queue_stopped(netdev))
		netif_wake_queue(netdev);
}

static netdev_tx_t gs_can_start_xmit(struct sk_buff *skb,
				     struct net_device *netdev)
{
	struct gs_can *dev = netdev_priv(netdev);
	struct net_device_stats *stats = &dev->netdev->stats;
	struct urb *urb;
	struct gs_host_frame *hf;
	struct can_frame *cf;
	int rc;
	unsigned int idx;
	struct gs_tx_context *txc;

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

	/* find an empty context to keep track of transmission */
	txc = gs_alloc_tx_context(dev);
	if (!txc)
		return NETDEV_TX_BUSY;

	/* create a URB, and a buffer for it */
	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb)
		goto nomem_urb;

	hf = usb_alloc_coherent(dev->udev, sizeof(*hf), GFP_ATOMIC,
				&urb->transfer_dma);
	if (!hf) {
		netdev_err(netdev, "No memory left for USB buffer\n");
		goto nomem_hf;
	}

	idx = txc->echo_id;

	if (idx >= GS_MAX_TX_URBS) {
		netdev_err(netdev, "Invalid tx context %d\n", idx);
		goto badidx;
	}

	hf->echo_id = idx;
	hf->channel = dev->channel;

	cf = (struct can_frame *)skb->data;

	hf->can_id = cf->can_id;
	hf->can_dlc = cf->can_dlc;
	memcpy(hf->data, cf->data, cf->can_dlc);

	usb_fill_bulk_urb(urb, dev->udev,
			  usb_sndbulkpipe(dev->udev, GSUSB_ENDPOINT_OUT),
			  hf,
			  sizeof(*hf),
			  gs_usb_xmit_callback,
			  txc);

	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
	usb_anchor_urb(urb, &dev->tx_submitted);

	can_put_echo_skb(skb, netdev, idx);

	atomic_inc(&dev->active_tx_urbs);

	rc = usb_submit_urb(urb, GFP_ATOMIC);
	if (unlikely(rc)) {			/* usb send failed */
		atomic_dec(&dev->active_tx_urbs);

		can_free_echo_skb(netdev, idx);
		gs_free_tx_context(txc);

		usb_unanchor_urb(urb);
		usb_free_coherent(dev->udev,
				  sizeof(*hf),
				  hf,
				  urb->transfer_dma);


		if (rc == -ENODEV) {
			netif_device_detach(netdev);
		} else {
			netdev_err(netdev, "usb_submit failed (err=%d)\n", rc);
			stats->tx_dropped++;
		}
	} else {
		/* Slow down tx path */
		if (atomic_read(&dev->active_tx_urbs) >= GS_MAX_TX_URBS)
			netif_stop_queue(netdev);
	}

	/* let usb core take care of this urb */
	usb_free_urb(urb);

	return NETDEV_TX_OK;

 badidx:
	usb_free_coherent(dev->udev,
			  sizeof(*hf),
			  hf,
			  urb->transfer_dma);
 nomem_hf:
	usb_free_urb(urb);

 nomem_urb:
	gs_free_tx_context(txc);
	dev_kfree_skb(skb);
	stats->tx_dropped++;
	return NETDEV_TX_OK;
}

static int gs_can_open(struct net_device *netdev)
{
	struct gs_can *dev = netdev_priv(netdev);
	struct gs_usb *parent = dev->parent;
	int rc, i;
	struct gs_device_mode *dm;
	u32 ctrlmode;

	rc = open_candev(netdev);
	if (rc)
		return rc;

	if (atomic_add_return(1, &parent->active_channels) == 1) {
		for (i = 0; i < GS_MAX_RX_URBS; i++) {
			struct urb *urb;
			u8 *buf;

			/* alloc rx urb */
			urb = usb_alloc_urb(0, GFP_KERNEL);
			if (!urb)
				return -ENOMEM;

			/* alloc rx buffer */
			buf = usb_alloc_coherent(dev->udev,
						 sizeof(struct gs_host_frame),
						 GFP_KERNEL,
						 &urb->transfer_dma);
			if (!buf) {
				netdev_err(netdev,
					   "No memory left for USB buffer\n");
				usb_free_urb(urb);
				return -ENOMEM;
			}

			/* fill, anchor, and submit rx urb */
			usb_fill_bulk_urb(urb,
					  dev->udev,
					  usb_rcvbulkpipe(dev->udev,
							  GSUSB_ENDPOINT_IN),
					  buf,
					  sizeof(struct gs_host_frame),
					  gs_usb_receive_bulk_callback,
					  parent);
			urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

			usb_anchor_urb(urb, &parent->rx_submitted);

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

				netdev_err(netdev,
					   "usb_submit failed (err=%d)\n",
					   rc);

				usb_unanchor_urb(urb);
				break;
			}

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

	dm = kmalloc(sizeof(*dm), GFP_KERNEL);
	if (!dm)
		return -ENOMEM;

	/* flags */
	ctrlmode = dev->can.ctrlmode;
	dm->flags = 0;

	if (ctrlmode & CAN_CTRLMODE_LOOPBACK)
		dm->flags |= GS_CAN_MODE_LOOP_BACK;
	else if (ctrlmode & CAN_CTRLMODE_LISTENONLY)
		dm->flags |= GS_CAN_MODE_LISTEN_ONLY;

	/* Controller is not allowed to retry TX
	 * this mode is unavailable on atmels uc3c hardware
	 */
	if (ctrlmode & CAN_CTRLMODE_ONE_SHOT)
		dm->flags |= GS_CAN_MODE_ONE_SHOT;

	if (ctrlmode & CAN_CTRLMODE_3_SAMPLES)
		dm->flags |= GS_CAN_MODE_TRIPLE_SAMPLE;

	/* finally start device */
	dm->mode = GS_CAN_MODE_START;
	rc = usb_control_msg(interface_to_usbdev(dev->iface),
			     usb_sndctrlpipe(interface_to_usbdev(dev->iface), 0),
			     GS_USB_BREQ_MODE,
			     USB_DIR_OUT | USB_TYPE_VENDOR |
			     USB_RECIP_INTERFACE,
			     dev->channel,
			     0,
			     dm,
			     sizeof(*dm),
			     1000);

	if (rc < 0) {
		netdev_err(netdev, "Couldn't start device (err=%d)\n", rc);
		kfree(dm);
		return rc;
	}

	kfree(dm);

	dev->can.state = CAN_STATE_ERROR_ACTIVE;

	if (!(dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
		netif_start_queue(netdev);

	return 0;
}

static int gs_can_close(struct net_device *netdev)
{
	int rc;
	struct gs_can *dev = netdev_priv(netdev);
	struct gs_usb *parent = dev->parent;

	netif_stop_queue(netdev);

	/* Stop polling */
	if (atomic_dec_and_test(&parent->active_channels))
		usb_kill_anchored_urbs(&parent->rx_submitted);

	/* Stop sending URBs */
	usb_kill_anchored_urbs(&dev->tx_submitted);
	atomic_set(&dev->active_tx_urbs, 0);

	/* reset the device */
	rc = gs_cmd_reset(parent, dev);
	if (rc < 0)
		netdev_warn(netdev, "Couldn't shutdown device (err=%d)", rc);

	/* reset tx contexts */
	for (rc = 0; rc < GS_MAX_TX_URBS; rc++) {
		dev->tx_context[rc].dev = dev;
		dev->tx_context[rc].echo_id = GS_MAX_TX_URBS;
	}

	/* close the netdev */
	close_candev(netdev);

	return 0;
}

static const struct net_device_ops gs_usb_netdev_ops = {
	.ndo_open = gs_can_open,
	.ndo_stop = gs_can_close,
	.ndo_start_xmit = gs_can_start_xmit,
	.ndo_change_mtu = can_change_mtu,
};

static int gs_usb_set_identify(struct net_device *netdev, bool do_identify)
{
	struct gs_can *dev = netdev_priv(netdev);
	struct gs_identify_mode imode;
	int rc;

	if (do_identify)
		imode.mode = GS_CAN_IDENTIFY_ON;
	else
		imode.mode = GS_CAN_IDENTIFY_OFF;

	rc = usb_control_msg(interface_to_usbdev(dev->iface),
			     usb_sndctrlpipe(interface_to_usbdev(dev->iface),
					     0),
			     GS_USB_BREQ_IDENTIFY,
			     USB_DIR_OUT | USB_TYPE_VENDOR |
			     USB_RECIP_INTERFACE,
			     dev->channel,
			     0,
			     &imode,
			     sizeof(imode),
			     100);

	return (rc > 0) ? 0 : rc;
}

/* blink LED's for finding the this interface */
static int gs_usb_set_phys_id(struct net_device *dev,
			      enum ethtool_phys_id_state state)
{
	int rc = 0;

	switch (state) {
	case ETHTOOL_ID_ACTIVE:
		rc = gs_usb_set_identify(dev, GS_CAN_IDENTIFY_ON);
		break;
	case ETHTOOL_ID_INACTIVE:
		rc = gs_usb_set_identify(dev, GS_CAN_IDENTIFY_OFF);
		break;
	default:
		break;
	}

	return rc;
}

static const struct ethtool_ops gs_usb_ethtool_ops = {
	.set_phys_id = gs_usb_set_phys_id,
};

static struct gs_can *gs_make_candev(unsigned int channel,
				     struct usb_interface *intf,
				     struct gs_device_config *dconf)
{
	struct gs_can *dev;
	struct net_device *netdev;
	int rc;
	struct gs_device_bt_const *bt_const;

	bt_const = kmalloc(sizeof(*bt_const), GFP_KERNEL);
	if (!bt_const)
		return ERR_PTR(-ENOMEM);

	/* fetch bit timing constants */
	rc = usb_control_msg(interface_to_usbdev(intf),
			     usb_rcvctrlpipe(interface_to_usbdev(intf), 0),
			     GS_USB_BREQ_BT_CONST,
			     USB_DIR_IN|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
			     channel,
			     0,
			     bt_const,
			     sizeof(*bt_const),
			     1000);

	if (rc < 0) {
		dev_err(&intf->dev,
			"Couldn't get bit timing const for channel (err=%d)\n",
			rc);
		kfree(bt_const);
		return ERR_PTR(rc);
	}

	/* create netdev */
	netdev = alloc_candev(sizeof(struct gs_can), GS_MAX_TX_URBS);
	if (!netdev) {
		dev_err(&intf->dev, "Couldn't allocate candev\n");
		kfree(bt_const);
		return ERR_PTR(-ENOMEM);
	}

	dev = netdev_priv(netdev);

	netdev->netdev_ops = &gs_usb_netdev_ops;

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

	/* dev settup */
	strcpy(dev->bt_const.name, "gs_usb");
	dev->bt_const.tseg1_min = bt_const->tseg1_min;
	dev->bt_const.tseg1_max = bt_const->tseg1_max;
	dev->bt_const.tseg2_min = bt_const->tseg2_min;
	dev->bt_const.tseg2_max = bt_const->tseg2_max;
	dev->bt_const.sjw_max = bt_const->sjw_max;
	dev->bt_const.brp_min = bt_const->brp_min;
	dev->bt_const.brp_max = bt_const->brp_max;
	dev->bt_const.brp_inc = bt_const->brp_inc;

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

	init_usb_anchor(&dev->tx_submitted);
	atomic_set(&dev->active_tx_urbs, 0);
	spin_lock_init(&dev->tx_ctx_lock);
	for (rc = 0; rc < GS_MAX_TX_URBS; rc++) {
		dev->tx_context[rc].dev = dev;
		dev->tx_context[rc].echo_id = GS_MAX_TX_URBS;
	}

	/* can settup */
	dev->can.state = CAN_STATE_STOPPED;
	dev->can.clock.freq = bt_const->fclk_can;
	dev->can.bittiming_const = &dev->bt_const;
	dev->can.do_set_bittiming = gs_usb_set_bittiming;

	dev->can.ctrlmode_supported = 0;

	if (bt_const->feature & GS_CAN_FEATURE_LISTEN_ONLY)
		dev->can.ctrlmode_supported |= CAN_CTRLMODE_LISTENONLY;

	if (bt_const->feature & GS_CAN_FEATURE_LOOP_BACK)
		dev->can.ctrlmode_supported |= CAN_CTRLMODE_LOOPBACK;

	if (bt_const->feature & GS_CAN_FEATURE_TRIPLE_SAMPLE)
		dev->can.ctrlmode_supported |= CAN_CTRLMODE_3_SAMPLES;

	if (bt_const->feature & GS_CAN_FEATURE_ONE_SHOT)
		dev->can.ctrlmode_supported |= CAN_CTRLMODE_ONE_SHOT;

	SET_NETDEV_DEV(netdev, &intf->dev);

	if (dconf->sw_version > 1)
		if (bt_const->feature & GS_CAN_FEATURE_IDENTIFY)
			netdev->ethtool_ops = &gs_usb_ethtool_ops;

	kfree(bt_const);

	rc = register_candev(dev->netdev);
	if (rc) {
		free_candev(dev->netdev);
		dev_err(&intf->dev, "Couldn't register candev (err=%d)\n", rc);
		return ERR_PTR(rc);
	}

	return dev;
}

static void gs_destroy_candev(struct gs_can *dev)
{
	unregister_candev(dev->netdev);
	usb_kill_anchored_urbs(&dev->tx_submitted);
	free_candev(dev->netdev);
}

static int gs_usb_probe(struct usb_interface *intf,
			const struct usb_device_id *id)
{
	struct gs_usb *dev;
	int rc = -ENOMEM;
	unsigned int icount, i;
	struct gs_host_config hconf = {
		.byte_order = 0x0000beef,
	};
	struct gs_device_config dconf;

	/* send host config */
	rc = usb_control_msg(interface_to_usbdev(intf),
			     usb_sndctrlpipe(interface_to_usbdev(intf), 0),
			     GS_USB_BREQ_HOST_FORMAT,
			     USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
			     1,
			     intf->altsetting[0].desc.bInterfaceNumber,
			     &hconf,
			     sizeof(hconf),
			     1000);

	if (rc < 0) {
		dev_err(&intf->dev, "Couldn't send data format (err=%d)\n",
			rc);
		return rc;
	}

	/* read device config */
	rc = usb_control_msg(interface_to_usbdev(intf),
			     usb_rcvctrlpipe(interface_to_usbdev(intf), 0),
			     GS_USB_BREQ_DEVICE_CONFIG,
			     USB_DIR_IN|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
			     1,
			     intf->altsetting[0].desc.bInterfaceNumber,
			     &dconf,
			     sizeof(dconf),
			     1000);
	if (rc < 0) {
		dev_err(&intf->dev, "Couldn't get device config: (err=%d)\n",
			rc);
		return rc;
	}

	icount = dconf.icount + 1;
	dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);

	if (icount > GS_MAX_INTF) {
		dev_err(&intf->dev,
			"Driver cannot handle more that %d CAN interfaces\n",
			GS_MAX_INTF);
		return -EINVAL;
	}

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;
	init_usb_anchor(&dev->rx_submitted);

	atomic_set(&dev->active_channels, 0);

	usb_set_intfdata(intf, dev);
	dev->udev = interface_to_usbdev(intf);

	for (i = 0; i < icount; i++) {
		dev->canch[i] = gs_make_candev(i, intf, &dconf);
		if (IS_ERR_OR_NULL(dev->canch[i])) {
			/* save error code to return later */
			rc = PTR_ERR(dev->canch[i]);

			/* on failure destroy previously created candevs */
			icount = i;
			for (i = 0; i < icount; i++)
				gs_destroy_candev(dev->canch[i]);

			usb_kill_anchored_urbs(&dev->rx_submitted);
			kfree(dev);
			return rc;
		}
		dev->canch[i]->parent = dev;
	}

	return 0;
}

static void gs_usb_disconnect(struct usb_interface *intf)
{
	unsigned i;
	struct gs_usb *dev = usb_get_intfdata(intf);
	usb_set_intfdata(intf, NULL);

	if (!dev) {
		dev_err(&intf->dev, "Disconnect (nodata)\n");
		return;
	}

	for (i = 0; i < GS_MAX_INTF; i++)
		if (dev->canch[i])
			gs_destroy_candev(dev->canch[i]);

	usb_kill_anchored_urbs(&dev->rx_submitted);
	kfree(dev);
}

static const struct usb_device_id gs_usb_table[] = {
	{ USB_DEVICE_INTERFACE_NUMBER(USB_GSUSB_1_VENDOR_ID,
				      USB_GSUSB_1_PRODUCT_ID, 0) },
	{ USB_DEVICE_INTERFACE_NUMBER(USB_CANDLELIGHT_VENDOR_ID,
				      USB_CANDLELIGHT_PRODUCT_ID, 0) },
	{} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, gs_usb_table);

static struct usb_driver gs_usb_driver = {
	.name       = "gs_usb",
	.probe      = gs_usb_probe,
	.disconnect = gs_usb_disconnect,
	.id_table   = gs_usb_table,
};

module_usb_driver(gs_usb_driver);

MODULE_AUTHOR("Maximilian Schneider <mws@schneidersoft.net>");
MODULE_DESCRIPTION(
"Socket CAN device driver for Geschwister Schneider Technologie-, "
"Entwicklungs- und Vertriebs UG. USB2.0 to CAN interfaces\n"
"and bytewerk.org candleLight USB CAN interfaces.");
MODULE_LICENSE("GPL v2");