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
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
/*
 * adutux - driver for ADU devices from Ontrak Control Systems
 * This is an experimental driver. Use at your own risk.
 * This driver is not supported by Ontrak Control Systems.
 *
 * Copyright (c) 2003 John Homppi (SCO, leave this notice here)
 *
 * 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; either version 2 of
 * the License, or (at your option) any later version.
 *
 * derived from the Lego USB Tower driver 0.56:
 * Copyright (c) 2003 David Glance <davidgsf@sourceforge.net>
 *               2001 Juergen Stuber <stuber@loria.fr>
 * that was derived from USB Skeleton driver - 0.5
 * Copyright (c) 2001 Greg Kroah-Hartman (greg@kroah.com)
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>

#ifdef CONFIG_USB_DEBUG
static int debug = 5;
#else
static int debug = 1;
#endif

/* Use our own dbg macro */
#undef dbg
#define dbg(lvl, format, arg...)	\
do {								\
	if (debug >= lvl)						\
		printk(KERN_DEBUG "%s: " format "\n", __FILE__, ##arg);	\
} while (0)


/* Version Information */
#define DRIVER_VERSION "v0.0.13"
#define DRIVER_AUTHOR "John Homppi"
#define DRIVER_DESC "adutux (see www.ontrak.net)"

/* Module parameters */
module_param(debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug enabled or not");

/* Define these values to match your device */
#define ADU_VENDOR_ID 0x0a07
#define ADU_PRODUCT_ID 0x0064

/* table of devices that work with this driver */
static const struct usb_device_id device_table[] = {
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID) },		/* ADU100 */
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+20) },	/* ADU120 */
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+30) },	/* ADU130 */
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+100) },	/* ADU200 */
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+108) },	/* ADU208 */
	{ USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+118) },	/* ADU218 */
	{ } /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, device_table);

#ifdef CONFIG_USB_DYNAMIC_MINORS
#define ADU_MINOR_BASE	0
#else
#define ADU_MINOR_BASE	67
#endif

/* we can have up to this number of device plugged in at once */
#define MAX_DEVICES	16

#define COMMAND_TIMEOUT	(2*HZ)	/* 60 second timeout for a command */

/*
 * The locking scheme is a vanilla 3-lock:
 *   adu_device.buflock: A spinlock, covers what IRQs touch.
 *   adutux_mutex:       A Static lock to cover open_count. It would also cover
 *                       any globals, but we don't have them in 2.6.
 *   adu_device.mtx:     A mutex to hold across sleepers like copy_from_user.
 *                       It covers all of adu_device, except the open_count
 *                       and what .buflock covers.
 */

/* Structure to hold all of our device specific stuff */
struct adu_device {
	struct mutex		mtx;
	struct usb_device *udev; /* save off the usb device pointer */
	struct usb_interface *interface;
	unsigned int		minor; /* the starting minor number for this device */
	char			serial_number[8];

	int			open_count; /* number of times this port has been opened */

	char		*read_buffer_primary;
	int			read_buffer_length;
	char		*read_buffer_secondary;
	int			secondary_head;
	int			secondary_tail;
	spinlock_t		buflock;

	wait_queue_head_t	read_wait;
	wait_queue_head_t	write_wait;

	char		*interrupt_in_buffer;
	struct usb_endpoint_descriptor *interrupt_in_endpoint;
	struct urb	*interrupt_in_urb;
	int			read_urb_finished;

	char		*interrupt_out_buffer;
	struct usb_endpoint_descriptor *interrupt_out_endpoint;
	struct urb	*interrupt_out_urb;
	int			out_urb_finished;
};

static DEFINE_MUTEX(adutux_mutex);

static struct usb_driver adu_driver;

static void adu_debug_data(int level, const char *function, int size,
			   const unsigned char *data)
{
	int i;

	if (debug < level)
		return;

	printk(KERN_DEBUG "%s: %s - length = %d, data = ",
	       __FILE__, function, size);
	for (i = 0; i < size; ++i)
		printk("%.2x ", data[i]);
	printk("\n");
}

/**
 * adu_abort_transfers
 *      aborts transfers and frees associated data structures
 */
static void adu_abort_transfers(struct adu_device *dev)
{
	unsigned long flags;

	dbg(2, " %s : enter", __func__);

	if (dev->udev == NULL) {
		dbg(1, " %s : udev is null", __func__);
		goto exit;
	}

	/* shutdown transfer */

	/* XXX Anchor these instead */
	spin_lock_irqsave(&dev->buflock, flags);
	if (!dev->read_urb_finished) {
		spin_unlock_irqrestore(&dev->buflock, flags);
		usb_kill_urb(dev->interrupt_in_urb);
	} else
		spin_unlock_irqrestore(&dev->buflock, flags);

	spin_lock_irqsave(&dev->buflock, flags);
	if (!dev->out_urb_finished) {
		spin_unlock_irqrestore(&dev->buflock, flags);
		usb_kill_urb(dev->interrupt_out_urb);
	} else
		spin_unlock_irqrestore(&dev->buflock, flags);

exit:
	dbg(2, " %s : leave", __func__);
}

static void adu_delete(struct adu_device *dev)
{
	dbg(2, "%s enter", __func__);

	/* free data structures */
	usb_free_urb(dev->interrupt_in_urb);
	usb_free_urb(dev->interrupt_out_urb);
	kfree(dev->read_buffer_primary);
	kfree(dev->read_buffer_secondary);
	kfree(dev->interrupt_in_buffer);
	kfree(dev->interrupt_out_buffer);
	kfree(dev);

	dbg(2, "%s : leave", __func__);
}

static void adu_interrupt_in_callback(struct urb *urb)
{
	struct adu_device *dev = urb->context;
	int status = urb->status;

	dbg(4, " %s : enter, status %d", __func__, status);
	adu_debug_data(5, __func__, urb->actual_length,
		       urb->transfer_buffer);

	spin_lock(&dev->buflock);

	if (status != 0) {
		if ((status != -ENOENT) && (status != -ECONNRESET) &&
			(status != -ESHUTDOWN)) {
			dbg(1, " %s : nonzero status received: %d",
			    __func__, status);
		}
		goto exit;
	}

	if (urb->actual_length > 0 && dev->interrupt_in_buffer[0] != 0x00) {
		if (dev->read_buffer_length <
		    (4 * usb_endpoint_maxp(dev->interrupt_in_endpoint)) -
		     (urb->actual_length)) {
			memcpy (dev->read_buffer_primary +
				dev->read_buffer_length,
				dev->interrupt_in_buffer, urb->actual_length);

			dev->read_buffer_length += urb->actual_length;
			dbg(2, " %s reading  %d ", __func__,
			    urb->actual_length);
		} else {
			dbg(1, " %s : read_buffer overflow", __func__);
		}
	}

exit:
	dev->read_urb_finished = 1;
	spin_unlock(&dev->buflock);
	/* always wake up so we recover from errors */
	wake_up_interruptible(&dev->read_wait);
	adu_debug_data(5, __func__, urb->actual_length,
		       urb->transfer_buffer);
	dbg(4, " %s : leave, status %d", __func__, status);
}

static void adu_interrupt_out_callback(struct urb *urb)
{
	struct adu_device *dev = urb->context;
	int status = urb->status;

	dbg(4, " %s : enter, status %d", __func__, status);
	adu_debug_data(5, __func__, urb->actual_length, urb->transfer_buffer);

	if (status != 0) {
		if ((status != -ENOENT) &&
		    (status != -ECONNRESET)) {
			dbg(1, " %s :nonzero status received: %d",
			    __func__, status);
		}
		goto exit;
	}

	spin_lock(&dev->buflock);
	dev->out_urb_finished = 1;
	wake_up(&dev->write_wait);
	spin_unlock(&dev->buflock);
exit:

	adu_debug_data(5, __func__, urb->actual_length,
		       urb->transfer_buffer);
	dbg(4, " %s : leave, status %d", __func__, status);
}

static int adu_open(struct inode *inode, struct file *file)
{
	struct adu_device *dev = NULL;
	struct usb_interface *interface;
	int subminor;
	int retval;

	dbg(2, "%s : enter", __func__);

	subminor = iminor(inode);

	retval = mutex_lock_interruptible(&adutux_mutex);
	if (retval) {
		dbg(2, "%s : mutex lock failed", __func__);
		goto exit_no_lock;
	}

	interface = usb_find_interface(&adu_driver, subminor);
	if (!interface) {
		printk(KERN_ERR "adutux: %s - error, can't find device for "
		       "minor %d\n", __func__, subminor);
		retval = -ENODEV;
		goto exit_no_device;
	}

	dev = usb_get_intfdata(interface);
	if (!dev || !dev->udev) {
		retval = -ENODEV;
		goto exit_no_device;
	}

	/* check that nobody else is using the device */
	if (dev->open_count) {
		retval = -EBUSY;
		goto exit_no_device;
	}

	++dev->open_count;
	dbg(2, "%s : open count %d", __func__, dev->open_count);

	/* save device in the file's private structure */
	file->private_data = dev;

	/* initialize in direction */
	dev->read_buffer_length = 0;

	/* fixup first read by having urb waiting for it */
	usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
			 usb_rcvintpipe(dev->udev,
					dev->interrupt_in_endpoint->bEndpointAddress),
			 dev->interrupt_in_buffer,
			 usb_endpoint_maxp(dev->interrupt_in_endpoint),
			 adu_interrupt_in_callback, dev,
			 dev->interrupt_in_endpoint->bInterval);
	dev->read_urb_finished = 0;
	if (usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL))
		dev->read_urb_finished = 1;
	/* we ignore failure */
	/* end of fixup for first read */

	/* initialize out direction */
	dev->out_urb_finished = 1;

	retval = 0;

exit_no_device:
	mutex_unlock(&adutux_mutex);
exit_no_lock:
	dbg(2, "%s : leave, return value %d ", __func__, retval);
	return retval;
}

static void adu_release_internal(struct adu_device *dev)
{
	dbg(2, " %s : enter", __func__);

	/* decrement our usage count for the device */
	--dev->open_count;
	dbg(2, " %s : open count %d", __func__, dev->open_count);
	if (dev->open_count <= 0) {
		adu_abort_transfers(dev);
		dev->open_count = 0;
	}

	dbg(2, " %s : leave", __func__);
}

static int adu_release(struct inode *inode, struct file *file)
{
	struct adu_device *dev;
	int retval = 0;

	dbg(2, " %s : enter", __func__);

	if (file == NULL) {
		dbg(1, " %s : file is NULL", __func__);
		retval = -ENODEV;
		goto exit;
	}

	dev = file->private_data;
	if (dev == NULL) {
		dbg(1, " %s : object is NULL", __func__);
		retval = -ENODEV;
		goto exit;
	}

	mutex_lock(&adutux_mutex); /* not interruptible */

	if (dev->open_count <= 0) {
		dbg(1, " %s : device not opened", __func__);
		retval = -ENODEV;
		goto unlock;
	}

	adu_release_internal(dev);
	if (dev->udev == NULL) {
		/* the device was unplugged before the file was released */
		if (!dev->open_count)	/* ... and we're the last user */
			adu_delete(dev);
	}
unlock:
	mutex_unlock(&adutux_mutex);
exit:
	dbg(2, " %s : leave, return value %d", __func__, retval);
	return retval;
}

static ssize_t adu_read(struct file *file, __user char *buffer, size_t count,
			loff_t *ppos)
{
	struct adu_device *dev;
	size_t bytes_read = 0;
	size_t bytes_to_read = count;
	int i;
	int retval = 0;
	int timeout = 0;
	int should_submit = 0;
	unsigned long flags;
	DECLARE_WAITQUEUE(wait, current);

	dbg(2, " %s : enter, count = %Zd, file=%p", __func__, count, file);

	dev = file->private_data;
	dbg(2, " %s : dev=%p", __func__, dev);

	if (mutex_lock_interruptible(&dev->mtx))
		return -ERESTARTSYS;

	/* verify that the device wasn't unplugged */
	if (dev->udev == NULL) {
		retval = -ENODEV;
		printk(KERN_ERR "adutux: No device or device unplugged %d\n",
		       retval);
		goto exit;
	}

	/* verify that some data was requested */
	if (count == 0) {
		dbg(1, " %s : read request of 0 bytes", __func__);
		goto exit;
	}

	timeout = COMMAND_TIMEOUT;
	dbg(2, " %s : about to start looping", __func__);
	while (bytes_to_read) {
		int data_in_secondary = dev->secondary_tail - dev->secondary_head;
		dbg(2, " %s : while, data_in_secondary=%d, status=%d",
		    __func__, data_in_secondary,
		    dev->interrupt_in_urb->status);

		if (data_in_secondary) {
			/* drain secondary buffer */
			int amount = bytes_to_read < data_in_secondary ? bytes_to_read : data_in_secondary;
			i = copy_to_user(buffer, dev->read_buffer_secondary+dev->secondary_head, amount);
			if (i) {
				retval = -EFAULT;
				goto exit;
			}
			dev->secondary_head += (amount - i);
			bytes_read += (amount - i);
			bytes_to_read -= (amount - i);
			if (i) {
				retval = bytes_read ? bytes_read : -EFAULT;
				goto exit;
			}
		} else {
			/* we check the primary buffer */
			spin_lock_irqsave (&dev->buflock, flags);
			if (dev->read_buffer_length) {
				/* we secure access to the primary */
				char *tmp;
				dbg(2, " %s : swap, read_buffer_length = %d",
				    __func__, dev->read_buffer_length);
				tmp = dev->read_buffer_secondary;
				dev->read_buffer_secondary = dev->read_buffer_primary;
				dev->read_buffer_primary = tmp;
				dev->secondary_head = 0;
				dev->secondary_tail = dev->read_buffer_length;
				dev->read_buffer_length = 0;
				spin_unlock_irqrestore(&dev->buflock, flags);
				/* we have a free buffer so use it */
				should_submit = 1;
			} else {
				/* even the primary was empty - we may need to do IO */
				if (!dev->read_urb_finished) {
					/* somebody is doing IO */
					spin_unlock_irqrestore(&dev->buflock, flags);
					dbg(2, " %s : submitted already", __func__);
				} else {
					/* we must initiate input */
					dbg(2, " %s : initiate input", __func__);
					dev->read_urb_finished = 0;
					spin_unlock_irqrestore(&dev->buflock, flags);

					usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
							usb_rcvintpipe(dev->udev,
								dev->interrupt_in_endpoint->bEndpointAddress),
							 dev->interrupt_in_buffer,
							 usb_endpoint_maxp(dev->interrupt_in_endpoint),
							 adu_interrupt_in_callback,
							 dev,
							 dev->interrupt_in_endpoint->bInterval);
					retval = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
					if (retval) {
						dev->read_urb_finished = 1;
						if (retval == -ENOMEM) {
							retval = bytes_read ? bytes_read : -ENOMEM;
						}
						dbg(2, " %s : submit failed", __func__);
						goto exit;
					}
				}

				/* we wait for I/O to complete */
				set_current_state(TASK_INTERRUPTIBLE);
				add_wait_queue(&dev->read_wait, &wait);
				spin_lock_irqsave(&dev->buflock, flags);
				if (!dev->read_urb_finished) {
					spin_unlock_irqrestore(&dev->buflock, flags);
					timeout = schedule_timeout(COMMAND_TIMEOUT);
				} else {
					spin_unlock_irqrestore(&dev->buflock, flags);
					set_current_state(TASK_RUNNING);
				}
				remove_wait_queue(&dev->read_wait, &wait);

				if (timeout <= 0) {
					dbg(2, " %s : timeout", __func__);
					retval = bytes_read ? bytes_read : -ETIMEDOUT;
					goto exit;
				}

				if (signal_pending(current)) {
					dbg(2, " %s : signal pending", __func__);
					retval = bytes_read ? bytes_read : -EINTR;
					goto exit;
				}
			}
		}
	}

	retval = bytes_read;
	/* if the primary buffer is empty then use it */
	spin_lock_irqsave(&dev->buflock, flags);
	if (should_submit && dev->read_urb_finished) {
		dev->read_urb_finished = 0;
		spin_unlock_irqrestore(&dev->buflock, flags);
		usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
				 usb_rcvintpipe(dev->udev,
					dev->interrupt_in_endpoint->bEndpointAddress),
				dev->interrupt_in_buffer,
				usb_endpoint_maxp(dev->interrupt_in_endpoint),
				adu_interrupt_in_callback,
				dev,
				dev->interrupt_in_endpoint->bInterval);
		if (usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL) != 0)
			dev->read_urb_finished = 1;
		/* we ignore failure */
	} else {
		spin_unlock_irqrestore(&dev->buflock, flags);
	}

exit:
	/* unlock the device */
	mutex_unlock(&dev->mtx);

	dbg(2, " %s : leave, return value %d", __func__, retval);
	return retval;
}

static ssize_t adu_write(struct file *file, const __user char *buffer,
			 size_t count, loff_t *ppos)
{
	DECLARE_WAITQUEUE(waita, current);
	struct adu_device *dev;
	size_t bytes_written = 0;
	size_t bytes_to_write;
	size_t buffer_size;
	unsigned long flags;
	int retval;

	dbg(2, " %s : enter, count = %Zd", __func__, count);

	dev = file->private_data;

	retval = mutex_lock_interruptible(&dev->mtx);
	if (retval)
		goto exit_nolock;

	/* verify that the device wasn't unplugged */
	if (dev->udev == NULL) {
		retval = -ENODEV;
		printk(KERN_ERR "adutux: No device or device unplugged %d\n",
		       retval);
		goto exit;
	}

	/* verify that we actually have some data to write */
	if (count == 0) {
		dbg(1, " %s : write request of 0 bytes", __func__);
		goto exit;
	}

	while (count > 0) {
		add_wait_queue(&dev->write_wait, &waita);
		set_current_state(TASK_INTERRUPTIBLE);
		spin_lock_irqsave(&dev->buflock, flags);
		if (!dev->out_urb_finished) {
			spin_unlock_irqrestore(&dev->buflock, flags);

			mutex_unlock(&dev->mtx);
			if (signal_pending(current)) {
				dbg(1, " %s : interrupted", __func__);
				set_current_state(TASK_RUNNING);
				retval = -EINTR;
				goto exit_onqueue;
			}
			if (schedule_timeout(COMMAND_TIMEOUT) == 0) {
				dbg(1, "%s - command timed out.", __func__);
				retval = -ETIMEDOUT;
				goto exit_onqueue;
			}
			remove_wait_queue(&dev->write_wait, &waita);
			retval = mutex_lock_interruptible(&dev->mtx);
			if (retval) {
				retval = bytes_written ? bytes_written : retval;
				goto exit_nolock;
			}

			dbg(4, " %s : in progress, count = %Zd", __func__, count);
		} else {
			spin_unlock_irqrestore(&dev->buflock, flags);
			set_current_state(TASK_RUNNING);
			remove_wait_queue(&dev->write_wait, &waita);
			dbg(4, " %s : sending, count = %Zd", __func__, count);

			/* write the data into interrupt_out_buffer from userspace */
			buffer_size = usb_endpoint_maxp(dev->interrupt_out_endpoint);
			bytes_to_write = count > buffer_size ? buffer_size : count;
			dbg(4, " %s : buffer_size = %Zd, count = %Zd, bytes_to_write = %Zd",
			    __func__, buffer_size, count, bytes_to_write);

			if (copy_from_user(dev->interrupt_out_buffer, buffer, bytes_to_write) != 0) {
				retval = -EFAULT;
				goto exit;
			}

			/* send off the urb */
			usb_fill_int_urb(
				dev->interrupt_out_urb,
				dev->udev,
				usb_sndintpipe(dev->udev, dev->interrupt_out_endpoint->bEndpointAddress),
				dev->interrupt_out_buffer,
				bytes_to_write,
				adu_interrupt_out_callback,
				dev,
				dev->interrupt_out_endpoint->bInterval);
			dev->interrupt_out_urb->actual_length = bytes_to_write;
			dev->out_urb_finished = 0;
			retval = usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL);
			if (retval < 0) {
				dev->out_urb_finished = 1;
				dev_err(&dev->udev->dev, "Couldn't submit "
					"interrupt_out_urb %d\n", retval);
				goto exit;
			}

			buffer += bytes_to_write;
			count -= bytes_to_write;

			bytes_written += bytes_to_write;
		}
	}
	mutex_unlock(&dev->mtx);
	return bytes_written;

exit:
	mutex_unlock(&dev->mtx);
exit_nolock:
	dbg(2, " %s : leave, return value %d", __func__, retval);
	return retval;

exit_onqueue:
	remove_wait_queue(&dev->write_wait, &waita);
	return retval;
}

/* file operations needed when we register this driver */
static const struct file_operations adu_fops = {
	.owner = THIS_MODULE,
	.read  = adu_read,
	.write = adu_write,
	.open = adu_open,
	.release = adu_release,
	.llseek = noop_llseek,
};

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with devfs and the driver core
 */
static struct usb_class_driver adu_class = {
	.name = "usb/adutux%d",
	.fops = &adu_fops,
	.minor_base = ADU_MINOR_BASE,
};

/**
 * adu_probe
 *
 * Called by the usb core when a new device is connected that it thinks
 * this driver might be interested in.
 */
static int adu_probe(struct usb_interface *interface,
		     const struct usb_device_id *id)
{
	struct usb_device *udev = interface_to_usbdev(interface);
	struct adu_device *dev = NULL;
	struct usb_host_interface *iface_desc;
	struct usb_endpoint_descriptor *endpoint;
	int retval = -ENODEV;
	int in_end_size;
	int out_end_size;
	int i;

	dbg(2, " %s : enter", __func__);

	if (udev == NULL) {
		dev_err(&interface->dev, "udev is NULL.\n");
		goto exit;
	}

	/* allocate memory for our device state and initialize it */
	dev = kzalloc(sizeof(struct adu_device), GFP_KERNEL);
	if (dev == NULL) {
		dev_err(&interface->dev, "Out of memory\n");
		retval = -ENOMEM;
		goto exit;
	}

	mutex_init(&dev->mtx);
	spin_lock_init(&dev->buflock);
	dev->udev = udev;
	init_waitqueue_head(&dev->read_wait);
	init_waitqueue_head(&dev->write_wait);

	iface_desc = &interface->altsetting[0];

	/* set up the endpoint information */
	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
		endpoint = &iface_desc->endpoint[i].desc;

		if (usb_endpoint_is_int_in(endpoint))
			dev->interrupt_in_endpoint = endpoint;

		if (usb_endpoint_is_int_out(endpoint))
			dev->interrupt_out_endpoint = endpoint;
	}
	if (dev->interrupt_in_endpoint == NULL) {
		dev_err(&interface->dev, "interrupt in endpoint not found\n");
		goto error;
	}
	if (dev->interrupt_out_endpoint == NULL) {
		dev_err(&interface->dev, "interrupt out endpoint not found\n");
		goto error;
	}

	in_end_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
	out_end_size = usb_endpoint_maxp(dev->interrupt_out_endpoint);

	dev->read_buffer_primary = kmalloc((4 * in_end_size), GFP_KERNEL);
	if (!dev->read_buffer_primary) {
		dev_err(&interface->dev, "Couldn't allocate read_buffer_primary\n");
		retval = -ENOMEM;
		goto error;
	}

	/* debug code prime the buffer */
	memset(dev->read_buffer_primary, 'a', in_end_size);
	memset(dev->read_buffer_primary + in_end_size, 'b', in_end_size);
	memset(dev->read_buffer_primary + (2 * in_end_size), 'c', in_end_size);
	memset(dev->read_buffer_primary + (3 * in_end_size), 'd', in_end_size);

	dev->read_buffer_secondary = kmalloc((4 * in_end_size), GFP_KERNEL);
	if (!dev->read_buffer_secondary) {
		dev_err(&interface->dev, "Couldn't allocate read_buffer_secondary\n");
		retval = -ENOMEM;
		goto error;
	}

	/* debug code prime the buffer */
	memset(dev->read_buffer_secondary, 'e', in_end_size);
	memset(dev->read_buffer_secondary + in_end_size, 'f', in_end_size);
	memset(dev->read_buffer_secondary + (2 * in_end_size), 'g', in_end_size);
	memset(dev->read_buffer_secondary + (3 * in_end_size), 'h', in_end_size);

	dev->interrupt_in_buffer = kmalloc(in_end_size, GFP_KERNEL);
	if (!dev->interrupt_in_buffer) {
		dev_err(&interface->dev, "Couldn't allocate interrupt_in_buffer\n");
		goto error;
	}

	/* debug code prime the buffer */
	memset(dev->interrupt_in_buffer, 'i', in_end_size);

	dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
	if (!dev->interrupt_in_urb) {
		dev_err(&interface->dev, "Couldn't allocate interrupt_in_urb\n");
		goto error;
	}
	dev->interrupt_out_buffer = kmalloc(out_end_size, GFP_KERNEL);
	if (!dev->interrupt_out_buffer) {
		dev_err(&interface->dev, "Couldn't allocate interrupt_out_buffer\n");
		goto error;
	}
	dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
	if (!dev->interrupt_out_urb) {
		dev_err(&interface->dev, "Couldn't allocate interrupt_out_urb\n");
		goto error;
	}

	if (!usb_string(udev, udev->descriptor.iSerialNumber, dev->serial_number,
			sizeof(dev->serial_number))) {
		dev_err(&interface->dev, "Could not retrieve serial number\n");
		goto error;
	}
	dbg(2, " %s : serial_number=%s", __func__, dev->serial_number);

	/* we can register the device now, as it is ready */
	usb_set_intfdata(interface, dev);

	retval = usb_register_dev(interface, &adu_class);

	if (retval) {
		/* something prevented us from registering this driver */
		dev_err(&interface->dev, "Not able to get a minor for this device.\n");
		usb_set_intfdata(interface, NULL);
		goto error;
	}

	dev->minor = interface->minor;

	/* let the user know what node this device is now attached to */
	dev_info(&interface->dev, "ADU%d %s now attached to /dev/usb/adutux%d\n",
		 le16_to_cpu(udev->descriptor.idProduct), dev->serial_number,
		 (dev->minor - ADU_MINOR_BASE));
exit:
	dbg(2, " %s : leave, return value %p (dev)", __func__, dev);

	return retval;

error:
	adu_delete(dev);
	return retval;
}

/**
 * adu_disconnect
 *
 * Called by the usb core when the device is removed from the system.
 */
static void adu_disconnect(struct usb_interface *interface)
{
	struct adu_device *dev;
	int minor;

	dbg(2, " %s : enter", __func__);

	dev = usb_get_intfdata(interface);

	mutex_lock(&dev->mtx);	/* not interruptible */
	dev->udev = NULL;	/* poison */
	minor = dev->minor;
	usb_deregister_dev(interface, &adu_class);
	mutex_unlock(&dev->mtx);

	mutex_lock(&adutux_mutex);
	usb_set_intfdata(interface, NULL);

	/* if the device is not opened, then we clean up right now */
	dbg(2, " %s : open count %d", __func__, dev->open_count);
	if (!dev->open_count)
		adu_delete(dev);

	mutex_unlock(&adutux_mutex);

	dev_info(&interface->dev, "ADU device adutux%d now disconnected\n",
		 (minor - ADU_MINOR_BASE));

	dbg(2, " %s : leave", __func__);
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver adu_driver = {
	.name = "adutux",
	.probe = adu_probe,
	.disconnect = adu_disconnect,
	.id_table = device_table,
};

module_usb_driver(adu_driver);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");