summaryrefslogtreecommitdiff
path: root/drivers/staging/comedi/drivers.c
blob: 42a02571ff1b7f131162a67fff16ea863232d608 (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
/*
    module/drivers.c
    functions for manipulating drivers

    COMEDI - Linux Control and Measurement Device Interface
    Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>

    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.

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#define _GNU_SOURCE

#define __NO_VERSION__
#include "comedi_fops.h"
#include <linux/device.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/usb.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/fcntl.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include "comedidev.h"
#include "wrapper.h"
#include <linux/highmem.h>	/* for SuSE brokenness */
#include <linux/vmalloc.h>
#include <linux/cdev.h>
#include <linux/dma-mapping.h>

#include <asm/io.h>
#include <asm/system.h>

static int postconfig(struct comedi_device *dev);
static int insn_rw_emulate_bits(struct comedi_device *dev, struct comedi_subdevice *s,
	struct comedi_insn *insn, unsigned int *data);
static void *comedi_recognize(struct comedi_driver * driv, const char *name);
static void comedi_report_boards(struct comedi_driver *driv);
static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s);
int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
	unsigned long new_size);

struct comedi_driver *comedi_drivers;

int comedi_modprobe(int minor)
{
	return -EINVAL;
}

static void cleanup_device(struct comedi_device *dev)
{
	int i;
	struct comedi_subdevice *s;

	if (dev->subdevices) {
		for (i = 0; i < dev->n_subdevices; i++) {
			s = dev->subdevices + i;
			comedi_free_subdevice_minor(s);
			if (s->async) {
				comedi_buf_alloc(dev, s, 0);
				kfree(s->async);
			}
		}
		kfree(dev->subdevices);
		dev->subdevices = NULL;
		dev->n_subdevices = 0;
	}
	kfree(dev->private);
	dev->private = NULL;
	dev->driver = 0;
	dev->board_name = NULL;
	dev->board_ptr = NULL;
	dev->iobase = 0;
	dev->irq = 0;
	dev->read_subdev = NULL;
	dev->write_subdev = NULL;
	dev->open = NULL;
	dev->close = NULL;
	comedi_set_hw_dev(dev, NULL);
}

static void __comedi_device_detach(struct comedi_device *dev)
{
	dev->attached = 0;
	if (dev->driver) {
		dev->driver->detach(dev);
	} else {
		printk("BUG: dev->driver=NULL in comedi_device_detach()\n");
	}
	cleanup_device(dev);
}

void comedi_device_detach(struct comedi_device *dev)
{
	if (!dev->attached)
		return;
	__comedi_device_detach(dev);
}

int comedi_device_attach(struct comedi_device *dev, struct comedi_devconfig *it)
{
	struct comedi_driver *driv;
	int ret;

	if (dev->attached)
		return -EBUSY;

	for (driv = comedi_drivers; driv; driv = driv->next) {
		if (!try_module_get(driv->module)) {
			printk("comedi: failed to increment module count, skipping\n");
			continue;
		}
		if (driv->num_names) {
			dev->board_ptr = comedi_recognize(driv, it->board_name);
			if (dev->board_ptr == NULL) {
				module_put(driv->module);
				continue;
			}
		} else {
			if (strcmp(driv->driver_name, it->board_name)) {
				module_put(driv->module);
				continue;
			}
		}
		/* initialize dev->driver here so comedi_error() can be called from attach */
		dev->driver = driv;
		ret = driv->attach(dev, it);
		if (ret < 0) {
			module_put(dev->driver->module);
			__comedi_device_detach(dev);
			return ret;
		}
		goto attached;
	}

	/*  recognize has failed if we get here */
	/*  report valid board names before returning error */
	for (driv = comedi_drivers; driv; driv = driv->next) {
		if (!try_module_get(driv->module)) {
			printk("comedi: failed to increment module count\n");
			continue;
		}
		comedi_report_boards(driv);
		module_put(driv->module);
	}
	return -EIO;

attached:
	/* do a little post-config cleanup */
	ret = postconfig(dev);
	module_put(dev->driver->module);
	if (ret < 0) {
		__comedi_device_detach(dev);
		return ret;
	}

	if (!dev->board_name) {
		printk("BUG: dev->board_name=<%p>\n", dev->board_name);
		dev->board_name = "BUG";
	}
	smp_wmb();
	dev->attached = 1;

	return 0;
}

int comedi_driver_register(struct comedi_driver *driver)
{
	driver->next = comedi_drivers;
	comedi_drivers = driver;

	return 0;
}

int comedi_driver_unregister(struct comedi_driver *driver)
{
	struct comedi_driver *prev;
	int i;

	/* check for devices using this driver */
	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; i++) {
		struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(i);
		struct comedi_device *dev;

		if (dev_file_info == NULL) continue;
		dev = dev_file_info->device;

		mutex_lock(&dev->mutex);
		if (dev->attached && dev->driver == driver) {
			if (dev->use_count)
				printk("BUG! detaching device with use_count=%d\n", dev->use_count);
			comedi_device_detach(dev);
		}
		mutex_unlock(&dev->mutex);
	}

	if (comedi_drivers == driver) {
		comedi_drivers = driver->next;
		return 0;
	}

	for (prev = comedi_drivers; prev->next; prev = prev->next) {
		if (prev->next == driver) {
			prev->next = driver->next;
			return 0;
		}
	}
	return -EINVAL;
}

static int postconfig(struct comedi_device *dev)
{
	int i;
	struct comedi_subdevice *s;
	struct comedi_async *async = NULL;
	int ret;

	for (i = 0; i < dev->n_subdevices; i++) {
		s = dev->subdevices + i;

		if (s->type == COMEDI_SUBD_UNUSED)
			continue;

		if (s->len_chanlist == 0)
			s->len_chanlist = 1;

		if (s->do_cmd) {
			BUG_ON((s->subdev_flags & (SDF_CMD_READ |
				SDF_CMD_WRITE)) == 0);
			BUG_ON(!s->do_cmdtest);

			async = kzalloc(sizeof(struct comedi_async), GFP_KERNEL);
			if (async == NULL) {
				printk("failed to allocate async struct\n");
				return -ENOMEM;
			}
			init_waitqueue_head(&async->wait_head);
			async->subdevice = s;
			s->async = async;

#define DEFAULT_BUF_MAXSIZE (64*1024)
#define DEFAULT_BUF_SIZE (64*1024)

			async->max_bufsize = DEFAULT_BUF_MAXSIZE;

			async->prealloc_buf = NULL;
			async->prealloc_bufsz = 0;
			if (comedi_buf_alloc(dev, s, DEFAULT_BUF_SIZE) < 0) {
				printk("Buffer allocation failed\n");
				return -ENOMEM;
			}
			if (s->buf_change) {
				ret = s->buf_change(dev, s, DEFAULT_BUF_SIZE);
				if (ret < 0)
					return ret;
			}
			comedi_alloc_subdevice_minor(dev, s);
		}

		if (!s->range_table && !s->range_table_list)
			s->range_table = &range_unknown;

		if (!s->insn_read && s->insn_bits)
			s->insn_read = insn_rw_emulate_bits;
		if (!s->insn_write && s->insn_bits)
			s->insn_write = insn_rw_emulate_bits;

		if (!s->insn_read)
			s->insn_read = insn_inval;
		if (!s->insn_write)
			s->insn_write = insn_inval;
		if (!s->insn_bits)
			s->insn_bits = insn_inval;
		if (!s->insn_config)
			s->insn_config = insn_inval;

		if (!s->poll)
			s->poll = poll_invalid;
	}

	return 0;
}

/*  generic recognize function for drivers that register their supported board names */
void *comedi_recognize(struct comedi_driver * driv, const char *name)
{
	unsigned i;
	const char *const *name_ptr = driv->board_name;
	for (i = 0; i < driv->num_names; i++) {
		if (strcmp(*name_ptr, name) == 0)
			return (void *)name_ptr;
		name_ptr =
			(const char *const *)((const char *)name_ptr +
			driv->offset);
	}

	return NULL;
}

void comedi_report_boards(struct comedi_driver *driv)
{
	unsigned int i;
	const char *const *name_ptr;

	printk("comedi: valid board names for %s driver are:\n",
		driv->driver_name);

	name_ptr = driv->board_name;
	for (i = 0; i < driv->num_names; i++) {
		printk(" %s\n", *name_ptr);
		name_ptr = (const char **)((char *)name_ptr + driv->offset);
	}

	if (driv->num_names == 0)
		printk(" %s\n", driv->driver_name);
}

static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s)
{
	return -EINVAL;
}

int insn_inval(struct comedi_device *dev, struct comedi_subdevice *s,
	struct comedi_insn *insn, unsigned int *data)
{
	return -EINVAL;
}

static int insn_rw_emulate_bits(struct comedi_device *dev, struct comedi_subdevice *s,
	struct comedi_insn *insn, unsigned int *data)
{
	struct comedi_insn new_insn;
	int ret;
	static const unsigned channels_per_bitfield = 32;

	unsigned chan = CR_CHAN(insn->chanspec);
	const unsigned base_bitfield_channel =
		(chan < channels_per_bitfield) ? 0 : chan;
	unsigned int new_data[2];
	memset(new_data, 0, sizeof(new_data));
	memset(&new_insn, 0, sizeof(new_insn));
	new_insn.insn = INSN_BITS;
	new_insn.chanspec = base_bitfield_channel;
	new_insn.n = 2;
	new_insn.data = new_data;
	new_insn.subdev = insn->subdev;

	if (insn->insn == INSN_WRITE) {
		if (!(s->subdev_flags & SDF_WRITABLE))
			return -EINVAL;
		new_data[0] = 1 << (chan - base_bitfield_channel);	/* mask */
		new_data[1] = data[0] ? (1 << (chan - base_bitfield_channel)) : 0;	/* bits */
	}

	ret = s->insn_bits(dev, s, &new_insn, new_data);
	if (ret < 0)
		return ret;

	if (insn->insn == INSN_READ) {
		data[0] = (new_data[1] >> (chan - base_bitfield_channel)) & 1;
	}

	return 1;
}

static inline unsigned long uvirt_to_kva(pgd_t *pgd, unsigned long adr)
{
	unsigned long ret = 0UL;
	pmd_t *pmd;
	pte_t *ptep, pte;
	pud_t *pud;

	if (!pgd_none(*pgd)) {
		pud = pud_offset(pgd, adr);
		pmd = pmd_offset(pud, adr);
		if (!pmd_none(*pmd)) {
			ptep = pte_offset_kernel(pmd, adr);
			pte = *ptep;
			if (pte_present(pte)) {
				ret = (unsigned long)
					page_address(pte_page(pte));
				ret |= (adr & (PAGE_SIZE - 1));
			}
		}
	}
	return ret;
}

static inline unsigned long kvirt_to_kva(unsigned long adr)
{
	unsigned long va, kva;

	va = adr;
	kva = uvirt_to_kva(pgd_offset_k(va), va);

	return kva;
}

int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
	unsigned long new_size)
{
	struct comedi_async *async = s->async;

	/* Round up new_size to multiple of PAGE_SIZE */
	new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;

	/* if no change is required, do nothing */
	if (async->prealloc_buf && async->prealloc_bufsz == new_size) {
		return 0;
	}
	/*  deallocate old buffer */
	if (async->prealloc_buf) {
		vunmap(async->prealloc_buf);
		async->prealloc_buf = NULL;
		async->prealloc_bufsz = 0;
	}
	if (async->buf_page_list) {
		unsigned i;
		for (i = 0; i < async->n_buf_pages; ++i) {
			if (async->buf_page_list[i].virt_addr) {
				mem_map_unreserve(virt_to_page(async->
						buf_page_list[i].virt_addr));
				if (s->async_dma_dir != DMA_NONE) {
					dma_free_coherent(dev->hw_dev,
						PAGE_SIZE,
						async->buf_page_list[i].
						virt_addr,
						async->buf_page_list[i].
						dma_addr);
				} else {
					free_page((unsigned long)async->
						buf_page_list[i].virt_addr);
				}
			}
		}
		vfree(async->buf_page_list);
		async->buf_page_list = NULL;
		async->n_buf_pages = 0;
	}
	/*  allocate new buffer */
	if (new_size) {
		unsigned i = 0;
		unsigned n_pages = new_size >> PAGE_SHIFT;
		struct page **pages = NULL;

		async->buf_page_list =
			vmalloc(sizeof(struct comedi_buf_page) * n_pages);
		if (async->buf_page_list) {
			memset(async->buf_page_list, 0,
				sizeof(struct comedi_buf_page) * n_pages);
			pages = vmalloc(sizeof(struct page *) * n_pages);
		}
		if (pages) {
			for (i = 0; i < n_pages; i++) {
				if (s->async_dma_dir != DMA_NONE) {
					async->buf_page_list[i].virt_addr =
						dma_alloc_coherent(dev->hw_dev,
						PAGE_SIZE,
						&async->buf_page_list[i].
						dma_addr,
						GFP_KERNEL | __GFP_COMP);
				} else {
					async->buf_page_list[i].virt_addr =
						(void *)
						get_zeroed_page(GFP_KERNEL);
				}
				if (async->buf_page_list[i].virt_addr == NULL) {
					break;
				}
				mem_map_reserve(virt_to_page(async->
						buf_page_list[i].virt_addr));
				pages[i] =
					virt_to_page(async->buf_page_list[i].
					virt_addr);
			}
		}
		if (i == n_pages) {
			async->prealloc_buf =
				vmap(pages, n_pages, VM_MAP,
				PAGE_KERNEL_NOCACHE);
		}
		if (pages) {
			vfree(pages);
		}
		if (async->prealloc_buf == NULL) {
			/* Some allocation failed above. */
			if (async->buf_page_list) {
				for (i = 0; i < n_pages; i++) {
					if (async->buf_page_list[i].virt_addr ==
						NULL) {
						break;
					}
					mem_map_unreserve(virt_to_page(async->
							buf_page_list[i].
							virt_addr));
					if (s->async_dma_dir != DMA_NONE) {
						dma_free_coherent(dev->hw_dev,
							PAGE_SIZE,
							async->buf_page_list[i].
							virt_addr,
							async->buf_page_list[i].
							dma_addr);
					} else {
						free_page((unsigned long)async->
							buf_page_list[i].
							virt_addr);
					}
				}
				vfree(async->buf_page_list);
				async->buf_page_list = NULL;
			}
			return -ENOMEM;
		}
		async->n_buf_pages = n_pages;
	}
	async->prealloc_bufsz = new_size;

	return 0;
}

/* munging is applied to data by core as it passes between user
 * and kernel space */
unsigned int comedi_buf_munge(struct comedi_async *async, unsigned int num_bytes)
{
	struct comedi_subdevice *s = async->subdevice;
	unsigned int count = 0;
	const unsigned num_sample_bytes = bytes_per_sample(s);

	if (s->munge == NULL || (async->cmd.flags & CMDF_RAWDATA)) {
		async->munge_count += num_bytes;
		BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);
		return num_bytes;
	}
	/* don't munge partial samples */
	num_bytes -= num_bytes % num_sample_bytes;
	while (count < num_bytes) {
		int block_size;

		block_size = num_bytes - count;
		if (block_size < 0) {
			printk("%s: %s: bug! block_size is negative\n",
				__FILE__, __func__);
			break;
		}
		if ((int)(async->munge_ptr + block_size -
				async->prealloc_bufsz) > 0)
			block_size = async->prealloc_bufsz - async->munge_ptr;

		s->munge(s->device, s, async->prealloc_buf + async->munge_ptr,
			block_size, async->munge_chan);

		smp_wmb();	/* barrier insures data is munged in buffer before munge_count is incremented */

		async->munge_chan += block_size / num_sample_bytes;
		async->munge_chan %= async->cmd.chanlist_len;
		async->munge_count += block_size;
		async->munge_ptr += block_size;
		async->munge_ptr %= async->prealloc_bufsz;
		count += block_size;
	}
	BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);
	return count;
}

unsigned int comedi_buf_write_n_available(struct comedi_async *async)
{
	unsigned int free_end;
	unsigned int nbytes;

	if (async == NULL)
		return 0;

	free_end = async->buf_read_count + async->prealloc_bufsz;
	nbytes = free_end - async->buf_write_alloc_count;
	nbytes -= nbytes % bytes_per_sample(async->subdevice);
	/* barrier insures the read of buf_read_count in this
	   query occurs before any following writes to the buffer which
	   might be based on the return value from this query.
	 */
	smp_mb();
	return nbytes;
}

/* allocates chunk for the writer from free buffer space */
unsigned int comedi_buf_write_alloc(struct comedi_async *async, unsigned int nbytes)
{
	unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;

	if ((int)(async->buf_write_alloc_count + nbytes - free_end) > 0) {
		nbytes = free_end - async->buf_write_alloc_count;
	}
	async->buf_write_alloc_count += nbytes;
	/* barrier insures the read of buf_read_count above occurs before
	   we write data to the write-alloc'ed buffer space */
	smp_mb();
	return nbytes;
}

/* allocates nothing unless it can completely fulfill the request */
unsigned int comedi_buf_write_alloc_strict(struct comedi_async *async,
	unsigned int nbytes)
{
	unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;

	if ((int)(async->buf_write_alloc_count + nbytes - free_end) > 0) {
		nbytes = 0;
	}
	async->buf_write_alloc_count += nbytes;
	/* barrier insures the read of buf_read_count above occurs before
	   we write data to the write-alloc'ed buffer space */
	smp_mb();
	return nbytes;
}

/* transfers a chunk from writer to filled buffer space */
unsigned comedi_buf_write_free(struct comedi_async *async, unsigned int nbytes)
{
	if ((int)(async->buf_write_count + nbytes -
			async->buf_write_alloc_count) > 0) {
		printk("comedi: attempted to write-free more bytes than have been write-allocated.\n");
		nbytes = async->buf_write_alloc_count - async->buf_write_count;
	}
	async->buf_write_count += nbytes;
	async->buf_write_ptr += nbytes;
	comedi_buf_munge(async, async->buf_write_count - async->munge_count);
	if (async->buf_write_ptr >= async->prealloc_bufsz) {
		async->buf_write_ptr %= async->prealloc_bufsz;
	}
	return nbytes;
}

/* allocates a chunk for the reader from filled (and munged) buffer space */
unsigned comedi_buf_read_alloc(struct comedi_async *async, unsigned nbytes)
{
	if ((int)(async->buf_read_alloc_count + nbytes - async->munge_count) >
		0) {
		nbytes = async->munge_count - async->buf_read_alloc_count;
	}
	async->buf_read_alloc_count += nbytes;
	/* barrier insures read of munge_count occurs before we actually read
	   data out of buffer */
	smp_rmb();
	return nbytes;
}

/* transfers control of a chunk from reader to free buffer space */
unsigned comedi_buf_read_free(struct comedi_async *async, unsigned int nbytes)
{
	/*  barrier insures data has been read out of buffer before read count is incremented */
	smp_mb();
	if ((int)(async->buf_read_count + nbytes -
			async->buf_read_alloc_count) > 0) {
		printk("comedi: attempted to read-free more bytes than have been read-allocated.\n");
		nbytes = async->buf_read_alloc_count - async->buf_read_count;
	}
	async->buf_read_count += nbytes;
	async->buf_read_ptr += nbytes;
	async->buf_read_ptr %= async->prealloc_bufsz;
	return nbytes;
}

void comedi_buf_memcpy_to(struct comedi_async *async, unsigned int offset,
	const void *data, unsigned int num_bytes)
{
	unsigned int write_ptr = async->buf_write_ptr + offset;

	if (write_ptr >= async->prealloc_bufsz)
		write_ptr %= async->prealloc_bufsz;

	while (num_bytes) {
		unsigned int block_size;

		if (write_ptr + num_bytes > async->prealloc_bufsz)
			block_size = async->prealloc_bufsz - write_ptr;
		else
			block_size = num_bytes;

		memcpy(async->prealloc_buf + write_ptr, data, block_size);

		data += block_size;
		num_bytes -= block_size;

		write_ptr = 0;
	}
}

void comedi_buf_memcpy_from(struct comedi_async *async, unsigned int offset,
	void *dest, unsigned int nbytes)
{
	void *src;
	unsigned int read_ptr = async->buf_read_ptr + offset;

	if (read_ptr >= async->prealloc_bufsz)
		read_ptr %= async->prealloc_bufsz;

	while (nbytes) {
		unsigned int block_size;

		src = async->prealloc_buf + read_ptr;

		if (nbytes >= async->prealloc_bufsz - read_ptr)
			block_size = async->prealloc_bufsz - read_ptr;
		else
			block_size = nbytes;

		memcpy(dest, src, block_size);
		nbytes -= block_size;
		dest += block_size;
		read_ptr = 0;
	}
}

unsigned int comedi_buf_read_n_available(struct comedi_async *async)
{
	unsigned num_bytes;

	if (async == NULL)
		return 0;
	num_bytes = async->munge_count - async->buf_read_count;
	/* barrier insures the read of munge_count in this
	   query occurs before any following reads of the buffer which
	   might be based on the return value from this query.
	 */
	smp_rmb();
	return num_bytes;
}

int comedi_buf_get(struct comedi_async *async, short *x)
{
	unsigned int n = comedi_buf_read_n_available(async);

	if (n < sizeof(short))
		return 0;
	comedi_buf_read_alloc(async, sizeof(short));
	*x = *(short *) (async->prealloc_buf + async->buf_read_ptr);
	comedi_buf_read_free(async, sizeof(short));
	return 1;
}

int comedi_buf_put(struct comedi_async *async, short x)
{
	unsigned int n = comedi_buf_write_alloc_strict(async, sizeof(short));

	if (n < sizeof(short)) {
		async->events |= COMEDI_CB_ERROR;
		return 0;
	}
	*(short *) (async->prealloc_buf + async->buf_write_ptr) = x;
	comedi_buf_write_free(async, sizeof(short));
	return 1;
}

void comedi_reset_async_buf(struct comedi_async *async)
{
	async->buf_write_alloc_count = 0;
	async->buf_write_count = 0;
	async->buf_read_alloc_count = 0;
	async->buf_read_count = 0;

	async->buf_write_ptr = 0;
	async->buf_read_ptr = 0;

	async->cur_chan = 0;
	async->scan_progress = 0;
	async->munge_chan = 0;
	async->munge_count = 0;
	async->munge_ptr = 0;

	async->events = 0;
}

int comedi_auto_config(struct device *hardware_device, const char *board_name, const int *options, unsigned num_options)
{
	struct comedi_devconfig it;
	int minor;
	struct comedi_device_file_info *dev_file_info;
	int retval;
	unsigned *private_data = NULL;

	if (!comedi_autoconfig) {
		dev_set_drvdata(hardware_device, NULL);
		return 0;
	}

	minor = comedi_alloc_board_minor(hardware_device);
	if (minor < 0) return minor;

	private_data = kmalloc(sizeof(unsigned), GFP_KERNEL);
	if (private_data == NULL) {
		retval = -ENOMEM;
		goto cleanup;
	}
	*private_data = minor;
	dev_set_drvdata(hardware_device, private_data);

	dev_file_info = comedi_get_device_file_info(minor);

	memset(&it, 0, sizeof(it));
	strncpy(it.board_name, board_name, COMEDI_NAMELEN);
	it.board_name[COMEDI_NAMELEN - 1] = '\0';
	BUG_ON(num_options > COMEDI_NDEVCONFOPTS);
	memcpy(it.options, options, num_options * sizeof(int));

	mutex_lock(&dev_file_info->device->mutex);
	retval = comedi_device_attach(dev_file_info->device, &it);
	mutex_unlock(&dev_file_info->device->mutex);

cleanup:
	if (retval < 0)
	{
		kfree(private_data);
		comedi_free_board_minor(minor);
	}
	return retval;
}

void comedi_auto_unconfig(struct device *hardware_device)
{
	unsigned *minor = (unsigned *)dev_get_drvdata(hardware_device);
	if (minor == NULL) return;

	BUG_ON(*minor >= COMEDI_NUM_BOARD_MINORS);

	comedi_free_board_minor(*minor);
	dev_set_drvdata(hardware_device, NULL);
	kfree(minor);
}

int comedi_pci_auto_config(struct pci_dev *pcidev, const char *board_name)
{
	int options[2];

	/*  pci bus */
	options[0] = pcidev->bus->number;
	/*  pci slot */
	options[1] = PCI_SLOT(pcidev->devfn);

	return comedi_auto_config(&pcidev->dev, board_name,
				  options, ARRAY_SIZE(options));
}

void comedi_pci_auto_unconfig(struct pci_dev *pcidev)
{
	comedi_auto_unconfig(&pcidev->dev);
}

int comedi_usb_auto_config(struct usb_device *usbdev,
	const char *board_name)
{
	BUG_ON(usbdev == NULL);
	return comedi_auto_config(&usbdev->dev, board_name, NULL, 0);
}

void comedi_usb_auto_unconfig(struct usb_device *usbdev)
{
	BUG_ON(usbdev == NULL);
	comedi_auto_unconfig(&usbdev->dev);
}