summaryrefslogtreecommitdiffstats
path: root/drivers/usb/storage/scsiglue.c
blob: 8c8b5e6041cc275e5b927e5be94b355b8440083f (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
// SPDX-License-Identifier: GPL-2.0+
/*
 * Driver for USB Mass Storage compliant devices
 * SCSI layer glue code
 *
 * Current development and maintenance by:
 *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
 *
 * Developed with the assistance of:
 *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
 *   (c) 2000 Stephen J. Gowdy (SGowdy@lbl.gov)
 *
 * Initial work by:
 *   (c) 1999 Michael Gee (michael@linuxspecific.com)
 *
 * This driver is based on the 'USB Mass Storage Class' document. This
 * describes in detail the protocol used to communicate with such
 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 * mind when they created this document.  The commands are all very
 * similar to commands in the SCSI-II and ATAPI specifications.
 *
 * It is important to note that in a number of cases this class
 * exhibits class-specific exemptions from the USB specification.
 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 * that they are used to communicate wait, failed and OK on commands.
 *
 * Also, for certain devices, the interrupt endpoint is used to convey
 * status of a command.
 */

#include <linux/blkdev.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <linux/mutex.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>

#include "usb.h"
#include "scsiglue.h"
#include "debug.h"
#include "transport.h"
#include "protocol.h"

/*
 * Vendor IDs for companies that seem to include the READ CAPACITY bug
 * in all their devices
 */
#define VENDOR_ID_NOKIA		0x0421
#define VENDOR_ID_NIKON		0x04b0
#define VENDOR_ID_PENTAX	0x0a17
#define VENDOR_ID_MOTOROLA	0x22b8

/***********************************************************************
 * Host functions 
 ***********************************************************************/

static const char* host_info(struct Scsi_Host *host)
{
	struct us_data *us = host_to_us(host);
	return us->scsi_name;
}

static int slave_alloc (struct scsi_device *sdev)
{
	struct us_data *us = host_to_us(sdev->host);

	/*
	 * Set the INQUIRY transfer length to 36.  We don't use any of
	 * the extra data and many devices choke if asked for more or
	 * less than 36 bytes.
	 */
	sdev->inquiry_len = 36;

	/* Tell the SCSI layer if we know there is more than one LUN */
	if (us->protocol == USB_PR_BULK && us->max_lun > 0)
		sdev->sdev_bflags |= BLIST_FORCELUN;

	/*
	 * Some USB storage devices reset if the IO advice hints grouping mode
	 * page is queried. Hence skip that mode page.
	 */
	sdev->sdev_bflags |= BLIST_SKIP_IO_HINTS;

	return 0;
}

static int device_configure(struct scsi_device *sdev, struct queue_limits *lim)
{
	struct us_data *us = host_to_us(sdev->host);
	struct device *dev = us->pusb_dev->bus->sysdev;

	/*
	 * Many devices have trouble transferring more than 32KB at a time,
	 * while others have trouble with more than 64K. At this time we
	 * are limiting both to 32K (64 sectores).
	 */
	if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN)) {
		unsigned int max_sectors = 64;

		if (us->fflags & US_FL_MAX_SECTORS_MIN)
			max_sectors = PAGE_SIZE >> 9;
		lim->max_hw_sectors = min(lim->max_hw_sectors, max_sectors);
	} else if (sdev->type == TYPE_TAPE) {
		/*
		 * Tapes need much higher max_sector limits, so just
		 * raise it to the maximum possible (4 GB / 512) and
		 * let the queue segment size sort out the real limit.
		 */
		lim->max_hw_sectors = 0x7FFFFF;
	} else if (us->pusb_dev->speed >= USB_SPEED_SUPER) {
		/*
		 * USB3 devices will be limited to 2048 sectors. This gives us
		 * better throughput on most devices.
		 */
		lim->max_hw_sectors = 2048;
	}

	/*
	 * The max_hw_sectors should be up to maximum size of a mapping for
	 * the device. Otherwise, a DMA API might fail on swiotlb environment.
	 */
	lim->max_hw_sectors = min_t(size_t,
		lim->max_hw_sectors, dma_max_mapping_size(dev) >> SECTOR_SHIFT);

	/*
	 * We can't put these settings in slave_alloc() because that gets
	 * called before the device type is known.  Consequently these
	 * settings can't be overridden via the scsi devinfo mechanism.
	 */
	if (sdev->type == TYPE_DISK) {

		/*
		 * Some vendors seem to put the READ CAPACITY bug into
		 * all their devices -- primarily makers of cell phones
		 * and digital cameras.  Since these devices always use
		 * flash media and can be expected to have an even number
		 * of sectors, we will always enable the CAPACITY_HEURISTICS
		 * flag unless told otherwise.
		 */
		switch (le16_to_cpu(us->pusb_dev->descriptor.idVendor)) {
		case VENDOR_ID_NOKIA:
		case VENDOR_ID_NIKON:
		case VENDOR_ID_PENTAX:
		case VENDOR_ID_MOTOROLA:
			if (!(us->fflags & (US_FL_FIX_CAPACITY |
					US_FL_CAPACITY_OK)))
				us->fflags |= US_FL_CAPACITY_HEURISTICS;
			break;
		}

		/*
		 * Disk-type devices use MODE SENSE(6) if the protocol
		 * (SubClass) is Transparent SCSI, otherwise they use
		 * MODE SENSE(10).
		 */
		if (us->subclass != USB_SC_SCSI && us->subclass != USB_SC_CYP_ATACB)
			sdev->use_10_for_ms = 1;

		/*
		 *Many disks only accept MODE SENSE transfer lengths of
		 * 192 bytes (that's what Windows uses).
		 */
		sdev->use_192_bytes_for_3f = 1;

		/*
		 * Some devices report generic values until the media has been
		 * accessed. Force a READ(10) prior to querying device
		 * characteristics.
		 */
		sdev->read_before_ms = 1;

		/*
		 * Some devices don't like MODE SENSE with page=0x3f,
		 * which is the command used for checking if a device
		 * is write-protected.  Now that we tell the sd driver
		 * to do a 192-byte transfer with this command the
		 * majority of devices work fine, but a few still can't
		 * handle it.  The sd driver will simply assume those
		 * devices are write-enabled.
		 */
		if (us->fflags & US_FL_NO_WP_DETECT)
			sdev->skip_ms_page_3f = 1;

		/*
		 * A number of devices have problems with MODE SENSE for
		 * page x08, so we will skip it.
		 */
		sdev->skip_ms_page_8 = 1;

		/*
		 * Some devices don't handle VPD pages correctly, so skip vpd
		 * pages if not forced by SCSI layer.
		 */
		sdev->skip_vpd_pages = !sdev->try_vpd_pages;

		/* Do not attempt to use REPORT SUPPORTED OPERATION CODES */
		sdev->no_report_opcodes = 1;

		/* Do not attempt to use WRITE SAME */
		sdev->no_write_same = 1;

		/*
		 * Some disks return the total number of blocks in response
		 * to READ CAPACITY rather than the highest block number.
		 * If this device makes that mistake, tell the sd driver.
		 */
		if (us->fflags & US_FL_FIX_CAPACITY)
			sdev->fix_capacity = 1;

		/*
		 * A few disks have two indistinguishable version, one of
		 * which reports the correct capacity and the other does not.
		 * The sd driver has to guess which is the case.
		 */
		if (us->fflags & US_FL_CAPACITY_HEURISTICS)
			sdev->guess_capacity = 1;

		/* Some devices cannot handle READ_CAPACITY_16 */
		if (us->fflags & US_FL_NO_READ_CAPACITY_16)
			sdev->no_read_capacity_16 = 1;

		/*
		 * Many devices do not respond properly to READ_CAPACITY_16.
		 * Tell the SCSI layer to try READ_CAPACITY_10 first.
		 * However some USB 3.0 drive enclosures return capacity
		 * modulo 2TB. Those must use READ_CAPACITY_16
		 */
		if (!(us->fflags & US_FL_NEEDS_CAP16))
			sdev->try_rc_10_first = 1;

		/*
		 * assume SPC3 or latter devices support sense size > 18
		 * unless US_FL_BAD_SENSE quirk is specified.
		 */
		if (sdev->scsi_level > SCSI_SPC_2 &&
		    !(us->fflags & US_FL_BAD_SENSE))
			us->fflags |= US_FL_SANE_SENSE;

		/*
		 * USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
		 * Hardware Error) when any low-level error occurs,
		 * recoverable or not.  Setting this flag tells the SCSI
		 * midlayer to retry such commands, which frequently will
		 * succeed and fix the error.  The worst this can lead to
		 * is an occasional series of retries that will all fail.
		 */
		sdev->retry_hwerror = 1;

		/*
		 * USB disks should allow restart.  Some drives spin down
		 * automatically, requiring a START-STOP UNIT command.
		 */
		sdev->allow_restart = 1;

		/*
		 * Some USB cardreaders have trouble reading an sdcard's last
		 * sector in a larger then 1 sector read, since the performance
		 * impact is negligible we set this flag for all USB disks
		 */
		sdev->last_sector_bug = 1;

		/*
		 * Enable last-sector hacks for single-target devices using
		 * the Bulk-only transport, unless we already know the
		 * capacity will be decremented or is correct.
		 */
		if (!(us->fflags & (US_FL_FIX_CAPACITY | US_FL_CAPACITY_OK |
					US_FL_SCM_MULT_TARG)) &&
				us->protocol == USB_PR_BULK)
			us->use_last_sector_hacks = 1;

		/* Check if write cache default on flag is set or not */
		if (us->fflags & US_FL_WRITE_CACHE)
			sdev->wce_default_on = 1;

		/* A few buggy USB-ATA bridges don't understand FUA */
		if (us->fflags & US_FL_BROKEN_FUA)
			sdev->broken_fua = 1;

		/* Some even totally fail to indicate a cache */
		if (us->fflags & US_FL_ALWAYS_SYNC) {
			/* don't read caching information */
			sdev->skip_ms_page_8 = 1;
			sdev->skip_ms_page_3f = 1;
			/* assume sync is needed */
			sdev->wce_default_on = 1;
		}
	} else {

		/*
		 * Non-disk-type devices don't need to ignore any pages
		 * or to force 192-byte transfer lengths for MODE SENSE.
		 * But they do need to use MODE SENSE(10).
		 */
		sdev->use_10_for_ms = 1;

		/* Some (fake) usb cdrom devices don't like READ_DISC_INFO */
		if (us->fflags & US_FL_NO_READ_DISC_INFO)
			sdev->no_read_disc_info = 1;
	}

	/*
	 * The CB and CBI transports have no way to pass LUN values
	 * other than the bits in the second byte of a CDB.  But those
	 * bits don't get set to the LUN value if the device reports
	 * scsi_level == 0 (UNKNOWN).  Hence such devices must necessarily
	 * be single-LUN.
	 */
	if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_CBI) &&
			sdev->scsi_level == SCSI_UNKNOWN)
		us->max_lun = 0;

	/*
	 * Some devices choke when they receive a PREVENT-ALLOW MEDIUM
	 * REMOVAL command, so suppress those commands.
	 */
	if (us->fflags & US_FL_NOT_LOCKABLE)
		sdev->lockable = 0;

	/*
	 * this is to satisfy the compiler, tho I don't think the 
	 * return code is ever checked anywhere.
	 */
	return 0;
}

static int target_alloc(struct scsi_target *starget)
{
	struct us_data *us = host_to_us(dev_to_shost(starget->dev.parent));

	/*
	 * Some USB drives don't support REPORT LUNS, even though they
	 * report a SCSI revision level above 2.  Tell the SCSI layer
	 * not to issue that command; it will perform a normal sequential
	 * scan instead.
	 */
	starget->no_report_luns = 1;

	/*
	 * The UFI spec treats the Peripheral Qualifier bits in an
	 * INQUIRY result as reserved and requires devices to set them
	 * to 0.  However the SCSI spec requires these bits to be set
	 * to 3 to indicate when a LUN is not present.
	 *
	 * Let the scanning code know if this target merely sets
	 * Peripheral Device Type to 0x1f to indicate no LUN.
	 */
	if (us->subclass == USB_SC_UFI)
		starget->pdt_1f_for_no_lun = 1;

	return 0;
}

/* queue a command */
/* This is always called with scsi_lock(host) held */
static int queuecommand_lck(struct scsi_cmnd *srb)
{
	void (*done)(struct scsi_cmnd *) = scsi_done;
	struct us_data *us = host_to_us(srb->device->host);

	/* check for state-transition errors */
	if (us->srb != NULL) {
		dev_err(&us->pusb_intf->dev,
			"Error in %s: us->srb = %p\n", __func__, us->srb);
		return SCSI_MLQUEUE_HOST_BUSY;
	}

	/* fail the command if we are disconnecting */
	if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
		usb_stor_dbg(us, "Fail command during disconnect\n");
		srb->result = DID_NO_CONNECT << 16;
		done(srb);
		return 0;
	}

	if ((us->fflags & US_FL_NO_ATA_1X) &&
			(srb->cmnd[0] == ATA_12 || srb->cmnd[0] == ATA_16)) {
		memcpy(srb->sense_buffer, usb_stor_sense_invalidCDB,
		       sizeof(usb_stor_sense_invalidCDB));
		srb->result = SAM_STAT_CHECK_CONDITION;
		done(srb);
		return 0;
	}

	/* enqueue the command and wake up the control thread */
	us->srb = srb;
	complete(&us->cmnd_ready);

	return 0;
}

static DEF_SCSI_QCMD(queuecommand)

/***********************************************************************
 * Error handling functions
 ***********************************************************************/

/* Command timeout and abort */
static int command_abort_matching(struct us_data *us, struct scsi_cmnd *srb_match)
{
	/*
	 * us->srb together with the TIMED_OUT, RESETTING, and ABORTING
	 * bits are protected by the host lock.
	 */
	scsi_lock(us_to_host(us));

	/* is there any active pending command to abort ? */
	if (!us->srb) {
		scsi_unlock(us_to_host(us));
		usb_stor_dbg(us, "-- nothing to abort\n");
		return SUCCESS;
	}

	/* Does the command match the passed srb if any ? */
	if (srb_match && us->srb != srb_match) {
		scsi_unlock(us_to_host(us));
		usb_stor_dbg(us, "-- pending command mismatch\n");
		return FAILED;
	}

	/*
	 * Set the TIMED_OUT bit.  Also set the ABORTING bit, but only if
	 * a device reset isn't already in progress (to avoid interfering
	 * with the reset).  Note that we must retain the host lock while
	 * calling usb_stor_stop_transport(); otherwise it might interfere
	 * with an auto-reset that begins as soon as we release the lock.
	 */
	set_bit(US_FLIDX_TIMED_OUT, &us->dflags);
	if (!test_bit(US_FLIDX_RESETTING, &us->dflags)) {
		set_bit(US_FLIDX_ABORTING, &us->dflags);
		usb_stor_stop_transport(us);
	}
	scsi_unlock(us_to_host(us));

	/* Wait for the aborted command to finish */
	wait_for_completion(&us->notify);
	return SUCCESS;
}

static int command_abort(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);

	usb_stor_dbg(us, "%s called\n", __func__);
	return command_abort_matching(us, srb);
}

/*
 * This invokes the transport reset mechanism to reset the state of the
 * device
 */
static int device_reset(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);
	int result;

	usb_stor_dbg(us, "%s called\n", __func__);

	/* abort any pending command before reset */
	command_abort_matching(us, NULL);

	/* lock the device pointers and do the reset */
	mutex_lock(&(us->dev_mutex));
	result = us->transport_reset(us);
	mutex_unlock(&us->dev_mutex);

	return result < 0 ? FAILED : SUCCESS;
}

/* Simulate a SCSI bus reset by resetting the device's USB port. */
static int bus_reset(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);
	int result;

	usb_stor_dbg(us, "%s called\n", __func__);

	result = usb_stor_port_reset(us);
	return result < 0 ? FAILED : SUCCESS;
}

/*
 * Report a driver-initiated device reset to the SCSI layer.
 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
 * The caller must own the SCSI host lock.
 */
void usb_stor_report_device_reset(struct us_data *us)
{
	int i;
	struct Scsi_Host *host = us_to_host(us);

	scsi_report_device_reset(host, 0, 0);
	if (us->fflags & US_FL_SCM_MULT_TARG) {
		for (i = 1; i < host->max_id; ++i)
			scsi_report_device_reset(host, 0, i);
	}
}

/*
 * Report a driver-initiated bus reset to the SCSI layer.
 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
 * The caller must not own the SCSI host lock.
 */
void usb_stor_report_bus_reset(struct us_data *us)
{
	struct Scsi_Host *host = us_to_host(us);

	scsi_lock(host);
	scsi_report_bus_reset(host, 0);
	scsi_unlock(host);
}

/***********************************************************************
 * /proc/scsi/ functions
 ***********************************************************************/

static int write_info(struct Scsi_Host *host, char *buffer, int length)
{
	/* if someone is sending us data, just throw it away */
	return length;
}

static int show_info (struct seq_file *m, struct Scsi_Host *host)
{
	struct us_data *us = host_to_us(host);
	const char *string;

	/* print the controller name */
	seq_printf(m, "   Host scsi%d: usb-storage\n", host->host_no);

	/* print product, vendor, and serial number strings */
	if (us->pusb_dev->manufacturer)
		string = us->pusb_dev->manufacturer;
	else if (us->unusual_dev->vendorName)
		string = us->unusual_dev->vendorName;
	else
		string = "Unknown";
	seq_printf(m, "       Vendor: %s\n", string);
	if (us->pusb_dev->product)
		string = us->pusb_dev->product;
	else if (us->unusual_dev->productName)
		string = us->unusual_dev->productName;
	else
		string = "Unknown";
	seq_printf(m, "      Product: %s\n", string);
	if (us->pusb_dev->serial)
		string = us->pusb_dev->serial;
	else
		string = "None";
	seq_printf(m, "Serial Number: %s\n", string);

	/* show the protocol and transport */
	seq_printf(m, "     Protocol: %s\n", us->protocol_name);
	seq_printf(m, "    Transport: %s\n", us->transport_name);

	/* show the device flags */
	seq_printf(m, "       Quirks:");

#define US_FLAG(name, value) \
	if (us->fflags & value) seq_printf(m, " " #name);
US_DO_ALL_FLAGS
#undef US_FLAG
	seq_putc(m, '\n');
	return 0;
}

/***********************************************************************
 * Sysfs interface
 ***********************************************************************/

/* Output routine for the sysfs max_sectors file */
static ssize_t max_sectors_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct scsi_device *sdev = to_scsi_device(dev);

	return sprintf(buf, "%u\n", queue_max_hw_sectors(sdev->request_queue));
}

/* Input routine for the sysfs max_sectors file */
static ssize_t max_sectors_store(struct device *dev, struct device_attribute *attr, const char *buf,
		size_t count)
{
	struct scsi_device *sdev = to_scsi_device(dev);
	struct queue_limits lim;
	unsigned short ms;
	int ret;

	if (sscanf(buf, "%hu", &ms) <= 0)
		return -EINVAL;

	blk_mq_freeze_queue(sdev->request_queue);
	lim = queue_limits_start_update(sdev->request_queue);
	lim.max_hw_sectors = ms;
	ret = queue_limits_commit_update(sdev->request_queue, &lim);
	blk_mq_unfreeze_queue(sdev->request_queue);

	if (ret)
		return ret;
	return count;
}
static DEVICE_ATTR_RW(max_sectors);

static struct attribute *usb_sdev_attrs[] = {
	&dev_attr_max_sectors.attr,
	NULL,
};

ATTRIBUTE_GROUPS(usb_sdev);

/*
 * this defines our host template, with which we'll allocate hosts
 */

static const struct scsi_host_template usb_stor_host_template = {
	/* basic userland interface stuff */
	.name =				"usb-storage",
	.proc_name =			"usb-storage",
	.show_info =			show_info,
	.write_info =			write_info,
	.info =				host_info,

	/* command interface -- queued only */
	.queuecommand =			queuecommand,

	/* error and abort handlers */
	.eh_abort_handler =		command_abort,
	.eh_device_reset_handler =	device_reset,
	.eh_bus_reset_handler =		bus_reset,

	/* queue commands only, only one command per LUN */
	.can_queue =			1,

	/* unknown initiator id */
	.this_id =			-1,

	.slave_alloc =			slave_alloc,
	.device_configure =		device_configure,
	.target_alloc =			target_alloc,

	/* lots of sg segments can be handled */
	.sg_tablesize =			SG_MAX_SEGMENTS,

	/*
	 * Some host controllers may have alignment requirements.
	 * We'll play it safe by requiring 512-byte alignment always.
	 */
	.dma_alignment =		511,

	/*
	 * Limit the total size of a transfer to 120 KB.
	 *
	 * Some devices are known to choke with anything larger. It seems like
	 * the problem stems from the fact that original IDE controllers had
	 * only an 8-bit register to hold the number of sectors in one transfer
	 * and even those couldn't handle a full 256 sectors.
	 *
	 * Because we want to make sure we interoperate with as many devices as
	 * possible, we will maintain a 240 sector transfer size limit for USB
	 * Mass Storage devices.
	 *
	 * Tests show that other operating have similar limits with Microsoft
	 * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
	 * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
	 * and 2048 for USB3 devices.
	 */
	.max_sectors =                  240,

	/* emulated HBA */
	.emulated =			1,

	/* we do our own delay after a device or bus reset */
	.skip_settle_delay =		1,

	/* sysfs device attributes */
	.sdev_groups =			usb_sdev_groups,

	/* module management */
	.module =			THIS_MODULE
};

void usb_stor_host_template_init(struct scsi_host_template *sht,
				 const char *name, struct module *owner)
{
	*sht = usb_stor_host_template;
	sht->name = name;
	sht->proc_name = name;
	sht->module = owner;
}
EXPORT_SYMBOL_GPL(usb_stor_host_template_init);

/* To Report "Illegal Request: Invalid Field in CDB */
unsigned char usb_stor_sense_invalidCDB[18] = {
	[0]	= 0x70,			    /* current error */
	[2]	= ILLEGAL_REQUEST,	    /* Illegal Request = 0x05 */
	[7]	= 0x0a,			    /* additional length */
	[12]	= 0x24			    /* Invalid Field in CDB */
};
EXPORT_SYMBOL_GPL(usb_stor_sense_invalidCDB);