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v6.8
  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Driver for USB Mass Storage compliant devices
  4 * SCSI layer glue code
  5 *
  6 * Current development and maintenance by:
  7 *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
  8 *
  9 * Developed with the assistance of:
 10 *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
 11 *   (c) 2000 Stephen J. Gowdy (SGowdy@lbl.gov)
 12 *
 13 * Initial work by:
 14 *   (c) 1999 Michael Gee (michael@linuxspecific.com)
 15 *
 16 * This driver is based on the 'USB Mass Storage Class' document. This
 17 * describes in detail the protocol used to communicate with such
 18 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 19 * mind when they created this document.  The commands are all very
 20 * similar to commands in the SCSI-II and ATAPI specifications.
 21 *
 22 * It is important to note that in a number of cases this class
 23 * exhibits class-specific exemptions from the USB specification.
 24 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 25 * that they are used to communicate wait, failed and OK on commands.
 26 *
 27 * Also, for certain devices, the interrupt endpoint is used to convey
 28 * status of a command.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 29 */
 30
 31#include <linux/blkdev.h>
 32#include <linux/dma-mapping.h>
 33#include <linux/module.h>
 34#include <linux/mutex.h>
 35
 36#include <scsi/scsi.h>
 37#include <scsi/scsi_cmnd.h>
 38#include <scsi/scsi_devinfo.h>
 39#include <scsi/scsi_device.h>
 40#include <scsi/scsi_eh.h>
 41
 42#include "usb.h"
 43#include <linux/usb/hcd.h>
 44#include "scsiglue.h"
 45#include "debug.h"
 46#include "transport.h"
 47#include "protocol.h"
 48
 49/*
 50 * Vendor IDs for companies that seem to include the READ CAPACITY bug
 51 * in all their devices
 52 */
 53#define VENDOR_ID_NOKIA		0x0421
 54#define VENDOR_ID_NIKON		0x04b0
 55#define VENDOR_ID_PENTAX	0x0a17
 56#define VENDOR_ID_MOTOROLA	0x22b8
 57
 58/***********************************************************************
 59 * Host functions 
 60 ***********************************************************************/
 61
 62static const char* host_info(struct Scsi_Host *host)
 63{
 64	struct us_data *us = host_to_us(host);
 65	return us->scsi_name;
 66}
 67
 68static int slave_alloc (struct scsi_device *sdev)
 69{
 70	struct us_data *us = host_to_us(sdev->host);
 71
 72	/*
 73	 * Set the INQUIRY transfer length to 36.  We don't use any of
 74	 * the extra data and many devices choke if asked for more or
 75	 * less than 36 bytes.
 76	 */
 77	sdev->inquiry_len = 36;
 78
 79	/*
 80	 * Some host controllers may have alignment requirements.
 81	 * We'll play it safe by requiring 512-byte alignment always.
 
 
 
 
 
 
 
 
 
 
 
 
 82	 */
 83	blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
 84
 85	/* Tell the SCSI layer if we know there is more than one LUN */
 86	if (us->protocol == USB_PR_BULK && us->max_lun > 0)
 87		sdev->sdev_bflags |= BLIST_FORCELUN;
 88
 89	return 0;
 90}
 91
 92static int slave_configure(struct scsi_device *sdev)
 93{
 94	struct us_data *us = host_to_us(sdev->host);
 95	struct device *dev = us->pusb_dev->bus->sysdev;
 96
 97	/*
 98	 * Many devices have trouble transferring more than 32KB at a time,
 99	 * while others have trouble with more than 64K. At this time we
100	 * are limiting both to 32K (64 sectores).
101	 */
102	if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN)) {
103		unsigned int max_sectors = 64;
104
105		if (us->fflags & US_FL_MAX_SECTORS_MIN)
106			max_sectors = PAGE_SIZE >> 9;
107		if (queue_max_hw_sectors(sdev->request_queue) > max_sectors)
108			blk_queue_max_hw_sectors(sdev->request_queue,
109					      max_sectors);
110	} else if (sdev->type == TYPE_TAPE) {
111		/*
112		 * Tapes need much higher max_sector limits, so just
113		 * raise it to the maximum possible (4 GB / 512) and
114		 * let the queue segment size sort out the real limit.
115		 */
116		blk_queue_max_hw_sectors(sdev->request_queue, 0x7FFFFF);
117	} else if (us->pusb_dev->speed >= USB_SPEED_SUPER) {
118		/*
119		 * USB3 devices will be limited to 2048 sectors. This gives us
120		 * better throughput on most devices.
121		 */
122		blk_queue_max_hw_sectors(sdev->request_queue, 2048);
123	}
124
125	/*
126	 * The max_hw_sectors should be up to maximum size of a mapping for
127	 * the device. Otherwise, a DMA API might fail on swiotlb environment.
128	 */
129	blk_queue_max_hw_sectors(sdev->request_queue,
130		min_t(size_t, queue_max_hw_sectors(sdev->request_queue),
131		      dma_max_mapping_size(dev) >> SECTOR_SHIFT));
132
133	/*
134	 * Some USB host controllers can't do DMA; they have to use PIO.
135	 * For such controllers we need to make sure the block layer sets
 
136	 * up bounce buffers in addressable memory.
137	 */
138	if (!hcd_uses_dma(bus_to_hcd(us->pusb_dev->bus)) ||
139			(bus_to_hcd(us->pusb_dev->bus)->localmem_pool != NULL))
140		blk_queue_bounce_limit(sdev->request_queue, BLK_BOUNCE_HIGH);
141
142	/*
143	 * We can't put these settings in slave_alloc() because that gets
144	 * called before the device type is known.  Consequently these
145	 * settings can't be overridden via the scsi devinfo mechanism.
146	 */
147	if (sdev->type == TYPE_DISK) {
148
149		/*
150		 * Some vendors seem to put the READ CAPACITY bug into
151		 * all their devices -- primarily makers of cell phones
152		 * and digital cameras.  Since these devices always use
153		 * flash media and can be expected to have an even number
154		 * of sectors, we will always enable the CAPACITY_HEURISTICS
155		 * flag unless told otherwise.
156		 */
157		switch (le16_to_cpu(us->pusb_dev->descriptor.idVendor)) {
158		case VENDOR_ID_NOKIA:
159		case VENDOR_ID_NIKON:
160		case VENDOR_ID_PENTAX:
161		case VENDOR_ID_MOTOROLA:
162			if (!(us->fflags & (US_FL_FIX_CAPACITY |
163					US_FL_CAPACITY_OK)))
164				us->fflags |= US_FL_CAPACITY_HEURISTICS;
165			break;
166		}
167
168		/*
169		 * Disk-type devices use MODE SENSE(6) if the protocol
170		 * (SubClass) is Transparent SCSI, otherwise they use
171		 * MODE SENSE(10).
172		 */
173		if (us->subclass != USB_SC_SCSI && us->subclass != USB_SC_CYP_ATACB)
174			sdev->use_10_for_ms = 1;
175
176		/*
177		 *Many disks only accept MODE SENSE transfer lengths of
178		 * 192 bytes (that's what Windows uses).
179		 */
180		sdev->use_192_bytes_for_3f = 1;
181
182		/*
183		 * Some devices report generic values until the media has been
184		 * accessed. Force a READ(10) prior to querying device
185		 * characteristics.
186		 */
187		sdev->read_before_ms = 1;
188
189		/*
190		 * Some devices don't like MODE SENSE with page=0x3f,
191		 * which is the command used for checking if a device
192		 * is write-protected.  Now that we tell the sd driver
193		 * to do a 192-byte transfer with this command the
194		 * majority of devices work fine, but a few still can't
195		 * handle it.  The sd driver will simply assume those
196		 * devices are write-enabled.
197		 */
198		if (us->fflags & US_FL_NO_WP_DETECT)
199			sdev->skip_ms_page_3f = 1;
200
201		/*
202		 * A number of devices have problems with MODE SENSE for
203		 * page x08, so we will skip it.
204		 */
205		sdev->skip_ms_page_8 = 1;
206
207		/*
208		 * Some devices don't handle VPD pages correctly, so skip vpd
209		 * pages if not forced by SCSI layer.
210		 */
211		sdev->skip_vpd_pages = !sdev->try_vpd_pages;
212
213		/* Do not attempt to use REPORT SUPPORTED OPERATION CODES */
214		sdev->no_report_opcodes = 1;
215
216		/* Do not attempt to use WRITE SAME */
217		sdev->no_write_same = 1;
218
219		/*
220		 * Some disks return the total number of blocks in response
221		 * to READ CAPACITY rather than the highest block number.
222		 * If this device makes that mistake, tell the sd driver.
223		 */
224		if (us->fflags & US_FL_FIX_CAPACITY)
225			sdev->fix_capacity = 1;
226
227		/*
228		 * A few disks have two indistinguishable version, one of
229		 * which reports the correct capacity and the other does not.
230		 * The sd driver has to guess which is the case.
231		 */
232		if (us->fflags & US_FL_CAPACITY_HEURISTICS)
233			sdev->guess_capacity = 1;
234
235		/* Some devices cannot handle READ_CAPACITY_16 */
236		if (us->fflags & US_FL_NO_READ_CAPACITY_16)
237			sdev->no_read_capacity_16 = 1;
238
239		/*
240		 * Many devices do not respond properly to READ_CAPACITY_16.
241		 * Tell the SCSI layer to try READ_CAPACITY_10 first.
242		 * However some USB 3.0 drive enclosures return capacity
243		 * modulo 2TB. Those must use READ_CAPACITY_16
244		 */
245		if (!(us->fflags & US_FL_NEEDS_CAP16))
246			sdev->try_rc_10_first = 1;
247
248		/*
249		 * assume SPC3 or latter devices support sense size > 18
250		 * unless US_FL_BAD_SENSE quirk is specified.
251		 */
252		if (sdev->scsi_level > SCSI_SPC_2 &&
253		    !(us->fflags & US_FL_BAD_SENSE))
254			us->fflags |= US_FL_SANE_SENSE;
255
256		/*
257		 * USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
258		 * Hardware Error) when any low-level error occurs,
259		 * recoverable or not.  Setting this flag tells the SCSI
260		 * midlayer to retry such commands, which frequently will
261		 * succeed and fix the error.  The worst this can lead to
262		 * is an occasional series of retries that will all fail.
263		 */
264		sdev->retry_hwerror = 1;
265
266		/*
267		 * USB disks should allow restart.  Some drives spin down
268		 * automatically, requiring a START-STOP UNIT command.
269		 */
270		sdev->allow_restart = 1;
271
272		/*
273		 * Some USB cardreaders have trouble reading an sdcard's last
274		 * sector in a larger then 1 sector read, since the performance
275		 * impact is negligible we set this flag for all USB disks
276		 */
277		sdev->last_sector_bug = 1;
278
279		/*
280		 * Enable last-sector hacks for single-target devices using
281		 * the Bulk-only transport, unless we already know the
282		 * capacity will be decremented or is correct.
283		 */
284		if (!(us->fflags & (US_FL_FIX_CAPACITY | US_FL_CAPACITY_OK |
285					US_FL_SCM_MULT_TARG)) &&
286				us->protocol == USB_PR_BULK)
287			us->use_last_sector_hacks = 1;
288
289		/* Check if write cache default on flag is set or not */
290		if (us->fflags & US_FL_WRITE_CACHE)
291			sdev->wce_default_on = 1;
292
293		/* A few buggy USB-ATA bridges don't understand FUA */
294		if (us->fflags & US_FL_BROKEN_FUA)
295			sdev->broken_fua = 1;
296
297		/* Some even totally fail to indicate a cache */
298		if (us->fflags & US_FL_ALWAYS_SYNC) {
299			/* don't read caching information */
300			sdev->skip_ms_page_8 = 1;
301			sdev->skip_ms_page_3f = 1;
302			/* assume sync is needed */
303			sdev->wce_default_on = 1;
304		}
305	} else {
306
307		/*
308		 * Non-disk-type devices don't need to ignore any pages
309		 * or to force 192-byte transfer lengths for MODE SENSE.
310		 * But they do need to use MODE SENSE(10).
311		 */
312		sdev->use_10_for_ms = 1;
313
314		/* Some (fake) usb cdrom devices don't like READ_DISC_INFO */
315		if (us->fflags & US_FL_NO_READ_DISC_INFO)
316			sdev->no_read_disc_info = 1;
317	}
318
319	/*
320	 * The CB and CBI transports have no way to pass LUN values
321	 * other than the bits in the second byte of a CDB.  But those
322	 * bits don't get set to the LUN value if the device reports
323	 * scsi_level == 0 (UNKNOWN).  Hence such devices must necessarily
324	 * be single-LUN.
325	 */
326	if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_CBI) &&
327			sdev->scsi_level == SCSI_UNKNOWN)
328		us->max_lun = 0;
329
330	/*
331	 * Some devices choke when they receive a PREVENT-ALLOW MEDIUM
332	 * REMOVAL command, so suppress those commands.
333	 */
334	if (us->fflags & US_FL_NOT_LOCKABLE)
335		sdev->lockable = 0;
336
337	/*
338	 * this is to satisfy the compiler, tho I don't think the 
339	 * return code is ever checked anywhere.
340	 */
341	return 0;
342}
343
344static int target_alloc(struct scsi_target *starget)
345{
346	struct us_data *us = host_to_us(dev_to_shost(starget->dev.parent));
347
348	/*
349	 * Some USB drives don't support REPORT LUNS, even though they
350	 * report a SCSI revision level above 2.  Tell the SCSI layer
351	 * not to issue that command; it will perform a normal sequential
352	 * scan instead.
353	 */
354	starget->no_report_luns = 1;
355
356	/*
357	 * The UFI spec treats the Peripheral Qualifier bits in an
358	 * INQUIRY result as reserved and requires devices to set them
359	 * to 0.  However the SCSI spec requires these bits to be set
360	 * to 3 to indicate when a LUN is not present.
361	 *
362	 * Let the scanning code know if this target merely sets
363	 * Peripheral Device Type to 0x1f to indicate no LUN.
364	 */
365	if (us->subclass == USB_SC_UFI)
366		starget->pdt_1f_for_no_lun = 1;
367
368	return 0;
369}
370
371/* queue a command */
372/* This is always called with scsi_lock(host) held */
373static int queuecommand_lck(struct scsi_cmnd *srb)
 
374{
375	void (*done)(struct scsi_cmnd *) = scsi_done;
376	struct us_data *us = host_to_us(srb->device->host);
377
378	/* check for state-transition errors */
379	if (us->srb != NULL) {
380		dev_err(&us->pusb_intf->dev,
381			"Error in %s: us->srb = %p\n", __func__, us->srb);
382		return SCSI_MLQUEUE_HOST_BUSY;
383	}
384
385	/* fail the command if we are disconnecting */
386	if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
387		usb_stor_dbg(us, "Fail command during disconnect\n");
388		srb->result = DID_NO_CONNECT << 16;
389		done(srb);
390		return 0;
391	}
392
393	if ((us->fflags & US_FL_NO_ATA_1X) &&
394			(srb->cmnd[0] == ATA_12 || srb->cmnd[0] == ATA_16)) {
395		memcpy(srb->sense_buffer, usb_stor_sense_invalidCDB,
396		       sizeof(usb_stor_sense_invalidCDB));
397		srb->result = SAM_STAT_CHECK_CONDITION;
398		done(srb);
399		return 0;
400	}
401
402	/* enqueue the command and wake up the control thread */
 
403	us->srb = srb;
404	complete(&us->cmnd_ready);
405
406	return 0;
407}
408
409static DEF_SCSI_QCMD(queuecommand)
410
411/***********************************************************************
412 * Error handling functions
413 ***********************************************************************/
414
415/* Command timeout and abort */
416static int command_abort_matching(struct us_data *us, struct scsi_cmnd *srb_match)
417{
 
 
 
 
418	/*
419	 * us->srb together with the TIMED_OUT, RESETTING, and ABORTING
420	 * bits are protected by the host lock.
421	 */
422	scsi_lock(us_to_host(us));
423
424	/* is there any active pending command to abort ? */
425	if (!us->srb) {
426		scsi_unlock(us_to_host(us));
427		usb_stor_dbg(us, "-- nothing to abort\n");
428		return SUCCESS;
429	}
430
431	/* Does the command match the passed srb if any ? */
432	if (srb_match && us->srb != srb_match) {
433		scsi_unlock(us_to_host(us));
434		usb_stor_dbg(us, "-- pending command mismatch\n");
435		return FAILED;
436	}
437
438	/*
439	 * Set the TIMED_OUT bit.  Also set the ABORTING bit, but only if
440	 * a device reset isn't already in progress (to avoid interfering
441	 * with the reset).  Note that we must retain the host lock while
442	 * calling usb_stor_stop_transport(); otherwise it might interfere
443	 * with an auto-reset that begins as soon as we release the lock.
444	 */
445	set_bit(US_FLIDX_TIMED_OUT, &us->dflags);
446	if (!test_bit(US_FLIDX_RESETTING, &us->dflags)) {
447		set_bit(US_FLIDX_ABORTING, &us->dflags);
448		usb_stor_stop_transport(us);
449	}
450	scsi_unlock(us_to_host(us));
451
452	/* Wait for the aborted command to finish */
453	wait_for_completion(&us->notify);
454	return SUCCESS;
455}
456
457static int command_abort(struct scsi_cmnd *srb)
458{
459	struct us_data *us = host_to_us(srb->device->host);
460
461	usb_stor_dbg(us, "%s called\n", __func__);
462	return command_abort_matching(us, srb);
463}
464
465/*
466 * This invokes the transport reset mechanism to reset the state of the
467 * device
468 */
469static int device_reset(struct scsi_cmnd *srb)
470{
471	struct us_data *us = host_to_us(srb->device->host);
472	int result;
473
474	usb_stor_dbg(us, "%s called\n", __func__);
475
476	/* abort any pending command before reset */
477	command_abort_matching(us, NULL);
478
479	/* lock the device pointers and do the reset */
480	mutex_lock(&(us->dev_mutex));
481	result = us->transport_reset(us);
482	mutex_unlock(&us->dev_mutex);
483
484	return result < 0 ? FAILED : SUCCESS;
485}
486
487/* Simulate a SCSI bus reset by resetting the device's USB port. */
488static int bus_reset(struct scsi_cmnd *srb)
489{
490	struct us_data *us = host_to_us(srb->device->host);
491	int result;
492
493	usb_stor_dbg(us, "%s called\n", __func__);
494
495	result = usb_stor_port_reset(us);
496	return result < 0 ? FAILED : SUCCESS;
497}
498
499/*
500 * Report a driver-initiated device reset to the SCSI layer.
501 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
502 * The caller must own the SCSI host lock.
503 */
504void usb_stor_report_device_reset(struct us_data *us)
505{
506	int i;
507	struct Scsi_Host *host = us_to_host(us);
508
509	scsi_report_device_reset(host, 0, 0);
510	if (us->fflags & US_FL_SCM_MULT_TARG) {
511		for (i = 1; i < host->max_id; ++i)
512			scsi_report_device_reset(host, 0, i);
513	}
514}
515
516/*
517 * Report a driver-initiated bus reset to the SCSI layer.
518 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
519 * The caller must not own the SCSI host lock.
520 */
521void usb_stor_report_bus_reset(struct us_data *us)
522{
523	struct Scsi_Host *host = us_to_host(us);
524
525	scsi_lock(host);
526	scsi_report_bus_reset(host, 0);
527	scsi_unlock(host);
528}
529
530/***********************************************************************
531 * /proc/scsi/ functions
532 ***********************************************************************/
533
534static int write_info(struct Scsi_Host *host, char *buffer, int length)
535{
536	/* if someone is sending us data, just throw it away */
537	return length;
538}
539
540static int show_info (struct seq_file *m, struct Scsi_Host *host)
541{
542	struct us_data *us = host_to_us(host);
543	const char *string;
544
545	/* print the controller name */
546	seq_printf(m, "   Host scsi%d: usb-storage\n", host->host_no);
547
548	/* print product, vendor, and serial number strings */
549	if (us->pusb_dev->manufacturer)
550		string = us->pusb_dev->manufacturer;
551	else if (us->unusual_dev->vendorName)
552		string = us->unusual_dev->vendorName;
553	else
554		string = "Unknown";
555	seq_printf(m, "       Vendor: %s\n", string);
556	if (us->pusb_dev->product)
557		string = us->pusb_dev->product;
558	else if (us->unusual_dev->productName)
559		string = us->unusual_dev->productName;
560	else
561		string = "Unknown";
562	seq_printf(m, "      Product: %s\n", string);
563	if (us->pusb_dev->serial)
564		string = us->pusb_dev->serial;
565	else
566		string = "None";
567	seq_printf(m, "Serial Number: %s\n", string);
568
569	/* show the protocol and transport */
570	seq_printf(m, "     Protocol: %s\n", us->protocol_name);
571	seq_printf(m, "    Transport: %s\n", us->transport_name);
572
573	/* show the device flags */
574	seq_printf(m, "       Quirks:");
575
576#define US_FLAG(name, value) \
577	if (us->fflags & value) seq_printf(m, " " #name);
578US_DO_ALL_FLAGS
579#undef US_FLAG
580	seq_putc(m, '\n');
581	return 0;
582}
583
584/***********************************************************************
585 * Sysfs interface
586 ***********************************************************************/
587
588/* Output routine for the sysfs max_sectors file */
589static ssize_t max_sectors_show(struct device *dev, struct device_attribute *attr, char *buf)
590{
591	struct scsi_device *sdev = to_scsi_device(dev);
592
593	return sprintf(buf, "%u\n", queue_max_hw_sectors(sdev->request_queue));
594}
595
596/* Input routine for the sysfs max_sectors file */
597static ssize_t max_sectors_store(struct device *dev, struct device_attribute *attr, const char *buf,
598		size_t count)
599{
600	struct scsi_device *sdev = to_scsi_device(dev);
601	unsigned short ms;
602
603	if (sscanf(buf, "%hu", &ms) > 0) {
604		blk_queue_max_hw_sectors(sdev->request_queue, ms);
605		return count;
606	}
607	return -EINVAL;
608}
609static DEVICE_ATTR_RW(max_sectors);
610
611static struct attribute *usb_sdev_attrs[] = {
612	&dev_attr_max_sectors.attr,
613	NULL,
614};
615
616ATTRIBUTE_GROUPS(usb_sdev);
617
618/*
619 * this defines our host template, with which we'll allocate hosts
620 */
621
622static const struct scsi_host_template usb_stor_host_template = {
623	/* basic userland interface stuff */
624	.name =				"usb-storage",
625	.proc_name =			"usb-storage",
626	.show_info =			show_info,
627	.write_info =			write_info,
628	.info =				host_info,
629
630	/* command interface -- queued only */
631	.queuecommand =			queuecommand,
632
633	/* error and abort handlers */
634	.eh_abort_handler =		command_abort,
635	.eh_device_reset_handler =	device_reset,
636	.eh_bus_reset_handler =		bus_reset,
637
638	/* queue commands only, only one command per LUN */
639	.can_queue =			1,
640
641	/* unknown initiator id */
642	.this_id =			-1,
643
644	.slave_alloc =			slave_alloc,
645	.slave_configure =		slave_configure,
646	.target_alloc =			target_alloc,
647
648	/* lots of sg segments can be handled */
649	.sg_tablesize =			SG_MAX_SEGMENTS,
650
651
652	/*
653	 * Limit the total size of a transfer to 120 KB.
654	 *
655	 * Some devices are known to choke with anything larger. It seems like
656	 * the problem stems from the fact that original IDE controllers had
657	 * only an 8-bit register to hold the number of sectors in one transfer
658	 * and even those couldn't handle a full 256 sectors.
659	 *
660	 * Because we want to make sure we interoperate with as many devices as
661	 * possible, we will maintain a 240 sector transfer size limit for USB
662	 * Mass Storage devices.
663	 *
664	 * Tests show that other operating have similar limits with Microsoft
665	 * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
666	 * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
667	 * and 2048 for USB3 devices.
668	 */
669	.max_sectors =                  240,
670
 
 
 
 
 
 
 
671	/* emulated HBA */
672	.emulated =			1,
673
674	/* we do our own delay after a device or bus reset */
675	.skip_settle_delay =		1,
676
677	/* sysfs device attributes */
678	.sdev_groups =			usb_sdev_groups,
679
680	/* module management */
681	.module =			THIS_MODULE
682};
683
684void usb_stor_host_template_init(struct scsi_host_template *sht,
685				 const char *name, struct module *owner)
686{
687	*sht = usb_stor_host_template;
688	sht->name = name;
689	sht->proc_name = name;
690	sht->module = owner;
691}
692EXPORT_SYMBOL_GPL(usb_stor_host_template_init);
693
694/* To Report "Illegal Request: Invalid Field in CDB */
695unsigned char usb_stor_sense_invalidCDB[18] = {
696	[0]	= 0x70,			    /* current error */
697	[2]	= ILLEGAL_REQUEST,	    /* Illegal Request = 0x05 */
698	[7]	= 0x0a,			    /* additional length */
699	[12]	= 0x24			    /* Invalid Field in CDB */
700};
701EXPORT_SYMBOL_GPL(usb_stor_sense_invalidCDB);
v4.10.11
 
  1/*
  2 * Driver for USB Mass Storage compliant devices
  3 * SCSI layer glue code
  4 *
  5 * Current development and maintenance by:
  6 *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
  7 *
  8 * Developed with the assistance of:
  9 *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
 10 *   (c) 2000 Stephen J. Gowdy (SGowdy@lbl.gov)
 11 *
 12 * Initial work by:
 13 *   (c) 1999 Michael Gee (michael@linuxspecific.com)
 14 *
 15 * This driver is based on the 'USB Mass Storage Class' document. This
 16 * describes in detail the protocol used to communicate with such
 17 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 18 * mind when they created this document.  The commands are all very
 19 * similar to commands in the SCSI-II and ATAPI specifications.
 20 *
 21 * It is important to note that in a number of cases this class
 22 * exhibits class-specific exemptions from the USB specification.
 23 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 24 * that they are used to communicate wait, failed and OK on commands.
 25 *
 26 * Also, for certain devices, the interrupt endpoint is used to convey
 27 * status of a command.
 28 *
 29 * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
 30 * information about this driver.
 31 *
 32 * This program is free software; you can redistribute it and/or modify it
 33 * under the terms of the GNU General Public License as published by the
 34 * Free Software Foundation; either version 2, or (at your option) any
 35 * later version.
 36 *
 37 * This program is distributed in the hope that it will be useful, but
 38 * WITHOUT ANY WARRANTY; without even the implied warranty of
 39 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 40 * General Public License for more details.
 41 *
 42 * You should have received a copy of the GNU General Public License along
 43 * with this program; if not, write to the Free Software Foundation, Inc.,
 44 * 675 Mass Ave, Cambridge, MA 02139, USA.
 45 */
 46
 
 
 47#include <linux/module.h>
 48#include <linux/mutex.h>
 49
 50#include <scsi/scsi.h>
 51#include <scsi/scsi_cmnd.h>
 52#include <scsi/scsi_devinfo.h>
 53#include <scsi/scsi_device.h>
 54#include <scsi/scsi_eh.h>
 55
 56#include "usb.h"
 
 57#include "scsiglue.h"
 58#include "debug.h"
 59#include "transport.h"
 60#include "protocol.h"
 61
 62/*
 63 * Vendor IDs for companies that seem to include the READ CAPACITY bug
 64 * in all their devices
 65 */
 66#define VENDOR_ID_NOKIA		0x0421
 67#define VENDOR_ID_NIKON		0x04b0
 68#define VENDOR_ID_PENTAX	0x0a17
 69#define VENDOR_ID_MOTOROLA	0x22b8
 70
 71/***********************************************************************
 72 * Host functions 
 73 ***********************************************************************/
 74
 75static const char* host_info(struct Scsi_Host *host)
 76{
 77	struct us_data *us = host_to_us(host);
 78	return us->scsi_name;
 79}
 80
 81static int slave_alloc (struct scsi_device *sdev)
 82{
 83	struct us_data *us = host_to_us(sdev->host);
 84
 85	/*
 86	 * Set the INQUIRY transfer length to 36.  We don't use any of
 87	 * the extra data and many devices choke if asked for more or
 88	 * less than 36 bytes.
 89	 */
 90	sdev->inquiry_len = 36;
 91
 92	/*
 93	 * USB has unusual DMA-alignment requirements: Although the
 94	 * starting address of each scatter-gather element doesn't matter,
 95	 * the length of each element except the last must be divisible
 96	 * by the Bulk maxpacket value.  There's currently no way to
 97	 * express this by block-layer constraints, so we'll cop out
 98	 * and simply require addresses to be aligned at 512-byte
 99	 * boundaries.  This is okay since most block I/O involves
100	 * hardware sectors that are multiples of 512 bytes in length,
101	 * and since host controllers up through USB 2.0 have maxpacket
102	 * values no larger than 512.
103	 *
104	 * But it doesn't suffice for Wireless USB, where Bulk maxpacket
105	 * values can be as large as 2048.  To make that work properly
106	 * will require changes to the block layer.
107	 */
108	blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
109
110	/* Tell the SCSI layer if we know there is more than one LUN */
111	if (us->protocol == USB_PR_BULK && us->max_lun > 0)
112		sdev->sdev_bflags |= BLIST_FORCELUN;
113
114	return 0;
115}
116
117static int slave_configure(struct scsi_device *sdev)
118{
119	struct us_data *us = host_to_us(sdev->host);
 
120
121	/*
122	 * Many devices have trouble transferring more than 32KB at a time,
123	 * while others have trouble with more than 64K. At this time we
124	 * are limiting both to 32K (64 sectores).
125	 */
126	if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN)) {
127		unsigned int max_sectors = 64;
128
129		if (us->fflags & US_FL_MAX_SECTORS_MIN)
130			max_sectors = PAGE_SIZE >> 9;
131		if (queue_max_hw_sectors(sdev->request_queue) > max_sectors)
132			blk_queue_max_hw_sectors(sdev->request_queue,
133					      max_sectors);
134	} else if (sdev->type == TYPE_TAPE) {
135		/*
136		 * Tapes need much higher max_sector limits, so just
137		 * raise it to the maximum possible (4 GB / 512) and
138		 * let the queue segment size sort out the real limit.
139		 */
140		blk_queue_max_hw_sectors(sdev->request_queue, 0x7FFFFF);
141	} else if (us->pusb_dev->speed >= USB_SPEED_SUPER) {
142		/*
143		 * USB3 devices will be limited to 2048 sectors. This gives us
144		 * better throughput on most devices.
145		 */
146		blk_queue_max_hw_sectors(sdev->request_queue, 2048);
147	}
148
149	/*
 
 
 
 
 
 
 
 
150	 * Some USB host controllers can't do DMA; they have to use PIO.
151	 * They indicate this by setting their dma_mask to NULL.  For
152	 * such controllers we need to make sure the block layer sets
153	 * up bounce buffers in addressable memory.
154	 */
155	if (!us->pusb_dev->bus->controller->dma_mask)
 
156		blk_queue_bounce_limit(sdev->request_queue, BLK_BOUNCE_HIGH);
157
158	/*
159	 * We can't put these settings in slave_alloc() because that gets
160	 * called before the device type is known.  Consequently these
161	 * settings can't be overridden via the scsi devinfo mechanism.
162	 */
163	if (sdev->type == TYPE_DISK) {
164
165		/*
166		 * Some vendors seem to put the READ CAPACITY bug into
167		 * all their devices -- primarily makers of cell phones
168		 * and digital cameras.  Since these devices always use
169		 * flash media and can be expected to have an even number
170		 * of sectors, we will always enable the CAPACITY_HEURISTICS
171		 * flag unless told otherwise.
172		 */
173		switch (le16_to_cpu(us->pusb_dev->descriptor.idVendor)) {
174		case VENDOR_ID_NOKIA:
175		case VENDOR_ID_NIKON:
176		case VENDOR_ID_PENTAX:
177		case VENDOR_ID_MOTOROLA:
178			if (!(us->fflags & (US_FL_FIX_CAPACITY |
179					US_FL_CAPACITY_OK)))
180				us->fflags |= US_FL_CAPACITY_HEURISTICS;
181			break;
182		}
183
184		/*
185		 * Disk-type devices use MODE SENSE(6) if the protocol
186		 * (SubClass) is Transparent SCSI, otherwise they use
187		 * MODE SENSE(10).
188		 */
189		if (us->subclass != USB_SC_SCSI && us->subclass != USB_SC_CYP_ATACB)
190			sdev->use_10_for_ms = 1;
191
192		/*
193		 *Many disks only accept MODE SENSE transfer lengths of
194		 * 192 bytes (that's what Windows uses).
195		 */
196		sdev->use_192_bytes_for_3f = 1;
197
198		/*
 
 
 
 
 
 
 
199		 * Some devices don't like MODE SENSE with page=0x3f,
200		 * which is the command used for checking if a device
201		 * is write-protected.  Now that we tell the sd driver
202		 * to do a 192-byte transfer with this command the
203		 * majority of devices work fine, but a few still can't
204		 * handle it.  The sd driver will simply assume those
205		 * devices are write-enabled.
206		 */
207		if (us->fflags & US_FL_NO_WP_DETECT)
208			sdev->skip_ms_page_3f = 1;
209
210		/*
211		 * A number of devices have problems with MODE SENSE for
212		 * page x08, so we will skip it.
213		 */
214		sdev->skip_ms_page_8 = 1;
215
216		/* Some devices don't handle VPD pages correctly */
217		sdev->skip_vpd_pages = 1;
 
 
 
218
219		/* Do not attempt to use REPORT SUPPORTED OPERATION CODES */
220		sdev->no_report_opcodes = 1;
221
222		/* Do not attempt to use WRITE SAME */
223		sdev->no_write_same = 1;
224
225		/*
226		 * Some disks return the total number of blocks in response
227		 * to READ CAPACITY rather than the highest block number.
228		 * If this device makes that mistake, tell the sd driver.
229		 */
230		if (us->fflags & US_FL_FIX_CAPACITY)
231			sdev->fix_capacity = 1;
232
233		/*
234		 * A few disks have two indistinguishable version, one of
235		 * which reports the correct capacity and the other does not.
236		 * The sd driver has to guess which is the case.
237		 */
238		if (us->fflags & US_FL_CAPACITY_HEURISTICS)
239			sdev->guess_capacity = 1;
240
241		/* Some devices cannot handle READ_CAPACITY_16 */
242		if (us->fflags & US_FL_NO_READ_CAPACITY_16)
243			sdev->no_read_capacity_16 = 1;
244
245		/*
246		 * Many devices do not respond properly to READ_CAPACITY_16.
247		 * Tell the SCSI layer to try READ_CAPACITY_10 first.
248		 * However some USB 3.0 drive enclosures return capacity
249		 * modulo 2TB. Those must use READ_CAPACITY_16
250		 */
251		if (!(us->fflags & US_FL_NEEDS_CAP16))
252			sdev->try_rc_10_first = 1;
253
254		/* assume SPC3 or latter devices support sense size > 18 */
255		if (sdev->scsi_level > SCSI_SPC_2)
 
 
 
 
256			us->fflags |= US_FL_SANE_SENSE;
257
258		/*
259		 * USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
260		 * Hardware Error) when any low-level error occurs,
261		 * recoverable or not.  Setting this flag tells the SCSI
262		 * midlayer to retry such commands, which frequently will
263		 * succeed and fix the error.  The worst this can lead to
264		 * is an occasional series of retries that will all fail.
265		 */
266		sdev->retry_hwerror = 1;
267
268		/*
269		 * USB disks should allow restart.  Some drives spin down
270		 * automatically, requiring a START-STOP UNIT command.
271		 */
272		sdev->allow_restart = 1;
273
274		/*
275		 * Some USB cardreaders have trouble reading an sdcard's last
276		 * sector in a larger then 1 sector read, since the performance
277		 * impact is negligible we set this flag for all USB disks
278		 */
279		sdev->last_sector_bug = 1;
280
281		/*
282		 * Enable last-sector hacks for single-target devices using
283		 * the Bulk-only transport, unless we already know the
284		 * capacity will be decremented or is correct.
285		 */
286		if (!(us->fflags & (US_FL_FIX_CAPACITY | US_FL_CAPACITY_OK |
287					US_FL_SCM_MULT_TARG)) &&
288				us->protocol == USB_PR_BULK)
289			us->use_last_sector_hacks = 1;
290
291		/* Check if write cache default on flag is set or not */
292		if (us->fflags & US_FL_WRITE_CACHE)
293			sdev->wce_default_on = 1;
294
295		/* A few buggy USB-ATA bridges don't understand FUA */
296		if (us->fflags & US_FL_BROKEN_FUA)
297			sdev->broken_fua = 1;
298
299		/* Some even totally fail to indicate a cache */
300		if (us->fflags & US_FL_ALWAYS_SYNC) {
301			/* don't read caching information */
302			sdev->skip_ms_page_8 = 1;
303			sdev->skip_ms_page_3f = 1;
304			/* assume sync is needed */
305			sdev->wce_default_on = 1;
306		}
307	} else {
308
309		/*
310		 * Non-disk-type devices don't need to blacklist any pages
311		 * or to force 192-byte transfer lengths for MODE SENSE.
312		 * But they do need to use MODE SENSE(10).
313		 */
314		sdev->use_10_for_ms = 1;
315
316		/* Some (fake) usb cdrom devices don't like READ_DISC_INFO */
317		if (us->fflags & US_FL_NO_READ_DISC_INFO)
318			sdev->no_read_disc_info = 1;
319	}
320
321	/*
322	 * The CB and CBI transports have no way to pass LUN values
323	 * other than the bits in the second byte of a CDB.  But those
324	 * bits don't get set to the LUN value if the device reports
325	 * scsi_level == 0 (UNKNOWN).  Hence such devices must necessarily
326	 * be single-LUN.
327	 */
328	if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_CBI) &&
329			sdev->scsi_level == SCSI_UNKNOWN)
330		us->max_lun = 0;
331
332	/*
333	 * Some devices choke when they receive a PREVENT-ALLOW MEDIUM
334	 * REMOVAL command, so suppress those commands.
335	 */
336	if (us->fflags & US_FL_NOT_LOCKABLE)
337		sdev->lockable = 0;
338
339	/*
340	 * this is to satisfy the compiler, tho I don't think the 
341	 * return code is ever checked anywhere.
342	 */
343	return 0;
344}
345
346static int target_alloc(struct scsi_target *starget)
347{
348	struct us_data *us = host_to_us(dev_to_shost(starget->dev.parent));
349
350	/*
351	 * Some USB drives don't support REPORT LUNS, even though they
352	 * report a SCSI revision level above 2.  Tell the SCSI layer
353	 * not to issue that command; it will perform a normal sequential
354	 * scan instead.
355	 */
356	starget->no_report_luns = 1;
357
358	/*
359	 * The UFI spec treats the Peripheral Qualifier bits in an
360	 * INQUIRY result as reserved and requires devices to set them
361	 * to 0.  However the SCSI spec requires these bits to be set
362	 * to 3 to indicate when a LUN is not present.
363	 *
364	 * Let the scanning code know if this target merely sets
365	 * Peripheral Device Type to 0x1f to indicate no LUN.
366	 */
367	if (us->subclass == USB_SC_UFI)
368		starget->pdt_1f_for_no_lun = 1;
369
370	return 0;
371}
372
373/* queue a command */
374/* This is always called with scsi_lock(host) held */
375static int queuecommand_lck(struct scsi_cmnd *srb,
376			void (*done)(struct scsi_cmnd *))
377{
 
378	struct us_data *us = host_to_us(srb->device->host);
379
380	/* check for state-transition errors */
381	if (us->srb != NULL) {
382		printk(KERN_ERR USB_STORAGE "Error in %s: us->srb = %p\n",
383			__func__, us->srb);
384		return SCSI_MLQUEUE_HOST_BUSY;
385	}
386
387	/* fail the command if we are disconnecting */
388	if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
389		usb_stor_dbg(us, "Fail command during disconnect\n");
390		srb->result = DID_NO_CONNECT << 16;
391		done(srb);
392		return 0;
393	}
394
 
 
 
 
 
 
 
 
 
395	/* enqueue the command and wake up the control thread */
396	srb->scsi_done = done;
397	us->srb = srb;
398	complete(&us->cmnd_ready);
399
400	return 0;
401}
402
403static DEF_SCSI_QCMD(queuecommand)
404
405/***********************************************************************
406 * Error handling functions
407 ***********************************************************************/
408
409/* Command timeout and abort */
410static int command_abort(struct scsi_cmnd *srb)
411{
412	struct us_data *us = host_to_us(srb->device->host);
413
414	usb_stor_dbg(us, "%s called\n", __func__);
415
416	/*
417	 * us->srb together with the TIMED_OUT, RESETTING, and ABORTING
418	 * bits are protected by the host lock.
419	 */
420	scsi_lock(us_to_host(us));
421
422	/* Is this command still active? */
423	if (us->srb != srb) {
424		scsi_unlock(us_to_host(us));
425		usb_stor_dbg(us, "-- nothing to abort\n");
 
 
 
 
 
 
 
426		return FAILED;
427	}
428
429	/*
430	 * Set the TIMED_OUT bit.  Also set the ABORTING bit, but only if
431	 * a device reset isn't already in progress (to avoid interfering
432	 * with the reset).  Note that we must retain the host lock while
433	 * calling usb_stor_stop_transport(); otherwise it might interfere
434	 * with an auto-reset that begins as soon as we release the lock.
435	 */
436	set_bit(US_FLIDX_TIMED_OUT, &us->dflags);
437	if (!test_bit(US_FLIDX_RESETTING, &us->dflags)) {
438		set_bit(US_FLIDX_ABORTING, &us->dflags);
439		usb_stor_stop_transport(us);
440	}
441	scsi_unlock(us_to_host(us));
442
443	/* Wait for the aborted command to finish */
444	wait_for_completion(&us->notify);
445	return SUCCESS;
446}
447
 
 
 
 
 
 
 
 
448/*
449 * This invokes the transport reset mechanism to reset the state of the
450 * device
451 */
452static int device_reset(struct scsi_cmnd *srb)
453{
454	struct us_data *us = host_to_us(srb->device->host);
455	int result;
456
457	usb_stor_dbg(us, "%s called\n", __func__);
458
 
 
 
459	/* lock the device pointers and do the reset */
460	mutex_lock(&(us->dev_mutex));
461	result = us->transport_reset(us);
462	mutex_unlock(&us->dev_mutex);
463
464	return result < 0 ? FAILED : SUCCESS;
465}
466
467/* Simulate a SCSI bus reset by resetting the device's USB port. */
468static int bus_reset(struct scsi_cmnd *srb)
469{
470	struct us_data *us = host_to_us(srb->device->host);
471	int result;
472
473	usb_stor_dbg(us, "%s called\n", __func__);
474
475	result = usb_stor_port_reset(us);
476	return result < 0 ? FAILED : SUCCESS;
477}
478
479/*
480 * Report a driver-initiated device reset to the SCSI layer.
481 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
482 * The caller must own the SCSI host lock.
483 */
484void usb_stor_report_device_reset(struct us_data *us)
485{
486	int i;
487	struct Scsi_Host *host = us_to_host(us);
488
489	scsi_report_device_reset(host, 0, 0);
490	if (us->fflags & US_FL_SCM_MULT_TARG) {
491		for (i = 1; i < host->max_id; ++i)
492			scsi_report_device_reset(host, 0, i);
493	}
494}
495
496/*
497 * Report a driver-initiated bus reset to the SCSI layer.
498 * Calling this for a SCSI-initiated reset is unnecessary but harmless.
499 * The caller must not own the SCSI host lock.
500 */
501void usb_stor_report_bus_reset(struct us_data *us)
502{
503	struct Scsi_Host *host = us_to_host(us);
504
505	scsi_lock(host);
506	scsi_report_bus_reset(host, 0);
507	scsi_unlock(host);
508}
509
510/***********************************************************************
511 * /proc/scsi/ functions
512 ***********************************************************************/
513
514static int write_info(struct Scsi_Host *host, char *buffer, int length)
515{
516	/* if someone is sending us data, just throw it away */
517	return length;
518}
519
520static int show_info (struct seq_file *m, struct Scsi_Host *host)
521{
522	struct us_data *us = host_to_us(host);
523	const char *string;
524
525	/* print the controller name */
526	seq_printf(m, "   Host scsi%d: usb-storage\n", host->host_no);
527
528	/* print product, vendor, and serial number strings */
529	if (us->pusb_dev->manufacturer)
530		string = us->pusb_dev->manufacturer;
531	else if (us->unusual_dev->vendorName)
532		string = us->unusual_dev->vendorName;
533	else
534		string = "Unknown";
535	seq_printf(m, "       Vendor: %s\n", string);
536	if (us->pusb_dev->product)
537		string = us->pusb_dev->product;
538	else if (us->unusual_dev->productName)
539		string = us->unusual_dev->productName;
540	else
541		string = "Unknown";
542	seq_printf(m, "      Product: %s\n", string);
543	if (us->pusb_dev->serial)
544		string = us->pusb_dev->serial;
545	else
546		string = "None";
547	seq_printf(m, "Serial Number: %s\n", string);
548
549	/* show the protocol and transport */
550	seq_printf(m, "     Protocol: %s\n", us->protocol_name);
551	seq_printf(m, "    Transport: %s\n", us->transport_name);
552
553	/* show the device flags */
554	seq_printf(m, "       Quirks:");
555
556#define US_FLAG(name, value) \
557	if (us->fflags & value) seq_printf(m, " " #name);
558US_DO_ALL_FLAGS
559#undef US_FLAG
560	seq_putc(m, '\n');
561	return 0;
562}
563
564/***********************************************************************
565 * Sysfs interface
566 ***********************************************************************/
567
568/* Output routine for the sysfs max_sectors file */
569static ssize_t max_sectors_show(struct device *dev, struct device_attribute *attr, char *buf)
570{
571	struct scsi_device *sdev = to_scsi_device(dev);
572
573	return sprintf(buf, "%u\n", queue_max_hw_sectors(sdev->request_queue));
574}
575
576/* Input routine for the sysfs max_sectors file */
577static ssize_t max_sectors_store(struct device *dev, struct device_attribute *attr, const char *buf,
578		size_t count)
579{
580	struct scsi_device *sdev = to_scsi_device(dev);
581	unsigned short ms;
582
583	if (sscanf(buf, "%hu", &ms) > 0) {
584		blk_queue_max_hw_sectors(sdev->request_queue, ms);
585		return count;
586	}
587	return -EINVAL;
588}
589static DEVICE_ATTR_RW(max_sectors);
590
591static struct device_attribute *sysfs_device_attr_list[] = {
592	&dev_attr_max_sectors,
593	NULL,
594};
595
 
 
596/*
597 * this defines our host template, with which we'll allocate hosts
598 */
599
600static const struct scsi_host_template usb_stor_host_template = {
601	/* basic userland interface stuff */
602	.name =				"usb-storage",
603	.proc_name =			"usb-storage",
604	.show_info =			show_info,
605	.write_info =			write_info,
606	.info =				host_info,
607
608	/* command interface -- queued only */
609	.queuecommand =			queuecommand,
610
611	/* error and abort handlers */
612	.eh_abort_handler =		command_abort,
613	.eh_device_reset_handler =	device_reset,
614	.eh_bus_reset_handler =		bus_reset,
615
616	/* queue commands only, only one command per LUN */
617	.can_queue =			1,
618
619	/* unknown initiator id */
620	.this_id =			-1,
621
622	.slave_alloc =			slave_alloc,
623	.slave_configure =		slave_configure,
624	.target_alloc =			target_alloc,
625
626	/* lots of sg segments can be handled */
627	.sg_tablesize =			SG_MAX_SEGMENTS,
628
629
630	/*
631	 * Limit the total size of a transfer to 120 KB.
632	 *
633	 * Some devices are known to choke with anything larger. It seems like
634	 * the problem stems from the fact that original IDE controllers had
635	 * only an 8-bit register to hold the number of sectors in one transfer
636	 * and even those couldn't handle a full 256 sectors.
637	 *
638	 * Because we want to make sure we interoperate with as many devices as
639	 * possible, we will maintain a 240 sector transfer size limit for USB
640	 * Mass Storage devices.
641	 *
642	 * Tests show that other operating have similar limits with Microsoft
643	 * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
644	 * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
645	 * and 2048 for USB3 devices.
646	 */
647	.max_sectors =                  240,
648
649	/*
650	 * merge commands... this seems to help performance, but
651	 * periodically someone should test to see which setting is more
652	 * optimal.
653	 */
654	.use_clustering =		1,
655
656	/* emulated HBA */
657	.emulated =			1,
658
659	/* we do our own delay after a device or bus reset */
660	.skip_settle_delay =		1,
661
662	/* sysfs device attributes */
663	.sdev_attrs =			sysfs_device_attr_list,
664
665	/* module management */
666	.module =			THIS_MODULE
667};
668
669void usb_stor_host_template_init(struct scsi_host_template *sht,
670				 const char *name, struct module *owner)
671{
672	*sht = usb_stor_host_template;
673	sht->name = name;
674	sht->proc_name = name;
675	sht->module = owner;
676}
677EXPORT_SYMBOL_GPL(usb_stor_host_template_init);
678
679/* To Report "Illegal Request: Invalid Field in CDB */
680unsigned char usb_stor_sense_invalidCDB[18] = {
681	[0]	= 0x70,			    /* current error */
682	[2]	= ILLEGAL_REQUEST,	    /* Illegal Request = 0x05 */
683	[7]	= 0x0a,			    /* additional length */
684	[12]	= 0x24			    /* Invalid Field in CDB */
685};
686EXPORT_SYMBOL_GPL(usb_stor_sense_invalidCDB);