drivers/usb/storage/scsiglue.c

   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
  75 static 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
  81 static 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
 117 static 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         } else {
 300
 301                 /*
 302                  * Non-disk-type devices don't need to blacklist any pages
 303                  * or to force 192-byte transfer lengths for MODE SENSE.
 304                  * But they do need to use MODE SENSE(10).
 305                  */
 306                 sdev->use_10_for_ms = 1;
 307
 308                 /* Some (fake) usb cdrom devices don't like READ_DISC_INFO */
 309                 if (us->fflags & US_FL_NO_READ_DISC_INFO)
 310                         sdev->no_read_disc_info = 1;
 311         }
 312
 313         /*
 314          * The CB and CBI transports have no way to pass LUN values
 315          * other than the bits in the second byte of a CDB.  But those
 316          * bits don't get set to the LUN value if the device reports
 317          * scsi_level == 0 (UNKNOWN).  Hence such devices must necessarily
 318          * be single-LUN.
 319          */
 320         if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_CBI) &&
 321                         sdev->scsi_level == SCSI_UNKNOWN)
 322                 us->max_lun = 0;
 323
 324         /*
 325          * Some devices choke when they receive a PREVENT-ALLOW MEDIUM
 326          * REMOVAL command, so suppress those commands.
 327          */
 328         if (us->fflags & US_FL_NOT_LOCKABLE)
 329                 sdev->lockable = 0;
 330
 331         /*
 332          * this is to satisfy the compiler, tho I don't think the
 333          * return code is ever checked anywhere.
 334          */
 335         return 0;
 336 }
 337
 338 static int target_alloc(struct scsi_target *starget)
 339 {
 340         struct us_data *us = host_to_us(dev_to_shost(starget->dev.parent));
 341
 342         /*
 343          * Some USB drives don't support REPORT LUNS, even though they
 344          * report a SCSI revision level above 2.  Tell the SCSI layer
 345          * not to issue that command; it will perform a normal sequential
 346          * scan instead.
 347          */
 348         starget->no_report_luns = 1;
 349
 350         /*
 351          * The UFI spec treats the Peripheral Qualifier bits in an
 352          * INQUIRY result as reserved and requires devices to set them
 353          * to 0.  However the SCSI spec requires these bits to be set
 354          * to 3 to indicate when a LUN is not present.
 355          *
 356          * Let the scanning code know if this target merely sets
 357          * Peripheral Device Type to 0x1f to indicate no LUN.
 358          */
 359         if (us->subclass == USB_SC_UFI)
 360                 starget->pdt_1f_for_no_lun = 1;
 361
 362         return 0;
 363 }
 364
 365 /* queue a command */
 366 /* This is always called with scsi_lock(host) held */
 367 static int queuecommand_lck(struct scsi_cmnd *srb,
 368                         void (*done)(struct scsi_cmnd *))
 369 {
 370         struct us_data *us = host_to_us(srb->device->host);
 371
 372         /* check for state-transition errors */
 373         if (us->srb != NULL) {
 374                 printk(KERN_ERR USB_STORAGE "Error in %s: us->srb = %p\n",
 375                         __func__, us->srb);
 376                 return SCSI_MLQUEUE_HOST_BUSY;
 377         }
 378
 379         /* fail the command if we are disconnecting */
 380         if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
 381                 usb_stor_dbg(us, "Fail command during disconnect\n");
 382                 srb->result = DID_NO_CONNECT << 16;
 383                 done(srb);
 384                 return 0;
 385         }
 386
 387         /* enqueue the command and wake up the control thread */
 388         srb->scsi_done = done;
 389         us->srb = srb;
 390         complete(&us->cmnd_ready);
 391
 392         return 0;
 393 }
 394
 395 static DEF_SCSI_QCMD(queuecommand)
 396
 397 /***********************************************************************
 398  * Error handling functions
 399  ***********************************************************************/
 400
 401 /* Command timeout and abort */
 402 static int command_abort(struct scsi_cmnd *srb)
 403 {
 404         struct us_data *us = host_to_us(srb->device->host);
 405
 406         usb_stor_dbg(us, "%s called\n", __func__);
 407
 408         /*
 409          * us->srb together with the TIMED_OUT, RESETTING, and ABORTING
 410          * bits are protected by the host lock.
 411          */
 412         scsi_lock(us_to_host(us));
 413
 414         /* Is this command still active? */
 415         if (us->srb != srb) {
 416                 scsi_unlock(us_to_host(us));
 417                 usb_stor_dbg(us, "-- nothing to abort\n");
 418                 return FAILED;
 419         }
 420
 421         /*
 422          * Set the TIMED_OUT bit.  Also set the ABORTING bit, but only if
 423          * a device reset isn't already in progress (to avoid interfering
 424          * with the reset).  Note that we must retain the host lock while
 425          * calling usb_stor_stop_transport(); otherwise it might interfere
 426          * with an auto-reset that begins as soon as we release the lock.
 427          */
 428         set_bit(US_FLIDX_TIMED_OUT, &us->dflags);
 429         if (!test_bit(US_FLIDX_RESETTING, &us->dflags)) {
 430                 set_bit(US_FLIDX_ABORTING, &us->dflags);
 431                 usb_stor_stop_transport(us);
 432         }
 433         scsi_unlock(us_to_host(us));
 434
 435         /* Wait for the aborted command to finish */
 436         wait_for_completion(&us->notify);
 437         return SUCCESS;
 438 }
 439
 440 /*
 441  * This invokes the transport reset mechanism to reset the state of the
 442  * device
 443  */
 444 static int device_reset(struct scsi_cmnd *srb)
 445 {
 446         struct us_data *us = host_to_us(srb->device->host);
 447         int result;
 448
 449         usb_stor_dbg(us, "%s called\n", __func__);
 450
 451         /* lock the device pointers and do the reset */
 452         mutex_lock(&(us->dev_mutex));
 453         result = us->transport_reset(us);
 454         mutex_unlock(&us->dev_mutex);
 455
 456         return result < 0 ? FAILED : SUCCESS;
 457 }
 458
 459 /* Simulate a SCSI bus reset by resetting the device's USB port. */
 460 static int bus_reset(struct scsi_cmnd *srb)
 461 {
 462         struct us_data *us = host_to_us(srb->device->host);
 463         int result;
 464
 465         usb_stor_dbg(us, "%s called\n", __func__);
 466
 467         result = usb_stor_port_reset(us);
 468         return result < 0 ? FAILED : SUCCESS;
 469 }
 470
 471 /*
 472  * Report a driver-initiated device reset to the SCSI layer.
 473  * Calling this for a SCSI-initiated reset is unnecessary but harmless.
 474  * The caller must own the SCSI host lock.
 475  */
 476 void usb_stor_report_device_reset(struct us_data *us)
 477 {
 478         int i;
 479         struct Scsi_Host *host = us_to_host(us);
 480
 481         scsi_report_device_reset(host, 0, 0);
 482         if (us->fflags & US_FL_SCM_MULT_TARG) {
 483                 for (i = 1; i < host->max_id; ++i)
 484                         scsi_report_device_reset(host, 0, i);
 485         }
 486 }
 487
 488 /*
 489  * Report a driver-initiated bus reset to the SCSI layer.
 490  * Calling this for a SCSI-initiated reset is unnecessary but harmless.
 491  * The caller must not own the SCSI host lock.
 492  */
 493 void usb_stor_report_bus_reset(struct us_data *us)
 494 {
 495         struct Scsi_Host *host = us_to_host(us);
 496
 497         scsi_lock(host);
 498         scsi_report_bus_reset(host, 0);
 499         scsi_unlock(host);
 500 }
 501
 502 /***********************************************************************
 503  * /proc/scsi/ functions
 504  ***********************************************************************/
 505
 506 static int write_info(struct Scsi_Host *host, char *buffer, int length)
 507 {
 508         /* if someone is sending us data, just throw it away */
 509         return length;
 510 }
 511
 512 static int show_info (struct seq_file *m, struct Scsi_Host *host)
 513 {
 514         struct us_data *us = host_to_us(host);
 515         const char *string;
 516
 517         /* print the controller name */
 518         seq_printf(m, "   Host scsi%d: usb-storage\n", host->host_no);
 519
 520         /* print product, vendor, and serial number strings */
 521         if (us->pusb_dev->manufacturer)
 522                 string = us->pusb_dev->manufacturer;
 523         else if (us->unusual_dev->vendorName)
 524                 string = us->unusual_dev->vendorName;
 525         else
 526                 string = "Unknown";
 527         seq_printf(m, "       Vendor: %s\n", string);
 528         if (us->pusb_dev->product)
 529                 string = us->pusb_dev->product;
 530         else if (us->unusual_dev->productName)
 531                 string = us->unusual_dev->productName;
 532         else
 533                 string = "Unknown";
 534         seq_printf(m, "      Product: %s\n", string);
 535         if (us->pusb_dev->serial)
 536                 string = us->pusb_dev->serial;
 537         else
 538                 string = "None";
 539         seq_printf(m, "Serial Number: %s\n", string);
 540
 541         /* show the protocol and transport */
 542         seq_printf(m, "     Protocol: %s\n", us->protocol_name);
 543         seq_printf(m, "    Transport: %s\n", us->transport_name);
 544
 545         /* show the device flags */
 546         seq_printf(m, "       Quirks:");
 547
 548 #define US_FLAG(name, value) \
 549         if (us->fflags & value) seq_printf(m, " " #name);
 550 US_DO_ALL_FLAGS
 551 #undef US_FLAG
 552         seq_putc(m, '\n');
 553         return 0;
 554 }
 555
 556 /***********************************************************************
 557  * Sysfs interface
 558  ***********************************************************************/
 559
 560 /* Output routine for the sysfs max_sectors file */
 561 static ssize_t max_sectors_show(struct device *dev, struct device_attribute *attr, char *buf)
 562 {
 563         struct scsi_device *sdev = to_scsi_device(dev);
 564
 565         return sprintf(buf, "%u\n", queue_max_hw_sectors(sdev->request_queue));
 566 }
 567
 568 /* Input routine for the sysfs max_sectors file */
 569 static ssize_t max_sectors_store(struct device *dev, struct device_attribute *attr, const char *buf,
 570                 size_t count)
 571 {
 572         struct scsi_device *sdev = to_scsi_device(dev);
 573         unsigned short ms;
 574
 575         if (sscanf(buf, "%hu", &ms) > 0) {
 576                 blk_queue_max_hw_sectors(sdev->request_queue, ms);
 577                 return count;
 578         }
 579         return -EINVAL;
 580 }
 581 static DEVICE_ATTR_RW(max_sectors);
 582
 583 static struct device_attribute *sysfs_device_attr_list[] = {
 584         &dev_attr_max_sectors,
 585         NULL,
 586 };
 587
 588 /*
 589  * this defines our host template, with which we'll allocate hosts
 590  */
 591
 592 static const struct scsi_host_template usb_stor_host_template = {
 593         /* basic userland interface stuff */
 594         .name =                         "usb-storage",
 595         .proc_name =                    "usb-storage",
 596         .show_info =                    show_info,
 597         .write_info =                   write_info,
 598         .info =                         host_info,
 599
 600         /* command interface -- queued only */
 601         .queuecommand =                 queuecommand,
 602
 603         /* error and abort handlers */
 604         .eh_abort_handler =             command_abort,
 605         .eh_device_reset_handler =      device_reset,
 606         .eh_bus_reset_handler =         bus_reset,
 607
 608         /* queue commands only, only one command per LUN */
 609         .can_queue =                    1,
 610
 611         /* unknown initiator id */
 612         .this_id =                      -1,
 613
 614         .slave_alloc =                  slave_alloc,
 615         .slave_configure =              slave_configure,
 616         .target_alloc =                 target_alloc,
 617
 618         /* lots of sg segments can be handled */
 619         .sg_tablesize =                 SG_MAX_SEGMENTS,
 620
 621
 622         /*
 623          * Limit the total size of a transfer to 120 KB.
 624          *
 625          * Some devices are known to choke with anything larger. It seems like
 626          * the problem stems from the fact that original IDE controllers had
 627          * only an 8-bit register to hold the number of sectors in one transfer
 628          * and even those couldn't handle a full 256 sectors.
 629          *
 630          * Because we want to make sure we interoperate with as many devices as
 631          * possible, we will maintain a 240 sector transfer size limit for USB
 632          * Mass Storage devices.
 633          *
 634          * Tests show that other operating have similar limits with Microsoft
 635          * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
 636          * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
 637          * and 2048 for USB3 devices.
 638          */
 639         .max_sectors =                  240,
 640
 641         /*
 642          * merge commands... this seems to help performance, but
 643          * periodically someone should test to see which setting is more
 644          * optimal.
 645          */
 646         .use_clustering =               1,
 647
 648         /* emulated HBA */
 649         .emulated =                     1,
 650
 651         /* we do our own delay after a device or bus reset */
 652         .skip_settle_delay =            1,
 653
 654         /* sysfs device attributes */
 655         .sdev_attrs =                   sysfs_device_attr_list,
 656
 657         /* module management */
 658         .module =                       THIS_MODULE
 659 };
 660
 661 void usb_stor_host_template_init(struct scsi_host_template *sht,
 662                                  const char *name, struct module *owner)
 663 {
 664         *sht = usb_stor_host_template;
 665         sht->name = name;
 666         sht->proc_name = name;
 667         sht->module = owner;
 668 }
 669 EXPORT_SYMBOL_GPL(usb_stor_host_template_init);
 670
 671 /* To Report "Illegal Request: Invalid Field in CDB */
 672 unsigned char usb_stor_sense_invalidCDB[18] = {
 673         [0]     = 0x70,                     /* current error */
 674         [2]     = ILLEGAL_REQUEST,          /* Illegal Request = 0x05 */
 675         [7]     = 0x0a,                     /* additional length */
 676         [12]    = 0x24                      /* Invalid Field in CDB */
 677 };
 678 EXPORT_SYMBOL_GPL(usb_stor_sense_invalidCDB);