drivers/usb/gadget/storage_common.c

   1 /*
   2  * storage_common.c -- Common definitions for mass storage functionality
   3  *
   4  * Copyright (C) 2003-2008 Alan Stern
   5  * Copyeight (C) 2009 Samsung Electronics
   6  * Author: Michal Nazarewicz (mina86@mina86.com)
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  */
  13
  14 /*
  15  * This file requires the following identifiers used in USB strings to
  16  * be defined (each of type pointer to char):
  17  *  - fsg_string_interface    -- name of the interface
  18  */
  19
  20 /*
  21  * When USB_GADGET_DEBUG_FILES is defined the module param num_buffers
  22  * sets the number of pipeline buffers (length of the fsg_buffhd array).
  23  * The valid range of num_buffers is: num >= 2 && num <= 4.
  24  */
  25
  26
  27 #include <linux/usb/storage.h>
  28 #include <scsi/scsi.h>
  29 #include <asm/unaligned.h>
  30
  31
  32 /*
  33  * Thanks to NetChip Technologies for donating this product ID.
  34  *
  35  * DO NOT REUSE THESE IDs with any other driver!!  Ever!!
  36  * Instead:  allocate your own, using normal USB-IF procedures.
  37  */
  38 #define FSG_VENDOR_ID   0x0525  /* NetChip */
  39 #define FSG_PRODUCT_ID  0xa4a5  /* Linux-USB File-backed Storage Gadget */
  40
  41
  42 /*-------------------------------------------------------------------------*/
  43
  44
  45 #ifndef DEBUG
  46 #undef VERBOSE_DEBUG
  47 #undef DUMP_MSGS
  48 #endif /* !DEBUG */
  49
  50 #ifdef VERBOSE_DEBUG
  51 #define VLDBG   LDBG
  52 #else
  53 #define VLDBG(lun, fmt, args...) do { } while (0)
  54 #endif /* VERBOSE_DEBUG */
  55
  56 #define LDBG(lun, fmt, args...)   dev_dbg (&(lun)->dev, fmt, ## args)
  57 #define LERROR(lun, fmt, args...) dev_err (&(lun)->dev, fmt, ## args)
  58 #define LWARN(lun, fmt, args...)  dev_warn(&(lun)->dev, fmt, ## args)
  59 #define LINFO(lun, fmt, args...)  dev_info(&(lun)->dev, fmt, ## args)
  60
  61
  62 #ifdef DUMP_MSGS
  63
  64 #  define dump_msg(fsg, /* const char * */ label,                       \
  65                    /* const u8 * */ buf, /* unsigned */ length) do {    \
  66         if (length < 512) {                                             \
  67                 DBG(fsg, "%s, length %u:\n", label, length);            \
  68                 print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,      \
  69                                16, 1, buf, length, 0);                  \
  70         }                                                               \
  71 } while (0)
  72
  73 #  define dump_cdb(fsg) do { } while (0)
  74
  75 #else
  76
  77 #  define dump_msg(fsg, /* const char * */ label, \
  78                    /* const u8 * */ buf, /* unsigned */ length) do { } while (0)
  79
  80 #  ifdef VERBOSE_DEBUG
  81
  82 #    define dump_cdb(fsg)                                               \
  83         print_hex_dump(KERN_DEBUG, "SCSI CDB: ", DUMP_PREFIX_NONE,      \
  84                        16, 1, (fsg)->cmnd, (fsg)->cmnd_size, 0)         \
  85
  86 #  else
  87
  88 #    define dump_cdb(fsg) do { } while (0)
  89
  90 #  endif /* VERBOSE_DEBUG */
  91
  92 #endif /* DUMP_MSGS */
  93
  94 /*-------------------------------------------------------------------------*/
  95
  96 /* Length of a SCSI Command Data Block */
  97 #define MAX_COMMAND_SIZE        16
  98
  99 /* SCSI Sense Key/Additional Sense Code/ASC Qualifier values */
 100 #define SS_NO_SENSE                             0
 101 #define SS_COMMUNICATION_FAILURE                0x040800
 102 #define SS_INVALID_COMMAND                      0x052000
 103 #define SS_INVALID_FIELD_IN_CDB                 0x052400
 104 #define SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE   0x052100
 105 #define SS_LOGICAL_UNIT_NOT_SUPPORTED           0x052500
 106 #define SS_MEDIUM_NOT_PRESENT                   0x023a00
 107 #define SS_MEDIUM_REMOVAL_PREVENTED             0x055302
 108 #define SS_NOT_READY_TO_READY_TRANSITION        0x062800
 109 #define SS_RESET_OCCURRED                       0x062900
 110 #define SS_SAVING_PARAMETERS_NOT_SUPPORTED      0x053900
 111 #define SS_UNRECOVERED_READ_ERROR               0x031100
 112 #define SS_WRITE_ERROR                          0x030c02
 113 #define SS_WRITE_PROTECTED                      0x072700
 114
 115 #define SK(x)           ((u8) ((x) >> 16))      /* Sense Key byte, etc. */
 116 #define ASC(x)          ((u8) ((x) >> 8))
 117 #define ASCQ(x)         ((u8) (x))
 118
 119
 120 /*-------------------------------------------------------------------------*/
 121
 122
 123 struct fsg_lun {
 124         struct file     *filp;
 125         loff_t          file_length;
 126         loff_t          num_sectors;
 127
 128         unsigned int    initially_ro:1;
 129         unsigned int    ro:1;
 130         unsigned int    removable:1;
 131         unsigned int    cdrom:1;
 132         unsigned int    prevent_medium_removal:1;
 133         unsigned int    registered:1;
 134         unsigned int    info_valid:1;
 135         unsigned int    nofua:1;
 136
 137         u32             sense_data;
 138         u32             sense_data_info;
 139         u32             unit_attention_data;
 140
 141         unsigned int    blkbits;        /* Bits of logical block size of bound block device */
 142         unsigned int    blksize;        /* logical block size of bound block device */
 143         struct device   dev;
 144 };
 145
 146 static inline bool fsg_lun_is_open(struct fsg_lun *curlun)
 147 {
 148         return curlun->filp != NULL;
 149 }
 150
 151 static inline struct fsg_lun *fsg_lun_from_dev(struct device *dev)
 152 {
 153         return container_of(dev, struct fsg_lun, dev);
 154 }
 155
 156
 157 /* Big enough to hold our biggest descriptor */
 158 #define EP0_BUFSIZE     256
 159 #define DELAYED_STATUS  (EP0_BUFSIZE + 999)     /* An impossibly large value */
 160
 161 #ifdef CONFIG_USB_GADGET_DEBUG_FILES
 162
 163 static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;
 164 module_param_named(num_buffers, fsg_num_buffers, uint, S_IRUGO);
 165 MODULE_PARM_DESC(num_buffers, "Number of pipeline buffers");
 166
 167 #else
 168
 169 /*
 170  * Number of buffers we will use.
 171  * 2 is usually enough for good buffering pipeline
 172  */
 173 #define fsg_num_buffers CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS
 174
 175 #endif /* CONFIG_USB_GADGET_DEBUG_FILES */
 176
 177 /* check if fsg_num_buffers is within a valid range */
 178 static inline int fsg_num_buffers_validate(void)
 179 {
 180         if (fsg_num_buffers >= 2 && fsg_num_buffers <= 4)
 181                 return 0;
 182         pr_err("fsg_num_buffers %u is out of range (%d to %d)\n",
 183                fsg_num_buffers, 2 ,4);
 184         return -EINVAL;
 185 }
 186
 187 /* Default size of buffer length. */
 188 #define FSG_BUFLEN      ((u32)16384)
 189
 190 /* Maximal number of LUNs supported in mass storage function */
 191 #define FSG_MAX_LUNS    8
 192
 193 enum fsg_buffer_state {
 194         BUF_STATE_EMPTY = 0,
 195         BUF_STATE_FULL,
 196         BUF_STATE_BUSY
 197 };
 198
 199 struct fsg_buffhd {
 200         void                            *buf;
 201         enum fsg_buffer_state           state;
 202         struct fsg_buffhd               *next;
 203
 204         /*
 205          * The NetChip 2280 is faster, and handles some protocol faults
 206          * better, if we don't submit any short bulk-out read requests.
 207          * So we will record the intended request length here.
 208          */
 209         unsigned int                    bulk_out_intended_length;
 210
 211         struct usb_request              *inreq;
 212         int                             inreq_busy;
 213         struct usb_request              *outreq;
 214         int                             outreq_busy;
 215 };
 216
 217 enum fsg_state {
 218         /* This one isn't used anywhere */
 219         FSG_STATE_COMMAND_PHASE = -10,
 220         FSG_STATE_DATA_PHASE,
 221         FSG_STATE_STATUS_PHASE,
 222
 223         FSG_STATE_IDLE = 0,
 224         FSG_STATE_ABORT_BULK_OUT,
 225         FSG_STATE_RESET,
 226         FSG_STATE_INTERFACE_CHANGE,
 227         FSG_STATE_CONFIG_CHANGE,
 228         FSG_STATE_DISCONNECT,
 229         FSG_STATE_EXIT,
 230         FSG_STATE_TERMINATED
 231 };
 232
 233 enum data_direction {
 234         DATA_DIR_UNKNOWN = 0,
 235         DATA_DIR_FROM_HOST,
 236         DATA_DIR_TO_HOST,
 237         DATA_DIR_NONE
 238 };
 239
 240
 241 /*-------------------------------------------------------------------------*/
 242
 243
 244 static inline u32 get_unaligned_be24(u8 *buf)
 245 {
 246         return 0xffffff & (u32) get_unaligned_be32(buf - 1);
 247 }
 248
 249
 250 /*-------------------------------------------------------------------------*/
 251
 252
 253 enum {
 254         FSG_STRING_INTERFACE
 255 };
 256
 257
 258 /* There is only one interface. */
 259
 260 static struct usb_interface_descriptor
 261 fsg_intf_desc = {
 262         .bLength =              sizeof fsg_intf_desc,
 263         .bDescriptorType =      USB_DT_INTERFACE,
 264
 265         .bNumEndpoints =        2,              /* Adjusted during fsg_bind() */
 266         .bInterfaceClass =      USB_CLASS_MASS_STORAGE,
 267         .bInterfaceSubClass =   USB_SC_SCSI,    /* Adjusted during fsg_bind() */
 268         .bInterfaceProtocol =   USB_PR_BULK,    /* Adjusted during fsg_bind() */
 269         .iInterface =           FSG_STRING_INTERFACE,
 270 };
 271
 272 /*
 273  * Three full-speed endpoint descriptors: bulk-in, bulk-out, and
 274  * interrupt-in.
 275  */
 276
 277 static struct usb_endpoint_descriptor
 278 fsg_fs_bulk_in_desc = {
 279         .bLength =              USB_DT_ENDPOINT_SIZE,
 280         .bDescriptorType =      USB_DT_ENDPOINT,
 281
 282         .bEndpointAddress =     USB_DIR_IN,
 283         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 284         /* wMaxPacketSize set by autoconfiguration */
 285 };
 286
 287 static struct usb_endpoint_descriptor
 288 fsg_fs_bulk_out_desc = {
 289         .bLength =              USB_DT_ENDPOINT_SIZE,
 290         .bDescriptorType =      USB_DT_ENDPOINT,
 291
 292         .bEndpointAddress =     USB_DIR_OUT,
 293         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 294         /* wMaxPacketSize set by autoconfiguration */
 295 };
 296
 297 static struct usb_descriptor_header *fsg_fs_function[] = {
 298         (struct usb_descriptor_header *) &fsg_intf_desc,
 299         (struct usb_descriptor_header *) &fsg_fs_bulk_in_desc,
 300         (struct usb_descriptor_header *) &fsg_fs_bulk_out_desc,
 301         NULL,
 302 };
 303
 304
 305 /*
 306  * USB 2.0 devices need to expose both high speed and full speed
 307  * descriptors, unless they only run at full speed.
 308  *
 309  * That means alternate endpoint descriptors (bigger packets)
 310  * and a "device qualifier" ... plus more construction options
 311  * for the configuration descriptor.
 312  */
 313 static struct usb_endpoint_descriptor
 314 fsg_hs_bulk_in_desc = {
 315         .bLength =              USB_DT_ENDPOINT_SIZE,
 316         .bDescriptorType =      USB_DT_ENDPOINT,
 317
 318         /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
 319         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 320         .wMaxPacketSize =       cpu_to_le16(512),
 321 };
 322
 323 static struct usb_endpoint_descriptor
 324 fsg_hs_bulk_out_desc = {
 325         .bLength =              USB_DT_ENDPOINT_SIZE,
 326         .bDescriptorType =      USB_DT_ENDPOINT,
 327
 328         /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
 329         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 330         .wMaxPacketSize =       cpu_to_le16(512),
 331         .bInterval =            1,      /* NAK every 1 uframe */
 332 };
 333
 334
 335 static struct usb_descriptor_header *fsg_hs_function[] = {
 336         (struct usb_descriptor_header *) &fsg_intf_desc,
 337         (struct usb_descriptor_header *) &fsg_hs_bulk_in_desc,
 338         (struct usb_descriptor_header *) &fsg_hs_bulk_out_desc,
 339         NULL,
 340 };
 341
 342 static struct usb_endpoint_descriptor
 343 fsg_ss_bulk_in_desc = {
 344         .bLength =              USB_DT_ENDPOINT_SIZE,
 345         .bDescriptorType =      USB_DT_ENDPOINT,
 346
 347         /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
 348         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 349         .wMaxPacketSize =       cpu_to_le16(1024),
 350 };
 351
 352 static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_in_comp_desc = {
 353         .bLength =              sizeof(fsg_ss_bulk_in_comp_desc),
 354         .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
 355
 356         /*.bMaxBurst =          DYNAMIC, */
 357 };
 358
 359 static struct usb_endpoint_descriptor
 360 fsg_ss_bulk_out_desc = {
 361         .bLength =              USB_DT_ENDPOINT_SIZE,
 362         .bDescriptorType =      USB_DT_ENDPOINT,
 363
 364         /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
 365         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 366         .wMaxPacketSize =       cpu_to_le16(1024),
 367 };
 368
 369 static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_out_comp_desc = {
 370         .bLength =              sizeof(fsg_ss_bulk_in_comp_desc),
 371         .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
 372
 373         /*.bMaxBurst =          DYNAMIC, */
 374 };
 375
 376 static struct usb_descriptor_header *fsg_ss_function[] = {
 377         (struct usb_descriptor_header *) &fsg_intf_desc,
 378         (struct usb_descriptor_header *) &fsg_ss_bulk_in_desc,
 379         (struct usb_descriptor_header *) &fsg_ss_bulk_in_comp_desc,
 380         (struct usb_descriptor_header *) &fsg_ss_bulk_out_desc,
 381         (struct usb_descriptor_header *) &fsg_ss_bulk_out_comp_desc,
 382         NULL,
 383 };
 384
 385 /* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
 386 static struct usb_string                fsg_strings[] = {
 387         {FSG_STRING_INTERFACE,          fsg_string_interface},
 388         {}
 389 };
 390
 391 static struct usb_gadget_strings        fsg_stringtab = {
 392         .language       = 0x0409,               /* en-us */
 393         .strings        = fsg_strings,
 394 };
 395
 396
 397  /*-------------------------------------------------------------------------*/
 398
 399 /*
 400  * If the next two routines are called while the gadget is registered,
 401  * the caller must own fsg->filesem for writing.
 402  */
 403
 404 static void fsg_lun_close(struct fsg_lun *curlun)
 405 {
 406         if (curlun->filp) {
 407                 LDBG(curlun, "close backing file\n");
 408                 fput(curlun->filp);
 409                 curlun->filp = NULL;
 410         }
 411 }
 412
 413
 414 static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
 415 {
 416         int                             ro;
 417         struct file                     *filp = NULL;
 418         int                             rc = -EINVAL;
 419         struct inode                    *inode = NULL;
 420         loff_t                          size;
 421         loff_t                          num_sectors;
 422         loff_t                          min_sectors;
 423         unsigned int                    blkbits;
 424         unsigned int                    blksize;
 425
 426         /* R/W if we can, R/O if we must */
 427         ro = curlun->initially_ro;
 428         if (!ro) {
 429                 filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
 430                 if (PTR_ERR(filp) == -EROFS || PTR_ERR(filp) == -EACCES)
 431                         ro = 1;
 432         }
 433         if (ro)
 434                 filp = filp_open(filename, O_RDONLY | O_LARGEFILE, 0);
 435         if (IS_ERR(filp)) {
 436                 LINFO(curlun, "unable to open backing file: %s\n", filename);
 437                 return PTR_ERR(filp);
 438         }
 439
 440         if (!(filp->f_mode & FMODE_WRITE))
 441                 ro = 1;
 442
 443         inode = file_inode(filp);
 444         if ((!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))) {
 445                 LINFO(curlun, "invalid file type: %s\n", filename);
 446                 goto out;
 447         }
 448
 449         /*
 450          * If we can't read the file, it's no good.
 451          * If we can't write the file, use it read-only.
 452          */
 453         if (!file_readable(filp)) {
 454                 LINFO(curlun, "file not readable: %s\n", filename);
 455                 goto out;
 456         }
 457         if (!file_writable(filp))
 458                 ro = 1;
 459
 460         size = i_size_read(inode->i_mapping->host);
 461         if (size < 0) {
 462                 LINFO(curlun, "unable to find file size: %s\n", filename);
 463                 rc = (int) size;
 464                 goto out;
 465         }
 466
 467         if (curlun->cdrom) {
 468                 blksize = 2048;
 469                 blkbits = 11;
 470         } else if (inode->i_bdev) {
 471                 blksize = bdev_logical_block_size(inode->i_bdev);
 472                 blkbits = blksize_bits(blksize);
 473         } else {
 474                 blksize = 512;
 475                 blkbits = 9;
 476         }
 477
 478         num_sectors = size >> blkbits; /* File size in logic-block-size blocks */
 479         min_sectors = 1;
 480         if (curlun->cdrom) {
 481                 min_sectors = 300;      /* Smallest track is 300 frames */
 482                 if (num_sectors >= 256*60*75) {
 483                         num_sectors = 256*60*75 - 1;
 484                         LINFO(curlun, "file too big: %s\n", filename);
 485                         LINFO(curlun, "using only first %d blocks\n",
 486                                         (int) num_sectors);
 487                 }
 488         }
 489         if (num_sectors < min_sectors) {
 490                 LINFO(curlun, "file too small: %s\n", filename);
 491                 rc = -ETOOSMALL;
 492                 goto out;
 493         }
 494
 495         if (fsg_lun_is_open(curlun))
 496                 fsg_lun_close(curlun);
 497
 498         curlun->blksize = blksize;
 499         curlun->blkbits = blkbits;
 500         curlun->ro = ro;
 501         curlun->filp = filp;
 502         curlun->file_length = size;
 503         curlun->num_sectors = num_sectors;
 504         LDBG(curlun, "open backing file: %s\n", filename);
 505         return 0;
 506
 507 out:
 508         fput(filp);
 509         return rc;
 510 }
 511
 512
 513 /*-------------------------------------------------------------------------*/
 514
 515 /*
 516  * Sync the file data, don't bother with the metadata.
 517  * This code was copied from fs/buffer.c:sys_fdatasync().
 518  */
 519 static int fsg_lun_fsync_sub(struct fsg_lun *curlun)
 520 {
 521         struct file     *filp = curlun->filp;
 522
 523         if (curlun->ro || !filp)
 524                 return 0;
 525         return vfs_fsync(filp, 1);
 526 }
 527
 528 static void store_cdrom_address(u8 *dest, int msf, u32 addr)
 529 {
 530         if (msf) {
 531                 /* Convert to Minutes-Seconds-Frames */
 532                 addr >>= 2;             /* Convert to 2048-byte frames */
 533                 addr += 2*75;           /* Lead-in occupies 2 seconds */
 534                 dest[3] = addr % 75;    /* Frames */
 535                 addr /= 75;
 536                 dest[2] = addr % 60;    /* Seconds */
 537                 addr /= 60;
 538                 dest[1] = addr;         /* Minutes */
 539                 dest[0] = 0;            /* Reserved */
 540         } else {
 541                 /* Absolute sector */
 542                 put_unaligned_be32(addr, dest);
 543         }
 544 }
 545
 546
 547 /*-------------------------------------------------------------------------*/
 548
 549
 550 static ssize_t ro_show(struct device *dev, struct device_attribute *attr,
 551                        char *buf)
 552 {
 553         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 554
 555         return sprintf(buf, "%d\n", fsg_lun_is_open(curlun)
 556                                   ? curlun->ro
 557                                   : curlun->initially_ro);
 558 }
 559
 560 static ssize_t nofua_show(struct device *dev, struct device_attribute *attr,
 561                           char *buf)
 562 {
 563         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 564
 565         return sprintf(buf, "%u\n", curlun->nofua);
 566 }
 567
 568 static ssize_t file_show(struct device *dev, struct device_attribute *attr,
 569                          char *buf)
 570 {
 571         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 572         struct rw_semaphore     *filesem = dev_get_drvdata(dev);
 573         char            *p;
 574         ssize_t         rc;
 575
 576         down_read(filesem);
 577         if (fsg_lun_is_open(curlun)) {  /* Get the complete pathname */
 578                 p = d_path(&curlun->filp->f_path, buf, PAGE_SIZE - 1);
 579                 if (IS_ERR(p))
 580                         rc = PTR_ERR(p);
 581                 else {
 582                         rc = strlen(p);
 583                         memmove(buf, p, rc);
 584                         buf[rc] = '\n';         /* Add a newline */
 585                         buf[++rc] = 0;
 586                 }
 587         } else {                                /* No file, return 0 bytes */
 588                 *buf = 0;
 589                 rc = 0;
 590         }
 591         up_read(filesem);
 592         return rc;
 593 }
 594
 595
 596 static ssize_t ro_store(struct device *dev, struct device_attribute *attr,
 597                         const char *buf, size_t count)
 598 {
 599         ssize_t         rc;
 600         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 601         struct rw_semaphore     *filesem = dev_get_drvdata(dev);
 602         unsigned        ro;
 603
 604         rc = kstrtouint(buf, 2, &ro);
 605         if (rc)
 606                 return rc;
 607
 608         /*
 609          * Allow the write-enable status to change only while the
 610          * backing file is closed.
 611          */
 612         down_read(filesem);
 613         if (fsg_lun_is_open(curlun)) {
 614                 LDBG(curlun, "read-only status change prevented\n");
 615                 rc = -EBUSY;
 616         } else {
 617                 curlun->ro = ro;
 618                 curlun->initially_ro = ro;
 619                 LDBG(curlun, "read-only status set to %d\n", curlun->ro);
 620                 rc = count;
 621         }
 622         up_read(filesem);
 623         return rc;
 624 }
 625
 626 static ssize_t nofua_store(struct device *dev, struct device_attribute *attr,
 627                            const char *buf, size_t count)
 628 {
 629         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 630         unsigned        nofua;
 631         int             ret;
 632
 633         ret = kstrtouint(buf, 2, &nofua);
 634         if (ret)
 635                 return ret;
 636
 637         /* Sync data when switching from async mode to sync */
 638         if (!nofua && curlun->nofua)
 639                 fsg_lun_fsync_sub(curlun);
 640
 641         curlun->nofua = nofua;
 642
 643         return count;
 644 }
 645
 646 static ssize_t file_store(struct device *dev, struct device_attribute *attr,
 647                           const char *buf, size_t count)
 648 {
 649         struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
 650         struct rw_semaphore     *filesem = dev_get_drvdata(dev);
 651         int             rc = 0;
 652
 653         if (curlun->prevent_medium_removal && fsg_lun_is_open(curlun)) {
 654                 LDBG(curlun, "eject attempt prevented\n");
 655                 return -EBUSY;                          /* "Door is locked" */
 656         }
 657
 658         /* Remove a trailing newline */
 659         if (count > 0 && buf[count-1] == '\n')
 660                 ((char *) buf)[count-1] = 0;            /* Ugh! */
 661
 662         /* Load new medium */
 663         down_write(filesem);
 664         if (count > 0 && buf[0]) {
 665                 /* fsg_lun_open() will close existing file if any. */
 666                 rc = fsg_lun_open(curlun, buf);
 667                 if (rc == 0)
 668                         curlun->unit_attention_data =
 669                                         SS_NOT_READY_TO_READY_TRANSITION;
 670         } else if (fsg_lun_is_open(curlun)) {
 671                 fsg_lun_close(curlun);
 672                 curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
 673         }
 674         up_write(filesem);
 675         return (rc < 0 ? rc : count);
 676 }