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 (m.nazarewicz@samsung.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  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22
  23
  24 /*
  25  * This file requires the following identifiers used in USB strings to
  26  * be defined (each of type pointer to char):
  27  *  - fsg_string_manufacturer -- name of the manufacturer
  28  *  - fsg_string_product      -- name of the product
  29  *  - fsg_string_serial       -- product's serial
  30  *  - fsg_string_config       -- name of the configuration
  31  *  - fsg_string_interface    -- name of the interface
  32  * The first four are only needed when FSG_DESCRIPTORS_DEVICE_STRINGS
  33  * macro is defined prior to including this file.
  34  */
  35
  36
  37 #include <asm/unaligned.h>
  38
  39
  40 /*-------------------------------------------------------------------------*/
  41
  42
  43 #ifndef DEBUG
  44 #undef VERBOSE_DEBUG
  45 #undef DUMP_MSGS
  46 #endif /* !DEBUG */
  47
  48 #ifdef VERBOSE_DEBUG
  49 #define VLDBG   LDBG
  50 #else
  51 #define VLDBG(lun, fmt, args...) do { } while (0)
  52 #endif /* VERBOSE_DEBUG */
  53
  54 #define LDBG(lun, fmt, args...)   dev_dbg (&(lun)->dev, fmt, ## args)
  55 #define LERROR(lun, fmt, args...) dev_err (&(lun)->dev, fmt, ## args)
  56 #define LWARN(lun, fmt, args...)  dev_warn(&(lun)->dev, fmt, ## args)
  57 #define LINFO(lun, fmt, args...)  dev_info(&(lun)->dev, fmt, ## args)
  58
  59 #define DBG(d, fmt, args...)      dev_dbg (&(d)->gadget->dev, fmt, ## args)
  60 #define VDBG(d, fmt, args...)     dev_vdbg(&(d)->gadget->dev, fmt, ## args)
  61 #define ERROR(d, fmt, args...)    dev_err (&(d)->gadget->dev, fmt, ## args)
  62 #define WARNING(d, fmt, args...)  dev_warn(&(d)->gadget->dev, fmt, ## args)
  63 #define INFO(d, fmt, args...)     dev_info(&(d)->gadget->dev, fmt, ## args)
  64
  65
  66
  67 #ifdef DUMP_MSGS
  68
  69 #  define dump_msg(fsg, /* const char * */ label,                       \
  70                  /* const u8 * */ buf, /* unsigned */ length) do {      \
  71         if (length < 512) {                                             \
  72                 DBG(fsg, "%s, length %u:\n", label, length);            \
  73                 print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,      \
  74                                16, 1, buf, length, 0);                  \
  75         }                                                               \
  76 } while (0)
  77
  78 #  define dump_cdb(fsg) do { } while (0)
  79
  80 #else
  81
  82 #  define dump_msg(fsg, /* const char * */ label, \
  83                  /* const u8 * */ buf, /* unsigned */ length) do { } while (0)
  84
  85 #  ifdef VERBOSE_DEBUG
  86
  87 #define dump_cdb(fsg)                                                   \
  88         print_hex_dump(KERN_DEBUG, "SCSI CDB: ", DUMP_PREFIX_NONE,      \
  89                        16, 1, (fsg)->cmnd, (fsg)->cmnd_size, 0)         \
  90
  91 #  else
  92
  93 #    define dump_cdb(fsg) do { } while (0)
  94
  95 #  endif /* VERBOSE_DEBUG */
  96
  97 #endif /* DUMP_MSGS */
  98
  99
 100
 101
 102
 103 /*-------------------------------------------------------------------------*/
 104
 105 /* SCSI device types */
 106 #define TYPE_DISK       0x00
 107 #define TYPE_CDROM      0x05
 108
 109 /* USB protocol value = the transport method */
 110 #define USB_PR_CBI      0x00            // Control/Bulk/Interrupt
 111 #define USB_PR_CB       0x01            // Control/Bulk w/o interrupt
 112 #define USB_PR_BULK     0x50            // Bulk-only
 113
 114 /* USB subclass value = the protocol encapsulation */
 115 #define USB_SC_RBC      0x01            // Reduced Block Commands (flash)
 116 #define USB_SC_8020     0x02            // SFF-8020i, MMC-2, ATAPI (CD-ROM)
 117 #define USB_SC_QIC      0x03            // QIC-157 (tape)
 118 #define USB_SC_UFI      0x04            // UFI (floppy)
 119 #define USB_SC_8070     0x05            // SFF-8070i (removable)
 120 #define USB_SC_SCSI     0x06            // Transparent SCSI
 121
 122 /* Bulk-only data structures */
 123
 124 /* Command Block Wrapper */
 125 struct fsg_bulk_cb_wrap {
 126         __le32  Signature;              // Contains 'USBC'
 127         u32     Tag;                    // Unique per command id
 128         __le32  DataTransferLength;     // Size of the data
 129         u8      Flags;                  // Direction in bit 7
 130         u8      Lun;                    // LUN (normally 0)
 131         u8      Length;                 // Of the CDB, <= MAX_COMMAND_SIZE
 132         u8      CDB[16];                // Command Data Block
 133 };
 134
 135 #define USB_BULK_CB_WRAP_LEN    31
 136 #define USB_BULK_CB_SIG         0x43425355      // Spells out USBC
 137 #define USB_BULK_IN_FLAG        0x80
 138
 139 /* Command Status Wrapper */
 140 struct bulk_cs_wrap {
 141         __le32  Signature;              // Should = 'USBS'
 142         u32     Tag;                    // Same as original command
 143         __le32  Residue;                // Amount not transferred
 144         u8      Status;                 // See below
 145 };
 146
 147 #define USB_BULK_CS_WRAP_LEN    13
 148 #define USB_BULK_CS_SIG         0x53425355      // Spells out 'USBS'
 149 #define USB_STATUS_PASS         0
 150 #define USB_STATUS_FAIL         1
 151 #define USB_STATUS_PHASE_ERROR  2
 152
 153 /* Bulk-only class specific requests */
 154 #define USB_BULK_RESET_REQUEST          0xff
 155 #define USB_BULK_GET_MAX_LUN_REQUEST    0xfe
 156
 157
 158 /* CBI Interrupt data structure */
 159 struct interrupt_data {
 160         u8      bType;
 161         u8      bValue;
 162 };
 163
 164 #define CBI_INTERRUPT_DATA_LEN          2
 165
 166 /* CBI Accept Device-Specific Command request */
 167 #define USB_CBI_ADSC_REQUEST            0x00
 168
 169
 170 #define MAX_COMMAND_SIZE        16      // Length of a SCSI Command Data Block
 171
 172 /* SCSI commands that we recognize */
 173 #define SC_FORMAT_UNIT                  0x04
 174 #define SC_INQUIRY                      0x12
 175 #define SC_MODE_SELECT_6                0x15
 176 #define SC_MODE_SELECT_10               0x55
 177 #define SC_MODE_SENSE_6                 0x1a
 178 #define SC_MODE_SENSE_10                0x5a
 179 #define SC_PREVENT_ALLOW_MEDIUM_REMOVAL 0x1e
 180 #define SC_READ_6                       0x08
 181 #define SC_READ_10                      0x28
 182 #define SC_READ_12                      0xa8
 183 #define SC_READ_CAPACITY                0x25
 184 #define SC_READ_FORMAT_CAPACITIES       0x23
 185 #define SC_READ_HEADER                  0x44
 186 #define SC_READ_TOC                     0x43
 187 #define SC_RELEASE                      0x17
 188 #define SC_REQUEST_SENSE                0x03
 189 #define SC_RESERVE                      0x16
 190 #define SC_SEND_DIAGNOSTIC              0x1d
 191 #define SC_START_STOP_UNIT              0x1b
 192 #define SC_SYNCHRONIZE_CACHE            0x35
 193 #define SC_TEST_UNIT_READY              0x00
 194 #define SC_VERIFY                       0x2f
 195 #define SC_WRITE_6                      0x0a
 196 #define SC_WRITE_10                     0x2a
 197 #define SC_WRITE_12                     0xaa
 198
 199 /* SCSI Sense Key/Additional Sense Code/ASC Qualifier values */
 200 #define SS_NO_SENSE                             0
 201 #define SS_COMMUNICATION_FAILURE                0x040800
 202 #define SS_INVALID_COMMAND                      0x052000
 203 #define SS_INVALID_FIELD_IN_CDB                 0x052400
 204 #define SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE   0x052100
 205 #define SS_LOGICAL_UNIT_NOT_SUPPORTED           0x052500
 206 #define SS_MEDIUM_NOT_PRESENT                   0x023a00
 207 #define SS_MEDIUM_REMOVAL_PREVENTED             0x055302
 208 #define SS_NOT_READY_TO_READY_TRANSITION        0x062800
 209 #define SS_RESET_OCCURRED                       0x062900
 210 #define SS_SAVING_PARAMETERS_NOT_SUPPORTED      0x053900
 211 #define SS_UNRECOVERED_READ_ERROR               0x031100
 212 #define SS_WRITE_ERROR                          0x030c02
 213 #define SS_WRITE_PROTECTED                      0x072700
 214
 215 #define SK(x)           ((u8) ((x) >> 16))      // Sense Key byte, etc.
 216 #define ASC(x)          ((u8) ((x) >> 8))
 217 #define ASCQ(x)         ((u8) (x))
 218
 219
 220 /*-------------------------------------------------------------------------*/
 221
 222
 223 struct fsg_lun {
 224         struct file     *filp;
 225         loff_t          file_length;
 226         loff_t          num_sectors;
 227
 228         unsigned int    ro : 1;
 229         unsigned int    prevent_medium_removal : 1;
 230         unsigned int    registered : 1;
 231         unsigned int    info_valid : 1;
 232
 233         u32             sense_data;
 234         u32             sense_data_info;
 235         u32             unit_attention_data;
 236
 237         struct device   dev;
 238 };
 239
 240 #define fsg_lun_is_open(curlun) ((curlun)->filp != NULL)
 241
 242 static struct fsg_lun *fsg_lun_from_dev(struct device *dev)
 243 {
 244         return container_of(dev, struct fsg_lun, dev);
 245 }
 246
 247
 248 /* Big enough to hold our biggest descriptor */
 249 #define EP0_BUFSIZE     256
 250 #define DELAYED_STATUS  (EP0_BUFSIZE + 999)     // An impossibly large value
 251
 252 /* Number of buffers we will use.  2 is enough for double-buffering */
 253 #define FSG_NUM_BUFFERS 2
 254
 255 enum fsg_buffer_state {
 256         BUF_STATE_EMPTY = 0,
 257         BUF_STATE_FULL,
 258         BUF_STATE_BUSY
 259 };
 260
 261 struct fsg_buffhd {
 262         void                            *buf;
 263         enum fsg_buffer_state           state;
 264         struct fsg_buffhd               *next;
 265
 266         /* The NetChip 2280 is faster, and handles some protocol faults
 267          * better, if we don't submit any short bulk-out read requests.
 268          * So we will record the intended request length here. */
 269         unsigned int                    bulk_out_intended_length;
 270
 271         struct usb_request              *inreq;
 272         int                             inreq_busy;
 273         struct usb_request              *outreq;
 274         int                             outreq_busy;
 275 };
 276
 277 enum fsg_state {
 278         FSG_STATE_COMMAND_PHASE = -10,          // This one isn't used anywhere
 279         FSG_STATE_DATA_PHASE,
 280         FSG_STATE_STATUS_PHASE,
 281
 282         FSG_STATE_IDLE = 0,
 283         FSG_STATE_ABORT_BULK_OUT,
 284         FSG_STATE_RESET,
 285         FSG_STATE_INTERFACE_CHANGE,
 286         FSG_STATE_CONFIG_CHANGE,
 287         FSG_STATE_DISCONNECT,
 288         FSG_STATE_EXIT,
 289         FSG_STATE_TERMINATED
 290 };
 291
 292 enum data_direction {
 293         DATA_DIR_UNKNOWN = 0,
 294         DATA_DIR_FROM_HOST,
 295         DATA_DIR_TO_HOST,
 296         DATA_DIR_NONE
 297 };
 298
 299
 300 /*-------------------------------------------------------------------------*/
 301
 302
 303 static inline u32 get_unaligned_be24(u8 *buf)
 304 {
 305         return 0xffffff & (u32) get_unaligned_be32(buf - 1);
 306 }
 307
 308
 309 /*-------------------------------------------------------------------------*/
 310
 311
 312 enum {
 313         FSG_STRING_MANUFACTURER = 1,
 314         FSG_STRING_PRODUCT,
 315         FSG_STRING_SERIAL,
 316         FSG_STRING_CONFIG,
 317         FSG_STRING_INTERFACE
 318 };
 319
 320
 321 static struct usb_otg_descriptor
 322 fsg_otg_desc = {
 323         .bLength =              sizeof fsg_otg_desc,
 324         .bDescriptorType =      USB_DT_OTG,
 325
 326         .bmAttributes =         USB_OTG_SRP,
 327 };
 328
 329 /* There is only one interface. */
 330
 331 static struct usb_interface_descriptor
 332 fsg_intf_desc = {
 333         .bLength =              sizeof fsg_intf_desc,
 334         .bDescriptorType =      USB_DT_INTERFACE,
 335
 336         .bNumEndpoints =        2,              // Adjusted during fsg_bind()
 337         .bInterfaceClass =      USB_CLASS_MASS_STORAGE,
 338         .bInterfaceSubClass =   USB_SC_SCSI,    // Adjusted during fsg_bind()
 339         .bInterfaceProtocol =   USB_PR_BULK,    // Adjusted during fsg_bind()
 340         .iInterface =           FSG_STRING_INTERFACE,
 341 };
 342
 343 /* Three full-speed endpoint descriptors: bulk-in, bulk-out,
 344  * and interrupt-in. */
 345
 346 static struct usb_endpoint_descriptor
 347 fsg_fs_bulk_in_desc = {
 348         .bLength =              USB_DT_ENDPOINT_SIZE,
 349         .bDescriptorType =      USB_DT_ENDPOINT,
 350
 351         .bEndpointAddress =     USB_DIR_IN,
 352         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 353         /* wMaxPacketSize set by autoconfiguration */
 354 };
 355
 356 static struct usb_endpoint_descriptor
 357 fsg_fs_bulk_out_desc = {
 358         .bLength =              USB_DT_ENDPOINT_SIZE,
 359         .bDescriptorType =      USB_DT_ENDPOINT,
 360
 361         .bEndpointAddress =     USB_DIR_OUT,
 362         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 363         /* wMaxPacketSize set by autoconfiguration */
 364 };
 365
 366 static struct usb_endpoint_descriptor
 367 fsg_fs_intr_in_desc = {
 368         .bLength =              USB_DT_ENDPOINT_SIZE,
 369         .bDescriptorType =      USB_DT_ENDPOINT,
 370
 371         .bEndpointAddress =     USB_DIR_IN,
 372         .bmAttributes =         USB_ENDPOINT_XFER_INT,
 373         .wMaxPacketSize =       cpu_to_le16(2),
 374         .bInterval =            32,     // frames -> 32 ms
 375 };
 376
 377 static const struct usb_descriptor_header *fsg_fs_function[] = {
 378         (struct usb_descriptor_header *) &fsg_otg_desc,
 379         (struct usb_descriptor_header *) &fsg_intf_desc,
 380         (struct usb_descriptor_header *) &fsg_fs_bulk_in_desc,
 381         (struct usb_descriptor_header *) &fsg_fs_bulk_out_desc,
 382         (struct usb_descriptor_header *) &fsg_fs_intr_in_desc,
 383         NULL,
 384 };
 385 #define FSG_FS_FUNCTION_PRE_EP_ENTRIES  2
 386
 387
 388 /*
 389  * USB 2.0 devices need to expose both high speed and full speed
 390  * descriptors, unless they only run at full speed.
 391  *
 392  * That means alternate endpoint descriptors (bigger packets)
 393  * and a "device qualifier" ... plus more construction options
 394  * for the config descriptor.
 395  */
 396 static struct usb_endpoint_descriptor
 397 fsg_hs_bulk_in_desc = {
 398         .bLength =              USB_DT_ENDPOINT_SIZE,
 399         .bDescriptorType =      USB_DT_ENDPOINT,
 400
 401         /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
 402         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 403         .wMaxPacketSize =       cpu_to_le16(512),
 404 };
 405
 406 static struct usb_endpoint_descriptor
 407 fsg_hs_bulk_out_desc = {
 408         .bLength =              USB_DT_ENDPOINT_SIZE,
 409         .bDescriptorType =      USB_DT_ENDPOINT,
 410
 411         /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
 412         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 413         .wMaxPacketSize =       cpu_to_le16(512),
 414         .bInterval =            1,      // NAK every 1 uframe
 415 };
 416
 417 static struct usb_endpoint_descriptor
 418 fsg_hs_intr_in_desc = {
 419         .bLength =              USB_DT_ENDPOINT_SIZE,
 420         .bDescriptorType =      USB_DT_ENDPOINT,
 421
 422         /* bEndpointAddress copied from fs_intr_in_desc during fsg_bind() */
 423         .bmAttributes =         USB_ENDPOINT_XFER_INT,
 424         .wMaxPacketSize =       cpu_to_le16(2),
 425         .bInterval =            9,      // 2**(9-1) = 256 uframes -> 32 ms
 426 };
 427
 428 static const struct usb_descriptor_header *fsg_hs_function[] = {
 429         (struct usb_descriptor_header *) &fsg_otg_desc,
 430         (struct usb_descriptor_header *) &fsg_intf_desc,
 431         (struct usb_descriptor_header *) &fsg_hs_bulk_in_desc,
 432         (struct usb_descriptor_header *) &fsg_hs_bulk_out_desc,
 433         (struct usb_descriptor_header *) &fsg_hs_intr_in_desc,
 434         NULL,
 435 };
 436 #define FSG_HS_FUNCTION_PRE_EP_ENTRIES  2
 437
 438 /* Maxpacket and other transfer characteristics vary by speed. */
 439 static struct usb_endpoint_descriptor *
 440 fsg_ep_desc(struct usb_gadget *g, struct usb_endpoint_descriptor *fs,
 441                 struct usb_endpoint_descriptor *hs)
 442 {
 443         if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
 444                 return hs;
 445         return fs;
 446 }
 447
 448
 449 /* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
 450 static struct usb_string                fsg_strings[] = {
 451         {FSG_STRING_MANUFACTURER,       fsg_string_manufacturer},
 452         {FSG_STRING_PRODUCT,            fsg_string_product},
 453         {FSG_STRING_SERIAL,             fsg_string_serial},
 454         {FSG_STRING_CONFIG,             fsg_string_config},
 455         {FSG_STRING_INTERFACE,          fsg_string_interface},
 456         {}
 457 };
 458
 459 static struct usb_gadget_strings        fsg_stringtab = {
 460         .language       = 0x0409,               // en-us
 461         .strings        = fsg_strings,
 462 };
 463
 464
 465  /*-------------------------------------------------------------------------*/
 466
 467 /* If the next two routines are called while the gadget is registered,
 468  * the caller must own fsg->filesem for writing. */
 469
 470 static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
 471 {
 472         int                             ro;
 473         struct file                     *filp = NULL;
 474         int                             rc = -EINVAL;
 475         struct inode                    *inode = NULL;
 476         loff_t                          size;
 477         loff_t                          num_sectors;
 478         loff_t                          min_sectors;
 479
 480         /* R/W if we can, R/O if we must */
 481         ro = curlun->ro;
 482         if (!ro) {
 483                 filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
 484                 if (-EROFS == PTR_ERR(filp))
 485                         ro = 1;
 486         }
 487         if (ro)
 488                 filp = filp_open(filename, O_RDONLY | O_LARGEFILE, 0);
 489         if (IS_ERR(filp)) {
 490                 LINFO(curlun, "unable to open backing file: %s\n", filename);
 491                 return PTR_ERR(filp);
 492         }
 493
 494         if (!(filp->f_mode & FMODE_WRITE))
 495                 ro = 1;
 496
 497         if (filp->f_path.dentry)
 498                 inode = filp->f_path.dentry->d_inode;
 499         if (inode && S_ISBLK(inode->i_mode)) {
 500                 if (bdev_read_only(inode->i_bdev))
 501                         ro = 1;
 502         } else if (!inode || !S_ISREG(inode->i_mode)) {
 503                 LINFO(curlun, "invalid file type: %s\n", filename);
 504                 goto out;
 505         }
 506
 507         /* If we can't read the file, it's no good.
 508          * If we can't write the file, use it read-only. */
 509         if (!filp->f_op || !(filp->f_op->read || filp->f_op->aio_read)) {
 510                 LINFO(curlun, "file not readable: %s\n", filename);
 511                 goto out;
 512         }
 513         if (!(filp->f_op->write || filp->f_op->aio_write))
 514                 ro = 1;
 515
 516         size = i_size_read(inode->i_mapping->host);
 517         if (size < 0) {
 518                 LINFO(curlun, "unable to find file size: %s\n", filename);
 519                 rc = (int) size;
 520                 goto out;
 521         }
 522         num_sectors = size >> 9;        // File size in 512-byte blocks
 523         min_sectors = 1;
 524         if (mod_data.cdrom) {
 525                 num_sectors &= ~3;      // Reduce to a multiple of 2048
 526                 min_sectors = 300*4;    // Smallest track is 300 frames
 527                 if (num_sectors >= 256*60*75*4) {
 528                         num_sectors = (256*60*75 - 1) * 4;
 529                         LINFO(curlun, "file too big: %s\n", filename);
 530                         LINFO(curlun, "using only first %d blocks\n",
 531                                         (int) num_sectors);
 532                 }
 533         }
 534         if (num_sectors < min_sectors) {
 535                 LINFO(curlun, "file too small: %s\n", filename);
 536                 rc = -ETOOSMALL;
 537                 goto out;
 538         }
 539
 540         get_file(filp);
 541         curlun->ro = ro;
 542         curlun->filp = filp;
 543         curlun->file_length = size;
 544         curlun->num_sectors = num_sectors;
 545         LDBG(curlun, "open backing file: %s\n", filename);
 546         rc = 0;
 547
 548 out:
 549         filp_close(filp, current->files);
 550         return rc;
 551 }
 552
 553
 554 static void fsg_lun_close(struct fsg_lun *curlun)
 555 {
 556         if (curlun->filp) {
 557                 LDBG(curlun, "close backing file\n");
 558                 fput(curlun->filp);
 559                 curlun->filp = NULL;
 560         }
 561 }
 562
 563
 564 /*-------------------------------------------------------------------------*/
 565
 566 /* Sync the file data, don't bother with the metadata.
 567  * This code was copied from fs/buffer.c:sys_fdatasync(). */
 568 static int fsg_lun_fsync_sub(struct fsg_lun *curlun)
 569 {
 570         struct file     *filp = curlun->filp;
 571
 572         if (curlun->ro || !filp)
 573                 return 0;
 574         return vfs_fsync(filp, filp->f_path.dentry, 1);
 575 }
 576
 577 static void store_cdrom_address(u8 *dest, int msf, u32 addr)
 578 {
 579         if (msf) {
 580                 /* Convert to Minutes-Seconds-Frames */
 581                 addr >>= 2;             /* Convert to 2048-byte frames */
 582                 addr += 2*75;           /* Lead-in occupies 2 seconds */
 583                 dest[3] = addr % 75;    /* Frames */
 584                 addr /= 75;
 585                 dest[2] = addr % 60;    /* Seconds */
 586                 addr /= 60;
 587                 dest[1] = addr;         /* Minutes */
 588                 dest[0] = 0;            /* Reserved */
 589         } else {
 590                 /* Absolute sector */
 591                 put_unaligned_be32(addr, dest);
 592         }
 593 }