Documentation/DocBook/mtdnand.tmpl

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   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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   4
   5 <book id="MTD-NAND-Guide">
   6  <bookinfo>
   7   <title>MTD NAND Driver Programming Interface</title>
   8
   9   <authorgroup>
  10    <author>
  11     <firstname>Thomas</firstname>
  12     <surname>Gleixner</surname>
  13     <affiliation>
  14      <address>
  15       <email>tglx@linutronix.de</email>
  16      </address>
  17     </affiliation>
  18    </author>
  19   </authorgroup>
  20
  21   <copyright>
  22    <year>2004</year>
  23    <holder>Thomas Gleixner</holder>
  24   </copyright>
  25
  26   <legalnotice>
  27    <para>
  28      This documentation is free software; you can redistribute
  29      it and/or modify it under the terms of the GNU General Public
  30      License version 2 as published by the Free Software Foundation.
  31    </para>
  32
  33    <para>
  34      This program is distributed in the hope that it will be
  35      useful, but WITHOUT ANY WARRANTY; without even the implied
  36      warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  37      See the GNU General Public License for more details.
  38    </para>
  39
  40    <para>
  41      You should have received a copy of the GNU General Public
  42      License along with this program; if not, write to the Free
  43      Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  44      MA 02111-1307 USA
  45    </para>
  46
  47    <para>
  48      For more details see the file COPYING in the source
  49      distribution of Linux.
  50    </para>
  51   </legalnotice>
  52  </bookinfo>
  53
  54 <toc></toc>
  55
  56   <chapter id="intro">
  57       <title>Introduction</title>
  58   <para>
  59         The generic NAND driver supports almost all NAND and AG-AND based
  60         chips and connects them to the Memory Technology Devices (MTD)
  61         subsystem of the Linux Kernel.
  62   </para>
  63   <para>
  64         This documentation is provided for developers who want to implement
  65         board drivers or filesystem drivers suitable for NAND devices.
  66   </para>
  67   </chapter>
  68
  69   <chapter id="bugs">
  70      <title>Known Bugs And Assumptions</title>
  71   <para>
  72         None.
  73   </para>
  74   </chapter>
  75
  76   <chapter id="dochints">
  77      <title>Documentation hints</title>
  78      <para>
  79      The function and structure docs are autogenerated. Each function and
  80      struct member has a short description which is marked with an [XXX] identifier.
  81      The following chapters explain the meaning of those identifiers.
  82      </para>
  83      <sect1 id="Function_identifiers_XXX">
  84         <title>Function identifiers [XXX]</title>
  85         <para>
  86         The functions are marked with [XXX] identifiers in the short
  87         comment. The identifiers explain the usage and scope of the
  88         functions. Following identifiers are used:
  89         </para>
  90         <itemizedlist>
  91                 <listitem><para>
  92                 [MTD Interface]</para><para>
  93                 These functions provide the interface to the MTD kernel API.
  94                 They are not replacable and provide functionality
  95                 which is complete hardware independent.
  96                 </para></listitem>
  97                 <listitem><para>
  98                 [NAND Interface]</para><para>
  99                 These functions are exported and provide the interface to the NAND kernel API.
 100                 </para></listitem>
 101                 <listitem><para>
 102                 [GENERIC]</para><para>
 103                 Generic functions are not replacable and provide functionality
 104                 which is complete hardware independent.
 105                 </para></listitem>
 106                 <listitem><para>
 107                 [DEFAULT]</para><para>
 108                 Default functions provide hardware related functionality which is suitable
 109                 for most of the implementations. These functions can be replaced by the
 110                 board driver if neccecary. Those functions are called via pointers in the
 111                 NAND chip description structure. The board driver can set the functions which
 112                 should be replaced by board dependent functions before calling nand_scan().
 113                 If the function pointer is NULL on entry to nand_scan() then the pointer
 114                 is set to the default function which is suitable for the detected chip type.
 115                 </para></listitem>
 116         </itemizedlist>
 117      </sect1>
 118      <sect1 id="Struct_member_identifiers_XXX">
 119         <title>Struct member identifiers [XXX]</title>
 120         <para>
 121         The struct members are marked with [XXX] identifiers in the
 122         comment. The identifiers explain the usage and scope of the
 123         members. Following identifiers are used:
 124         </para>
 125         <itemizedlist>
 126                 <listitem><para>
 127                 [INTERN]</para><para>
 128                 These members are for NAND driver internal use only and must not be
 129                 modified. Most of these values are calculated from the chip geometry
 130                 information which is evaluated during nand_scan().
 131                 </para></listitem>
 132                 <listitem><para>
 133                 [REPLACEABLE]</para><para>
 134                 Replaceable members hold hardware related functions which can be
 135                 provided by the board driver. The board driver can set the functions which
 136                 should be replaced by board dependent functions before calling nand_scan().
 137                 If the function pointer is NULL on entry to nand_scan() then the pointer
 138                 is set to the default function which is suitable for the detected chip type.
 139                 </para></listitem>
 140                 <listitem><para>
 141                 [BOARDSPECIFIC]</para><para>
 142                 Board specific members hold hardware related information which must
 143                 be provided by the board driver. The board driver must set the function
 144                 pointers and datafields before calling nand_scan().
 145                 </para></listitem>
 146                 <listitem><para>
 147                 [OPTIONAL]</para><para>
 148                 Optional members can hold information relevant for the board driver. The
 149                 generic NAND driver code does not use this information.
 150                 </para></listitem>
 151         </itemizedlist>
 152      </sect1>
 153   </chapter>
 154
 155   <chapter id="basicboarddriver">
 156         <title>Basic board driver</title>
 157         <para>
 158                 For most boards it will be sufficient to provide just the
 159                 basic functions and fill out some really board dependent
 160                 members in the nand chip description structure.
 161         </para>
 162         <sect1 id="Basic_defines">
 163                 <title>Basic defines</title>
 164                 <para>
 165                         At least you have to provide a mtd structure and
 166                         a storage for the ioremap'ed chip address.
 167                         You can allocate the mtd structure using kmalloc
 168                         or you can allocate it statically.
 169                         In case of static allocation you have to allocate
 170                         a nand_chip structure too.
 171                 </para>
 172                 <para>
 173                         Kmalloc based example
 174                 </para>
 175                 <programlisting>
 176 static struct mtd_info *board_mtd;
 177 static unsigned long baseaddr;
 178                 </programlisting>
 179                 <para>
 180                         Static example
 181                 </para>
 182                 <programlisting>
 183 static struct mtd_info board_mtd;
 184 static struct nand_chip board_chip;
 185 static unsigned long baseaddr;
 186                 </programlisting>
 187         </sect1>
 188         <sect1 id="Partition_defines">
 189                 <title>Partition defines</title>
 190                 <para>
 191                         If you want to divide your device into partitions, then
 192                         enable the configuration switch CONFIG_MTD_PARTITIONS and define
 193                         a partitioning scheme suitable to your board.
 194                 </para>
 195                 <programlisting>
 196 #define NUM_PARTITIONS 2
 197 static struct mtd_partition partition_info[] = {
 198         { .name = "Flash partition 1",
 199           .offset =  0,
 200           .size =    8 * 1024 * 1024 },
 201         { .name = "Flash partition 2",
 202           .offset =  MTDPART_OFS_NEXT,
 203           .size =    MTDPART_SIZ_FULL },
 204 };
 205                 </programlisting>
 206         </sect1>
 207         <sect1 id="Hardware_control_functions">
 208                 <title>Hardware control function</title>
 209                 <para>
 210                         The hardware control function provides access to the
 211                         control pins of the NAND chip(s).
 212                         The access can be done by GPIO pins or by address lines.
 213                         If you use address lines, make sure that the timing
 214                         requirements are met.
 215                 </para>
 216                 <para>
 217                         <emphasis>GPIO based example</emphasis>
 218                 </para>
 219                 <programlisting>
 220 static void board_hwcontrol(struct mtd_info *mtd, int cmd)
 221 {
 222         switch(cmd){
 223                 case NAND_CTL_SETCLE: /* Set CLE pin high */ break;
 224                 case NAND_CTL_CLRCLE: /* Set CLE pin low */ break;
 225                 case NAND_CTL_SETALE: /* Set ALE pin high */ break;
 226                 case NAND_CTL_CLRALE: /* Set ALE pin low */ break;
 227                 case NAND_CTL_SETNCE: /* Set nCE pin low */ break;
 228                 case NAND_CTL_CLRNCE: /* Set nCE pin high */ break;
 229         }
 230 }
 231                 </programlisting>
 232                 <para>
 233                         <emphasis>Address lines based example.</emphasis> It's assumed that the
 234                         nCE pin is driven by a chip select decoder.
 235                 </para>
 236                 <programlisting>
 237 static void board_hwcontrol(struct mtd_info *mtd, int cmd)
 238 {
 239         struct nand_chip *this = (struct nand_chip *) mtd->priv;
 240         switch(cmd){
 241                 case NAND_CTL_SETCLE: this->IO_ADDR_W |= CLE_ADRR_BIT;  break;
 242                 case NAND_CTL_CLRCLE: this->IO_ADDR_W &amp;= ~CLE_ADRR_BIT; break;
 243                 case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT;  break;
 244                 case NAND_CTL_CLRALE: this->IO_ADDR_W &amp;= ~ALE_ADRR_BIT; break;
 245         }
 246 }
 247                 </programlisting>
 248         </sect1>
 249         <sect1 id="Device_ready_function">
 250                 <title>Device ready function</title>
 251                 <para>
 252                         If the hardware interface has the ready busy pin of the NAND chip connected to a
 253                         GPIO or other accesible I/O pin, this function is used to read back the state of the
 254                         pin. The function has no arguments and should return 0, if the device is busy (R/B pin
 255                         is low) and 1, if the device is ready (R/B pin is high).
 256                         If the hardware interface does not give access to the ready busy pin, then
 257                         the function must not be defined and the function pointer this->dev_ready is set to NULL.
 258                 </para>
 259         </sect1>
 260         <sect1 id="Init_function">
 261                 <title>Init function</title>
 262                 <para>
 263                         The init function allocates memory and sets up all the board
 264                         specific parameters and function pointers. When everything
 265                         is set up nand_scan() is called. This function tries to
 266                         detect and identify then chip. If a chip is found all the
 267                         internal data fields are initialized accordingly.
 268                         The structure(s) have to be zeroed out first and then filled with the neccecary
 269                         information about the device.
 270                 </para>
 271                 <programlisting>
 272 int __init board_init (void)
 273 {
 274         struct nand_chip *this;
 275         int err = 0;
 276
 277         /* Allocate memory for MTD device structure and private data */
 278         board_mtd = kzalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip), GFP_KERNEL);
 279         if (!board_mtd) {
 280                 printk ("Unable to allocate NAND MTD device structure.\n");
 281                 err = -ENOMEM;
 282                 goto out;
 283         }
 284
 285         /* map physical address */
 286         baseaddr = (unsigned long)ioremap(CHIP_PHYSICAL_ADDRESS, 1024);
 287         if(!baseaddr){
 288                 printk("Ioremap to access NAND chip failed\n");
 289                 err = -EIO;
 290                 goto out_mtd;
 291         }
 292
 293         /* Get pointer to private data */
 294         this = (struct nand_chip *) ();
 295         /* Link the private data with the MTD structure */
 296         board_mtd->priv = this;
 297
 298         /* Set address of NAND IO lines */
 299         this->IO_ADDR_R = baseaddr;
 300         this->IO_ADDR_W = baseaddr;
 301         /* Reference hardware control function */
 302         this->hwcontrol = board_hwcontrol;
 303         /* Set command delay time, see datasheet for correct value */
 304         this->chip_delay = CHIP_DEPENDEND_COMMAND_DELAY;
 305         /* Assign the device ready function, if available */
 306         this->dev_ready = board_dev_ready;
 307         this->eccmode = NAND_ECC_SOFT;
 308
 309         /* Scan to find existence of the device */
 310         if (nand_scan (board_mtd, 1)) {
 311                 err = -ENXIO;
 312                 goto out_ior;
 313         }
 314
 315         add_mtd_partitions(board_mtd, partition_info, NUM_PARTITIONS);
 316         goto out;
 317
 318 out_ior:
 319         iounmap((void *)baseaddr);
 320 out_mtd:
 321         kfree (board_mtd);
 322 out:
 323         return err;
 324 }
 325 module_init(board_init);
 326                 </programlisting>
 327         </sect1>
 328         <sect1 id="Exit_function">
 329                 <title>Exit function</title>
 330                 <para>
 331                         The exit function is only neccecary if the driver is
 332                         compiled as a module. It releases all resources which
 333                         are held by the chip driver and unregisters the partitions
 334                         in the MTD layer.
 335                 </para>
 336                 <programlisting>
 337 #ifdef MODULE
 338 static void __exit board_cleanup (void)
 339 {
 340         /* Release resources, unregister device */
 341         nand_release (board_mtd);
 342
 343         /* unmap physical address */
 344         iounmap((void *)baseaddr);
 345
 346         /* Free the MTD device structure */
 347         kfree (board_mtd);
 348 }
 349 module_exit(board_cleanup);
 350 #endif
 351                 </programlisting>
 352         </sect1>
 353   </chapter>
 354
 355   <chapter id="boarddriversadvanced">
 356         <title>Advanced board driver functions</title>
 357         <para>
 358                 This chapter describes the advanced functionality of the NAND
 359                 driver. For a list of functions which can be overridden by the board
 360                 driver see the documentation of the nand_chip structure.
 361         </para>
 362         <sect1 id="Multiple_chip_control">
 363                 <title>Multiple chip control</title>
 364                 <para>
 365                         The nand driver can control chip arrays. Therefor the
 366                         board driver must provide an own select_chip function. This
 367                         function must (de)select the requested chip.
 368                         The function pointer in the nand_chip structure must
 369                         be set before calling nand_scan(). The maxchip parameter
 370                         of nand_scan() defines the maximum number of chips to
 371                         scan for. Make sure that the select_chip function can
 372                         handle the requested number of chips.
 373                 </para>
 374                 <para>
 375                         The nand driver concatenates the chips to one virtual
 376                         chip and provides this virtual chip to the MTD layer.
 377                 </para>
 378                 <para>
 379                         <emphasis>Note: The driver can only handle linear chip arrays
 380                         of equally sized chips. There is no support for
 381                         parallel arrays which extend the buswidth.</emphasis>
 382                 </para>
 383                 <para>
 384                         <emphasis>GPIO based example</emphasis>
 385                 </para>
 386                 <programlisting>
 387 static void board_select_chip (struct mtd_info *mtd, int chip)
 388 {
 389         /* Deselect all chips, set all nCE pins high */
 390         GPIO(BOARD_NAND_NCE) |= 0xff;
 391         if (chip >= 0)
 392                 GPIO(BOARD_NAND_NCE) &amp;= ~ (1 &lt;&lt; chip);
 393 }
 394                 </programlisting>
 395                 <para>
 396                         <emphasis>Address lines based example.</emphasis>
 397                         Its assumed that the nCE pins are connected to an
 398                         address decoder.
 399                 </para>
 400                 <programlisting>
 401 static void board_select_chip (struct mtd_info *mtd, int chip)
 402 {
 403         struct nand_chip *this = (struct nand_chip *) mtd->priv;
 404
 405         /* Deselect all chips */
 406         this->IO_ADDR_R &amp;= ~BOARD_NAND_ADDR_MASK;
 407         this->IO_ADDR_W &amp;= ~BOARD_NAND_ADDR_MASK;
 408         switch (chip) {
 409         case 0:
 410                 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIP0;
 411                 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIP0;
 412                 break;
 413         ....
 414         case n:
 415                 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIPn;
 416                 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIPn;
 417                 break;
 418         }
 419 }
 420                 </programlisting>
 421         </sect1>
 422         <sect1 id="Hardware_ECC_support">
 423                 <title>Hardware ECC support</title>
 424                 <sect2 id="Functions_and_constants">
 425                         <title>Functions and constants</title>
 426                         <para>
 427                                 The nand driver supports three different types of
 428                                 hardware ECC.
 429                                 <itemizedlist>
 430                                 <listitem><para>NAND_ECC_HW3_256</para><para>
 431                                 Hardware ECC generator providing 3 bytes ECC per
 432                                 256 byte.
 433                                 </para> </listitem>
 434                                 <listitem><para>NAND_ECC_HW3_512</para><para>
 435                                 Hardware ECC generator providing 3 bytes ECC per
 436                                 512 byte.
 437                                 </para> </listitem>
 438                                 <listitem><para>NAND_ECC_HW6_512</para><para>
 439                                 Hardware ECC generator providing 6 bytes ECC per
 440                                 512 byte.
 441                                 </para> </listitem>
 442                                 <listitem><para>NAND_ECC_HW8_512</para><para>
 443                                 Hardware ECC generator providing 6 bytes ECC per
 444                                 512 byte.
 445                                 </para> </listitem>
 446                                 </itemizedlist>
 447                                 If your hardware generator has a different functionality
 448                                 add it at the appropriate place in nand_base.c
 449                         </para>
 450                         <para>
 451                                 The board driver must provide following functions:
 452                                 <itemizedlist>
 453                                 <listitem><para>enable_hwecc</para><para>
 454                                 This function is called before reading / writing to
 455                                 the chip. Reset or initialize the hardware generator
 456                                 in this function. The function is called with an
 457                                 argument which let you distinguish between read
 458                                 and write operations.
 459                                 </para> </listitem>
 460                                 <listitem><para>calculate_ecc</para><para>
 461                                 This function is called after read / write from / to
 462                                 the chip. Transfer the ECC from the hardware to
 463                                 the buffer. If the option NAND_HWECC_SYNDROME is set
 464                                 then the function is only called on write. See below.
 465                                 </para> </listitem>
 466                                 <listitem><para>correct_data</para><para>
 467                                 In case of an ECC error this function is called for
 468                                 error detection and correction. Return 1 respectively 2
 469                                 in case the error can be corrected. If the error is
 470                                 not correctable return -1. If your hardware generator
 471                                 matches the default algorithm of the nand_ecc software
 472                                 generator then use the correction function provided
 473                                 by nand_ecc instead of implementing duplicated code.
 474                                 </para> </listitem>
 475                                 </itemizedlist>
 476                         </para>
 477                 </sect2>
 478                 <sect2 id="Hardware_ECC_with_syndrome_calculation">
 479                 <title>Hardware ECC with syndrome calculation</title>
 480                         <para>
 481                                 Many hardware ECC implementations provide Reed-Solomon
 482                                 codes and calculate an error syndrome on read. The syndrome
 483                                 must be converted to a standard Reed-Solomon syndrome
 484                                 before calling the error correction code in the generic
 485                                 Reed-Solomon library.
 486                         </para>
 487                         <para>
 488                                 The ECC bytes must be placed immidiately after the data
 489                                 bytes in order to make the syndrome generator work. This
 490                                 is contrary to the usual layout used by software ECC. The
 491                                 seperation of data and out of band area is not longer
 492                                 possible. The nand driver code handles this layout and
 493                                 the remaining free bytes in the oob area are managed by
 494                                 the autoplacement code. Provide a matching oob-layout
 495                                 in this case. See rts_from4.c and diskonchip.c for
 496                                 implementation reference. In those cases we must also
 497                                 use bad block tables on FLASH, because the ECC layout is
 498                                 interferring with the bad block marker positions.
 499                                 See bad block table support for details.
 500                         </para>
 501                 </sect2>
 502         </sect1>
 503         <sect1 id="Bad_Block_table_support">
 504                 <title>Bad block table support</title>
 505                 <para>
 506                         Most NAND chips mark the bad blocks at a defined
 507                         position in the spare area. Those blocks must
 508                         not be erased under any circumstances as the bad
 509                         block information would be lost.
 510                         It is possible to check the bad block mark each
 511                         time when the blocks are accessed by reading the
 512                         spare area of the first page in the block. This
 513                         is time consuming so a bad block table is used.
 514                 </para>
 515                 <para>
 516                         The nand driver supports various types of bad block
 517                         tables.
 518                         <itemizedlist>
 519                         <listitem><para>Per device</para><para>
 520                         The bad block table contains all bad block information
 521                         of the device which can consist of multiple chips.
 522                         </para> </listitem>
 523                         <listitem><para>Per chip</para><para>
 524                         A bad block table is used per chip and contains the
 525                         bad block information for this particular chip.
 526                         </para> </listitem>
 527                         <listitem><para>Fixed offset</para><para>
 528                         The bad block table is located at a fixed offset
 529                         in the chip (device). This applies to various
 530                         DiskOnChip devices.
 531                         </para> </listitem>
 532                         <listitem><para>Automatic placed</para><para>
 533                         The bad block table is automatically placed and
 534                         detected either at the end or at the beginning
 535                         of a chip (device)
 536                         </para> </listitem>
 537                         <listitem><para>Mirrored tables</para><para>
 538                         The bad block table is mirrored on the chip (device) to
 539                         allow updates of the bad block table without data loss.
 540                         </para> </listitem>
 541                         </itemizedlist>
 542                 </para>
 543                 <para>
 544                         nand_scan() calls the function nand_default_bbt().
 545                         nand_default_bbt() selects appropriate default
 546                         bad block table desriptors depending on the chip information
 547                         which was retrieved by nand_scan().
 548                 </para>
 549                 <para>
 550                         The standard policy is scanning the device for bad
 551                         blocks and build a ram based bad block table which
 552                         allows faster access than always checking the
 553                         bad block information on the flash chip itself.
 554                 </para>
 555                 <sect2 id="Flash_based_tables">
 556                         <title>Flash based tables</title>
 557                         <para>
 558                                 It may be desired or neccecary to keep a bad block table in FLASH.
 559                                 For AG-AND chips this is mandatory, as they have no factory marked
 560                                 bad blocks. They have factory marked good blocks. The marker pattern
 561                                 is erased when the block is erased to be reused. So in case of
 562                                 powerloss before writing the pattern back to the chip this block
 563                                 would be lost and added to the bad blocks. Therefor we scan the
 564                                 chip(s) when we detect them the first time for good blocks and
 565                                 store this information in a bad block table before erasing any
 566                                 of the blocks.
 567                         </para>
 568                         <para>
 569                                 The blocks in which the tables are stored are procteted against
 570                                 accidental access by marking them bad in the memory bad block
 571                                 table. The bad block table management functions are allowed
 572                                 to circumvernt this protection.
 573                         </para>
 574                         <para>
 575                                 The simplest way to activate the FLASH based bad block table support
 576                                 is to set the option NAND_USE_FLASH_BBT in the option field of
 577                                 the nand chip structure before calling nand_scan(). For AG-AND
 578                                 chips is this done by default.
 579                                 This activates the default FLASH based bad block table functionality
 580                                 of the NAND driver. The default bad block table options are
 581                                 <itemizedlist>
 582                                 <listitem><para>Store bad block table per chip</para></listitem>
 583                                 <listitem><para>Use 2 bits per block</para></listitem>
 584                                 <listitem><para>Automatic placement at the end of the chip</para></listitem>
 585                                 <listitem><para>Use mirrored tables with version numbers</para></listitem>
 586                                 <listitem><para>Reserve 4 blocks at the end of the chip</para></listitem>
 587                                 </itemizedlist>
 588                         </para>
 589                 </sect2>
 590                 <sect2 id="User_defined_tables">
 591                         <title>User defined tables</title>
 592                         <para>
 593                                 User defined tables are created by filling out a
 594                                 nand_bbt_descr structure and storing the pointer in the
 595                                 nand_chip structure member bbt_td before calling nand_scan().
 596                                 If a mirror table is neccecary a second structure must be
 597                                 created and a pointer to this structure must be stored
 598                                 in bbt_md inside the nand_chip structure. If the bbt_md
 599                                 member is set to NULL then only the main table is used
 600                                 and no scan for the mirrored table is performed.
 601                         </para>
 602                         <para>
 603                                 The most important field in the nand_bbt_descr structure
 604                                 is the options field. The options define most of the
 605                                 table properties. Use the predefined constants from
 606                                 nand.h to define the options.
 607                                 <itemizedlist>
 608                                 <listitem><para>Number of bits per block</para>
 609                                 <para>The supported number of bits is 1, 2, 4, 8.</para></listitem>
 610                                 <listitem><para>Table per chip</para>
 611                                 <para>Setting the constant NAND_BBT_PERCHIP selects that
 612                                 a bad block table is managed for each chip in a chip array.
 613                                 If this option is not set then a per device bad block table
 614                                 is used.</para></listitem>
 615                                 <listitem><para>Table location is absolute</para>
 616                                 <para>Use the option constant NAND_BBT_ABSPAGE and
 617                                 define the absolute page number where the bad block
 618                                 table starts in the field pages. If you have selected bad block
 619                                 tables per chip and you have a multi chip array then the start page
 620                                 must be given for each chip in the chip array. Note: there is no scan
 621                                 for a table ident pattern performed, so the fields
 622                                 pattern, veroffs, offs, len can be left uninitialized</para></listitem>
 623                                 <listitem><para>Table location is automatically detected</para>
 624                                 <para>The table can either be located in the first or the last good
 625                                 blocks of the chip (device). Set NAND_BBT_LASTBLOCK to place
 626                                 the bad block table at the end of the chip (device). The
 627                                 bad block tables are marked and identified by a pattern which
 628                                 is stored in the spare area of the first page in the block which
 629                                 holds the bad block table. Store a pointer to the pattern
 630                                 in the pattern field. Further the length of the pattern has to be
 631                                 stored in len and the offset in the spare area must be given
 632                                 in the offs member of the nand_bbt_descr stucture. For mirrored
 633                                 bad block tables different patterns are mandatory.</para></listitem>
 634                                 <listitem><para>Table creation</para>
 635                                 <para>Set the option NAND_BBT_CREATE to enable the table creation
 636                                 if no table can be found during the scan. Usually this is done only
 637                                 once if a new chip is found. </para></listitem>
 638                                 <listitem><para>Table write support</para>
 639                                 <para>Set the option NAND_BBT_WRITE to enable the table write support.
 640                                 This allows the update of the bad block table(s) in case a block has
 641                                 to be marked bad due to wear. The MTD interface function block_markbad
 642                                 is calling the update function of the bad block table. If the write
 643                                 support is enabled then the table is updated on FLASH.</para>
 644                                 <para>
 645                                 Note: Write support should only be enabled for mirrored tables with
 646                                 version control.
 647                                 </para></listitem>
 648                                 <listitem><para>Table version control</para>
 649                                 <para>Set the option NAND_BBT_VERSION to enable the table version control.
 650                                 It's highly recommended to enable this for mirrored tables with write
 651                                 support. It makes sure that the risk of loosing the bad block
 652                                 table information is reduced to the loss of the information about the
 653                                 one worn out block which should be marked bad. The version is stored in
 654                                 4 consecutive bytes in the spare area of the device. The position of
 655                                 the version number is defined by the member veroffs in the bad block table
 656                                 descriptor.</para></listitem>
 657                                 <listitem><para>Save block contents on write</para>
 658                                 <para>
 659                                 In case that the block which holds the bad block table does contain
 660                                 other useful information, set the option NAND_BBT_SAVECONTENT. When
 661                                 the bad block table is written then the whole block is read the bad
 662                                 block table is updated and the block is erased and everything is
 663                                 written back. If this option is not set only the bad block table
 664                                 is written and everything else in the block is ignored and erased.
 665                                 </para></listitem>
 666                                 <listitem><para>Number of reserved blocks</para>
 667                                 <para>
 668                                 For automatic placement some blocks must be reserved for
 669                                 bad block table storage. The number of reserved blocks is defined
 670                                 in the maxblocks member of the babd block table description structure.
 671                                 Reserving 4 blocks for mirrored tables should be a reasonable number.
 672                                 This also limits the number of blocks which are scanned for the bad
 673                                 block table ident pattern.
 674                                 </para></listitem>
 675                                 </itemizedlist>
 676                         </para>
 677                 </sect2>
 678         </sect1>
 679         <sect1 id="Spare_area_placement">
 680                 <title>Spare area (auto)placement</title>
 681                 <para>
 682                         The nand driver implements different possibilities for
 683                         placement of filesystem data in the spare area,
 684                         <itemizedlist>
 685                         <listitem><para>Placement defined by fs driver</para></listitem>
 686                         <listitem><para>Automatic placement</para></listitem>
 687                         </itemizedlist>
 688                         The default placement function is automatic placement. The
 689                         nand driver has built in default placement schemes for the
 690                         various chiptypes. If due to hardware ECC functionality the
 691                         default placement does not fit then the board driver can
 692                         provide a own placement scheme.
 693                 </para>
 694                 <para>
 695                         File system drivers can provide a own placement scheme which
 696                         is used instead of the default placement scheme.
 697                 </para>
 698                 <para>
 699                         Placement schemes are defined by a nand_oobinfo structure
 700                         <programlisting>
 701 struct nand_oobinfo {
 702         int     useecc;
 703         int     eccbytes;
 704         int     eccpos[24];
 705         int     oobfree[8][2];
 706 };
 707                         </programlisting>
 708                         <itemizedlist>
 709                         <listitem><para>useecc</para><para>
 710                                 The useecc member controls the ecc and placement function. The header
 711                                 file include/mtd/mtd-abi.h contains constants to select ecc and
 712                                 placement. MTD_NANDECC_OFF switches off the ecc complete. This is
 713                                 not recommended and available for testing and diagnosis only.
 714                                 MTD_NANDECC_PLACE selects caller defined placement, MTD_NANDECC_AUTOPLACE
 715                                 selects automatic placement.
 716                         </para></listitem>
 717                         <listitem><para>eccbytes</para><para>
 718                                 The eccbytes member defines the number of ecc bytes per page.
 719                         </para></listitem>
 720                         <listitem><para>eccpos</para><para>
 721                                 The eccpos array holds the byte offsets in the spare area where
 722                                 the ecc codes are placed.
 723                         </para></listitem>
 724                         <listitem><para>oobfree</para><para>
 725                                 The oobfree array defines the areas in the spare area which can be
 726                                 used for automatic placement. The information is given in the format
 727                                 {offset, size}. offset defines the start of the usable area, size the
 728                                 length in bytes. More than one area can be defined. The list is terminated
 729                                 by an {0, 0} entry.
 730                         </para></listitem>
 731                         </itemizedlist>
 732                 </para>
 733                 <sect2 id="Placement_defined_by_fs_driver">
 734                         <title>Placement defined by fs driver</title>
 735                         <para>
 736                                 The calling function provides a pointer to a nand_oobinfo
 737                                 structure which defines the ecc placement. For writes the
 738                                 caller must provide a spare area buffer along with the
 739                                 data buffer. The spare area buffer size is (number of pages) *
 740                                 (size of spare area). For reads the buffer size is
 741                                 (number of pages) * ((size of spare area) + (number of ecc
 742                                 steps per page) * sizeof (int)). The driver stores the
 743                                 result of the ecc check for each tuple in the spare buffer.
 744                                 The storage sequence is
 745                         </para>
 746                         <para>
 747                                 &lt;spare data page 0&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
 748                         </para>
 749                         <para>
 750                                 ...
 751                         </para>
 752                         <para>
 753                                 &lt;spare data page n&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
 754                         </para>
 755                         <para>
 756                                 This is a legacy mode used by YAFFS1.
 757                         </para>
 758                         <para>
 759                                 If the spare area buffer is NULL then only the ECC placement is
 760                                 done according to the given scheme in the nand_oobinfo structure.
 761                         </para>
 762                 </sect2>
 763                 <sect2 id="Automatic_placement">
 764                         <title>Automatic placement</title>
 765                         <para>
 766                                 Automatic placement uses the built in defaults to place the
 767                                 ecc bytes in the spare area. If filesystem data have to be stored /
 768                                 read into the spare area then the calling function must provide a
 769                                 buffer. The buffer size per page is determined by the oobfree array in
 770                                 the nand_oobinfo structure.
 771                         </para>
 772                         <para>
 773                                 If the spare area buffer is NULL then only the ECC placement is
 774                                 done according to the default builtin scheme.
 775                         </para>
 776                 </sect2>
 777                 <sect2 id="User_space_placement_selection">
 778                         <title>User space placement selection</title>
 779                 <para>
 780                         All non ecc functions like mtd->read and mtd->write use an internal
 781                         structure, which can be set by an ioctl. This structure is preset
 782                         to the autoplacement default.
 783                         <programlisting>
 784         ioctl (fd, MEMSETOOBSEL, oobsel);
 785                         </programlisting>
 786                         oobsel is a pointer to a user supplied structure of type
 787                         nand_oobconfig. The contents of this structure must match the
 788                         criteria of the filesystem, which will be used. See an example in utils/nandwrite.c.
 789                 </para>
 790                 </sect2>
 791         </sect1>
 792         <sect1 id="Spare_area_autoplacement_default">
 793                 <title>Spare area autoplacement default schemes</title>
 794                 <sect2 id="pagesize_256">
 795                         <title>256 byte pagesize</title>
 796 <informaltable><tgroup cols="3"><tbody>
 797 <row>
 798 <entry>Offset</entry>
 799 <entry>Content</entry>
 800 <entry>Comment</entry>
 801 </row>
 802 <row>
 803 <entry>0x00</entry>
 804 <entry>ECC byte 0</entry>
 805 <entry>Error correction code byte 0</entry>
 806 </row>
 807 <row>
 808 <entry>0x01</entry>
 809 <entry>ECC byte 1</entry>
 810 <entry>Error correction code byte 1</entry>
 811 </row>
 812 <row>
 813 <entry>0x02</entry>
 814 <entry>ECC byte 2</entry>
 815 <entry>Error correction code byte 2</entry>
 816 </row>
 817 <row>
 818 <entry>0x03</entry>
 819 <entry>Autoplace 0</entry>
 820 <entry></entry>
 821 </row>
 822 <row>
 823 <entry>0x04</entry>
 824 <entry>Autoplace 1</entry>
 825 <entry></entry>
 826 </row>
 827 <row>
 828 <entry>0x05</entry>
 829 <entry>Bad block marker</entry>
 830 <entry>If any bit in this byte is zero, then this block is bad.
 831 This applies only to the first page in a block. In the remaining
 832 pages this byte is reserved</entry>
 833 </row>
 834 <row>
 835 <entry>0x06</entry>
 836 <entry>Autoplace 2</entry>
 837 <entry></entry>
 838 </row>
 839 <row>
 840 <entry>0x07</entry>
 841 <entry>Autoplace 3</entry>
 842 <entry></entry>
 843 </row>
 844 </tbody></tgroup></informaltable>
 845                 </sect2>
 846                 <sect2 id="pagesize_512">
 847                         <title>512 byte pagesize</title>
 848 <informaltable><tgroup cols="3"><tbody>
 849 <row>
 850 <entry>Offset</entry>
 851 <entry>Content</entry>
 852 <entry>Comment</entry>
 853 </row>
 854 <row>
 855 <entry>0x00</entry>
 856 <entry>ECC byte 0</entry>
 857 <entry>Error correction code byte 0 of the lower 256 Byte data in
 858 this page</entry>
 859 </row>
 860 <row>
 861 <entry>0x01</entry>
 862 <entry>ECC byte 1</entry>
 863 <entry>Error correction code byte 1 of the lower 256 Bytes of data
 864 in this page</entry>
 865 </row>
 866 <row>
 867 <entry>0x02</entry>
 868 <entry>ECC byte 2</entry>
 869 <entry>Error correction code byte 2 of the lower 256 Bytes of data
 870 in this page</entry>
 871 </row>
 872 <row>
 873 <entry>0x03</entry>
 874 <entry>ECC byte 3</entry>
 875 <entry>Error correction code byte 0 of the upper 256 Bytes of data
 876 in this page</entry>
 877 </row>
 878 <row>
 879 <entry>0x04</entry>
 880 <entry>reserved</entry>
 881 <entry>reserved</entry>
 882 </row>
 883 <row>
 884 <entry>0x05</entry>
 885 <entry>Bad block marker</entry>
 886 <entry>If any bit in this byte is zero, then this block is bad.
 887 This applies only to the first page in a block. In the remaining
 888 pages this byte is reserved</entry>
 889 </row>
 890 <row>
 891 <entry>0x06</entry>
 892 <entry>ECC byte 4</entry>
 893 <entry>Error correction code byte 1 of the upper 256 Bytes of data
 894 in this page</entry>
 895 </row>
 896 <row>
 897 <entry>0x07</entry>
 898 <entry>ECC byte 5</entry>
 899 <entry>Error correction code byte 2 of the upper 256 Bytes of data
 900 in this page</entry>
 901 </row>
 902 <row>
 903 <entry>0x08 - 0x0F</entry>
 904 <entry>Autoplace 0 - 7</entry>
 905 <entry></entry>
 906 </row>
 907 </tbody></tgroup></informaltable>
 908                 </sect2>
 909                 <sect2 id="pagesize_2048">
 910                         <title>2048 byte pagesize</title>
 911 <informaltable><tgroup cols="3"><tbody>
 912 <row>
 913 <entry>Offset</entry>
 914 <entry>Content</entry>
 915 <entry>Comment</entry>
 916 </row>
 917 <row>
 918 <entry>0x00</entry>
 919 <entry>Bad block marker</entry>
 920 <entry>If any bit in this byte is zero, then this block is bad.
 921 This applies only to the first page in a block. In the remaining
 922 pages this byte is reserved</entry>
 923 </row>
 924 <row>
 925 <entry>0x01</entry>
 926 <entry>Reserved</entry>
 927 <entry>Reserved</entry>
 928 </row>
 929 <row>
 930 <entry>0x02-0x27</entry>
 931 <entry>Autoplace 0 - 37</entry>
 932 <entry></entry>
 933 </row>
 934 <row>
 935 <entry>0x28</entry>
 936 <entry>ECC byte 0</entry>
 937 <entry>Error correction code byte 0 of the first 256 Byte data in
 938 this page</entry>
 939 </row>
 940 <row>
 941 <entry>0x29</entry>
 942 <entry>ECC byte 1</entry>
 943 <entry>Error correction code byte 1 of the first 256 Bytes of data
 944 in this page</entry>
 945 </row>
 946 <row>
 947 <entry>0x2A</entry>
 948 <entry>ECC byte 2</entry>
 949 <entry>Error correction code byte 2 of the first 256 Bytes data in
 950 this page</entry>
 951 </row>
 952 <row>
 953 <entry>0x2B</entry>
 954 <entry>ECC byte 3</entry>
 955 <entry>Error correction code byte 0 of the second 256 Bytes of data
 956 in this page</entry>
 957 </row>
 958 <row>
 959 <entry>0x2C</entry>
 960 <entry>ECC byte 4</entry>
 961 <entry>Error correction code byte 1 of the second 256 Bytes of data
 962 in this page</entry>
 963 </row>
 964 <row>
 965 <entry>0x2D</entry>
 966 <entry>ECC byte 5</entry>
 967 <entry>Error correction code byte 2 of the second 256 Bytes of data
 968 in this page</entry>
 969 </row>
 970 <row>
 971 <entry>0x2E</entry>
 972 <entry>ECC byte 6</entry>
 973 <entry>Error correction code byte 0 of the third 256 Bytes of data
 974 in this page</entry>
 975 </row>
 976 <row>
 977 <entry>0x2F</entry>
 978 <entry>ECC byte 7</entry>
 979 <entry>Error correction code byte 1 of the third 256 Bytes of data
 980 in this page</entry>
 981 </row>
 982 <row>
 983 <entry>0x30</entry>
 984 <entry>ECC byte 8</entry>
 985 <entry>Error correction code byte 2 of the third 256 Bytes of data
 986 in this page</entry>
 987 </row>
 988 <row>
 989 <entry>0x31</entry>
 990 <entry>ECC byte 9</entry>
 991 <entry>Error correction code byte 0 of the fourth 256 Bytes of data
 992 in this page</entry>
 993 </row>
 994 <row>
 995 <entry>0x32</entry>
 996 <entry>ECC byte 10</entry>
 997 <entry>Error correction code byte 1 of the fourth 256 Bytes of data
 998 in this page</entry>
 999 </row>
1000 <row>
1001 <entry>0x33</entry>
1002 <entry>ECC byte 11</entry>
1003 <entry>Error correction code byte 2 of the fourth 256 Bytes of data
1004 in this page</entry>
1005 </row>
1006 <row>
1007 <entry>0x34</entry>
1008 <entry>ECC byte 12</entry>
1009 <entry>Error correction code byte 0 of the fifth 256 Bytes of data
1010 in this page</entry>
1011 </row>
1012 <row>
1013 <entry>0x35</entry>
1014 <entry>ECC byte 13</entry>
1015 <entry>Error correction code byte 1 of the fifth 256 Bytes of data
1016 in this page</entry>
1017 </row>
1018 <row>
1019 <entry>0x36</entry>
1020 <entry>ECC byte 14</entry>
1021 <entry>Error correction code byte 2 of the fifth 256 Bytes of data
1022 in this page</entry>
1023 </row>
1024 <row>
1025 <entry>0x37</entry>
1026 <entry>ECC byte 15</entry>
1027 <entry>Error correction code byte 0 of the sixt 256 Bytes of data
1028 in this page</entry>
1029 </row>
1030 <row>
1031 <entry>0x38</entry>
1032 <entry>ECC byte 16</entry>
1033 <entry>Error correction code byte 1 of the sixt 256 Bytes of data
1034 in this page</entry>
1035 </row>
1036 <row>
1037 <entry>0x39</entry>
1038 <entry>ECC byte 17</entry>
1039 <entry>Error correction code byte 2 of the sixt 256 Bytes of data
1040 in this page</entry>
1041 </row>
1042 <row>
1043 <entry>0x3A</entry>
1044 <entry>ECC byte 18</entry>
1045 <entry>Error correction code byte 0 of the seventh 256 Bytes of
1046 data in this page</entry>
1047 </row>
1048 <row>
1049 <entry>0x3B</entry>
1050 <entry>ECC byte 19</entry>
1051 <entry>Error correction code byte 1 of the seventh 256 Bytes of
1052 data in this page</entry>
1053 </row>
1054 <row>
1055 <entry>0x3C</entry>
1056 <entry>ECC byte 20</entry>
1057 <entry>Error correction code byte 2 of the seventh 256 Bytes of
1058 data in this page</entry>
1059 </row>
1060 <row>
1061 <entry>0x3D</entry>
1062 <entry>ECC byte 21</entry>
1063 <entry>Error correction code byte 0 of the eigth 256 Bytes of data
1064 in this page</entry>
1065 </row>
1066 <row>
1067 <entry>0x3E</entry>
1068 <entry>ECC byte 22</entry>
1069 <entry>Error correction code byte 1 of the eigth 256 Bytes of data
1070 in this page</entry>
1071 </row>
1072 <row>
1073 <entry>0x3F</entry>
1074 <entry>ECC byte 23</entry>
1075 <entry>Error correction code byte 2 of the eigth 256 Bytes of data
1076 in this page</entry>
1077 </row>
1078 </tbody></tgroup></informaltable>
1079                 </sect2>
1080         </sect1>
1081   </chapter>
1082
1083   <chapter id="filesystems">
1084         <title>Filesystem support</title>
1085         <para>
1086                 The NAND driver provides all neccecary functions for a
1087                 filesystem via the MTD interface.
1088         </para>
1089         <para>
1090                 Filesystems must be aware of the NAND pecularities and
1091                 restrictions. One major restrictions of NAND Flash is, that you cannot
1092                 write as often as you want to a page. The consecutive writes to a page,
1093                 before erasing it again, are restricted to 1-3 writes, depending on the
1094                 manufacturers specifications. This applies similar to the spare area.
1095         </para>
1096         <para>
1097                 Therefor NAND aware filesystems must either write in page size chunks
1098                 or hold a writebuffer to collect smaller writes until they sum up to
1099                 pagesize. Available NAND aware filesystems: JFFS2, YAFFS.
1100         </para>
1101         <para>
1102                 The spare area usage to store filesystem data is controlled by
1103                 the spare area placement functionality which is described in one
1104                 of the earlier chapters.
1105         </para>
1106   </chapter>
1107   <chapter id="tools">
1108         <title>Tools</title>
1109         <para>
1110                 The MTD project provides a couple of helpful tools to handle NAND Flash.
1111                 <itemizedlist>
1112                 <listitem><para>flasherase, flasheraseall: Erase and format FLASH partitions</para></listitem>
1113                 <listitem><para>nandwrite: write filesystem images to NAND FLASH</para></listitem>
1114                 <listitem><para>nanddump: dump the contents of a NAND FLASH partitions</para></listitem>
1115                 </itemizedlist>
1116         </para>
1117         <para>
1118                 These tools are aware of the NAND restrictions. Please use those tools
1119                 instead of complaining about errors which are caused by non NAND aware
1120                 access methods.
1121         </para>
1122   </chapter>
1123
1124   <chapter id="defines">
1125      <title>Constants</title>
1126      <para>
1127      This chapter describes the constants which might be relevant for a driver developer.
1128      </para>
1129      <sect1 id="Chip_option_constants">
1130         <title>Chip option constants</title>
1131         <sect2 id="Constants_for_chip_id_table">
1132                 <title>Constants for chip id table</title>
1133                 <para>
1134                 These constants are defined in nand.h. They are ored together to describe
1135                 the chip functionality.
1136                 <programlisting>
1137 /* Chip can not auto increment pages */
1138 #define NAND_NO_AUTOINCR        0x00000001
1139 /* Buswitdh is 16 bit */
1140 #define NAND_BUSWIDTH_16        0x00000002
1141 /* Device supports partial programming without padding */
1142 #define NAND_NO_PADDING         0x00000004
1143 /* Chip has cache program function */
1144 #define NAND_CACHEPRG           0x00000008
1145 /* Chip has copy back function */
1146 #define NAND_COPYBACK           0x00000010
1147 /* AND Chip which has 4 banks and a confusing page / block
1148  * assignment. See Renesas datasheet for further information */
1149 #define NAND_IS_AND             0x00000020
1150 /* Chip has a array of 4 pages which can be read without
1151  * additional ready /busy waits */
1152 #define NAND_4PAGE_ARRAY        0x00000040
1153                 </programlisting>
1154                 </para>
1155         </sect2>
1156         <sect2 id="Constants_for_runtime_options">
1157                 <title>Constants for runtime options</title>
1158                 <para>
1159                 These constants are defined in nand.h. They are ored together to describe
1160                 the functionality.
1161                 <programlisting>
1162 /* Use a flash based bad block table. This option is parsed by the
1163  * default bad block table function (nand_default_bbt). */
1164 #define NAND_USE_FLASH_BBT      0x00010000
1165 /* The hw ecc generator provides a syndrome instead a ecc value on read
1166  * This can only work if we have the ecc bytes directly behind the
1167  * data bytes. Applies for DOC and AG-AND Renesas HW Reed Solomon generators */
1168 #define NAND_HWECC_SYNDROME     0x00020000
1169                 </programlisting>
1170                 </para>
1171         </sect2>
1172      </sect1>
1173
1174      <sect1 id="EEC_selection_constants">
1175         <title>ECC selection constants</title>
1176         <para>
1177         Use these constants to select the ECC algorithm.
1178         <programlisting>
1179 /* No ECC. Usage is not recommended ! */
1180 #define NAND_ECC_NONE           0
1181 /* Software ECC 3 byte ECC per 256 Byte data */
1182 #define NAND_ECC_SOFT           1
1183 /* Hardware ECC 3 byte ECC per 256 Byte data */
1184 #define NAND_ECC_HW3_256        2
1185 /* Hardware ECC 3 byte ECC per 512 Byte data */
1186 #define NAND_ECC_HW3_512        3
1187 /* Hardware ECC 6 byte ECC per 512 Byte data */
1188 #define NAND_ECC_HW6_512        4
1189 /* Hardware ECC 6 byte ECC per 512 Byte data */
1190 #define NAND_ECC_HW8_512        6
1191         </programlisting>
1192         </para>
1193      </sect1>
1194
1195      <sect1 id="Hardware_control_related_constants">
1196         <title>Hardware control related constants</title>
1197         <para>
1198         These constants describe the requested hardware access function when
1199         the boardspecific hardware control function is called
1200         <programlisting>
1201 /* Select the chip by setting nCE to low */
1202 #define NAND_CTL_SETNCE         1
1203 /* Deselect the chip by setting nCE to high */
1204 #define NAND_CTL_CLRNCE         2
1205 /* Select the command latch by setting CLE to high */
1206 #define NAND_CTL_SETCLE         3
1207 /* Deselect the command latch by setting CLE to low */
1208 #define NAND_CTL_CLRCLE         4
1209 /* Select the address latch by setting ALE to high */
1210 #define NAND_CTL_SETALE         5
1211 /* Deselect the address latch by setting ALE to low */
1212 #define NAND_CTL_CLRALE         6
1213 /* Set write protection by setting WP to high. Not used! */
1214 #define NAND_CTL_SETWP          7
1215 /* Clear write protection by setting WP to low. Not used! */
1216 #define NAND_CTL_CLRWP          8
1217         </programlisting>
1218         </para>
1219      </sect1>
1220
1221      <sect1 id="Bad_block_table_constants">
1222         <title>Bad block table related constants</title>
1223         <para>
1224         These constants describe the options used for bad block
1225         table descriptors.
1226         <programlisting>
1227 /* Options for the bad block table descriptors */
1228
1229 /* The number of bits used per block in the bbt on the device */
1230 #define NAND_BBT_NRBITS_MSK     0x0000000F
1231 #define NAND_BBT_1BIT           0x00000001
1232 #define NAND_BBT_2BIT           0x00000002
1233 #define NAND_BBT_4BIT           0x00000004
1234 #define NAND_BBT_8BIT           0x00000008
1235 /* The bad block table is in the last good block of the device */
1236 #define NAND_BBT_LASTBLOCK      0x00000010
1237 /* The bbt is at the given page, else we must scan for the bbt */
1238 #define NAND_BBT_ABSPAGE        0x00000020
1239 /* The bbt is at the given page, else we must scan for the bbt */
1240 #define NAND_BBT_SEARCH         0x00000040
1241 /* bbt is stored per chip on multichip devices */
1242 #define NAND_BBT_PERCHIP        0x00000080
1243 /* bbt has a version counter at offset veroffs */
1244 #define NAND_BBT_VERSION        0x00000100
1245 /* Create a bbt if none axists */
1246 #define NAND_BBT_CREATE         0x00000200
1247 /* Search good / bad pattern through all pages of a block */
1248 #define NAND_BBT_SCANALLPAGES   0x00000400
1249 /* Scan block empty during good / bad block scan */
1250 #define NAND_BBT_SCANEMPTY      0x00000800
1251 /* Write bbt if neccecary */
1252 #define NAND_BBT_WRITE          0x00001000
1253 /* Read and write back block contents when writing bbt */
1254 #define NAND_BBT_SAVECONTENT    0x00002000
1255         </programlisting>
1256         </para>
1257      </sect1>
1258
1259   </chapter>
1260
1261   <chapter id="structs">
1262      <title>Structures</title>
1263      <para>
1264      This chapter contains the autogenerated documentation of the structures which are
1265      used in the NAND driver and might be relevant for a driver developer. Each
1266      struct member has a short description which is marked with an [XXX] identifier.
1267      See the chapter "Documentation hints" for an explanation.
1268      </para>
1269 !Iinclude/linux/mtd/nand.h
1270   </chapter>
1271
1272   <chapter id="pubfunctions">
1273      <title>Public Functions Provided</title>
1274      <para>
1275      This chapter contains the autogenerated documentation of the NAND kernel API functions
1276       which are exported. Each function has a short description which is marked with an [XXX] identifier.
1277      See the chapter "Documentation hints" for an explanation.
1278      </para>
1279 !Edrivers/mtd/nand/nand_base.c
1280 !Edrivers/mtd/nand/nand_bbt.c
1281 !Edrivers/mtd/nand/nand_ecc.c
1282   </chapter>
1283
1284   <chapter id="intfunctions">
1285      <title>Internal Functions Provided</title>
1286      <para>
1287      This chapter contains the autogenerated documentation of the NAND driver internal functions.
1288      Each function has a short description which is marked with an [XXX] identifier.
1289      See the chapter "Documentation hints" for an explanation.
1290      The functions marked with [DEFAULT] might be relevant for a board driver developer.
1291      </para>
1292 !Idrivers/mtd/nand/nand_base.c
1293 !Idrivers/mtd/nand/nand_bbt.c
1294 <!-- No internal functions for kernel-doc:
1295 X!Idrivers/mtd/nand/nand_ecc.c
1296 -->
1297   </chapter>
1298
1299   <chapter id="credits">
1300      <title>Credits</title>
1301         <para>
1302                 The following people have contributed to the NAND driver:
1303                 <orderedlist>
1304                         <listitem><para>Steven J. Hill<email>sjhill@realitydiluted.com</email></para></listitem>
1305                         <listitem><para>David Woodhouse<email>dwmw2@infradead.org</email></para></listitem>
1306                         <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem>
1307                 </orderedlist>
1308                 A lot of users have provided bugfixes, improvements and helping hands for testing.
1309                 Thanks a lot.
1310         </para>
1311         <para>
1312                 The following people have contributed to this document:
1313                 <orderedlist>
1314                         <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem>
1315                 </orderedlist>
1316         </para>
1317   </chapter>
1318 </book>