linux/drivers/i2c/algos/i2c-algo-bit.c
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   1/* -------------------------------------------------------------------------
   2 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
   3 * -------------------------------------------------------------------------
   4 *   Copyright (C) 1995-2000 Simon G. Vogl
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15 * ------------------------------------------------------------------------- */
  16
  17/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
  18   <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de> */
  19
  20#include <linux/kernel.h>
  21#include <linux/module.h>
  22#include <linux/delay.h>
  23#include <linux/errno.h>
  24#include <linux/sched.h>
  25#include <linux/i2c.h>
  26#include <linux/i2c-algo-bit.h>
  27
  28
  29/* ----- global defines ----------------------------------------------- */
  30
  31#ifdef DEBUG
  32#define bit_dbg(level, dev, format, args...) \
  33        do { \
  34                if (i2c_debug >= level) \
  35                        dev_dbg(dev, format, ##args); \
  36        } while (0)
  37#else
  38#define bit_dbg(level, dev, format, args...) \
  39        do {} while (0)
  40#endif /* DEBUG */
  41
  42/* ----- global variables --------------------------------------------- */
  43
  44static int bit_test;    /* see if the line-setting functions work       */
  45module_param(bit_test, int, S_IRUGO);
  46MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
  47
  48#ifdef DEBUG
  49static int i2c_debug = 1;
  50module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
  51MODULE_PARM_DESC(i2c_debug,
  52                 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
  53#endif
  54
  55/* --- setting states on the bus with the right timing: --------------- */
  56
  57#define setsda(adap, val)       adap->setsda(adap->data, val)
  58#define setscl(adap, val)       adap->setscl(adap->data, val)
  59#define getsda(adap)            adap->getsda(adap->data)
  60#define getscl(adap)            adap->getscl(adap->data)
  61
  62static inline void sdalo(struct i2c_algo_bit_data *adap)
  63{
  64        setsda(adap, 0);
  65        udelay((adap->udelay + 1) / 2);
  66}
  67
  68static inline void sdahi(struct i2c_algo_bit_data *adap)
  69{
  70        setsda(adap, 1);
  71        udelay((adap->udelay + 1) / 2);
  72}
  73
  74static inline void scllo(struct i2c_algo_bit_data *adap)
  75{
  76        setscl(adap, 0);
  77        udelay(adap->udelay / 2);
  78}
  79
  80/*
  81 * Raise scl line, and do checking for delays. This is necessary for slower
  82 * devices.
  83 */
  84static int sclhi(struct i2c_algo_bit_data *adap)
  85{
  86        unsigned long start;
  87
  88        setscl(adap, 1);
  89
  90        /* Not all adapters have scl sense line... */
  91        if (!adap->getscl)
  92                goto done;
  93
  94        start = jiffies;
  95        while (!getscl(adap)) {
  96                /* This hw knows how to read the clock line, so we wait
  97                 * until it actually gets high.  This is safer as some
  98                 * chips may hold it low ("clock stretching") while they
  99                 * are processing data internally.
 100                 */
 101                if (time_after(jiffies, start + adap->timeout)) {
 102                        /* Test one last time, as we may have been preempted
 103                         * between last check and timeout test.
 104                         */
 105                        if (getscl(adap))
 106                                break;
 107                        return -ETIMEDOUT;
 108                }
 109                cpu_relax();
 110        }
 111#ifdef DEBUG
 112        if (jiffies != start && i2c_debug >= 3)
 113                pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
 114                         "high\n", jiffies - start);
 115#endif
 116
 117done:
 118        udelay(adap->udelay);
 119        return 0;
 120}
 121
 122
 123/* --- other auxiliary functions -------------------------------------- */
 124static void i2c_start(struct i2c_algo_bit_data *adap)
 125{
 126        /* assert: scl, sda are high */
 127        setsda(adap, 0);
 128        udelay(adap->udelay);
 129        scllo(adap);
 130}
 131
 132static void i2c_repstart(struct i2c_algo_bit_data *adap)
 133{
 134        /* assert: scl is low */
 135        sdahi(adap);
 136        sclhi(adap);
 137        setsda(adap, 0);
 138        udelay(adap->udelay);
 139        scllo(adap);
 140}
 141
 142
 143static void i2c_stop(struct i2c_algo_bit_data *adap)
 144{
 145        /* assert: scl is low */
 146        sdalo(adap);
 147        sclhi(adap);
 148        setsda(adap, 1);
 149        udelay(adap->udelay);
 150}
 151
 152
 153
 154/* send a byte without start cond., look for arbitration,
 155   check ackn. from slave */
 156/* returns:
 157 * 1 if the device acknowledged
 158 * 0 if the device did not ack
 159 * -ETIMEDOUT if an error occurred (while raising the scl line)
 160 */
 161static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
 162{
 163        int i;
 164        int sb;
 165        int ack;
 166        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 167
 168        /* assert: scl is low */
 169        for (i = 7; i >= 0; i--) {
 170                sb = (c >> i) & 1;
 171                setsda(adap, sb);
 172                udelay((adap->udelay + 1) / 2);
 173                if (sclhi(adap) < 0) { /* timed out */
 174                        bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 175                                "timeout at bit #%d\n", (int)c, i);
 176                        return -ETIMEDOUT;
 177                }
 178                /* FIXME do arbitration here:
 179                 * if (sb && !getsda(adap)) -> ouch! Get out of here.
 180                 *
 181                 * Report a unique code, so higher level code can retry
 182                 * the whole (combined) message and *NOT* issue STOP.
 183                 */
 184                scllo(adap);
 185        }
 186        sdahi(adap);
 187        if (sclhi(adap) < 0) { /* timeout */
 188                bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 189                        "timeout at ack\n", (int)c);
 190                return -ETIMEDOUT;
 191        }
 192
 193        /* read ack: SDA should be pulled down by slave, or it may
 194         * NAK (usually to report problems with the data we wrote).
 195         */
 196        ack = !getsda(adap);    /* ack: sda is pulled low -> success */
 197        bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 198                ack ? "A" : "NA");
 199
 200        scllo(adap);
 201        return ack;
 202        /* assert: scl is low (sda undef) */
 203}
 204
 205
 206static int i2c_inb(struct i2c_adapter *i2c_adap)
 207{
 208        /* read byte via i2c port, without start/stop sequence  */
 209        /* acknowledge is sent in i2c_read.                     */
 210        int i;
 211        unsigned char indata = 0;
 212        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 213
 214        /* assert: scl is low */
 215        sdahi(adap);
 216        for (i = 0; i < 8; i++) {
 217                if (sclhi(adap) < 0) { /* timeout */
 218                        bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 219                                "#%d\n", 7 - i);
 220                        return -ETIMEDOUT;
 221                }
 222                indata *= 2;
 223                if (getsda(adap))
 224                        indata |= 0x01;
 225                setscl(adap, 0);
 226                udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 227        }
 228        /* assert: scl is low */
 229        return indata;
 230}
 231
 232/*
 233 * Sanity check for the adapter hardware - check the reaction of
 234 * the bus lines only if it seems to be idle.
 235 */
 236static int test_bus(struct i2c_adapter *i2c_adap)
 237{
 238        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 239        const char *name = i2c_adap->name;
 240        int scl, sda, ret;
 241
 242        if (adap->pre_xfer) {
 243                ret = adap->pre_xfer(i2c_adap);
 244                if (ret < 0)
 245                        return -ENODEV;
 246        }
 247
 248        if (adap->getscl == NULL)
 249                pr_info("%s: Testing SDA only, SCL is not readable\n", name);
 250
 251        sda = getsda(adap);
 252        scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 253        if (!scl || !sda) {
 254                printk(KERN_WARNING
 255                       "%s: bus seems to be busy (scl=%d, sda=%d)\n",
 256                       name, scl, sda);
 257                goto bailout;
 258        }
 259
 260        sdalo(adap);
 261        sda = getsda(adap);
 262        scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 263        if (sda) {
 264                printk(KERN_WARNING "%s: SDA stuck high!\n", name);
 265                goto bailout;
 266        }
 267        if (!scl) {
 268                printk(KERN_WARNING "%s: SCL unexpected low "
 269                       "while pulling SDA low!\n", name);
 270                goto bailout;
 271        }
 272
 273        sdahi(adap);
 274        sda = getsda(adap);
 275        scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 276        if (!sda) {
 277                printk(KERN_WARNING "%s: SDA stuck low!\n", name);
 278                goto bailout;
 279        }
 280        if (!scl) {
 281                printk(KERN_WARNING "%s: SCL unexpected low "
 282                       "while pulling SDA high!\n", name);
 283                goto bailout;
 284        }
 285
 286        scllo(adap);
 287        sda = getsda(adap);
 288        scl = (adap->getscl == NULL) ? 0 : getscl(adap);
 289        if (scl) {
 290                printk(KERN_WARNING "%s: SCL stuck high!\n", name);
 291                goto bailout;
 292        }
 293        if (!sda) {
 294                printk(KERN_WARNING "%s: SDA unexpected low "
 295                       "while pulling SCL low!\n", name);
 296                goto bailout;
 297        }
 298
 299        sclhi(adap);
 300        sda = getsda(adap);
 301        scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 302        if (!scl) {
 303                printk(KERN_WARNING "%s: SCL stuck low!\n", name);
 304                goto bailout;
 305        }
 306        if (!sda) {
 307                printk(KERN_WARNING "%s: SDA unexpected low "
 308                       "while pulling SCL high!\n", name);
 309                goto bailout;
 310        }
 311
 312        if (adap->post_xfer)
 313                adap->post_xfer(i2c_adap);
 314
 315        pr_info("%s: Test OK\n", name);
 316        return 0;
 317bailout:
 318        sdahi(adap);
 319        sclhi(adap);
 320
 321        if (adap->post_xfer)
 322                adap->post_xfer(i2c_adap);
 323
 324        return -ENODEV;
 325}
 326
 327/* ----- Utility functions
 328 */
 329
 330/* try_address tries to contact a chip for a number of
 331 * times before it gives up.
 332 * return values:
 333 * 1 chip answered
 334 * 0 chip did not answer
 335 * -x transmission error
 336 */
 337static int try_address(struct i2c_adapter *i2c_adap,
 338                       unsigned char addr, int retries)
 339{
 340        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 341        int i, ret = 0;
 342
 343        for (i = 0; i <= retries; i++) {
 344                ret = i2c_outb(i2c_adap, addr);
 345                if (ret == 1 || i == retries)
 346                        break;
 347                bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 348                i2c_stop(adap);
 349                udelay(adap->udelay);
 350                yield();
 351                bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 352                i2c_start(adap);
 353        }
 354        if (i && ret)
 355                bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
 356                        "0x%02x: %s\n", i + 1,
 357                        addr & 1 ? "read from" : "write to", addr >> 1,
 358                        ret == 1 ? "success" : "failed, timeout?");
 359        return ret;
 360}
 361
 362static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 363{
 364        const unsigned char *temp = msg->buf;
 365        int count = msg->len;
 366        unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 367        int retval;
 368        int wrcount = 0;
 369
 370        while (count > 0) {
 371                retval = i2c_outb(i2c_adap, *temp);
 372
 373                /* OK/ACK; or ignored NAK */
 374                if ((retval > 0) || (nak_ok && (retval == 0))) {
 375                        count--;
 376                        temp++;
 377                        wrcount++;
 378
 379                /* A slave NAKing the master means the slave didn't like
 380                 * something about the data it saw.  For example, maybe
 381                 * the SMBus PEC was wrong.
 382                 */
 383                } else if (retval == 0) {
 384                        dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
 385                        return -EIO;
 386
 387                /* Timeout; or (someday) lost arbitration
 388                 *
 389                 * FIXME Lost ARB implies retrying the transaction from
 390                 * the first message, after the "winning" master issues
 391                 * its STOP.  As a rule, upper layer code has no reason
 392                 * to know or care about this ... it is *NOT* an error.
 393                 */
 394                } else {
 395                        dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
 396                                        retval);
 397                        return retval;
 398                }
 399        }
 400        return wrcount;
 401}
 402
 403static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 404{
 405        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 406
 407        /* assert: sda is high */
 408        if (is_ack)             /* send ack */
 409                setsda(adap, 0);
 410        udelay((adap->udelay + 1) / 2);
 411        if (sclhi(adap) < 0) {  /* timeout */
 412                dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 413                return -ETIMEDOUT;
 414        }
 415        scllo(adap);
 416        return 0;
 417}
 418
 419static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 420{
 421        int inval;
 422        int rdcount = 0;        /* counts bytes read */
 423        unsigned char *temp = msg->buf;
 424        int count = msg->len;
 425        const unsigned flags = msg->flags;
 426
 427        while (count > 0) {
 428                inval = i2c_inb(i2c_adap);
 429                if (inval >= 0) {
 430                        *temp = inval;
 431                        rdcount++;
 432                } else {   /* read timed out */
 433                        break;
 434                }
 435
 436                temp++;
 437                count--;
 438
 439                /* Some SMBus transactions require that we receive the
 440                   transaction length as the first read byte. */
 441                if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 442                        if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 443                                if (!(flags & I2C_M_NO_RD_ACK))
 444                                        acknak(i2c_adap, 0);
 445                                dev_err(&i2c_adap->dev, "readbytes: invalid "
 446                                        "block length (%d)\n", inval);
 447                                return -EPROTO;
 448                        }
 449                        /* The original count value accounts for the extra
 450                           bytes, that is, either 1 for a regular transaction,
 451                           or 2 for a PEC transaction. */
 452                        count += inval;
 453                        msg->len += inval;
 454                }
 455
 456                bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 457                        inval,
 458                        (flags & I2C_M_NO_RD_ACK)
 459                                ? "(no ack/nak)"
 460                                : (count ? "A" : "NA"));
 461
 462                if (!(flags & I2C_M_NO_RD_ACK)) {
 463                        inval = acknak(i2c_adap, count);
 464                        if (inval < 0)
 465                                return inval;
 466                }
 467        }
 468        return rdcount;
 469}
 470
 471/* doAddress initiates the transfer by generating the start condition (in
 472 * try_address) and transmits the address in the necessary format to handle
 473 * reads, writes as well as 10bit-addresses.
 474 * returns:
 475 *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 476 * -x an error occurred (like: -ENXIO if the device did not answer, or
 477 *      -ETIMEDOUT, for example if the lines are stuck...)
 478 */
 479static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 480{
 481        unsigned short flags = msg->flags;
 482        unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 483        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 484
 485        unsigned char addr;
 486        int ret, retries;
 487
 488        retries = nak_ok ? 0 : i2c_adap->retries;
 489
 490        if (flags & I2C_M_TEN) {
 491                /* a ten bit address */
 492                addr = 0xf0 | ((msg->addr >> 7) & 0x06);
 493                bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 494                /* try extended address code...*/
 495                ret = try_address(i2c_adap, addr, retries);
 496                if ((ret != 1) && !nak_ok)  {
 497                        dev_err(&i2c_adap->dev,
 498                                "died at extended address code\n");
 499                        return -ENXIO;
 500                }
 501                /* the remaining 8 bit address */
 502                ret = i2c_outb(i2c_adap, msg->addr & 0xff);
 503                if ((ret != 1) && !nak_ok) {
 504                        /* the chip did not ack / xmission error occurred */
 505                        dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 506                        return -ENXIO;
 507                }
 508                if (flags & I2C_M_RD) {
 509                        bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 510                                "start condition\n");
 511                        i2c_repstart(adap);
 512                        /* okay, now switch into reading mode */
 513                        addr |= 0x01;
 514                        ret = try_address(i2c_adap, addr, retries);
 515                        if ((ret != 1) && !nak_ok) {
 516                                dev_err(&i2c_adap->dev,
 517                                        "died at repeated address code\n");
 518                                return -EIO;
 519                        }
 520                }
 521        } else {                /* normal 7bit address  */
 522                addr = msg->addr << 1;
 523                if (flags & I2C_M_RD)
 524                        addr |= 1;
 525                if (flags & I2C_M_REV_DIR_ADDR)
 526                        addr ^= 1;
 527                ret = try_address(i2c_adap, addr, retries);
 528                if ((ret != 1) && !nak_ok)
 529                        return -ENXIO;
 530        }
 531
 532        return 0;
 533}
 534
 535static int bit_xfer(struct i2c_adapter *i2c_adap,
 536                    struct i2c_msg msgs[], int num)
 537{
 538        struct i2c_msg *pmsg;
 539        struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 540        int i, ret;
 541        unsigned short nak_ok;
 542
 543        if (adap->pre_xfer) {
 544                ret = adap->pre_xfer(i2c_adap);
 545                if (ret < 0)
 546                        return ret;
 547        }
 548
 549        bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 550        i2c_start(adap);
 551        for (i = 0; i < num; i++) {
 552                pmsg = &msgs[i];
 553                nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 554                if (!(pmsg->flags & I2C_M_NOSTART)) {
 555                        if (i) {
 556                                bit_dbg(3, &i2c_adap->dev, "emitting "
 557                                        "repeated start condition\n");
 558                                i2c_repstart(adap);
 559                        }
 560                        ret = bit_doAddress(i2c_adap, pmsg);
 561                        if ((ret != 0) && !nak_ok) {
 562                                bit_dbg(1, &i2c_adap->dev, "NAK from "
 563                                        "device addr 0x%02x msg #%d\n",
 564                                        msgs[i].addr, i);
 565                                goto bailout;
 566                        }
 567                }
 568                if (pmsg->flags & I2C_M_RD) {
 569                        /* read bytes into buffer*/
 570                        ret = readbytes(i2c_adap, pmsg);
 571                        if (ret >= 1)
 572                                bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 573                                        ret, ret == 1 ? "" : "s");
 574                        if (ret < pmsg->len) {
 575                                if (ret >= 0)
 576                                        ret = -EIO;
 577                                goto bailout;
 578                        }
 579                } else {
 580                        /* write bytes from buffer */
 581                        ret = sendbytes(i2c_adap, pmsg);
 582                        if (ret >= 1)
 583                                bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 584                                        ret, ret == 1 ? "" : "s");
 585                        if (ret < pmsg->len) {
 586                                if (ret >= 0)
 587                                        ret = -EIO;
 588                                goto bailout;
 589                        }
 590                }
 591        }
 592        ret = i;
 593
 594bailout:
 595        bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 596        i2c_stop(adap);
 597
 598        if (adap->post_xfer)
 599                adap->post_xfer(i2c_adap);
 600        return ret;
 601}
 602
 603static u32 bit_func(struct i2c_adapter *adap)
 604{
 605        return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
 606               I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 607               I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 608               I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 609}
 610
 611
 612/* -----exported algorithm data: -------------------------------------  */
 613
 614const struct i2c_algorithm i2c_bit_algo = {
 615        .master_xfer    = bit_xfer,
 616        .functionality  = bit_func,
 617};
 618EXPORT_SYMBOL(i2c_bit_algo);
 619
 620static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
 621        .flags = I2C_AQ_NO_CLK_STRETCH,
 622};
 623
 624/*
 625 * registering functions to load algorithms at runtime
 626 */
 627static int __i2c_bit_add_bus(struct i2c_adapter *adap,
 628                             int (*add_adapter)(struct i2c_adapter *))
 629{
 630        struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 631        int ret;
 632
 633        if (bit_test) {
 634                ret = test_bus(adap);
 635                if (bit_test >= 2 && ret < 0)
 636                        return -ENODEV;
 637        }
 638
 639        /* register new adapter to i2c module... */
 640        adap->algo = &i2c_bit_algo;
 641        adap->retries = 3;
 642        if (bit_adap->getscl == NULL)
 643                adap->quirks = &i2c_bit_quirk_no_clk_stretch;
 644
 645        ret = add_adapter(adap);
 646        if (ret < 0)
 647                return ret;
 648
 649        /* Complain if SCL can't be read */
 650        if (bit_adap->getscl == NULL) {
 651                dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
 652                dev_warn(&adap->dev, "Bus may be unreliable\n");
 653        }
 654        return 0;
 655}
 656
 657int i2c_bit_add_bus(struct i2c_adapter *adap)
 658{
 659        return __i2c_bit_add_bus(adap, i2c_add_adapter);
 660}
 661EXPORT_SYMBOL(i2c_bit_add_bus);
 662
 663int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 664{
 665        return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
 666}
 667EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 668
 669MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 670MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 671MODULE_LICENSE("GPL");
 672