drivers/i2c/algos/i2c-algo-bit.c

   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     You should have received a copy of the GNU General Public License
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  19     MA 02110-1301 USA.
  20  * ------------------------------------------------------------------------- */
  21
  22 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
  23    <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
  24
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/delay.h>
  28 #include <linux/init.h>
  29 #include <linux/errno.h>
  30 #include <linux/sched.h>
  31 #include <linux/i2c.h>
  32 #include <linux/i2c-algo-bit.h>
  33
  34
  35 /* ----- global defines ----------------------------------------------- */
  36
  37 #ifdef DEBUG
  38 #define bit_dbg(level, dev, format, args...) \
  39         do { \
  40                 if (i2c_debug >= level) \
  41                         dev_dbg(dev, format, ##args); \
  42         } while (0)
  43 #else
  44 #define bit_dbg(level, dev, format, args...) \
  45         do {} while (0)
  46 #endif /* DEBUG */
  47
  48 /* ----- global variables --------------------------------------------- */
  49
  50 static int bit_test;    /* see if the line-setting functions work       */
  51 module_param(bit_test, int, S_IRUGO);
  52 MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
  53
  54 #ifdef DEBUG
  55 static int i2c_debug = 1;
  56 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
  57 MODULE_PARM_DESC(i2c_debug,
  58                  "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
  59 #endif
  60
  61 /* --- setting states on the bus with the right timing: --------------- */
  62
  63 #define setsda(adap, val)       adap->setsda(adap->data, val)
  64 #define setscl(adap, val)       adap->setscl(adap->data, val)
  65 #define getsda(adap)            adap->getsda(adap->data)
  66 #define getscl(adap)            adap->getscl(adap->data)
  67
  68 static inline void sdalo(struct i2c_algo_bit_data *adap)
  69 {
  70         setsda(adap, 0);
  71         udelay((adap->udelay + 1) / 2);
  72 }
  73
  74 static inline void sdahi(struct i2c_algo_bit_data *adap)
  75 {
  76         setsda(adap, 1);
  77         udelay((adap->udelay + 1) / 2);
  78 }
  79
  80 static inline void scllo(struct i2c_algo_bit_data *adap)
  81 {
  82         setscl(adap, 0);
  83         udelay(adap->udelay / 2);
  84 }
  85
  86 /*
  87  * Raise scl line, and do checking for delays. This is necessary for slower
  88  * devices.
  89  */
  90 static int sclhi(struct i2c_algo_bit_data *adap)
  91 {
  92         unsigned long start;
  93
  94         setscl(adap, 1);
  95
  96         /* Not all adapters have scl sense line... */
  97         if (!adap->getscl)
  98                 goto done;
  99
 100         start = jiffies;
 101         while (!getscl(adap)) {
 102                 /* This hw knows how to read the clock line, so we wait
 103                  * until it actually gets high.  This is safer as some
 104                  * chips may hold it low ("clock stretching") while they
 105                  * are processing data internally.
 106                  */
 107                 if (time_after(jiffies, start + adap->timeout)) {
 108                         /* Test one last time, as we may have been preempted
 109                          * between last check and timeout test.
 110                          */
 111                         if (getscl(adap))
 112                                 break;
 113                         return -ETIMEDOUT;
 114                 }
 115                 cpu_relax();
 116         }
 117 #ifdef DEBUG
 118         if (jiffies != start && i2c_debug >= 3)
 119                 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
 120                          "high\n", jiffies - start);
 121 #endif
 122
 123 done:
 124         udelay(adap->udelay);
 125         return 0;
 126 }
 127
 128
 129 /* --- other auxiliary functions -------------------------------------- */
 130 static void i2c_start(struct i2c_algo_bit_data *adap)
 131 {
 132         /* assert: scl, sda are high */
 133         setsda(adap, 0);
 134         udelay(adap->udelay);
 135         scllo(adap);
 136 }
 137
 138 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 139 {
 140         /* assert: scl is low */
 141         sdahi(adap);
 142         sclhi(adap);
 143         setsda(adap, 0);
 144         udelay(adap->udelay);
 145         scllo(adap);
 146 }
 147
 148
 149 static void i2c_stop(struct i2c_algo_bit_data *adap)
 150 {
 151         /* assert: scl is low */
 152         sdalo(adap);
 153         sclhi(adap);
 154         setsda(adap, 1);
 155         udelay(adap->udelay);
 156 }
 157
 158
 159
 160 /* send a byte without start cond., look for arbitration,
 161    check ackn. from slave */
 162 /* returns:
 163  * 1 if the device acknowledged
 164  * 0 if the device did not ack
 165  * -ETIMEDOUT if an error occurred (while raising the scl line)
 166  */
 167 static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
 168 {
 169         int i;
 170         int sb;
 171         int ack;
 172         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 173
 174         /* assert: scl is low */
 175         for (i = 7; i >= 0; i--) {
 176                 sb = (c >> i) & 1;
 177                 setsda(adap, sb);
 178                 udelay((adap->udelay + 1) / 2);
 179                 if (sclhi(adap) < 0) { /* timed out */
 180                         bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 181                                 "timeout at bit #%d\n", (int)c, i);
 182                         return -ETIMEDOUT;
 183                 }
 184                 /* FIXME do arbitration here:
 185                  * if (sb && !getsda(adap)) -> ouch! Get out of here.
 186                  *
 187                  * Report a unique code, so higher level code can retry
 188                  * the whole (combined) message and *NOT* issue STOP.
 189                  */
 190                 scllo(adap);
 191         }
 192         sdahi(adap);
 193         if (sclhi(adap) < 0) { /* timeout */
 194                 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 195                         "timeout at ack\n", (int)c);
 196                 return -ETIMEDOUT;
 197         }
 198
 199         /* read ack: SDA should be pulled down by slave, or it may
 200          * NAK (usually to report problems with the data we wrote).
 201          */
 202         ack = !getsda(adap);    /* ack: sda is pulled low -> success */
 203         bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 204                 ack ? "A" : "NA");
 205
 206         scllo(adap);
 207         return ack;
 208         /* assert: scl is low (sda undef) */
 209 }
 210
 211
 212 static int i2c_inb(struct i2c_adapter *i2c_adap)
 213 {
 214         /* read byte via i2c port, without start/stop sequence  */
 215         /* acknowledge is sent in i2c_read.                     */
 216         int i;
 217         unsigned char indata = 0;
 218         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 219
 220         /* assert: scl is low */
 221         sdahi(adap);
 222         for (i = 0; i < 8; i++) {
 223                 if (sclhi(adap) < 0) { /* timeout */
 224                         bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 225                                 "#%d\n", 7 - i);
 226                         return -ETIMEDOUT;
 227                 }
 228                 indata *= 2;
 229                 if (getsda(adap))
 230                         indata |= 0x01;
 231                 setscl(adap, 0);
 232                 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 233         }
 234         /* assert: scl is low */
 235         return indata;
 236 }
 237
 238 /*
 239  * Sanity check for the adapter hardware - check the reaction of
 240  * the bus lines only if it seems to be idle.
 241  */
 242 static int test_bus(struct i2c_adapter *i2c_adap)
 243 {
 244         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 245         const char *name = i2c_adap->name;
 246         int scl, sda, ret;
 247
 248         if (adap->pre_xfer) {
 249                 ret = adap->pre_xfer(i2c_adap);
 250                 if (ret < 0)
 251                         return -ENODEV;
 252         }
 253
 254         if (adap->getscl == NULL)
 255                 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
 256
 257         sda = getsda(adap);
 258         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 259         if (!scl || !sda) {
 260                 printk(KERN_WARNING
 261                        "%s: bus seems to be busy (scl=%d, sda=%d)\n",
 262                        name, scl, sda);
 263                 goto bailout;
 264         }
 265
 266         sdalo(adap);
 267         sda = getsda(adap);
 268         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 269         if (sda) {
 270                 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
 271                 goto bailout;
 272         }
 273         if (!scl) {
 274                 printk(KERN_WARNING "%s: SCL unexpected low "
 275                        "while pulling SDA low!\n", name);
 276                 goto bailout;
 277         }
 278
 279         sdahi(adap);
 280         sda = getsda(adap);
 281         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 282         if (!sda) {
 283                 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
 284                 goto bailout;
 285         }
 286         if (!scl) {
 287                 printk(KERN_WARNING "%s: SCL unexpected low "
 288                        "while pulling SDA high!\n", name);
 289                 goto bailout;
 290         }
 291
 292         scllo(adap);
 293         sda = getsda(adap);
 294         scl = (adap->getscl == NULL) ? 0 : getscl(adap);
 295         if (scl) {
 296                 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
 297                 goto bailout;
 298         }
 299         if (!sda) {
 300                 printk(KERN_WARNING "%s: SDA unexpected low "
 301                        "while pulling SCL low!\n", name);
 302                 goto bailout;
 303         }
 304
 305         sclhi(adap);
 306         sda = getsda(adap);
 307         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 308         if (!scl) {
 309                 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
 310                 goto bailout;
 311         }
 312         if (!sda) {
 313                 printk(KERN_WARNING "%s: SDA unexpected low "
 314                        "while pulling SCL high!\n", name);
 315                 goto bailout;
 316         }
 317
 318         if (adap->post_xfer)
 319                 adap->post_xfer(i2c_adap);
 320
 321         pr_info("%s: Test OK\n", name);
 322         return 0;
 323 bailout:
 324         sdahi(adap);
 325         sclhi(adap);
 326
 327         if (adap->post_xfer)
 328                 adap->post_xfer(i2c_adap);
 329
 330         return -ENODEV;
 331 }
 332
 333 /* ----- Utility functions
 334  */
 335
 336 /* try_address tries to contact a chip for a number of
 337  * times before it gives up.
 338  * return values:
 339  * 1 chip answered
 340  * 0 chip did not answer
 341  * -x transmission error
 342  */
 343 static int try_address(struct i2c_adapter *i2c_adap,
 344                        unsigned char addr, int retries)
 345 {
 346         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 347         int i, ret = 0;
 348
 349         for (i = 0; i <= retries; i++) {
 350                 ret = i2c_outb(i2c_adap, addr);
 351                 if (ret == 1 || i == retries)
 352                         break;
 353                 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 354                 i2c_stop(adap);
 355                 udelay(adap->udelay);
 356                 yield();
 357                 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 358                 i2c_start(adap);
 359         }
 360         if (i && ret)
 361                 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
 362                         "0x%02x: %s\n", i + 1,
 363                         addr & 1 ? "read from" : "write to", addr >> 1,
 364                         ret == 1 ? "success" : "failed, timeout?");
 365         return ret;
 366 }
 367
 368 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 369 {
 370         const unsigned char *temp = msg->buf;
 371         int count = msg->len;
 372         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 373         int retval;
 374         int wrcount = 0;
 375
 376         while (count > 0) {
 377                 retval = i2c_outb(i2c_adap, *temp);
 378
 379                 /* OK/ACK; or ignored NAK */
 380                 if ((retval > 0) || (nak_ok && (retval == 0))) {
 381                         count--;
 382                         temp++;
 383                         wrcount++;
 384
 385                 /* A slave NAKing the master means the slave didn't like
 386                  * something about the data it saw.  For example, maybe
 387                  * the SMBus PEC was wrong.
 388                  */
 389                 } else if (retval == 0) {
 390                         dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
 391                         return -EIO;
 392
 393                 /* Timeout; or (someday) lost arbitration
 394                  *
 395                  * FIXME Lost ARB implies retrying the transaction from
 396                  * the first message, after the "winning" master issues
 397                  * its STOP.  As a rule, upper layer code has no reason
 398                  * to know or care about this ... it is *NOT* an error.
 399                  */
 400                 } else {
 401                         dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
 402                                         retval);
 403                         return retval;
 404                 }
 405         }
 406         return wrcount;
 407 }
 408
 409 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 410 {
 411         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 412
 413         /* assert: sda is high */
 414         if (is_ack)             /* send ack */
 415                 setsda(adap, 0);
 416         udelay((adap->udelay + 1) / 2);
 417         if (sclhi(adap) < 0) {  /* timeout */
 418                 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 419                 return -ETIMEDOUT;
 420         }
 421         scllo(adap);
 422         return 0;
 423 }
 424
 425 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 426 {
 427         int inval;
 428         int rdcount = 0;        /* counts bytes read */
 429         unsigned char *temp = msg->buf;
 430         int count = msg->len;
 431         const unsigned flags = msg->flags;
 432
 433         while (count > 0) {
 434                 inval = i2c_inb(i2c_adap);
 435                 if (inval >= 0) {
 436                         *temp = inval;
 437                         rdcount++;
 438                 } else {   /* read timed out */
 439                         break;
 440                 }
 441
 442                 temp++;
 443                 count--;
 444
 445                 /* Some SMBus transactions require that we receive the
 446                    transaction length as the first read byte. */
 447                 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 448                         if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 449                                 if (!(flags & I2C_M_NO_RD_ACK))
 450                                         acknak(i2c_adap, 0);
 451                                 dev_err(&i2c_adap->dev, "readbytes: invalid "
 452                                         "block length (%d)\n", inval);
 453                                 return -EPROTO;
 454                         }
 455                         /* The original count value accounts for the extra
 456                            bytes, that is, either 1 for a regular transaction,
 457                            or 2 for a PEC transaction. */
 458                         count += inval;
 459                         msg->len += inval;
 460                 }
 461
 462                 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 463                         inval,
 464                         (flags & I2C_M_NO_RD_ACK)
 465                                 ? "(no ack/nak)"
 466                                 : (count ? "A" : "NA"));
 467
 468                 if (!(flags & I2C_M_NO_RD_ACK)) {
 469                         inval = acknak(i2c_adap, count);
 470                         if (inval < 0)
 471                                 return inval;
 472                 }
 473         }
 474         return rdcount;
 475 }
 476
 477 /* doAddress initiates the transfer by generating the start condition (in
 478  * try_address) and transmits the address in the necessary format to handle
 479  * reads, writes as well as 10bit-addresses.
 480  * returns:
 481  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 482  * -x an error occurred (like: -ENXIO if the device did not answer, or
 483  *      -ETIMEDOUT, for example if the lines are stuck...)
 484  */
 485 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 486 {
 487         unsigned short flags = msg->flags;
 488         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 489         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 490
 491         unsigned char addr;
 492         int ret, retries;
 493
 494         retries = nak_ok ? 0 : i2c_adap->retries;
 495
 496         if (flags & I2C_M_TEN) {
 497                 /* a ten bit address */
 498                 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
 499                 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 500                 /* try extended address code...*/
 501                 ret = try_address(i2c_adap, addr, retries);
 502                 if ((ret != 1) && !nak_ok)  {
 503                         dev_err(&i2c_adap->dev,
 504                                 "died at extended address code\n");
 505                         return -ENXIO;
 506                 }
 507                 /* the remaining 8 bit address */
 508                 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
 509                 if ((ret != 1) && !nak_ok) {
 510                         /* the chip did not ack / xmission error occurred */
 511                         dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 512                         return -ENXIO;
 513                 }
 514                 if (flags & I2C_M_RD) {
 515                         bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 516                                 "start condition\n");
 517                         i2c_repstart(adap);
 518                         /* okay, now switch into reading mode */
 519                         addr |= 0x01;
 520                         ret = try_address(i2c_adap, addr, retries);
 521                         if ((ret != 1) && !nak_ok) {
 522                                 dev_err(&i2c_adap->dev,
 523                                         "died at repeated address code\n");
 524                                 return -EIO;
 525                         }
 526                 }
 527         } else {                /* normal 7bit address  */
 528                 addr = msg->addr << 1;
 529                 if (flags & I2C_M_RD)
 530                         addr |= 1;
 531                 if (flags & I2C_M_REV_DIR_ADDR)
 532                         addr ^= 1;
 533                 ret = try_address(i2c_adap, addr, retries);
 534                 if ((ret != 1) && !nak_ok)
 535                         return -ENXIO;
 536         }
 537
 538         return 0;
 539 }
 540
 541 static int bit_xfer(struct i2c_adapter *i2c_adap,
 542                     struct i2c_msg msgs[], int num)
 543 {
 544         struct i2c_msg *pmsg;
 545         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 546         int i, ret;
 547         unsigned short nak_ok;
 548
 549         if (adap->pre_xfer) {
 550                 ret = adap->pre_xfer(i2c_adap);
 551                 if (ret < 0)
 552                         return ret;
 553         }
 554
 555         bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 556         i2c_start(adap);
 557         for (i = 0; i < num; i++) {
 558                 pmsg = &msgs[i];
 559                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 560                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 561                         if (i) {
 562                                 bit_dbg(3, &i2c_adap->dev, "emitting "
 563                                         "repeated start condition\n");
 564                                 i2c_repstart(adap);
 565                         }
 566                         ret = bit_doAddress(i2c_adap, pmsg);
 567                         if ((ret != 0) && !nak_ok) {
 568                                 bit_dbg(1, &i2c_adap->dev, "NAK from "
 569                                         "device addr 0x%02x msg #%d\n",
 570                                         msgs[i].addr, i);
 571                                 goto bailout;
 572                         }
 573                 }
 574                 if (pmsg->flags & I2C_M_RD) {
 575                         /* read bytes into buffer*/
 576                         ret = readbytes(i2c_adap, pmsg);
 577                         if (ret >= 1)
 578                                 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 579                                         ret, ret == 1 ? "" : "s");
 580                         if (ret < pmsg->len) {
 581                                 if (ret >= 0)
 582                                         ret = -EIO;
 583                                 goto bailout;
 584                         }
 585                 } else {
 586                         /* write bytes from buffer */
 587                         ret = sendbytes(i2c_adap, pmsg);
 588                         if (ret >= 1)
 589                                 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 590                                         ret, ret == 1 ? "" : "s");
 591                         if (ret < pmsg->len) {
 592                                 if (ret >= 0)
 593                                         ret = -EIO;
 594                                 goto bailout;
 595                         }
 596                 }
 597         }
 598         ret = i;
 599
 600 bailout:
 601         bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 602         i2c_stop(adap);
 603
 604         if (adap->post_xfer)
 605                 adap->post_xfer(i2c_adap);
 606         return ret;
 607 }
 608
 609 static u32 bit_func(struct i2c_adapter *adap)
 610 {
 611         return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
 612                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 613                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 614                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 615 }
 616
 617
 618 /* -----exported algorithm data: -------------------------------------  */
 619
 620 const struct i2c_algorithm i2c_bit_algo = {
 621         .master_xfer    = bit_xfer,
 622         .functionality  = bit_func,
 623 };
 624 EXPORT_SYMBOL(i2c_bit_algo);
 625
 626 /*
 627  * registering functions to load algorithms at runtime
 628  */
 629 static int __i2c_bit_add_bus(struct i2c_adapter *adap,
 630                              int (*add_adapter)(struct i2c_adapter *))
 631 {
 632         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 633         int ret;
 634
 635         if (bit_test) {
 636                 ret = test_bus(adap);
 637                 if (bit_test >= 2 && ret < 0)
 638                         return -ENODEV;
 639         }
 640
 641         /* register new adapter to i2c module... */
 642         adap->algo = &i2c_bit_algo;
 643         adap->retries = 3;
 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
 657 int i2c_bit_add_bus(struct i2c_adapter *adap)
 658 {
 659         return __i2c_bit_add_bus(adap, i2c_add_adapter);
 660 }
 661 EXPORT_SYMBOL(i2c_bit_add_bus);
 662
 663 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 664 {
 665         return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
 666 }
 667 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 668
 669 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 670 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 671 MODULE_LICENSE("GPL");