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