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., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  * ------------------------------------------------------------------------- */
  20
  21 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
  22    <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/delay.h>
  27 #include <linux/init.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, bool, 0);
  51 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is 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                 cond_resched();
 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 "%s: bus seems to be busy\n", name);
 260                 goto bailout;
 261         }
 262
 263         sdalo(adap);
 264         sda = getsda(adap);
 265         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 266         if (sda) {
 267                 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
 268                 goto bailout;
 269         }
 270         if (!scl) {
 271                 printk(KERN_WARNING "%s: SCL unexpected low "
 272                        "while pulling SDA low!\n", name);
 273                 goto bailout;
 274         }
 275
 276         sdahi(adap);
 277         sda = getsda(adap);
 278         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 279         if (!sda) {
 280                 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
 281                 goto bailout;
 282         }
 283         if (!scl) {
 284                 printk(KERN_WARNING "%s: SCL unexpected low "
 285                        "while pulling SDA high!\n", name);
 286                 goto bailout;
 287         }
 288
 289         scllo(adap);
 290         sda = getsda(adap);
 291         scl = (adap->getscl == NULL) ? 0 : getscl(adap);
 292         if (scl) {
 293                 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
 294                 goto bailout;
 295         }
 296         if (!sda) {
 297                 printk(KERN_WARNING "%s: SDA unexpected low "
 298                        "while pulling SCL low!\n", name);
 299                 goto bailout;
 300         }
 301
 302         sclhi(adap);
 303         sda = getsda(adap);
 304         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 305         if (!scl) {
 306                 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
 307                 goto bailout;
 308         }
 309         if (!sda) {
 310                 printk(KERN_WARNING "%s: SDA unexpected low "
 311                        "while pulling SCL high!\n", name);
 312                 goto bailout;
 313         }
 314
 315         if (adap->post_xfer)
 316                 adap->post_xfer(i2c_adap);
 317
 318         pr_info("%s: Test OK\n", name);
 319         return 0;
 320 bailout:
 321         sdahi(adap);
 322         sclhi(adap);
 323
 324         if (adap->post_xfer)
 325                 adap->post_xfer(i2c_adap);
 326
 327         return -ENODEV;
 328 }
 329
 330 /* ----- Utility functions
 331  */
 332
 333 /* try_address tries to contact a chip for a number of
 334  * times before it gives up.
 335  * return values:
 336  * 1 chip answered
 337  * 0 chip did not answer
 338  * -x transmission error
 339  */
 340 static int try_address(struct i2c_adapter *i2c_adap,
 341                        unsigned char addr, int retries)
 342 {
 343         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 344         int i, ret = 0;
 345
 346         for (i = 0; i <= retries; i++) {
 347                 ret = i2c_outb(i2c_adap, addr);
 348                 if (ret == 1 || i == retries)
 349                         break;
 350                 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 351                 i2c_stop(adap);
 352                 udelay(adap->udelay);
 353                 yield();
 354                 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 355                 i2c_start(adap);
 356         }
 357         if (i && ret)
 358                 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
 359                         "0x%02x: %s\n", i + 1,
 360                         addr & 1 ? "read from" : "write to", addr >> 1,
 361                         ret == 1 ? "success" : "failed, timeout?");
 362         return ret;
 363 }
 364
 365 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 366 {
 367         const unsigned char *temp = msg->buf;
 368         int count = msg->len;
 369         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 370         int retval;
 371         int wrcount = 0;
 372
 373         while (count > 0) {
 374                 retval = i2c_outb(i2c_adap, *temp);
 375
 376                 /* OK/ACK; or ignored NAK */
 377                 if ((retval > 0) || (nak_ok && (retval == 0))) {
 378                         count--;
 379                         temp++;
 380                         wrcount++;
 381
 382                 /* A slave NAKing the master means the slave didn't like
 383                  * something about the data it saw.  For example, maybe
 384                  * the SMBus PEC was wrong.
 385                  */
 386                 } else if (retval == 0) {
 387                         dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
 388                         return -EIO;
 389
 390                 /* Timeout; or (someday) lost arbitration
 391                  *
 392                  * FIXME Lost ARB implies retrying the transaction from
 393                  * the first message, after the "winning" master issues
 394                  * its STOP.  As a rule, upper layer code has no reason
 395                  * to know or care about this ... it is *NOT* an error.
 396                  */
 397                 } else {
 398                         dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
 399                                         retval);
 400                         return retval;
 401                 }
 402         }
 403         return wrcount;
 404 }
 405
 406 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 407 {
 408         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 409
 410         /* assert: sda is high */
 411         if (is_ack)             /* send ack */
 412                 setsda(adap, 0);
 413         udelay((adap->udelay + 1) / 2);
 414         if (sclhi(adap) < 0) {  /* timeout */
 415                 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 416                 return -ETIMEDOUT;
 417         }
 418         scllo(adap);
 419         return 0;
 420 }
 421
 422 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 423 {
 424         int inval;
 425         int rdcount = 0;        /* counts bytes read */
 426         unsigned char *temp = msg->buf;
 427         int count = msg->len;
 428         const unsigned flags = msg->flags;
 429
 430         while (count > 0) {
 431                 inval = i2c_inb(i2c_adap);
 432                 if (inval >= 0) {
 433                         *temp = inval;
 434                         rdcount++;
 435                 } else {   /* read timed out */
 436                         break;
 437                 }
 438
 439                 temp++;
 440                 count--;
 441
 442                 /* Some SMBus transactions require that we receive the
 443                    transaction length as the first read byte. */
 444                 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 445                         if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 446                                 if (!(flags & I2C_M_NO_RD_ACK))
 447                                         acknak(i2c_adap, 0);
 448                                 dev_err(&i2c_adap->dev, "readbytes: invalid "
 449                                         "block length (%d)\n", inval);
 450                                 return -EREMOTEIO;
 451                         }
 452                         /* The original count value accounts for the extra
 453                            bytes, that is, either 1 for a regular transaction,
 454                            or 2 for a PEC transaction. */
 455                         count += inval;
 456                         msg->len += inval;
 457                 }
 458
 459                 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 460                         inval,
 461                         (flags & I2C_M_NO_RD_ACK)
 462                                 ? "(no ack/nak)"
 463                                 : (count ? "A" : "NA"));
 464
 465                 if (!(flags & I2C_M_NO_RD_ACK)) {
 466                         inval = acknak(i2c_adap, count);
 467                         if (inval < 0)
 468                                 return inval;
 469                 }
 470         }
 471         return rdcount;
 472 }
 473
 474 /* doAddress initiates the transfer by generating the start condition (in
 475  * try_address) and transmits the address in the necessary format to handle
 476  * reads, writes as well as 10bit-addresses.
 477  * returns:
 478  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 479  * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 480  *      -ETIMEDOUT, for example if the lines are stuck...)
 481  */
 482 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 483 {
 484         unsigned short flags = msg->flags;
 485         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 486         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 487
 488         unsigned char addr;
 489         int ret, retries;
 490
 491         retries = nak_ok ? 0 : i2c_adap->retries;
 492
 493         if (flags & I2C_M_TEN) {
 494                 /* a ten bit address */
 495                 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
 496                 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 497                 /* try extended address code...*/
 498                 ret = try_address(i2c_adap, addr, retries);
 499                 if ((ret != 1) && !nak_ok)  {
 500                         dev_err(&i2c_adap->dev,
 501                                 "died at extended address code\n");
 502                         return -EREMOTEIO;
 503                 }
 504                 /* the remaining 8 bit address */
 505                 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
 506                 if ((ret != 1) && !nak_ok) {
 507                         /* the chip did not ack / xmission error occurred */
 508                         dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 509                         return -EREMOTEIO;
 510                 }
 511                 if (flags & I2C_M_RD) {
 512                         bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 513                                 "start condition\n");
 514                         i2c_repstart(adap);
 515                         /* okay, now switch into reading mode */
 516                         addr |= 0x01;
 517                         ret = try_address(i2c_adap, addr, retries);
 518                         if ((ret != 1) && !nak_ok) {
 519                                 dev_err(&i2c_adap->dev,
 520                                         "died at repeated address code\n");
 521                                 return -EREMOTEIO;
 522                         }
 523                 }
 524         } else {                /* normal 7bit address  */
 525                 addr = msg->addr << 1;
 526                 if (flags & I2C_M_RD)
 527                         addr |= 1;
 528                 if (flags & I2C_M_REV_DIR_ADDR)
 529                         addr ^= 1;
 530                 ret = try_address(i2c_adap, addr, retries);
 531                 if ((ret != 1) && !nak_ok)
 532                         return -ENXIO;
 533         }
 534
 535         return 0;
 536 }
 537
 538 static int bit_xfer(struct i2c_adapter *i2c_adap,
 539                     struct i2c_msg msgs[], int num)
 540 {
 541         struct i2c_msg *pmsg;
 542         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 543         int i, ret;
 544         unsigned short nak_ok;
 545
 546         if (adap->pre_xfer) {
 547                 ret = adap->pre_xfer(i2c_adap);
 548                 if (ret < 0)
 549                         return ret;
 550         }
 551
 552         bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 553         i2c_start(adap);
 554         for (i = 0; i < num; i++) {
 555                 pmsg = &msgs[i];
 556                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 557                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 558                         if (i) {
 559                                 bit_dbg(3, &i2c_adap->dev, "emitting "
 560                                         "repeated start condition\n");
 561                                 i2c_repstart(adap);
 562                         }
 563                         ret = bit_doAddress(i2c_adap, pmsg);
 564                         if ((ret != 0) && !nak_ok) {
 565                                 bit_dbg(1, &i2c_adap->dev, "NAK from "
 566                                         "device addr 0x%02x msg #%d\n",
 567                                         msgs[i].addr, i);
 568                                 goto bailout;
 569                         }
 570                 }
 571                 if (pmsg->flags & I2C_M_RD) {
 572                         /* read bytes into buffer*/
 573                         ret = readbytes(i2c_adap, pmsg);
 574                         if (ret >= 1)
 575                                 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 576                                         ret, ret == 1 ? "" : "s");
 577                         if (ret < pmsg->len) {
 578                                 if (ret >= 0)
 579                                         ret = -EREMOTEIO;
 580                                 goto bailout;
 581                         }
 582                 } else {
 583                         /* write bytes from buffer */
 584                         ret = sendbytes(i2c_adap, pmsg);
 585                         if (ret >= 1)
 586                                 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 587                                         ret, ret == 1 ? "" : "s");
 588                         if (ret < pmsg->len) {
 589                                 if (ret >= 0)
 590                                         ret = -EREMOTEIO;
 591                                 goto bailout;
 592                         }
 593                 }
 594         }
 595         ret = i;
 596
 597 bailout:
 598         bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 599         i2c_stop(adap);
 600
 601         if (adap->post_xfer)
 602                 adap->post_xfer(i2c_adap);
 603         return ret;
 604 }
 605
 606 static u32 bit_func(struct i2c_adapter *adap)
 607 {
 608         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 609                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 610                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 611                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 612 }
 613
 614
 615 /* -----exported algorithm data: -------------------------------------  */
 616
 617 static const struct i2c_algorithm i2c_bit_algo = {
 618         .master_xfer    = bit_xfer,
 619         .functionality  = bit_func,
 620 };
 621
 622 /*
 623  * registering functions to load algorithms at runtime
 624  */
 625 static int __i2c_bit_add_bus(struct i2c_adapter *adap,
 626                              int (*add_adapter)(struct i2c_adapter *))
 627 {
 628         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 629         int ret;
 630
 631         if (bit_test) {
 632                 ret = test_bus(adap);
 633                 if (ret < 0)
 634                         return -ENODEV;
 635         }
 636
 637         /* register new adapter to i2c module... */
 638         adap->algo = &i2c_bit_algo;
 639         adap->retries = 3;
 640
 641         ret = add_adapter(adap);
 642         if (ret < 0)
 643                 return ret;
 644
 645         /* Complain if SCL can't be read */
 646         if (bit_adap->getscl == NULL) {
 647                 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
 648                 dev_warn(&adap->dev, "Bus may be unreliable\n");
 649         }
 650         return 0;
 651 }
 652
 653 int i2c_bit_add_bus(struct i2c_adapter *adap)
 654 {
 655         return __i2c_bit_add_bus(adap, i2c_add_adapter);
 656 }
 657 EXPORT_SYMBOL(i2c_bit_add_bus);
 658
 659 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 660 {
 661         return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
 662 }
 663 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 664
 665 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 666 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 667 MODULE_LICENSE("GPL");