Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0+
2 : /*
3 : * i2c-algo-bit.c: i2c driver algorithms for bit-shift adapters
4 : *
5 : * Copyright (C) 1995-2000 Simon G. Vogl
6 : *
7 : * With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
8 : * <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de>
9 : */
10 :
11 : #include <linux/kernel.h>
12 : #include <linux/module.h>
13 : #include <linux/delay.h>
14 : #include <linux/errno.h>
15 : #include <linux/sched.h>
16 : #include <linux/i2c.h>
17 : #include <linux/i2c-algo-bit.h>
18 :
19 :
20 : /* ----- global defines ----------------------------------------------- */
21 :
22 : #ifdef DEBUG
23 : #define bit_dbg(level, dev, format, args...) \
24 : do { \
25 : if (i2c_debug >= level) \
26 : dev_dbg(dev, format, ##args); \
27 : } while (0)
28 : #else
29 : #define bit_dbg(level, dev, format, args...) \
30 : do {} while (0)
31 : #endif /* DEBUG */
32 :
33 : /* ----- global variables --------------------------------------------- */
34 :
35 : static int bit_test; /* see if the line-setting functions work */
36 : module_param(bit_test, int, S_IRUGO);
37 : MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
38 :
39 : #ifdef DEBUG
40 : static int i2c_debug = 1;
41 : module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
42 : MODULE_PARM_DESC(i2c_debug,
43 : "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
44 : #endif
45 :
46 : /* --- setting states on the bus with the right timing: --------------- */
47 :
48 : #define setsda(adap, val) adap->setsda(adap->data, val)
49 : #define setscl(adap, val) adap->setscl(adap->data, val)
50 : #define getsda(adap) adap->getsda(adap->data)
51 : #define getscl(adap) adap->getscl(adap->data)
52 :
53 0 : static inline void sdalo(struct i2c_algo_bit_data *adap)
54 : {
55 0 : setsda(adap, 0);
56 0 : udelay((adap->udelay + 1) / 2);
57 0 : }
58 :
59 0 : static inline void sdahi(struct i2c_algo_bit_data *adap)
60 : {
61 0 : setsda(adap, 1);
62 0 : udelay((adap->udelay + 1) / 2);
63 0 : }
64 :
65 0 : static inline void scllo(struct i2c_algo_bit_data *adap)
66 : {
67 0 : setscl(adap, 0);
68 0 : udelay(adap->udelay / 2);
69 0 : }
70 :
71 : /*
72 : * Raise scl line, and do checking for delays. This is necessary for slower
73 : * devices.
74 : */
75 0 : static int sclhi(struct i2c_algo_bit_data *adap)
76 : {
77 : unsigned long start;
78 :
79 0 : setscl(adap, 1);
80 :
81 : /* Not all adapters have scl sense line... */
82 0 : if (!adap->getscl)
83 : goto done;
84 :
85 0 : start = jiffies;
86 0 : while (!getscl(adap)) {
87 : /* This hw knows how to read the clock line, so we wait
88 : * until it actually gets high. This is safer as some
89 : * chips may hold it low ("clock stretching") while they
90 : * are processing data internally.
91 : */
92 0 : if (time_after(jiffies, start + adap->timeout)) {
93 : /* Test one last time, as we may have been preempted
94 : * between last check and timeout test.
95 : */
96 0 : if (getscl(adap))
97 : break;
98 : return -ETIMEDOUT;
99 : }
100 : cpu_relax();
101 : }
102 : #ifdef DEBUG
103 : if (jiffies != start && i2c_debug >= 3)
104 : pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go high\n",
105 : jiffies - start);
106 : #endif
107 :
108 : done:
109 0 : udelay(adap->udelay);
110 0 : return 0;
111 : }
112 :
113 :
114 : /* --- other auxiliary functions -------------------------------------- */
115 0 : static void i2c_start(struct i2c_algo_bit_data *adap)
116 : {
117 : /* assert: scl, sda are high */
118 0 : setsda(adap, 0);
119 0 : udelay(adap->udelay);
120 0 : scllo(adap);
121 0 : }
122 :
123 0 : static void i2c_repstart(struct i2c_algo_bit_data *adap)
124 : {
125 : /* assert: scl is low */
126 0 : sdahi(adap);
127 0 : sclhi(adap);
128 0 : setsda(adap, 0);
129 0 : udelay(adap->udelay);
130 0 : scllo(adap);
131 0 : }
132 :
133 :
134 0 : static void i2c_stop(struct i2c_algo_bit_data *adap)
135 : {
136 : /* assert: scl is low */
137 0 : sdalo(adap);
138 0 : sclhi(adap);
139 0 : setsda(adap, 1);
140 0 : udelay(adap->udelay);
141 0 : }
142 :
143 :
144 :
145 : /* send a byte without start cond., look for arbitration,
146 : check ackn. from slave */
147 : /* returns:
148 : * 1 if the device acknowledged
149 : * 0 if the device did not ack
150 : * -ETIMEDOUT if an error occurred (while raising the scl line)
151 : */
152 0 : static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
153 : {
154 : int i;
155 : int sb;
156 : int ack;
157 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
158 :
159 : /* assert: scl is low */
160 0 : for (i = 7; i >= 0; i--) {
161 0 : sb = (c >> i) & 1;
162 0 : setsda(adap, sb);
163 0 : udelay((adap->udelay + 1) / 2);
164 0 : if (sclhi(adap) < 0) { /* timed out */
165 : bit_dbg(1, &i2c_adap->dev,
166 : "i2c_outb: 0x%02x, timeout at bit #%d\n",
167 : (int)c, i);
168 : return -ETIMEDOUT;
169 : }
170 : /* FIXME do arbitration here:
171 : * if (sb && !getsda(adap)) -> ouch! Get out of here.
172 : *
173 : * Report a unique code, so higher level code can retry
174 : * the whole (combined) message and *NOT* issue STOP.
175 : */
176 0 : scllo(adap);
177 : }
178 0 : sdahi(adap);
179 0 : if (sclhi(adap) < 0) { /* timeout */
180 : bit_dbg(1, &i2c_adap->dev,
181 : "i2c_outb: 0x%02x, timeout at ack\n", (int)c);
182 : return -ETIMEDOUT;
183 : }
184 :
185 : /* read ack: SDA should be pulled down by slave, or it may
186 : * NAK (usually to report problems with the data we wrote).
187 : */
188 0 : ack = !getsda(adap); /* ack: sda is pulled low -> success */
189 : bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
190 : ack ? "A" : "NA");
191 :
192 0 : scllo(adap);
193 0 : return ack;
194 : /* assert: scl is low (sda undef) */
195 : }
196 :
197 :
198 0 : static int i2c_inb(struct i2c_adapter *i2c_adap)
199 : {
200 : /* read byte via i2c port, without start/stop sequence */
201 : /* acknowledge is sent in i2c_read. */
202 : int i;
203 0 : unsigned char indata = 0;
204 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
205 :
206 : /* assert: scl is low */
207 0 : sdahi(adap);
208 0 : for (i = 0; i < 8; i++) {
209 0 : if (sclhi(adap) < 0) { /* timeout */
210 : bit_dbg(1, &i2c_adap->dev,
211 : "i2c_inb: timeout at bit #%d\n",
212 : 7 - i);
213 : return -ETIMEDOUT;
214 : }
215 0 : indata *= 2;
216 0 : if (getsda(adap))
217 0 : indata |= 0x01;
218 0 : setscl(adap, 0);
219 0 : udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
220 : }
221 : /* assert: scl is low */
222 0 : return indata;
223 : }
224 :
225 : /*
226 : * Sanity check for the adapter hardware - check the reaction of
227 : * the bus lines only if it seems to be idle.
228 : */
229 0 : static int test_bus(struct i2c_adapter *i2c_adap)
230 : {
231 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
232 0 : const char *name = i2c_adap->name;
233 : int scl, sda, ret;
234 :
235 0 : if (adap->pre_xfer) {
236 0 : ret = adap->pre_xfer(i2c_adap);
237 0 : if (ret < 0)
238 : return -ENODEV;
239 : }
240 :
241 0 : if (adap->getscl == NULL)
242 0 : pr_info("%s: Testing SDA only, SCL is not readable\n", name);
243 :
244 0 : sda = getsda(adap);
245 0 : scl = (adap->getscl == NULL) ? 1 : getscl(adap);
246 0 : if (!scl || !sda) {
247 0 : printk(KERN_WARNING
248 : "%s: bus seems to be busy (scl=%d, sda=%d)\n",
249 : name, scl, sda);
250 0 : goto bailout;
251 : }
252 :
253 0 : sdalo(adap);
254 0 : sda = getsda(adap);
255 0 : scl = (adap->getscl == NULL) ? 1 : getscl(adap);
256 0 : if (sda) {
257 0 : printk(KERN_WARNING "%s: SDA stuck high!\n", name);
258 0 : goto bailout;
259 : }
260 0 : if (!scl) {
261 0 : printk(KERN_WARNING
262 : "%s: SCL unexpected low while pulling SDA low!\n",
263 : name);
264 0 : goto bailout;
265 : }
266 :
267 0 : sdahi(adap);
268 0 : sda = getsda(adap);
269 0 : scl = (adap->getscl == NULL) ? 1 : getscl(adap);
270 0 : if (!sda) {
271 0 : printk(KERN_WARNING "%s: SDA stuck low!\n", name);
272 0 : goto bailout;
273 : }
274 0 : if (!scl) {
275 0 : printk(KERN_WARNING
276 : "%s: SCL unexpected low while pulling SDA high!\n",
277 : name);
278 0 : goto bailout;
279 : }
280 :
281 0 : scllo(adap);
282 0 : sda = getsda(adap);
283 0 : scl = (adap->getscl == NULL) ? 0 : getscl(adap);
284 0 : if (scl) {
285 0 : printk(KERN_WARNING "%s: SCL stuck high!\n", name);
286 0 : goto bailout;
287 : }
288 0 : if (!sda) {
289 0 : printk(KERN_WARNING
290 : "%s: SDA unexpected low while pulling SCL low!\n",
291 : name);
292 0 : goto bailout;
293 : }
294 :
295 0 : sclhi(adap);
296 0 : sda = getsda(adap);
297 0 : scl = (adap->getscl == NULL) ? 1 : getscl(adap);
298 0 : if (!scl) {
299 0 : printk(KERN_WARNING "%s: SCL stuck low!\n", name);
300 0 : goto bailout;
301 : }
302 0 : if (!sda) {
303 0 : printk(KERN_WARNING
304 : "%s: SDA unexpected low while pulling SCL high!\n",
305 : name);
306 0 : goto bailout;
307 : }
308 :
309 0 : if (adap->post_xfer)
310 0 : adap->post_xfer(i2c_adap);
311 :
312 0 : pr_info("%s: Test OK\n", name);
313 0 : return 0;
314 : bailout:
315 0 : sdahi(adap);
316 0 : sclhi(adap);
317 :
318 0 : if (adap->post_xfer)
319 0 : adap->post_xfer(i2c_adap);
320 :
321 : return -ENODEV;
322 : }
323 :
324 : /* ----- Utility functions
325 : */
326 :
327 : /* try_address tries to contact a chip for a number of
328 : * times before it gives up.
329 : * return values:
330 : * 1 chip answered
331 : * 0 chip did not answer
332 : * -x transmission error
333 : */
334 0 : static int try_address(struct i2c_adapter *i2c_adap,
335 : unsigned char addr, int retries)
336 : {
337 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
338 0 : int i, ret = 0;
339 :
340 0 : for (i = 0; i <= retries; i++) {
341 0 : ret = i2c_outb(i2c_adap, addr);
342 0 : if (ret == 1 || i == retries)
343 : break;
344 : bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
345 0 : i2c_stop(adap);
346 0 : udelay(adap->udelay);
347 0 : yield();
348 : bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
349 0 : i2c_start(adap);
350 : }
351 : if (i && ret)
352 : bit_dbg(1, &i2c_adap->dev,
353 : "Used %d tries to %s client at 0x%02x: %s\n", i + 1,
354 : addr & 1 ? "read from" : "write to", addr >> 1,
355 : ret == 1 ? "success" : "failed, timeout?");
356 0 : return ret;
357 : }
358 :
359 0 : static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
360 : {
361 0 : const unsigned char *temp = msg->buf;
362 0 : int count = msg->len;
363 0 : unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
364 : int retval;
365 0 : int wrcount = 0;
366 :
367 0 : while (count > 0) {
368 0 : retval = i2c_outb(i2c_adap, *temp);
369 :
370 : /* OK/ACK; or ignored NAK */
371 0 : if ((retval > 0) || (nak_ok && (retval == 0))) {
372 0 : count--;
373 0 : temp++;
374 0 : wrcount++;
375 :
376 : /* A slave NAKing the master means the slave didn't like
377 : * something about the data it saw. For example, maybe
378 : * the SMBus PEC was wrong.
379 : */
380 0 : } else if (retval == 0) {
381 0 : dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
382 : return -EIO;
383 :
384 : /* Timeout; or (someday) lost arbitration
385 : *
386 : * FIXME Lost ARB implies retrying the transaction from
387 : * the first message, after the "winning" master issues
388 : * its STOP. As a rule, upper layer code has no reason
389 : * to know or care about this ... it is *NOT* an error.
390 : */
391 : } else {
392 0 : dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
393 : retval);
394 : return retval;
395 : }
396 : }
397 : return wrcount;
398 : }
399 :
400 0 : static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
401 : {
402 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
403 :
404 : /* assert: sda is high */
405 0 : if (is_ack) /* send ack */
406 0 : setsda(adap, 0);
407 0 : udelay((adap->udelay + 1) / 2);
408 0 : if (sclhi(adap) < 0) { /* timeout */
409 0 : dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
410 0 : return -ETIMEDOUT;
411 : }
412 0 : scllo(adap);
413 0 : return 0;
414 : }
415 :
416 0 : static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
417 : {
418 : int inval;
419 0 : int rdcount = 0; /* counts bytes read */
420 0 : unsigned char *temp = msg->buf;
421 0 : int count = msg->len;
422 0 : const unsigned flags = msg->flags;
423 :
424 0 : while (count > 0) {
425 0 : inval = i2c_inb(i2c_adap);
426 0 : if (inval >= 0) {
427 0 : *temp = inval;
428 0 : rdcount++;
429 : } else { /* read timed out */
430 : break;
431 : }
432 :
433 0 : temp++;
434 0 : count--;
435 :
436 : /* Some SMBus transactions require that we receive the
437 : transaction length as the first read byte. */
438 0 : if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
439 0 : if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
440 0 : if (!(flags & I2C_M_NO_RD_ACK))
441 0 : acknak(i2c_adap, 0);
442 0 : dev_err(&i2c_adap->dev,
443 : "readbytes: invalid block length (%d)\n",
444 : inval);
445 0 : return -EPROTO;
446 : }
447 : /* The original count value accounts for the extra
448 : bytes, that is, either 1 for a regular transaction,
449 : or 2 for a PEC transaction. */
450 0 : count += inval;
451 0 : msg->len += inval;
452 : }
453 :
454 : bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
455 : inval,
456 : (flags & I2C_M_NO_RD_ACK)
457 : ? "(no ack/nak)"
458 : : (count ? "A" : "NA"));
459 :
460 0 : if (!(flags & I2C_M_NO_RD_ACK)) {
461 0 : inval = acknak(i2c_adap, count);
462 0 : if (inval < 0)
463 : return inval;
464 : }
465 : }
466 : return rdcount;
467 : }
468 :
469 : /* doAddress initiates the transfer by generating the start condition (in
470 : * try_address) and transmits the address in the necessary format to handle
471 : * reads, writes as well as 10bit-addresses.
472 : * returns:
473 : * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
474 : * -x an error occurred (like: -ENXIO if the device did not answer, or
475 : * -ETIMEDOUT, for example if the lines are stuck...)
476 : */
477 0 : static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
478 : {
479 0 : unsigned short flags = msg->flags;
480 0 : unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
481 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
482 :
483 : unsigned char addr;
484 : int ret, retries;
485 :
486 0 : retries = nak_ok ? 0 : i2c_adap->retries;
487 :
488 0 : if (flags & I2C_M_TEN) {
489 : /* a ten bit address */
490 0 : addr = 0xf0 | ((msg->addr >> 7) & 0x06);
491 : bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
492 : /* try extended address code...*/
493 0 : ret = try_address(i2c_adap, addr, retries);
494 0 : if ((ret != 1) && !nak_ok) {
495 0 : dev_err(&i2c_adap->dev,
496 : "died at extended address code\n");
497 0 : return -ENXIO;
498 : }
499 : /* the remaining 8 bit address */
500 0 : ret = i2c_outb(i2c_adap, msg->addr & 0xff);
501 0 : if ((ret != 1) && !nak_ok) {
502 : /* the chip did not ack / xmission error occurred */
503 0 : dev_err(&i2c_adap->dev, "died at 2nd address code\n");
504 0 : return -ENXIO;
505 : }
506 0 : if (flags & I2C_M_RD) {
507 : bit_dbg(3, &i2c_adap->dev,
508 : "emitting repeated start condition\n");
509 0 : i2c_repstart(adap);
510 : /* okay, now switch into reading mode */
511 0 : addr |= 0x01;
512 0 : ret = try_address(i2c_adap, addr, retries);
513 0 : if ((ret != 1) && !nak_ok) {
514 0 : dev_err(&i2c_adap->dev,
515 : "died at repeated address code\n");
516 0 : return -EIO;
517 : }
518 : }
519 : } else { /* normal 7bit address */
520 0 : addr = i2c_8bit_addr_from_msg(msg);
521 0 : if (flags & I2C_M_REV_DIR_ADDR)
522 0 : addr ^= 1;
523 0 : ret = try_address(i2c_adap, addr, retries);
524 0 : if ((ret != 1) && !nak_ok)
525 : return -ENXIO;
526 : }
527 :
528 : return 0;
529 : }
530 :
531 0 : static int bit_xfer(struct i2c_adapter *i2c_adap,
532 : struct i2c_msg msgs[], int num)
533 : {
534 : struct i2c_msg *pmsg;
535 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
536 : int i, ret;
537 : unsigned short nak_ok;
538 :
539 0 : if (adap->pre_xfer) {
540 0 : ret = adap->pre_xfer(i2c_adap);
541 0 : if (ret < 0)
542 : return ret;
543 : }
544 :
545 : bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
546 0 : i2c_start(adap);
547 0 : for (i = 0; i < num; i++) {
548 0 : pmsg = &msgs[i];
549 0 : nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
550 0 : if (!(pmsg->flags & I2C_M_NOSTART)) {
551 0 : if (i) {
552 0 : if (msgs[i - 1].flags & I2C_M_STOP) {
553 : bit_dbg(3, &i2c_adap->dev,
554 : "emitting enforced stop/start condition\n");
555 0 : i2c_stop(adap);
556 0 : i2c_start(adap);
557 : } else {
558 : bit_dbg(3, &i2c_adap->dev,
559 : "emitting repeated start condition\n");
560 0 : i2c_repstart(adap);
561 : }
562 : }
563 0 : ret = bit_doAddress(i2c_adap, pmsg);
564 0 : if ((ret != 0) && !nak_ok) {
565 : bit_dbg(1, &i2c_adap->dev,
566 : "NAK from device addr 0x%02x msg #%d\n",
567 : msgs[i].addr, i);
568 : goto bailout;
569 : }
570 : }
571 0 : if (pmsg->flags & I2C_M_RD) {
572 : /* read bytes into buffer*/
573 0 : 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 0 : if (ret < pmsg->len) {
578 0 : if (ret >= 0)
579 0 : ret = -EIO;
580 : goto bailout;
581 : }
582 : } else {
583 : /* write bytes from buffer */
584 0 : 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 0 : if (ret < pmsg->len) {
589 0 : if (ret >= 0)
590 0 : ret = -EIO;
591 : goto bailout;
592 : }
593 : }
594 : }
595 : ret = i;
596 :
597 : bailout:
598 : bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
599 0 : i2c_stop(adap);
600 :
601 0 : if (adap->post_xfer)
602 0 : adap->post_xfer(i2c_adap);
603 : return ret;
604 : }
605 :
606 : /*
607 : * We print a warning when we are not flagged to support atomic transfers but
608 : * will try anyhow. That's what the I2C core would do as well. Sadly, we can't
609 : * modify the algorithm struct at probe time because this struct is exported
610 : * 'const'.
611 : */
612 0 : static int bit_xfer_atomic(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
613 : int num)
614 : {
615 0 : struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
616 :
617 0 : if (!adap->can_do_atomic)
618 0 : dev_warn(&i2c_adap->dev, "not flagged for atomic transfers\n");
619 :
620 0 : return bit_xfer(i2c_adap, msgs, num);
621 : }
622 :
623 0 : static u32 bit_func(struct i2c_adapter *adap)
624 : {
625 0 : return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL_ALL |
626 : I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
627 : }
628 :
629 :
630 : /* -----exported algorithm data: ------------------------------------- */
631 :
632 : const struct i2c_algorithm i2c_bit_algo = {
633 : .master_xfer = bit_xfer,
634 : .master_xfer_atomic = bit_xfer_atomic,
635 : .functionality = bit_func,
636 : };
637 : EXPORT_SYMBOL(i2c_bit_algo);
638 :
639 : static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
640 : .flags = I2C_AQ_NO_CLK_STRETCH,
641 : };
642 :
643 : /*
644 : * registering functions to load algorithms at runtime
645 : */
646 0 : static int __i2c_bit_add_bus(struct i2c_adapter *adap,
647 : int (*add_adapter)(struct i2c_adapter *))
648 : {
649 0 : struct i2c_algo_bit_data *bit_adap = adap->algo_data;
650 : int ret;
651 :
652 0 : if (bit_test) {
653 0 : ret = test_bus(adap);
654 0 : if (bit_test >= 2 && ret < 0)
655 : return -ENODEV;
656 : }
657 :
658 : /* register new adapter to i2c module... */
659 0 : adap->algo = &i2c_bit_algo;
660 0 : adap->retries = 3;
661 0 : if (bit_adap->getscl == NULL)
662 0 : adap->quirks = &i2c_bit_quirk_no_clk_stretch;
663 :
664 : /*
665 : * We tried forcing SCL/SDA to an initial state here. But that caused a
666 : * regression, sadly. Check Bugzilla #200045 for details.
667 : */
668 :
669 0 : ret = add_adapter(adap);
670 0 : if (ret < 0)
671 : return ret;
672 :
673 : /* Complain if SCL can't be read */
674 0 : if (bit_adap->getscl == NULL) {
675 0 : dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
676 0 : dev_warn(&adap->dev, "Bus may be unreliable\n");
677 : }
678 : return 0;
679 : }
680 :
681 0 : int i2c_bit_add_bus(struct i2c_adapter *adap)
682 : {
683 0 : return __i2c_bit_add_bus(adap, i2c_add_adapter);
684 : }
685 : EXPORT_SYMBOL(i2c_bit_add_bus);
686 :
687 0 : int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
688 : {
689 0 : return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
690 : }
691 : EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
692 :
693 : MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
694 : MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
695 : MODULE_LICENSE("GPL");
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