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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 
sdalo(struct i2c_algo_bit_data * adap)53 static inline void sdalo(struct i2c_algo_bit_data *adap)
54 {
55 	setsda(adap, 0);
56 	udelay((adap->udelay + 1) / 2);
57 }
58 
sdahi(struct i2c_algo_bit_data * adap)59 static inline void sdahi(struct i2c_algo_bit_data *adap)
60 {
61 	setsda(adap, 1);
62 	udelay((adap->udelay + 1) / 2);
63 }
64 
scllo(struct i2c_algo_bit_data * adap)65 static inline void scllo(struct i2c_algo_bit_data *adap)
66 {
67 	setscl(adap, 0);
68 	udelay(adap->udelay / 2);
69 }
70 
71 /*
72  * Raise scl line, and do checking for delays. This is necessary for slower
73  * devices.
74  */
sclhi(struct i2c_algo_bit_data * adap)75 static int sclhi(struct i2c_algo_bit_data *adap)
76 {
77 	unsigned long start;
78 
79 	setscl(adap, 1);
80 
81 	/* Not all adapters have scl sense line... */
82 	if (!adap->getscl)
83 		goto done;
84 
85 	start = jiffies;
86 	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 		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 			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 	udelay(adap->udelay);
110 	return 0;
111 }
112 
113 
114 /* --- other auxiliary functions --------------------------------------	*/
i2c_start(struct i2c_algo_bit_data * adap)115 static void i2c_start(struct i2c_algo_bit_data *adap)
116 {
117 	/* assert: scl, sda are high */
118 	setsda(adap, 0);
119 	udelay(adap->udelay);
120 	scllo(adap);
121 }
122 
i2c_repstart(struct i2c_algo_bit_data * adap)123 static void i2c_repstart(struct i2c_algo_bit_data *adap)
124 {
125 	/* assert: scl is low */
126 	sdahi(adap);
127 	sclhi(adap);
128 	setsda(adap, 0);
129 	udelay(adap->udelay);
130 	scllo(adap);
131 }
132 
133 
i2c_stop(struct i2c_algo_bit_data * adap)134 static void i2c_stop(struct i2c_algo_bit_data *adap)
135 {
136 	/* assert: scl is low */
137 	sdalo(adap);
138 	sclhi(adap);
139 	setsda(adap, 1);
140 	udelay(adap->udelay);
141 }
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  */
i2c_outb(struct i2c_adapter * i2c_adap,unsigned char c)152 static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
153 {
154 	int i;
155 	int sb;
156 	int ack;
157 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
158 
159 	/* assert: scl is low */
160 	for (i = 7; i >= 0; i--) {
161 		sb = (c >> i) & 1;
162 		setsda(adap, sb);
163 		udelay((adap->udelay + 1) / 2);
164 		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 		scllo(adap);
177 	}
178 	sdahi(adap);
179 	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 	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 	scllo(adap);
193 	return ack;
194 	/* assert: scl is low (sda undef) */
195 }
196 
197 
i2c_inb(struct i2c_adapter * i2c_adap)198 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 	unsigned char indata = 0;
204 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
205 
206 	/* assert: scl is low */
207 	sdahi(adap);
208 	for (i = 0; i < 8; i++) {
209 		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 		indata *= 2;
216 		if (getsda(adap))
217 			indata |= 0x01;
218 		setscl(adap, 0);
219 		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
220 	}
221 	/* assert: scl is low */
222 	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  */
test_bus(struct i2c_adapter * i2c_adap)229 static int test_bus(struct i2c_adapter *i2c_adap)
230 {
231 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
232 	const char *name = i2c_adap->name;
233 	int scl, sda, ret;
234 
235 	if (adap->pre_xfer) {
236 		ret = adap->pre_xfer(i2c_adap);
237 		if (ret < 0)
238 			return -ENODEV;
239 	}
240 
241 	if (adap->getscl == NULL)
242 		pr_info("%s: Testing SDA only, SCL is not readable\n", name);
243 
244 	sda = getsda(adap);
245 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
246 	if (!scl || !sda) {
247 		printk(KERN_WARNING
248 		       "%s: bus seems to be busy (scl=%d, sda=%d)\n",
249 		       name, scl, sda);
250 		goto bailout;
251 	}
252 
253 	sdalo(adap);
254 	sda = getsda(adap);
255 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
256 	if (sda) {
257 		printk(KERN_WARNING "%s: SDA stuck high!\n", name);
258 		goto bailout;
259 	}
260 	if (!scl) {
261 		printk(KERN_WARNING
262 		       "%s: SCL unexpected low while pulling SDA low!\n",
263 		       name);
264 		goto bailout;
265 	}
266 
267 	sdahi(adap);
268 	sda = getsda(adap);
269 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
270 	if (!sda) {
271 		printk(KERN_WARNING "%s: SDA stuck low!\n", name);
272 		goto bailout;
273 	}
274 	if (!scl) {
275 		printk(KERN_WARNING
276 		       "%s: SCL unexpected low while pulling SDA high!\n",
277 		       name);
278 		goto bailout;
279 	}
280 
281 	scllo(adap);
282 	sda = getsda(adap);
283 	scl = (adap->getscl == NULL) ? 0 : getscl(adap);
284 	if (scl) {
285 		printk(KERN_WARNING "%s: SCL stuck high!\n", name);
286 		goto bailout;
287 	}
288 	if (!sda) {
289 		printk(KERN_WARNING
290 		       "%s: SDA unexpected low while pulling SCL low!\n",
291 		       name);
292 		goto bailout;
293 	}
294 
295 	sclhi(adap);
296 	sda = getsda(adap);
297 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
298 	if (!scl) {
299 		printk(KERN_WARNING "%s: SCL stuck low!\n", name);
300 		goto bailout;
301 	}
302 	if (!sda) {
303 		printk(KERN_WARNING
304 		       "%s: SDA unexpected low while pulling SCL high!\n",
305 		       name);
306 		goto bailout;
307 	}
308 
309 	if (adap->post_xfer)
310 		adap->post_xfer(i2c_adap);
311 
312 	pr_info("%s: Test OK\n", name);
313 	return 0;
314 bailout:
315 	sdahi(adap);
316 	sclhi(adap);
317 
318 	if (adap->post_xfer)
319 		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  */
try_address(struct i2c_adapter * i2c_adap,unsigned char addr,int retries)334 static int try_address(struct i2c_adapter *i2c_adap,
335 		       unsigned char addr, int retries)
336 {
337 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
338 	int i, ret = 0;
339 
340 	for (i = 0; i <= retries; i++) {
341 		ret = i2c_outb(i2c_adap, addr);
342 		if (ret == 1 || i == retries)
343 			break;
344 		bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
345 		i2c_stop(adap);
346 		udelay(adap->udelay);
347 		yield();
348 		bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
349 		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 	return ret;
357 }
358 
sendbytes(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)359 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
360 {
361 	const unsigned char *temp = msg->buf;
362 	int count = msg->len;
363 	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
364 	int retval;
365 	int wrcount = 0;
366 
367 	while (count > 0) {
368 		retval = i2c_outb(i2c_adap, *temp);
369 
370 		/* OK/ACK; or ignored NAK */
371 		if ((retval > 0) || (nak_ok && (retval == 0))) {
372 			count--;
373 			temp++;
374 			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 		} else if (retval == 0) {
381 			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 			dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
393 					retval);
394 			return retval;
395 		}
396 	}
397 	return wrcount;
398 }
399 
acknak(struct i2c_adapter * i2c_adap,int is_ack)400 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
401 {
402 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
403 
404 	/* assert: sda is high */
405 	if (is_ack)		/* send ack */
406 		setsda(adap, 0);
407 	udelay((adap->udelay + 1) / 2);
408 	if (sclhi(adap) < 0) {	/* timeout */
409 		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
410 		return -ETIMEDOUT;
411 	}
412 	scllo(adap);
413 	return 0;
414 }
415 
readbytes(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)416 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
417 {
418 	int inval;
419 	int rdcount = 0;	/* counts bytes read */
420 	unsigned char *temp = msg->buf;
421 	int count = msg->len;
422 	const unsigned flags = msg->flags;
423 
424 	while (count > 0) {
425 		inval = i2c_inb(i2c_adap);
426 		if (inval >= 0) {
427 			*temp = inval;
428 			rdcount++;
429 		} else {   /* read timed out */
430 			break;
431 		}
432 
433 		temp++;
434 		count--;
435 
436 		/* Some SMBus transactions require that we receive the
437 		   transaction length as the first read byte. */
438 		if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
439 			if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
440 				if (!(flags & I2C_M_NO_RD_ACK))
441 					acknak(i2c_adap, 0);
442 				dev_err(&i2c_adap->dev,
443 					"readbytes: invalid block length (%d)\n",
444 					inval);
445 				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 			count += inval;
451 			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 		if (!(flags & I2C_M_NO_RD_ACK)) {
461 			inval = acknak(i2c_adap, count);
462 			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  */
bit_doAddress(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)477 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
478 {
479 	unsigned short flags = msg->flags;
480 	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
481 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
482 
483 	unsigned char addr;
484 	int ret, retries;
485 
486 	retries = nak_ok ? 0 : i2c_adap->retries;
487 
488 	if (flags & I2C_M_TEN) {
489 		/* a ten bit address */
490 		addr = 0xf0 | ((msg->addr >> 7) & 0x06);
491 		bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
492 		/* try extended address code...*/
493 		ret = try_address(i2c_adap, addr, retries);
494 		if ((ret != 1) && !nak_ok)  {
495 			dev_err(&i2c_adap->dev,
496 				"died at extended address code\n");
497 			return -ENXIO;
498 		}
499 		/* the remaining 8 bit address */
500 		ret = i2c_outb(i2c_adap, msg->addr & 0xff);
501 		if ((ret != 1) && !nak_ok) {
502 			/* the chip did not ack / xmission error occurred */
503 			dev_err(&i2c_adap->dev, "died at 2nd address code\n");
504 			return -ENXIO;
505 		}
506 		if (flags & I2C_M_RD) {
507 			bit_dbg(3, &i2c_adap->dev,
508 				"emitting repeated start condition\n");
509 			i2c_repstart(adap);
510 			/* okay, now switch into reading mode */
511 			addr |= 0x01;
512 			ret = try_address(i2c_adap, addr, retries);
513 			if ((ret != 1) && !nak_ok) {
514 				dev_err(&i2c_adap->dev,
515 					"died at repeated address code\n");
516 				return -EIO;
517 			}
518 		}
519 	} else {		/* normal 7bit address	*/
520 		addr = i2c_8bit_addr_from_msg(msg);
521 		if (flags & I2C_M_REV_DIR_ADDR)
522 			addr ^= 1;
523 		ret = try_address(i2c_adap, addr, retries);
524 		if ((ret != 1) && !nak_ok)
525 			return -ENXIO;
526 	}
527 
528 	return 0;
529 }
530 
bit_xfer(struct i2c_adapter * i2c_adap,struct i2c_msg msgs[],int num)531 static int bit_xfer(struct i2c_adapter *i2c_adap,
532 		    struct i2c_msg msgs[], int num)
533 {
534 	struct i2c_msg *pmsg;
535 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
536 	int i, ret;
537 	unsigned short nak_ok;
538 
539 	if (adap->pre_xfer) {
540 		ret = adap->pre_xfer(i2c_adap);
541 		if (ret < 0)
542 			return ret;
543 	}
544 
545 	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
546 	i2c_start(adap);
547 	for (i = 0; i < num; i++) {
548 		pmsg = &msgs[i];
549 		nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
550 		if (!(pmsg->flags & I2C_M_NOSTART)) {
551 			if (i) {
552 				if (msgs[i - 1].flags & I2C_M_STOP) {
553 					bit_dbg(3, &i2c_adap->dev,
554 						"emitting enforced stop/start condition\n");
555 					i2c_stop(adap);
556 					i2c_start(adap);
557 				} else {
558 					bit_dbg(3, &i2c_adap->dev,
559 						"emitting repeated start condition\n");
560 					i2c_repstart(adap);
561 				}
562 			}
563 			ret = bit_doAddress(i2c_adap, pmsg);
564 			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 		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 = -EIO;
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 = -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 	i2c_stop(adap);
600 
601 	if (adap->post_xfer)
602 		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  */
bit_xfer_atomic(struct i2c_adapter * i2c_adap,struct i2c_msg msgs[],int num)612 static int bit_xfer_atomic(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
613 			   int num)
614 {
615 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
616 
617 	if (!adap->can_do_atomic)
618 		dev_warn(&i2c_adap->dev, "not flagged for atomic transfers\n");
619 
620 	return bit_xfer(i2c_adap, msgs, num);
621 }
622 
bit_func(struct i2c_adapter * adap)623 static u32 bit_func(struct i2c_adapter *adap)
624 {
625 	return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
626 	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
627 	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
628 	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
629 }
630 
631 
632 /* -----exported algorithm data: -------------------------------------	*/
633 
634 const struct i2c_algorithm i2c_bit_algo = {
635 	.master_xfer = bit_xfer,
636 	.master_xfer_atomic = bit_xfer_atomic,
637 	.functionality = bit_func,
638 };
639 EXPORT_SYMBOL(i2c_bit_algo);
640 
641 static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
642 	.flags = I2C_AQ_NO_CLK_STRETCH,
643 };
644 
645 /*
646  * registering functions to load algorithms at runtime
647  */
__i2c_bit_add_bus(struct i2c_adapter * adap,int (* add_adapter)(struct i2c_adapter *))648 static int __i2c_bit_add_bus(struct i2c_adapter *adap,
649 			     int (*add_adapter)(struct i2c_adapter *))
650 {
651 	struct i2c_algo_bit_data *bit_adap = adap->algo_data;
652 	int ret;
653 
654 	if (bit_test) {
655 		ret = test_bus(adap);
656 		if (bit_test >= 2 && ret < 0)
657 			return -ENODEV;
658 	}
659 
660 	/* register new adapter to i2c module... */
661 	adap->algo = &i2c_bit_algo;
662 	adap->retries = 3;
663 	if (bit_adap->getscl == NULL)
664 		adap->quirks = &i2c_bit_quirk_no_clk_stretch;
665 
666 	/*
667 	 * We tried forcing SCL/SDA to an initial state here. But that caused a
668 	 * regression, sadly. Check Bugzilla #200045 for details.
669 	 */
670 
671 	ret = add_adapter(adap);
672 	if (ret < 0)
673 		return ret;
674 
675 	/* Complain if SCL can't be read */
676 	if (bit_adap->getscl == NULL) {
677 		dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
678 		dev_warn(&adap->dev, "Bus may be unreliable\n");
679 	}
680 	return 0;
681 }
682 
i2c_bit_add_bus(struct i2c_adapter * adap)683 int i2c_bit_add_bus(struct i2c_adapter *adap)
684 {
685 	return __i2c_bit_add_bus(adap, i2c_add_adapter);
686 }
687 EXPORT_SYMBOL(i2c_bit_add_bus);
688 
i2c_bit_add_numbered_bus(struct i2c_adapter * adap)689 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
690 {
691 	return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
692 }
693 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
694 
695 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
696 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
697 MODULE_LICENSE("GPL");
698