[linux.git] / drivers / w1 / w1_io.c

/*
 *	w1_io.c
 *
 * Copyright (c) 2004 Evgeniy Polyakov <[email protected]>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <asm/io.h>

#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/module.h>

#include "w1.h"
#include "w1_log.h"

static int w1_delay_parm = 1;
module_param_named(delay_coef, w1_delay_parm, int, 0);

static u8 w1_crc8_table[] = {
	0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
	157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
	35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
	190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
	70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
	219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
	101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
	248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
	140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
	17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
	175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
	50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
	202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
	87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
	233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
	116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
};

static void w1_delay(unsigned long tm)
{
	udelay(tm * w1_delay_parm);
}

static void w1_write_bit(struct w1_master *dev, int bit);
static u8 w1_read_bit(struct w1_master *dev);

/**
 * Generates a write-0 or write-1 cycle and samples the level.
 */
static u8 w1_touch_bit(struct w1_master *dev, int bit)
{
	if (dev->bus_master->touch_bit)
		return dev->bus_master->touch_bit(dev->bus_master->data, bit);
	else if (bit)
		return w1_read_bit(dev);
	else {
		w1_write_bit(dev, 0);
		return(0);
	}
}

/**
 * Generates a write-0 or write-1 cycle.
 * Only call if dev->bus_master->touch_bit is NULL
 */
static void w1_write_bit(struct w1_master *dev, int bit)
{
	if (bit) {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		w1_delay(6);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(64);
	} else {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		w1_delay(60);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(10);
	}
}

/**
 * Pre-write operation, currently only supporting strong pullups.
 * Program the hardware for a strong pullup, if one has been requested and
 * the hardware supports it.
 *
 * @param dev     the master device
 */
static void w1_pre_write(struct w1_master *dev)
{
	if (dev->pullup_duration &&
		dev->enable_pullup && dev->bus_master->set_pullup) {
		dev->bus_master->set_pullup(dev->bus_master->data,
			dev->pullup_duration);
	}
}

/**
 * Post-write operation, currently only supporting strong pullups.
 * If a strong pullup was requested, clear it if the hardware supports
 * them, or execute the delay otherwise, in either case clear the request.
 *
 * @param dev     the master device
 */
static void w1_post_write(struct w1_master *dev)
{
	if (dev->pullup_duration) {
		if (dev->enable_pullup && dev->bus_master->set_pullup)
			dev->bus_master->set_pullup(dev->bus_master->data, 0);
		else
			msleep(dev->pullup_duration);
		dev->pullup_duration = 0;
	}
}

/**
 * Writes 8 bits.
 *
 * @param dev     the master device
 * @param byte    the byte to write
 */
void w1_write_8(struct w1_master *dev, u8 byte)
{
	int i;

	if (dev->bus_master->write_byte) {
		w1_pre_write(dev);
		dev->bus_master->write_byte(dev->bus_master->data, byte);
	}
	else
		for (i = 0; i < 8; ++i) {
			if (i == 7)
				w1_pre_write(dev);
			w1_touch_bit(dev, (byte >> i) & 0x1);
		}
	w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_8);


/**
 * Generates a write-1 cycle and samples the level.
 * Only call if dev->bus_master->touch_bit is NULL
 */
static u8 w1_read_bit(struct w1_master *dev)
{
	int result;

	dev->bus_master->write_bit(dev->bus_master->data, 0);
	w1_delay(6);
	dev->bus_master->write_bit(dev->bus_master->data, 1);
	w1_delay(9);

	result = dev->bus_master->read_bit(dev->bus_master->data);
	w1_delay(55);

	return result & 0x1;
}

/**
 * Does a triplet - used for searching ROM addresses.
 * Return bits:
 *  bit 0 = id_bit
 *  bit 1 = comp_bit
 *  bit 2 = dir_taken
 * If both bits 0 & 1 are set, the search should be restarted.
 *
 * @param dev     the master device
 * @param bdir    the bit to write if both id_bit and comp_bit are 0
 * @return        bit fields - see above
 */
u8 w1_triplet(struct w1_master *dev, int bdir)
{
	if ( dev->bus_master->triplet )
		return(dev->bus_master->triplet(dev->bus_master->data, bdir));
	else {
		u8 id_bit   = w1_touch_bit(dev, 1);
		u8 comp_bit = w1_touch_bit(dev, 1);
		u8 retval;

		if ( id_bit && comp_bit )
			return(0x03);  /* error */

		if ( !id_bit && !comp_bit ) {
			/* Both bits are valid, take the direction given */
			retval = bdir ? 0x04 : 0;
		} else {
			/* Only one bit is valid, take that direction */
			bdir = id_bit;
			retval = id_bit ? 0x05 : 0x02;
		}

		if ( dev->bus_master->touch_bit )
			w1_touch_bit(dev, bdir);
		else
			w1_write_bit(dev, bdir);
		return(retval);
	}
}

/**
 * Reads 8 bits.
 *
 * @param dev     the master device
 * @return        the byte read
 */
static u8 w1_read_8(struct w1_master * dev)
{
	int i;
	u8 res = 0;

	if (dev->bus_master->read_byte)
		res = dev->bus_master->read_byte(dev->bus_master->data);
	else
		for (i = 0; i < 8; ++i)
			res |= (w1_touch_bit(dev,1) << i);

	return res;
}

/**
 * Writes a series of bytes.
 *
 * @param dev     the master device
 * @param buf     pointer to the data to write
 * @param len     the number of bytes to write
 * @return        the byte read
 */
void w1_write_block(struct w1_master *dev, const u8 *buf, int len)
{
	int i;

	if (dev->bus_master->write_block) {
		w1_pre_write(dev);
		dev->bus_master->write_block(dev->bus_master->data, buf, len);
	}
	else
		for (i = 0; i < len; ++i)
			w1_write_8(dev, buf[i]); /* calls w1_pre_write */
	w1_post_write(dev);
}
EXPORT_SYMBOL_GPL(w1_write_block);

/**
 * Reads a series of bytes.
 *
 * @param dev     the master device
 * @param buf     pointer to the buffer to fill
 * @param len     the number of bytes to read
 * @return        the number of bytes read
 */
u8 w1_read_block(struct w1_master *dev, u8 *buf, int len)
{
	int i;
	u8 ret;

	if (dev->bus_master->read_block)
		ret = dev->bus_master->read_block(dev->bus_master->data, buf, len);
	else {
		for (i = 0; i < len; ++i)
			buf[i] = w1_read_8(dev);
		ret = len;
	}

	return ret;
}
EXPORT_SYMBOL_GPL(w1_read_block);

/**
 * Issues a reset bus sequence.
 *
 * @param  dev The bus master pointer
 * @return     0=Device present, 1=No device present or error
 */
int w1_reset_bus(struct w1_master *dev)
{
	int result;

	if (dev->bus_master->reset_bus)
		result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
	else {
		dev->bus_master->write_bit(dev->bus_master->data, 0);
		/* minimum 480, max ? us
		 * be nice and sleep, except 18b20 spec lists 960us maximum,
		 * so until we can sleep with microsecond accuracy, spin.
		 * Feel free to come up with some other way to give up the
		 * cpu for such a short amount of time AND get it back in
		 * the maximum amount of time.
		 */
		w1_delay(480);
		dev->bus_master->write_bit(dev->bus_master->data, 1);
		w1_delay(70);

		result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
		/* minmum 70 (above) + 410 = 480 us
		 * There aren't any timing requirements between a reset and
		 * the following transactions.  Sleeping is safe here.
		 */
		/* w1_delay(410); min required time */
		msleep(1);
	}

	return result;
}
EXPORT_SYMBOL_GPL(w1_reset_bus);

u8 w1_calc_crc8(u8 * data, int len)
{
	u8 crc = 0;

	while (len--)
		crc = w1_crc8_table[crc ^ *data++];

	return crc;
}
EXPORT_SYMBOL_GPL(w1_calc_crc8);

void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
{
	dev->attempts++;
	if (dev->bus_master->search)
		dev->bus_master->search(dev->bus_master->data, dev,
			search_type, cb);
	else
		w1_search(dev, search_type, cb);
}

/**
 * Resets the bus and then selects the slave by sending either a skip rom
 * or a rom match.
 * The w1 master lock must be held.
 *
 * @param sl	the slave to select
 * @return 	0=success, anything else=error
 */
int w1_reset_select_slave(struct w1_slave *sl)
{
	if (w1_reset_bus(sl->master))
		return -1;

	if (sl->master->slave_count == 1)
		w1_write_8(sl->master, W1_SKIP_ROM);
	else {
		u8 match[9] = {W1_MATCH_ROM, };
		memcpy(&match[1], (u8 *)&sl->reg_num, 8);
		w1_write_block(sl->master, match, 9);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(w1_reset_select_slave);

/**
 * Put out a strong pull-up of the specified duration after the next write
 * operation.  Not all hardware supports strong pullups.  Hardware that
 * doesn't support strong pullups will sleep for the given time after the
 * write operation without a strong pullup.  This is a one shot request for
 * the next write, specifying zero will clear a previous request.
 * The w1 master lock must be held.
 *
 * @param delay	time in milliseconds
 * @return	0=success, anything else=error
 */
void w1_next_pullup(struct w1_master *dev, int delay)
{
	dev->pullup_duration = delay;
}
EXPORT_SYMBOL_GPL(w1_next_pullup);
Commit	Line	Data
1da177e4	1	/*
7785925d	2	* w1_io.c
1da177e4 LT	3	*
1da177e4 LT	4	* Copyright (c) 2004 Evgeniy Polyakov <[email protected]>
7785925d	5	*
1da177e4 LT	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License as published by
	9	* the Free Software Foundation; either version 2 of the License, or
	10	* (at your option) any later version.
	11	*
	12	* This program is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	* GNU General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU General Public License
	18	* along with this program; if not, write to the Free Software
	19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	20	*/
	21
	22	#include <asm/io.h>
	23
	24	#include <linux/delay.h>
	25	#include <linux/moduleparam.h>
339f0723	26	#include <linux/module.h>
1da177e4 LT	27
	28	#include "w1.h"
	29	#include "w1_log.h"
1da177e4	30
a9fb1c7b	31	static int w1_delay_parm = 1;
1da177e4 LT	32	module_param_named(delay_coef, w1_delay_parm, int, 0);
	33
	34	static u8 w1_crc8_table[] = {
	35	0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
	36	157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
	37	35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
	38	190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
	39	70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
	40	219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
	41	101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
	42	248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
	43	140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
	44	17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
	45	175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
	46	50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
	47	202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
	48	87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
	49	233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
	50	116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
	51	};
	52
70d484bf	53	static void w1_delay(unsigned long tm)
1da177e4 LT	54	{
	55	udelay(tm * w1_delay_parm);
	56	}
	57
be57ce26 EP	58	static void w1_write_bit(struct w1_master *dev, int bit);
	59	static u8 w1_read_bit(struct w1_master *dev);
	60
	61	/**
	62	* Generates a write-0 or write-1 cycle and samples the level.
	63	*/
70d484bf	64	static u8 w1_touch_bit(struct w1_master *dev, int bit)
1da177e4 LT	65	{
	66	if (dev->bus_master->touch_bit)
	67	return dev->bus_master->touch_bit(dev->bus_master->data, bit);
be57ce26	68	else if (bit)
1da177e4	69	return w1_read_bit(dev);
be57ce26 EP	70	else {
	71	w1_write_bit(dev, 0);
	72	return(0);
	73	}
1da177e4 LT	74	}
1da177e4 LT	75
be57ce26 EP	76	/**
	77	* Generates a write-0 or write-1 cycle.
	78	* Only call if dev->bus_master->touch_bit is NULL
	79	*/
	80	static void w1_write_bit(struct w1_master *dev, int bit)
1da177e4 LT	81	{
	82	if (bit) {
	83	dev->bus_master->write_bit(dev->bus_master->data, 0);
	84	w1_delay(6);
	85	dev->bus_master->write_bit(dev->bus_master->data, 1);
	86	w1_delay(64);
	87	} else {
	88	dev->bus_master->write_bit(dev->bus_master->data, 0);
	89	w1_delay(60);
	90	dev->bus_master->write_bit(dev->bus_master->data, 1);
	91	w1_delay(10);
	92	}
	93	}
	94
6a158c0d DF	95	/**
	96	* Pre-write operation, currently only supporting strong pullups.
	97	* Program the hardware for a strong pullup, if one has been requested and
	98	* the hardware supports it.
	99	*
	100	* @param dev the master device
	101	*/
	102	static void w1_pre_write(struct w1_master *dev)
	103	{
	104	if (dev->pullup_duration &&
	105	dev->enable_pullup && dev->bus_master->set_pullup) {
	106	dev->bus_master->set_pullup(dev->bus_master->data,
	107	dev->pullup_duration);
	108	}
	109	}
	110
	111	/**
	112	* Post-write operation, currently only supporting strong pullups.
	113	* If a strong pullup was requested, clear it if the hardware supports
	114	* them, or execute the delay otherwise, in either case clear the request.
	115	*
	116	* @param dev the master device
	117	*/
	118	static void w1_post_write(struct w1_master *dev)
	119	{
	120	if (dev->pullup_duration) {
	121	if (dev->enable_pullup && dev->bus_master->set_pullup)
	122	dev->bus_master->set_pullup(dev->bus_master->data, 0);
	123	else
	124	msleep(dev->pullup_duration);
	125	dev->pullup_duration = 0;
	126	}
	127	}
	128
be57ce26 EP	129	/**
	130	* Writes 8 bits.
	131	*
	132	* @param dev the master device
	133	* @param byte the byte to write
	134	*/
1da177e4 LT	135	void w1_write_8(struct w1_master *dev, u8 byte)
	136	{
	137	int i;
	138
6a158c0d DF	139	if (dev->bus_master->write_byte) {
6a158c0d DF	140	w1_pre_write(dev);
1da177e4	141	dev->bus_master->write_byte(dev->bus_master->data, byte);
6a158c0d	142	}
1da177e4	143	else
6a158c0d DF	144	for (i = 0; i < 8; ++i) {
	145	if (i == 7)
	146	w1_pre_write(dev);
be57ce26	147	w1_touch_bit(dev, (byte >> i) & 0x1);
6a158c0d DF	148	}
6a158c0d DF	149	w1_post_write(dev);
1da177e4	150	}
339f0723	151	EXPORT_SYMBOL_GPL(w1_write_8);
1da177e4	152
be57ce26 EP	153
	154	/**
	155	* Generates a write-1 cycle and samples the level.
	156	* Only call if dev->bus_master->touch_bit is NULL
	157	*/
	158	static u8 w1_read_bit(struct w1_master *dev)
1da177e4 LT	159	{
	160	int result;
	161
	162	dev->bus_master->write_bit(dev->bus_master->data, 0);
	163	w1_delay(6);
	164	dev->bus_master->write_bit(dev->bus_master->data, 1);
	165	w1_delay(9);
	166
	167	result = dev->bus_master->read_bit(dev->bus_master->data);
	168	w1_delay(55);
	169
	170	return result & 0x1;
	171	}
	172
6b729861 EP	173	/**
	174	* Does a triplet - used for searching ROM addresses.
	175	* Return bits:
	176	* bit 0 = id_bit
	177	* bit 1 = comp_bit
	178	* bit 2 = dir_taken
	179	* If both bits 0 & 1 are set, the search should be restarted.
	180	*
	181	* @param dev the master device
	182	* @param bdir the bit to write if both id_bit and comp_bit are 0
	183	* @return bit fields - see above
	184	*/
	185	u8 w1_triplet(struct w1_master *dev, int bdir)
	186	{
	187	if ( dev->bus_master->triplet )
	188	return(dev->bus_master->triplet(dev->bus_master->data, bdir));
	189	else {
	190	u8 id_bit = w1_touch_bit(dev, 1);
	191	u8 comp_bit = w1_touch_bit(dev, 1);
	192	u8 retval;
	193
	194	if ( id_bit && comp_bit )
	195	return(0x03); /* error */
	196
	197	if ( !id_bit && !comp_bit ) {
	198	/* Both bits are valid, take the direction given */
	199	retval = bdir ? 0x04 : 0;
	200	} else {
	201	/* Only one bit is valid, take that direction */
	202	bdir = id_bit;
	203	retval = id_bit ? 0x05 : 0x02;
	204	}
	205
	206	if ( dev->bus_master->touch_bit )
	207	w1_touch_bit(dev, bdir);
	208	else
	209	w1_write_bit(dev, bdir);
	210	return(retval);
	211	}
	212	}
	213
be57ce26 EP	214	/**
	215	* Reads 8 bits.
	216	*
	217	* @param dev the master device
	218	* @return the byte read
	219	*/
70d484bf	220	static u8 w1_read_8(struct w1_master * dev)
1da177e4 LT	221	{
	222	int i;
	223	u8 res = 0;
	224
	225	if (dev->bus_master->read_byte)
	226	res = dev->bus_master->read_byte(dev->bus_master->data);
	227	else
	228	for (i = 0; i < 8; ++i)
be57ce26	229	res \|= (w1_touch_bit(dev,1) << i);
1da177e4 LT	230
	231	return res;
	232	}
	233
be57ce26 EP	234	/**
	235	* Writes a series of bytes.
	236	*
	237	* @param dev the master device
	238	* @param buf pointer to the data to write
	239	* @param len the number of bytes to write
	240	* @return the byte read
	241	*/
	242	void w1_write_block(struct w1_master dev, const u8 buf, int len)
1da177e4 LT	243	{
	244	int i;
	245
6a158c0d DF	246	if (dev->bus_master->write_block) {
6a158c0d DF	247	w1_pre_write(dev);
1da177e4	248	dev->bus_master->write_block(dev->bus_master->data, buf, len);
6a158c0d	249	}
1da177e4 LT	250	else
1da177e4 LT	251	for (i = 0; i < len; ++i)
6a158c0d DF	252	w1_write_8(dev, buf[i]); /* calls w1_pre_write */
6a158c0d DF	253	w1_post_write(dev);
1da177e4	254	}
339f0723	255	EXPORT_SYMBOL_GPL(w1_write_block);
1da177e4	256
be57ce26 EP	257	/**
	258	* Reads a series of bytes.
	259	*
	260	* @param dev the master device
	261	* @param buf pointer to the buffer to fill
	262	* @param len the number of bytes to read
	263	* @return the number of bytes read
	264	*/
1da177e4 LT	265	u8 w1_read_block(struct w1_master dev, u8 buf, int len)
	266	{
	267	int i;
	268	u8 ret;
	269
	270	if (dev->bus_master->read_block)
	271	ret = dev->bus_master->read_block(dev->bus_master->data, buf, len);
	272	else {
	273	for (i = 0; i < len; ++i)
	274	buf[i] = w1_read_8(dev);
	275	ret = len;
	276	}
	277
	278	return ret;
	279	}
339f0723	280	EXPORT_SYMBOL_GPL(w1_read_block);
1da177e4	281
be57ce26 EP	282	/**
	283	* Issues a reset bus sequence.
	284	*
	285	* @param dev The bus master pointer
	286	* @return 0=Device present, 1=No device present or error
	287	*/
1da177e4 LT	288	int w1_reset_bus(struct w1_master *dev)
1da177e4 LT	289	{
be57ce26	290	int result;
1da177e4 LT	291
	292	if (dev->bus_master->reset_bus)
	293	result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
	294	else {
	295	dev->bus_master->write_bit(dev->bus_master->data, 0);
8e3dae2b DF	296	/* minimum 480, max ? us
	297	* be nice and sleep, except 18b20 spec lists 960us maximum,
	298	* so until we can sleep with microsecond accuracy, spin.
	299	* Feel free to come up with some other way to give up the
	300	* cpu for such a short amount of time AND get it back in
	301	* the maximum amount of time.
	302	*/
1da177e4 LT	303	w1_delay(480);
	304	dev->bus_master->write_bit(dev->bus_master->data, 1);
	305	w1_delay(70);
	306
	307	result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
8e3dae2b DF	308	/* minmum 70 (above) + 410 = 480 us
	309	* There aren't any timing requirements between a reset and
	310	* the following transactions. Sleeping is safe here.
	311	*/
	312	/* w1_delay(410); min required time */
	313	msleep(1);
1da177e4 LT	314	}
	315
	316	return result;
	317	}
339f0723	318	EXPORT_SYMBOL_GPL(w1_reset_bus);
1da177e4 LT	319
	320	u8 w1_calc_crc8(u8 * data, int len)
	321	{
	322	u8 crc = 0;
	323
	324	while (len--)
	325	crc = w1_crc8_table[crc ^ *data++];
	326
	327	return crc;
	328	}
339f0723	329	EXPORT_SYMBOL_GPL(w1_calc_crc8);
1da177e4	330
12003375	331	void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
1da177e4 LT	332	{
	333	dev->attempts++;
	334	if (dev->bus_master->search)
c30c9b15 DF	335	dev->bus_master->search(dev->bus_master->data, dev,
c30c9b15 DF	336	search_type, cb);
1da177e4	337	else
12003375	338	w1_search(dev, search_type, cb);
1da177e4 LT	339	}
1da177e4 LT	340
ea7d8f65 EP	341	/**
	342	* Resets the bus and then selects the slave by sending either a skip rom
	343	* or a rom match.
	344	* The w1 master lock must be held.
	345	*
	346	* @param sl the slave to select
	347	* @return 0=success, anything else=error
	348	*/
	349	int w1_reset_select_slave(struct w1_slave *sl)
	350	{
	351	if (w1_reset_bus(sl->master))
	352	return -1;
	353
	354	if (sl->master->slave_count == 1)
	355	w1_write_8(sl->master, W1_SKIP_ROM);
	356	else {
	357	u8 match[9] = {W1_MATCH_ROM, };
	358	memcpy(&match[1], (u8 *)&sl->reg_num, 8);
	359	w1_write_block(sl->master, match, 9);
	360	}
	361	return 0;
	362	}
339f0723	363	EXPORT_SYMBOL_GPL(w1_reset_select_slave);
6a158c0d DF	364
	365	/**
	366	* Put out a strong pull-up of the specified duration after the next write
	367	* operation. Not all hardware supports strong pullups. Hardware that
	368	* doesn't support strong pullups will sleep for the given time after the
	369	* write operation without a strong pullup. This is a one shot request for
	370	* the next write, specifying zero will clear a previous request.
	371	* The w1 master lock must be held.
	372	*
	373	* @param delay time in milliseconds
	374	* @return 0=success, anything else=error
	375	*/
	376	void w1_next_pullup(struct w1_master *dev, int delay)
	377	{
	378	dev->pullup_duration = delay;
	379	}
	380	EXPORT_SYMBOL_GPL(w1_next_pullup);