/*
 * lm78.c - Part of lm_sensors, Linux kernel modules for hardware
 *	    monitoring
 * Copyright (c) 1998, 1999  Frodo Looijaard <frodol@dds.nl>
 * Copyright (c) 2007, 2011  Jean Delvare <jdelvare@suse.de>
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-vid.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.h>

#ifdef CONFIG_ISA
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/io.h>
#endif

/* Addresses to scan */
static const unsigned short normal_i2c[] = { 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
						0x2e, 0x2f, I2C_CLIENT_END };
enum chips { lm78, lm79 };

/* Many LM78 constants specified below */

/* Length of ISA address segment */
#define LM78_EXTENT 8

/* Where are the ISA address/data registers relative to the base address */
#define LM78_ADDR_REG_OFFSET 5
#define LM78_DATA_REG_OFFSET 6

/* The LM78 registers */
#define LM78_REG_IN_MAX(nr) (0x2b + (nr) * 2)
#define LM78_REG_IN_MIN(nr) (0x2c + (nr) * 2)
#define LM78_REG_IN(nr) (0x20 + (nr))

#define LM78_REG_FAN_MIN(nr) (0x3b + (nr))
#define LM78_REG_FAN(nr) (0x28 + (nr))

#define LM78_REG_TEMP 0x27
#define LM78_REG_TEMP_OVER 0x39
#define LM78_REG_TEMP_HYST 0x3a

#define LM78_REG_ALARM1 0x41
#define LM78_REG_ALARM2 0x42

#define LM78_REG_VID_FANDIV 0x47

#define LM78_REG_CONFIG 0x40
#define LM78_REG_CHIPID 0x49
#define LM78_REG_I2C_ADDR 0x48


/*
 * Conversions. Rounding and limit checking is only done on the TO_REG
 * variants.
 */

/*
 * IN: mV (0V to 4.08V)
 * REG: 16mV/bit
 */
static inline u8 IN_TO_REG(unsigned long val)
{
	unsigned long nval = clamp_val(val, 0, 4080);
	return (nval + 8) / 16;
}
#define IN_FROM_REG(val) ((val) *  16)

static inline u8 FAN_TO_REG(long rpm, int div)
{
	if (rpm <= 0)
		return 255;
	if (rpm > 1350000)
		return 1;
	return clamp_val((1350000 + rpm * div / 2) / (rpm * div), 1, 254);
}

static inline int FAN_FROM_REG(u8 val, int div)
{
	return val == 0 ? -1 : val == 255 ? 0 : 1350000 / (val * div);
}

/*
 * TEMP: mC (-128C to +127C)
 * REG: 1C/bit, two's complement
 */
static inline s8 TEMP_TO_REG(long val)
{
	int nval = clamp_val(val, -128000, 127000) ;
	return nval < 0 ? (nval - 500) / 1000 : (nval + 500) / 1000;
}

static inline int TEMP_FROM_REG(s8 val)
{
	return val * 1000;
}

#define DIV_FROM_REG(val) (1 << (val))

struct lm78_data {
	struct i2c_client *client;
	struct mutex lock;
	enum chips type;

	/* For ISA device only */
	const char *name;
	int isa_addr;

	struct mutex update_lock;
	char valid;		/* !=0 if following fields are valid */
	unsigned long last_updated;	/* In jiffies */

	u8 in[7];		/* Register value */
	u8 in_max[7];		/* Register value */
	u8 in_min[7];		/* Register value */
	u8 fan[3];		/* Register value */
	u8 fan_min[3];		/* Register value */
	s8 temp;		/* Register value */
	s8 temp_over;		/* Register value */
	s8 temp_hyst;		/* Register value */
	u8 fan_div[3];		/* Register encoding, shifted right */
	u8 vid;			/* Register encoding, combined */
	u16 alarms;		/* Register encoding, combined */
};


static int lm78_read_value(struct lm78_data *data, u8 reg);
static int lm78_write_value(struct lm78_data *data, u8 reg, u8 value);
static struct lm78_data *lm78_update_device(struct device *dev);
static void lm78_init_device(struct lm78_data *data);


/* 7 Voltages */
static ssize_t show_in(struct device *dev, struct device_attribute *da,
		       char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", IN_FROM_REG(data->in[attr->index]));
}

static ssize_t show_in_min(struct device *dev, struct device_attribute *da,
			   char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", IN_FROM_REG(data->in_min[attr->index]));
}

static ssize_t show_in_max(struct device *dev, struct device_attribute *da,
			   char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", IN_FROM_REG(data->in_max[attr->index]));
}

static ssize_t set_in_min(struct device *dev, struct device_attribute *da,
			  const char *buf, size_t count)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = dev_get_drvdata(dev);
	int nr = attr->index;
	unsigned long val;
	int err;

	err = kstrtoul(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	data->in_min[nr] = IN_TO_REG(val);
	lm78_write_value(data, LM78_REG_IN_MIN(nr), data->in_min[nr]);
	mutex_unlock(&data->update_lock);
	return count;
}

static ssize_t set_in_max(struct device *dev, struct device_attribute *da,
			  const char *buf, size_t count)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = dev_get_drvdata(dev);
	int nr = attr->index;
	unsigned long val;
	int err;

	err = kstrtoul(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	data->in_max[nr] = IN_TO_REG(val);
	lm78_write_value(data, LM78_REG_IN_MAX(nr), data->in_max[nr]);
	mutex_unlock(&data->update_lock);
	return count;
}

#define show_in_offset(offset)					\
static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO,		\
		show_in, NULL, offset);				\
static SENSOR_DEVICE_ATTR(in##offset##_min, S_IRUGO | S_IWUSR,	\
		show_in_min, set_in_min, offset);		\
static SENSOR_DEVICE_ATTR(in##offset##_max, S_IRUGO | S_IWUSR,	\
		show_in_max, set_in_max, offset);

show_in_offset(0);
show_in_offset(1);
show_in_offset(2);
show_in_offset(3);
show_in_offset(4);
show_in_offset(5);
show_in_offset(6);

/* Temperature */
static ssize_t temp1_input_show(struct device *dev,
				struct device_attribute *da, char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp));
}

static ssize_t temp1_max_show(struct device *dev, struct device_attribute *da,
			      char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp_over));
}

static ssize_t temp1_max_store(struct device *dev,
			       struct device_attribute *da, const char *buf,
			       size_t count)
{
	struct lm78_data *data = dev_get_drvdata(dev);
	long val;
	int err;

	err = kstrtol(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	data->temp_over = TEMP_TO_REG(val);
	lm78_write_value(data, LM78_REG_TEMP_OVER, data->temp_over);
	mutex_unlock(&data->update_lock);
	return count;
}

static ssize_t temp1_max_hyst_show(struct device *dev,
				   struct device_attribute *da, char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp_hyst));
}

static ssize_t temp1_max_hyst_store(struct device *dev,
				    struct device_attribute *da,
				    const char *buf, size_t count)
{
	struct lm78_data *data = dev_get_drvdata(dev);
	long val;
	int err;

	err = kstrtol(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	data->temp_hyst = TEMP_TO_REG(val);
	lm78_write_value(data, LM78_REG_TEMP_HYST, data->temp_hyst);
	mutex_unlock(&data->update_lock);
	return count;
}

static DEVICE_ATTR_RO(temp1_input);
static DEVICE_ATTR_RW(temp1_max);
static DEVICE_ATTR_RW(temp1_max_hyst);

/* 3 Fans */
static ssize_t show_fan(struct device *dev, struct device_attribute *da,
			char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	int nr = attr->index;
	return sprintf(buf, "%d\n", FAN_FROM_REG(data->fan[nr],
		DIV_FROM_REG(data->fan_div[nr])));
}

static ssize_t show_fan_min(struct device *dev, struct device_attribute *da,
			    char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	int nr = attr->index;
	return sprintf(buf, "%d\n", FAN_FROM_REG(data->fan_min[nr],
		DIV_FROM_REG(data->fan_div[nr])));
}

static ssize_t set_fan_min(struct device *dev, struct device_attribute *da,
			   const char *buf, size_t count)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = dev_get_drvdata(dev);
	int nr = attr->index;
	unsigned long val;
	int err;

	err = kstrtoul(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	data->fan_min[nr] = FAN_TO_REG(val, DIV_FROM_REG(data->fan_div[nr]));
	lm78_write_value(data, LM78_REG_FAN_MIN(nr), data->fan_min[nr]);
	mutex_unlock(&data->update_lock);
	return count;
}

static ssize_t show_fan_div(struct device *dev, struct device_attribute *da,
			    char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", DIV_FROM_REG(data->fan_div[attr->index]));
}

/*
 * Note: we save and restore the fan minimum here, because its value is
 * determined in part by the fan divisor.  This follows the principle of
 * least surprise; the user doesn't expect the fan minimum to change just
 * because the divisor changed.
 */
static ssize_t set_fan_div(struct device *dev, struct device_attribute *da,
			   const char *buf, size_t count)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct lm78_data *data = dev_get_drvdata(dev);
	int nr = attr->index;
	unsigned long min;
	u8 reg;
	unsigned long val;
	int err;

	err = kstrtoul(buf, 10, &val);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	min = FAN_FROM_REG(data->fan_min[nr],
			   DIV_FROM_REG(data->fan_div[nr]));

	switch (val) {
	case 1:
		data->fan_div[nr] = 0;
		break;
	case 2:
		data->fan_div[nr] = 1;
		break;
	case 4:
		data->fan_div[nr] = 2;
		break;
	case 8:
		data->fan_div[nr] = 3;
		break;
	default:
		dev_err(dev,
			"fan_div value %ld not supported. Choose one of 1, 2, 4 or 8!\n",
			val);
		mutex_unlock(&data->update_lock);
		return -EINVAL;
	}

	reg = lm78_read_value(data, LM78_REG_VID_FANDIV);
	switch (nr) {
	case 0:
		reg = (reg & 0xcf) | (data->fan_div[nr] << 4);
		break;
	case 1:
		reg = (reg & 0x3f) | (data->fan_div[nr] << 6);
		break;
	}
	lm78_write_value(data, LM78_REG_VID_FANDIV, reg);

	data->fan_min[nr] =
		FAN_TO_REG(min, DIV_FROM_REG(data->fan_div[nr]));
	lm78_write_value(data, LM78_REG_FAN_MIN(nr), data->fan_min[nr]);
	mutex_unlock(&data->update_lock);

	return count;
}

#define show_fan_offset(offset)				\
static SENSOR_DEVICE_ATTR(fan##offset##_input, S_IRUGO,		\
		show_fan, NULL, offset - 1);			\
static SENSOR_DEVICE_ATTR(fan##offset##_min, S_IRUGO | S_IWUSR,	\
		show_fan_min, set_fan_min, offset - 1);

show_fan_offset(1);
show_fan_offset(2);
show_fan_offset(3);

/* Fan 3 divisor is locked in H/W */
static SENSOR_DEVICE_ATTR(fan1_div, S_IRUGO | S_IWUSR,
		show_fan_div, set_fan_div, 0);
static SENSOR_DEVICE_ATTR(fan2_div, S_IRUGO | S_IWUSR,
		show_fan_div, set_fan_div, 1);
static SENSOR_DEVICE_ATTR(fan3_div, S_IRUGO, show_fan_div, NULL, 2);

/* VID */
static ssize_t cpu0_vid_show(struct device *dev, struct device_attribute *da,
			     char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%d\n", vid_from_reg(data->vid, 82));
}
static DEVICE_ATTR_RO(cpu0_vid);

/* Alarms */
static ssize_t alarms_show(struct device *dev, struct device_attribute *da,
			   char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	return sprintf(buf, "%u\n", data->alarms);
}
static DEVICE_ATTR_RO(alarms);

static ssize_t show_alarm(struct device *dev, struct device_attribute *da,
			  char *buf)
{
	struct lm78_data *data = lm78_update_device(dev);
	int nr = to_sensor_dev_attr(da)->index;
	return sprintf(buf, "%u\n", (data->alarms >> nr) & 1);
}
static SENSOR_DEVICE_ATTR(in0_alarm, S_IRUGO, show_alarm, NULL, 0);
static SENSOR_DEVICE_ATTR(in1_alarm, S_IRUGO, show_alarm, NULL, 1);
static SENSOR_DEVICE_ATTR(in2_alarm, S_IRUGO, show_alarm, NULL, 2);
static SENSOR_DEVICE_ATTR(in3_alarm, S_IRUGO, show_alarm, NULL, 3);
static SENSOR_DEVICE_ATTR(in4_alarm, S_IRUGO, show_alarm, NULL, 8);
static SENSOR_DEVICE_ATTR(in5_alarm, S_IRUGO, show_alarm, NULL, 9);
static SENSOR_DEVICE_ATTR(in6_alarm, S_IRUGO, show_alarm, NULL, 10);
static SENSOR_DEVICE_ATTR(fan1_alarm, S_IRUGO, show_alarm, NULL, 6);
static SENSOR_DEVICE_ATTR(fan2_alarm, S_IRUGO, show_alarm, NULL, 7);
static SENSOR_DEVICE_ATTR(fan3_alarm, S_IRUGO, show_alarm, NULL, 11);
static SENSOR_DEVICE_ATTR(temp1_alarm, S_IRUGO, show_alarm, NULL, 4);

static struct attribute *lm78_attrs[] = {
	&sensor_dev_attr_in0_input.dev_attr.attr,
	&sensor_dev_attr_in0_min.dev_attr.attr,
	&sensor_dev_attr_in0_max.dev_attr.attr,
	&sensor_dev_attr_in0_alarm.dev_attr.attr,
	&sensor_dev_attr_in1_input.dev_attr.attr,
	&sensor_dev_attr_in1_min.dev_attr.attr,
	&sensor_dev_attr_in1_max.dev_attr.attr,
	&sensor_dev_attr_in1_alarm.dev_attr.attr,
	&sensor_dev_attr_in2_input.dev_attr.attr,
	&sensor_dev_attr_in2_min.dev_attr.attr,
	&sensor_dev_attr_in2_max.dev_attr.attr,
	&sensor_dev_attr_in2_alarm.dev_attr.attr,
	&sensor_dev_attr_in3_input.dev_attr.attr,
	&sensor_dev_attr_in3_min.dev_attr.attr,
	&sensor_dev_attr_in3_max.dev_attr.attr,
	&sensor_dev_attr_in3_alarm.dev_attr.attr,
	&sensor_dev_attr_in4_input.dev_attr.attr,
	&sensor_dev_attr_in4_min.dev_attr.attr,
	&sensor_dev_attr_in4_max.dev_attr.attr,
	&sensor_dev_attr_in4_alarm.dev_attr.attr,
	&sensor_dev_attr_in5_input.dev_attr.attr,
	&sensor_dev_attr_in5_min.dev_attr.attr,
	&sensor_dev_attr_in5_max.dev_attr.attr,
	&sensor_dev_attr_in5_alarm.dev_attr.attr,
	&sensor_dev_attr_in6_input.dev_attr.attr,
	&sensor_dev_attr_in6_min.dev_attr.attr,
	&sensor_dev_attr_in6_max.dev_attr.attr,
	&sensor_dev_attr_in6_alarm.dev_attr.attr,
	&dev_attr_temp1_input.attr,
	&dev_attr_temp1_max.attr,
	&dev_attr_temp1_max_hyst.attr,
	&sensor_dev_attr_temp1_alarm.dev_attr.attr,
	&sensor_dev_attr_fan1_input.dev_attr.attr,
	&sensor_dev_attr_fan1_min.dev_attr.attr,
	&sensor_dev_attr_fan1_div.dev_attr.attr,
	&sensor_dev_attr_fan1_alarm.dev_attr.attr,
	&sensor_dev_attr_fan2_input.dev_attr.attr,
	&sensor_dev_attr_fan2_min.dev_attr.attr,
	&sensor_dev_attr_fan2_div.dev_attr.attr,
	&sensor_dev_attr_fan2_alarm.dev_attr.attr,
	&sensor_dev_attr_fan3_input.dev_attr.attr,
	&sensor_dev_attr_fan3_min.dev_attr.attr,
	&sensor_dev_attr_fan3_div.dev_attr.attr,
	&sensor_dev_attr_fan3_alarm.dev_attr.attr,
	&dev_attr_alarms.attr,
	&dev_attr_cpu0_vid.attr,

	NULL
};

ATTRIBUTE_GROUPS(lm78);

/*
 * ISA related code
 */
#ifdef CONFIG_ISA

/* ISA device, if found */
static struct platform_device *pdev;

static unsigned short isa_address = 0x290;

static struct lm78_data *lm78_data_if_isa(void)
{
	return pdev ? platform_get_drvdata(pdev) : NULL;
}

/* Returns 1 if the I2C chip appears to be an alias of the ISA chip */
static int lm78_alias_detect(struct i2c_client *client, u8 chipid)
{
	struct lm78_data *isa;
	int i;

	if (!pdev)	/* No ISA chip */
		return 0;
	isa = platform_get_drvdata(pdev);

	if (lm78_read_value(isa, LM78_REG_I2C_ADDR) != client->addr)
		return 0;	/* Address doesn't match */
	if ((lm78_read_value(isa, LM78_REG_CHIPID) & 0xfe) != (chipid & 0xfe))
		return 0;	/* Chip type doesn't match */

	/*
	 * We compare all the limit registers, the config register and the
	 * interrupt mask registers
	 */
	for (i = 0x2b; i <= 0x3d; i++) {
		if (lm78_read_value(isa, i) !=
		    i2c_smbus_read_byte_data(client, i))
			return 0;
	}
	if (lm78_read_value(isa, LM78_REG_CONFIG) !=
	    i2c_smbus_read_byte_data(client, LM78_REG_CONFIG))
		return 0;
	for (i = 0x43; i <= 0x46; i++) {
		if (lm78_read_value(isa, i) !=
		    i2c_smbus_read_byte_data(client, i))
			return 0;
	}

	return 1;
}
#else /* !CONFIG_ISA */

static int lm78_alias_detect(struct i2c_client *client, u8 chipid)
{
	return 0;
}

static struct lm78_data *lm78_data_if_isa(void)
{
	return NULL;
}
#endif /* CONFIG_ISA */

static int lm78_i2c_detect(struct i2c_client *client,
			   struct i2c_board_info *info)
{
	int i;
	struct lm78_data *isa = lm78_data_if_isa();
	const char *client_name;
	struct i2c_adapter *adapter = client->adapter;
	int address = client->addr;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
		return -ENODEV;

	/*
	 * We block updates of the ISA device to minimize the risk of
	 * concurrent access to the same LM78 chip through different
	 * interfaces.
	 */
	if (isa)
		mutex_lock(&isa->update_lock);

	if ((i2c_smbus_read_byte_data(client, LM78_REG_CONFIG) & 0x80)
	 || i2c_smbus_read_byte_data(client, LM78_REG_I2C_ADDR) != address)
		goto err_nodev;

	/* Explicitly prevent the misdetection of Winbond chips */
	i = i2c_smbus_read_byte_data(client, 0x4f);
	if (i == 0xa3 || i == 0x5c)
		goto err_nodev;

	/* Determine the chip type. */
	i = i2c_smbus_read_byte_data(client, LM78_REG_CHIPID);
	if (i == 0x00 || i == 0x20	/* LM78 */
	 || i == 0x40)			/* LM78-J */
		client_name = "lm78";
	else if ((i & 0xfe) == 0xc0)
		client_name = "lm79";
	else
		goto err_nodev;

	if (lm78_alias_detect(client, i)) {
		dev_dbg(&adapter->dev,
			"Device at 0x%02x appears to be the same as ISA device\n",
			address);
		goto err_nodev;
	}

	if (isa)
		mutex_unlock(&isa->update_lock);

	strlcpy(info->type, client_name, I2C_NAME_SIZE);

	return 0;

 err_nodev:
	if (isa)
		mutex_unlock(&isa->update_lock);
	return -ENODEV;
}

static int lm78_i2c_probe(struct i2c_client *client,
			  const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct lm78_data *data;

	data = devm_kzalloc(dev, sizeof(struct lm78_data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->client = client;
	data->type = id->driver_data;

	/* Initialize the LM78 chip */
	lm78_init_device(data);

	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
							   data, lm78_groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id lm78_i2c_id[] = {
	{ "lm78", lm78 },
	{ "lm79", lm79 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, lm78_i2c_id);

static struct i2c_driver lm78_driver = {
	.class		= I2C_CLASS_HWMON,
	.driver = {
		.name	= "lm78",
	},
	.probe		= lm78_i2c_probe,
	.id_table	= lm78_i2c_id,
	.detect		= lm78_i2c_detect,
	.address_list	= normal_i2c,
};

/*
 * The SMBus locks itself, but ISA access must be locked explicitly!
 * We don't want to lock the whole ISA bus, so we lock each client
 * separately.
 * We ignore the LM78 BUSY flag at this moment - it could lead to deadlocks,
 * would slow down the LM78 access and should not be necessary.
 */
static int lm78_read_value(struct lm78_data *data, u8 reg)
{
	struct i2c_client *client = data->client;

#ifdef CONFIG_ISA
	if (!client) { /* ISA device */
		int res;
		mutex_lock(&data->lock);
		outb_p(reg, data->isa_addr + LM78_ADDR_REG_OFFSET);
		res = inb_p(data->isa_addr + LM78_DATA_REG_OFFSET);
		mutex_unlock(&data->lock);
		return res;
	} else
#endif
		return i2c_smbus_read_byte_data(client, reg);
}

static int lm78_write_value(struct lm78_data *data, u8 reg, u8 value)
{
	struct i2c_client *client = data->client;

#ifdef CONFIG_ISA
	if (!client) { /* ISA device */
		mutex_lock(&data->lock);
		outb_p(reg, data->isa_addr + LM78_ADDR_REG_OFFSET);
		outb_p(value, data->isa_addr + LM78_DATA_REG_OFFSET);
		mutex_unlock(&data->lock);
		return 0;
	} else
#endif
		return i2c_smbus_write_byte_data(client, reg, value);
}

static void lm78_init_device(struct lm78_data *data)
{
	u8 config;
	int i;

	/* Start monitoring */
	config = lm78_read_value(data, LM78_REG_CONFIG);
	if ((config & 0x09) != 0x01)
		lm78_write_value(data, LM78_REG_CONFIG,
				 (config & 0xf7) | 0x01);

	/* A few vars need to be filled upon startup */
	for (i = 0; i < 3; i++) {
		data->fan_min[i] = lm78_read_value(data,
					LM78_REG_FAN_MIN(i));
	}

	mutex_init(&data->update_lock);
}

static struct lm78_data *lm78_update_device(struct device *dev)
{
	struct lm78_data *data = dev_get_drvdata(dev);
	int i;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
	    || !data->valid) {

		dev_dbg(dev, "Starting lm78 update\n");

		for (i = 0; i <= 6; i++) {
			data->in[i] =
			    lm78_read_value(data, LM78_REG_IN(i));
			data->in_min[i] =
			    lm78_read_value(data, LM78_REG_IN_MIN(i));
			data->in_max[i] =
			    lm78_read_value(data, LM78_REG_IN_MAX(i));
		}
		for (i = 0; i < 3; i++) {
			data->fan[i] =
			    lm78_read_value(data, LM78_REG_FAN(i));
			data->fan_min[i] =
			    lm78_read_value(data, LM78_REG_FAN_MIN(i));
		}
		data->temp = lm78_read_value(data, LM78_REG_TEMP);
		data->temp_over =
		    lm78_read_value(data, LM78_REG_TEMP_OVER);
		data->temp_hyst =
		    lm78_read_value(data, LM78_REG_TEMP_HYST);
		i = lm78_read_value(data, LM78_REG_VID_FANDIV);
		data->vid = i & 0x0f;
		if (data->type == lm79)
			data->vid |=
			    (lm78_read_value(data, LM78_REG_CHIPID) &
			     0x01) << 4;
		else
			data->vid |= 0x10;
		data->fan_div[0] = (i >> 4) & 0x03;
		data->fan_div[1] = i >> 6;
		data->alarms = lm78_read_value(data, LM78_REG_ALARM1) +
		    (lm78_read_value(data, LM78_REG_ALARM2) << 8);
		data->last_updated = jiffies;
		data->valid = 1;

		data->fan_div[2] = 1;
	}

	mutex_unlock(&data->update_lock);

	return data;
}

#ifdef CONFIG_ISA
static int lm78_isa_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct device *hwmon_dev;
	struct lm78_data *data;
	struct resource *res;

	/* Reserve the ISA region */
	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
	if (!devm_request_region(dev, res->start + LM78_ADDR_REG_OFFSET,
				 2, "lm78"))
		return -EBUSY;

	data = devm_kzalloc(dev, sizeof(struct lm78_data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	mutex_init(&data->lock);
	data->isa_addr = res->start;
	platform_set_drvdata(pdev, data);

	if (lm78_read_value(data, LM78_REG_CHIPID) & 0x80) {
		data->type = lm79;
		data->name = "lm79";
	} else {
		data->type = lm78;
		data->name = "lm78";
	}

	/* Initialize the LM78 chip */
	lm78_init_device(data);

	hwmon_dev = devm_hwmon_device_register_with_groups(dev, data->name,
							   data, lm78_groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static struct platform_driver lm78_isa_driver = {
	.driver = {
		.name	= "lm78",
	},
	.probe		= lm78_isa_probe,
};

/* return 1 if a supported chip is found, 0 otherwise */
static int __init lm78_isa_found(unsigned short address)
{
	int val, save, found = 0;
	int port;

	/*
	 * Some boards declare base+0 to base+7 as a PNP device, some base+4
	 * to base+7 and some base+5 to base+6. So we better request each port
	 * individually for the probing phase.
	 */
	for (port = address; port < address + LM78_EXTENT; port++) {
		if (!request_region(port, 1, "lm78")) {
			pr_debug("Failed to request port 0x%x\n", port);
			goto release;
		}
	}

#define REALLY_SLOW_IO
	/*
	 * We need the timeouts for at least some LM78-like
	 * chips. But only if we read 'undefined' registers.
	 */
	val = inb_p(address + 1);
	if (inb_p(address + 2) != val
	 || inb_p(address + 3) != val
	 || inb_p(address + 7) != val)
		goto release;
#undef REALLY_SLOW_IO

	/*
	 * We should be able to change the 7 LSB of the address port. The
	 * MSB (busy flag) should be clear initially, set after the write.
	 */
	save = inb_p(address + LM78_ADDR_REG_OFFSET);
	if (save & 0x80)
		goto release;
	val = ~save & 0x7f;
	outb_p(val, address + LM78_ADDR_REG_OFFSET);
	if (inb_p(address + LM78_ADDR_REG_OFFSET) != (val | 0x80)) {
		outb_p(save, address + LM78_ADDR_REG_OFFSET);
		goto release;
	}

	/* We found a device, now see if it could be an LM78 */
	outb_p(LM78_REG_CONFIG, address + LM78_ADDR_REG_OFFSET);
	val = inb_p(address + LM78_DATA_REG_OFFSET);
	if (val & 0x80)
		goto release;
	outb_p(LM78_REG_I2C_ADDR, address + LM78_ADDR_REG_OFFSET);
	val = inb_p(address + LM78_DATA_REG_OFFSET);
	if (val < 0x03 || val > 0x77)	/* Not a valid I2C address */
		goto release;

	/* The busy flag should be clear again */
	if (inb_p(address + LM78_ADDR_REG_OFFSET) & 0x80)
		goto release;

	/* Explicitly prevent the misdetection of Winbond chips */
	outb_p(0x4f, address + LM78_ADDR_REG_OFFSET);
	val = inb_p(address + LM78_DATA_REG_OFFSET);
	if (val == 0xa3 || val == 0x5c)
		goto release;

	/* Explicitly prevent the misdetection of ITE chips */
	outb_p(0x58, address + LM78_ADDR_REG_OFFSET);
	val = inb_p(address + LM78_DATA_REG_OFFSET);
	if (val == 0x90)
		goto release;

	/* Determine the chip type */
	outb_p(LM78_REG_CHIPID, address + LM78_ADDR_REG_OFFSET);
	val = inb_p(address + LM78_DATA_REG_OFFSET);
	if (val == 0x00 || val == 0x20	/* LM78 */
	 || val == 0x40			/* LM78-J */
	 || (val & 0xfe) == 0xc0)	/* LM79 */
		found = 1;

	if (found)
		pr_info("Found an %s chip at %#x\n",
			val & 0x80 ? "LM79" : "LM78", (int)address);

 release:
	for (port--; port >= address; port--)
		release_region(port, 1);
	return found;
}

static int __init lm78_isa_device_add(unsigned short address)
{
	struct resource res = {
		.start	= address,
		.end	= address + LM78_EXTENT - 1,
		.name	= "lm78",
		.flags	= IORESOURCE_IO,
	};
	int err;

	pdev = platform_device_alloc("lm78", address);
	if (!pdev) {
		err = -ENOMEM;
		pr_err("Device allocation failed\n");
		goto exit;
	}

	err = platform_device_add_resources(pdev, &res, 1);
	if (err) {
		pr_err("Device resource addition failed (%d)\n", err);
		goto exit_device_put;
	}

	err = platform_device_add(pdev);
	if (err) {
		pr_err("Device addition failed (%d)\n", err);
		goto exit_device_put;
	}

	return 0;

 exit_device_put:
	platform_device_put(pdev);
 exit:
	pdev = NULL;
	return err;
}

static int __init lm78_isa_register(void)
{
	int res;

	if (lm78_isa_found(isa_address)) {
		res = platform_driver_register(&lm78_isa_driver);
		if (res)
			goto exit;

		/* Sets global pdev as a side effect */
		res = lm78_isa_device_add(isa_address);
		if (res)
			goto exit_unreg_isa_driver;
	}

	return 0;

 exit_unreg_isa_driver:
	platform_driver_unregister(&lm78_isa_driver);
 exit:
	return res;
}

static void lm78_isa_unregister(void)
{
	if (pdev) {
		platform_device_unregister(pdev);
		platform_driver_unregister(&lm78_isa_driver);
	}
}
#else /* !CONFIG_ISA */

static int __init lm78_isa_register(void)
{
	return 0;
}

static void lm78_isa_unregister(void)
{
}
#endif /* CONFIG_ISA */

static int __init sm_lm78_init(void)
{
	int res;

	/*
	 * We register the ISA device first, so that we can skip the
	 * registration of an I2C interface to the same device.
	 */
	res = lm78_isa_register();
	if (res)
		goto exit;

	res = i2c_add_driver(&lm78_driver);
	if (res)
		goto exit_unreg_isa_device;

	return 0;

 exit_unreg_isa_device:
	lm78_isa_unregister();
 exit:
	return res;
}

static void __exit sm_lm78_exit(void)
{
	lm78_isa_unregister();
	i2c_del_driver(&lm78_driver);
}

MODULE_AUTHOR("Frodo Looijaard, Jean Delvare <jdelvare@suse.de>");
MODULE_DESCRIPTION("LM78/LM79 driver");
MODULE_LICENSE("GPL");

module_init(sm_lm78_init);
module_exit(sm_lm78_exit);
