hw/sensor/lsm303dlhc_mag.c - qemu - Git at Google

 /*
  * LSM303DLHC I2C magnetometer.
  *
  * Copyright (C) 2021 Linaro Ltd.
  * Written by Kevin Townsend <kevin.townsend@linaro.org>
  *
  * Based on: https://www.st.com/resource/en/datasheet/lsm303dlhc.pdf
  *
  * SPDX-License-Identifier: GPL-2.0-or-later
  */

 /*
  * The I2C address associated with this device is set on the command-line when
  * initialising the machine, but the following address is standard: 0x1E.
  *
  * Get and set functions for 'mag-x', 'mag-y' and 'mag-z' assume that
  * 1 = 0.001 uT. (NOTE the 1 gauss = 100 uT, so setting a value of 100,000
  * would be equal to 1 gauss or 100 uT.)
  *
  * Get and set functions for 'temperature' assume that 1 = 0.001 C, so 23.6 C
  * would be equal to 23600.
  */

 #include "qemu/osdep.h"
 #include "hw/i2c/i2c.h"
 #include "migration/vmstate.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
 #include "qemu/module.h"
 #include "qemu/log.h"
 #include "qemu/bswap.h"

 enum LSM303DLHCMagReg {
     LSM303DLHC_MAG_REG_CRA          = 0x00,
     LSM303DLHC_MAG_REG_CRB          = 0x01,
     LSM303DLHC_MAG_REG_MR           = 0x02,
     LSM303DLHC_MAG_REG_OUT_X_H      = 0x03,
     LSM303DLHC_MAG_REG_OUT_X_L      = 0x04,
     LSM303DLHC_MAG_REG_OUT_Z_H      = 0x05,
     LSM303DLHC_MAG_REG_OUT_Z_L      = 0x06,
     LSM303DLHC_MAG_REG_OUT_Y_H      = 0x07,
     LSM303DLHC_MAG_REG_OUT_Y_L      = 0x08,
     LSM303DLHC_MAG_REG_SR           = 0x09,
     LSM303DLHC_MAG_REG_IRA          = 0x0A,
     LSM303DLHC_MAG_REG_IRB          = 0x0B,
     LSM303DLHC_MAG_REG_IRC          = 0x0C,
     LSM303DLHC_MAG_REG_TEMP_OUT_H   = 0x31,
     LSM303DLHC_MAG_REG_TEMP_OUT_L   = 0x32
 };

 typedef struct LSM303DLHCMagState {
     I2CSlave parent_obj;
     uint8_t cra;
     uint8_t crb;
     uint8_t mr;
     int16_t x;
     int16_t z;
     int16_t y;
     int16_t x_lock;
     int16_t z_lock;
     int16_t y_lock;
     uint8_t sr;
     uint8_t ira;
     uint8_t irb;
     uint8_t irc;
     int16_t temperature;
     int16_t temperature_lock;
     uint8_t len;
     uint8_t buf;
     uint8_t pointer;
 } LSM303DLHCMagState;

 #define TYPE_LSM303DLHC_MAG "lsm303dlhc_mag"
 OBJECT_DECLARE_SIMPLE_TYPE(LSM303DLHCMagState, LSM303DLHC_MAG)

 /*
  * Conversion factor from Gauss to sensor values for each GN gain setting,
  * in units "lsb per Gauss" (see data sheet table 3). There is no documented
  * behaviour if the GN setting in CRB is incorrectly set to 0b000;
  * we arbitrarily make it the same as 0b001.
  */
 uint32_t xy_gain[] = { 1100, 1100, 855, 670, 450, 400, 330, 230 };
 uint32_t z_gain[] = { 980, 980, 760, 600, 400, 355, 295, 205 };

 static void lsm303dlhc_mag_get_x(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int gm = extract32(s->crb, 5, 3);

     /* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
     int64_t value = muldiv64(s->x, 100000, xy_gain[gm]);
     visit_type_int(v, name, &value, errp);
 }

 static void lsm303dlhc_mag_get_y(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int gm = extract32(s->crb, 5, 3);

     /* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
     int64_t value = muldiv64(s->y, 100000, xy_gain[gm]);
     visit_type_int(v, name, &value, errp);
 }

 static void lsm303dlhc_mag_get_z(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int gm = extract32(s->crb, 5, 3);

     /* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
     int64_t value = muldiv64(s->z, 100000, z_gain[gm]);
     visit_type_int(v, name, &value, errp);
 }

 static void lsm303dlhc_mag_set_x(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int64_t value;
     int64_t reg;
     int gm = extract32(s->crb, 5, 3);

     if (!visit_type_int(v, name, &value, errp)) {
         return;
     }

     reg = muldiv64(value, xy_gain[gm], 100000);

     /* Make sure we are within a 12-bit limit. */
     if (reg > 2047 || reg < -2048) {
         error_setg(errp, "value %" PRId64 " out of register's range", value);
         return;
     }

     s->x = (int16_t)reg;
 }

 static void lsm303dlhc_mag_set_y(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int64_t value;
     int64_t reg;
     int gm = extract32(s->crb, 5, 3);

     if (!visit_type_int(v, name, &value, errp)) {
         return;
     }

     reg = muldiv64(value, xy_gain[gm], 100000);

     /* Make sure we are within a 12-bit limit. */
     if (reg > 2047 || reg < -2048) {
         error_setg(errp, "value %" PRId64 " out of register's range", value);
         return;
     }

     s->y = (int16_t)reg;
 }

 static void lsm303dlhc_mag_set_z(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int64_t value;
     int64_t reg;
     int gm = extract32(s->crb, 5, 3);

     if (!visit_type_int(v, name, &value, errp)) {
         return;
     }

     reg = muldiv64(value, z_gain[gm], 100000);

     /* Make sure we are within a 12-bit limit. */
     if (reg > 2047 || reg < -2048) {
         error_setg(errp, "value %" PRId64 " out of register's range", value);
         return;
     }

     s->z = (int16_t)reg;
 }

 /*
  * Get handler for the temperature property.
  */
 static void lsm303dlhc_mag_get_temperature(Object *obj, Visitor *v,
                                            const char *name, void *opaque,
                                            Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int64_t value;

     /* Convert to 1 lsb = 0.125 C to 1 = 0.001 C for 'temperature' property. */
     value = s->temperature * 125;

     visit_type_int(v, name, &value, errp);
 }

 /*
  * Set handler for the temperature property.
  */
 static void lsm303dlhc_mag_set_temperature(Object *obj, Visitor *v,
                                            const char *name, void *opaque,
                                            Error **errp)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
     int64_t value;

     if (!visit_type_int(v, name, &value, errp)) {
         return;
     }

     /* Input temperature is in 0.001 C units. Convert to 1 lsb = 0.125 C. */
     value /= 125;

     if (value > 2047 || value < -2048) {
         error_setg(errp, "value %" PRId64 " lsb is out of range", value);
         return;
     }

     s->temperature = (int16_t)value;
 }

 /*
  * Callback handler whenever a 'I2C_START_RECV' (read) event is received.
  */
 static void lsm303dlhc_mag_read(LSM303DLHCMagState *s)
 {
     /*
      * Set the LOCK bit whenever a new read attempt is made. This will be
      * cleared in I2C_FINISH. Note that DRDY is always set to 1 in this driver.
      */
     s->sr = 0x3;

     /*
      * Copy the current X/Y/Z and temp. values into the locked registers so
      * that 'mag-x', 'mag-y', 'mag-z' and 'temperature' can continue to be
      * updated via QOM, etc., without corrupting the current read event.
      */
     s->x_lock = s->x;
     s->z_lock = s->z;
     s->y_lock = s->y;
     s->temperature_lock = s->temperature;
 }

 /*
  * Callback handler whenever a 'I2C_FINISH' event is received.
  */
 static void lsm303dlhc_mag_finish(LSM303DLHCMagState *s)
 {
     /*
      * Clear the LOCK bit when the read attempt terminates.
      * This bit is initially set in the I2C_START_RECV handler.
      */
     s->sr = 0x1;
 }

 /*
  * Callback handler when a device attempts to write to a register.
  */
 static void lsm303dlhc_mag_write(LSM303DLHCMagState *s)
 {
     switch (s->pointer) {
     case LSM303DLHC_MAG_REG_CRA:
         s->cra = s->buf;
         break;
     case LSM303DLHC_MAG_REG_CRB:
         /* Make sure gain is at least 1, falling back to 1 on an error. */
         if (s->buf >> 5 == 0) {
             s->buf = 1 << 5;
         }
         s->crb = s->buf;
         break;
     case LSM303DLHC_MAG_REG_MR:
         s->mr = s->buf;
         break;
     case LSM303DLHC_MAG_REG_SR:
         s->sr = s->buf;
         break;
     case LSM303DLHC_MAG_REG_IRA:
         s->ira = s->buf;
         break;
     case LSM303DLHC_MAG_REG_IRB:
         s->irb = s->buf;
         break;
     case LSM303DLHC_MAG_REG_IRC:
         s->irc = s->buf;
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR, "reg is read-only: 0x%02X", s->buf);
         break;
     }
 }

 /*
  * Low-level master-to-slave transaction handler.
  */
 static int lsm303dlhc_mag_send(I2CSlave *i2c, uint8_t data)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

     if (s->len == 0) {
         /* First byte is the reg pointer */
         s->pointer = data;
         s->len++;
     } else if (s->len == 1) {
         /* Second byte is the new register value. */
         s->buf = data;
         lsm303dlhc_mag_write(s);
     } else {
         g_assert_not_reached();
     }

     return 0;
 }

 /*
  * Low-level slave-to-master transaction handler (read attempts).
  */
 static uint8_t lsm303dlhc_mag_recv(I2CSlave *i2c)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);
     uint8_t resp;

     switch (s->pointer) {
     case LSM303DLHC_MAG_REG_CRA:
         resp = s->cra;
         break;
     case LSM303DLHC_MAG_REG_CRB:
         resp = s->crb;
         break;
     case LSM303DLHC_MAG_REG_MR:
         resp = s->mr;
         break;
     case LSM303DLHC_MAG_REG_OUT_X_H:
         resp = (uint8_t)(s->x_lock >> 8);
         break;
     case LSM303DLHC_MAG_REG_OUT_X_L:
         resp = (uint8_t)(s->x_lock);
         break;
     case LSM303DLHC_MAG_REG_OUT_Z_H:
         resp = (uint8_t)(s->z_lock >> 8);
         break;
     case LSM303DLHC_MAG_REG_OUT_Z_L:
         resp = (uint8_t)(s->z_lock);
         break;
     case LSM303DLHC_MAG_REG_OUT_Y_H:
         resp = (uint8_t)(s->y_lock >> 8);
         break;
     case LSM303DLHC_MAG_REG_OUT_Y_L:
         resp = (uint8_t)(s->y_lock);
         break;
     case LSM303DLHC_MAG_REG_SR:
         resp = s->sr;
         break;
     case LSM303DLHC_MAG_REG_IRA:
         resp = s->ira;
         break;
     case LSM303DLHC_MAG_REG_IRB:
         resp = s->irb;
         break;
     case LSM303DLHC_MAG_REG_IRC:
         resp = s->irc;
         break;
     case LSM303DLHC_MAG_REG_TEMP_OUT_H:
         /* Check if the temperature sensor is enabled or not (CRA & 0x80). */
         if (s->cra & 0x80) {
             resp = (uint8_t)(s->temperature_lock >> 8);
         } else {
             resp = 0;
         }
         break;
     case LSM303DLHC_MAG_REG_TEMP_OUT_L:
         if (s->cra & 0x80) {
             resp = (uint8_t)(s->temperature_lock & 0xff);
         } else {
             resp = 0;
         }
         break;
     default:
         resp = 0;
         break;
     }

     /*
      * The address pointer on the LSM303DLHC auto-increments whenever a byte
      * is read, without the master device having to request the next address.
      *
      * The auto-increment process has the following logic:
      *
      *   - if (s->pointer == 8) then s->pointer = 3
      *   - else: if (s->pointer == 12) then s->pointer = 0
      *   - else: s->pointer += 1
      *
      * Reading an invalid address return 0.
      */
     if (s->pointer == LSM303DLHC_MAG_REG_OUT_Y_L) {
         s->pointer = LSM303DLHC_MAG_REG_OUT_X_H;
     } else if (s->pointer == LSM303DLHC_MAG_REG_IRC) {
         s->pointer = LSM303DLHC_MAG_REG_CRA;
     } else {
         s->pointer++;
     }

     return resp;
 }

 /*
  * Bus state change handler.
  */
 static int lsm303dlhc_mag_event(I2CSlave *i2c, enum i2c_event event)
 {
     LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

     switch (event) {
     case I2C_START_SEND:
         break;
     case I2C_START_RECV:
         lsm303dlhc_mag_read(s);
         break;
     case I2C_FINISH:
         lsm303dlhc_mag_finish(s);
         break;
     case I2C_NACK:
         break;
     default:
         return -1;
     }

     s->len = 0;
     return 0;
 }

 /*
  * Device data description using VMSTATE macros.
  */
 static const VMStateDescription vmstate_lsm303dlhc_mag = {
     .name = "LSM303DLHC_MAG",
     .version_id = 0,
     .minimum_version_id = 0,
     .fields = (const VMStateField[]) {

         VMSTATE_I2C_SLAVE(parent_obj, LSM303DLHCMagState),
         VMSTATE_UINT8(len, LSM303DLHCMagState),
         VMSTATE_UINT8(buf, LSM303DLHCMagState),
         VMSTATE_UINT8(pointer, LSM303DLHCMagState),
         VMSTATE_UINT8(cra, LSM303DLHCMagState),
         VMSTATE_UINT8(crb, LSM303DLHCMagState),
         VMSTATE_UINT8(mr, LSM303DLHCMagState),
         VMSTATE_INT16(x, LSM303DLHCMagState),
         VMSTATE_INT16(z, LSM303DLHCMagState),
         VMSTATE_INT16(y, LSM303DLHCMagState),
         VMSTATE_INT16(x_lock, LSM303DLHCMagState),
         VMSTATE_INT16(z_lock, LSM303DLHCMagState),
         VMSTATE_INT16(y_lock, LSM303DLHCMagState),
         VMSTATE_UINT8(sr, LSM303DLHCMagState),
         VMSTATE_UINT8(ira, LSM303DLHCMagState),
         VMSTATE_UINT8(irb, LSM303DLHCMagState),
         VMSTATE_UINT8(irc, LSM303DLHCMagState),
         VMSTATE_INT16(temperature, LSM303DLHCMagState),
         VMSTATE_INT16(temperature_lock, LSM303DLHCMagState),
         VMSTATE_END_OF_LIST()
     }
 };

 /*
  * Put the device into post-reset default state.
  */
 static void lsm303dlhc_mag_default_cfg(LSM303DLHCMagState *s)
 {
     /* Set the device into is default reset state. */
     s->len = 0;
     s->pointer = 0;         /* Current register. */
     s->buf = 0;             /* Shared buffer. */
     s->cra = 0x10;          /* Temp Enabled = 0, Data Rate = 15.0 Hz. */
     s->crb = 0x20;          /* Gain = +/- 1.3 Gauss. */
     s->mr = 0x3;            /* Operating Mode = Sleep. */
     s->x = 0;
     s->z = 0;
     s->y = 0;
     s->x_lock = 0;
     s->z_lock = 0;
     s->y_lock = 0;
     s->sr = 0x1;            /* DRDY = 1. */
     s->ira = 0x48;
     s->irb = 0x34;
     s->irc = 0x33;
     s->temperature = 0;     /* Default to 0 degrees C (0/8 lsb = 0 C). */
     s->temperature_lock = 0;
 }

 /*
  * Callback handler when DeviceState 'reset' is set to true.
  */
 static void lsm303dlhc_mag_reset(DeviceState *dev)
 {
     I2CSlave *i2c = I2C_SLAVE(dev);
     LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

     /* Set the device into its default reset state. */
     lsm303dlhc_mag_default_cfg(s);
 }

 /*
  * Initialisation of any public properties.
  */
 static void lsm303dlhc_mag_initfn(Object *obj)
 {
     object_property_add(obj, "mag-x", "int",
                 lsm303dlhc_mag_get_x,
                 lsm303dlhc_mag_set_x, NULL, NULL);

     object_property_add(obj, "mag-y", "int",
                 lsm303dlhc_mag_get_y,
                 lsm303dlhc_mag_set_y, NULL, NULL);

     object_property_add(obj, "mag-z", "int",
                 lsm303dlhc_mag_get_z,
                 lsm303dlhc_mag_set_z, NULL, NULL);

     object_property_add(obj, "temperature", "int",
                 lsm303dlhc_mag_get_temperature,
                 lsm303dlhc_mag_set_temperature, NULL, NULL);
 }

 /*
  * Set the virtual method pointers (bus state change, tx/rx, etc.).
  */
 static void lsm303dlhc_mag_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);

     dc->reset = lsm303dlhc_mag_reset;
     dc->vmsd = &vmstate_lsm303dlhc_mag;
     k->event = lsm303dlhc_mag_event;
     k->recv = lsm303dlhc_mag_recv;
     k->send = lsm303dlhc_mag_send;
 }

 static const TypeInfo lsm303dlhc_mag_info = {
     .name = TYPE_LSM303DLHC_MAG,
     .parent = TYPE_I2C_SLAVE,
     .instance_size = sizeof(LSM303DLHCMagState),
     .instance_init = lsm303dlhc_mag_initfn,
     .class_init = lsm303dlhc_mag_class_init,
 };

 static void lsm303dlhc_mag_register_types(void)
 {
     type_register_static(&lsm303dlhc_mag_info);
 }

 type_init(lsm303dlhc_mag_register_types)
	/*
	* LSM303DLHC I2C magnetometer.
	*
	* Copyright (C) 2021 Linaro Ltd.
	* Written by Kevin Townsend <kevin.townsend@linaro.org>
	*
	* Based on: https://www.st.com/resource/en/datasheet/lsm303dlhc.pdf
	*
	* SPDX-License-Identifier: GPL-2.0-or-later
	*/

	/*
	* The I2C address associated with this device is set on the command-line when
	* initialising the machine, but the following address is standard: 0x1E.
	*
	* Get and set functions for 'mag-x', 'mag-y' and 'mag-z' assume that
	* 1 = 0.001 uT. (NOTE the 1 gauss = 100 uT, so setting a value of 100,000
	* would be equal to 1 gauss or 100 uT.)
	*
	* Get and set functions for 'temperature' assume that 1 = 0.001 C, so 23.6 C
	* would be equal to 23600.
	*/

	#include "qemu/osdep.h"
	#include "hw/i2c/i2c.h"
	#include "migration/vmstate.h"
	#include "qapi/error.h"
	#include "qapi/visitor.h"
	#include "qemu/module.h"
	#include "qemu/log.h"
	#include "qemu/bswap.h"

	enum LSM303DLHCMagReg {
	LSM303DLHC_MAG_REG_CRA = 0x00,
	LSM303DLHC_MAG_REG_CRB = 0x01,
	LSM303DLHC_MAG_REG_MR = 0x02,
	LSM303DLHC_MAG_REG_OUT_X_H = 0x03,
	LSM303DLHC_MAG_REG_OUT_X_L = 0x04,
	LSM303DLHC_MAG_REG_OUT_Z_H = 0x05,
	LSM303DLHC_MAG_REG_OUT_Z_L = 0x06,
	LSM303DLHC_MAG_REG_OUT_Y_H = 0x07,
	LSM303DLHC_MAG_REG_OUT_Y_L = 0x08,
	LSM303DLHC_MAG_REG_SR = 0x09,
	LSM303DLHC_MAG_REG_IRA = 0x0A,
	LSM303DLHC_MAG_REG_IRB = 0x0B,
	LSM303DLHC_MAG_REG_IRC = 0x0C,
	LSM303DLHC_MAG_REG_TEMP_OUT_H = 0x31,
	LSM303DLHC_MAG_REG_TEMP_OUT_L = 0x32
	};

	typedef struct LSM303DLHCMagState {
	I2CSlave parent_obj;
	uint8_t cra;
	uint8_t crb;
	uint8_t mr;
	int16_t x;
	int16_t z;
	int16_t y;
	int16_t x_lock;
	int16_t z_lock;
	int16_t y_lock;
	uint8_t sr;
	uint8_t ira;
	uint8_t irb;
	uint8_t irc;
	int16_t temperature;
	int16_t temperature_lock;
	uint8_t len;
	uint8_t buf;
	uint8_t pointer;
	} LSM303DLHCMagState;

	#define TYPE_LSM303DLHC_MAG "lsm303dlhc_mag"
	OBJECT_DECLARE_SIMPLE_TYPE(LSM303DLHCMagState, LSM303DLHC_MAG)

	/*
	* Conversion factor from Gauss to sensor values for each GN gain setting,
	* in units "lsb per Gauss" (see data sheet table 3). There is no documented
	* behaviour if the GN setting in CRB is incorrectly set to 0b000;
	* we arbitrarily make it the same as 0b001.
	*/
	uint32_t xy_gain[] = { 1100, 1100, 855, 670, 450, 400, 330, 230 };
	uint32_t z_gain[] = { 980, 980, 760, 600, 400, 355, 295, 205 };

	static void lsm303dlhc_mag_get_x(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int gm = extract32(s->crb, 5, 3);

	/* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
	int64_t value = muldiv64(s->x, 100000, xy_gain[gm]);
	visit_type_int(v, name, &value, errp);
	}

	static void lsm303dlhc_mag_get_y(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int gm = extract32(s->crb, 5, 3);

	/* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
	int64_t value = muldiv64(s->y, 100000, xy_gain[gm]);
	visit_type_int(v, name, &value, errp);
	}

	static void lsm303dlhc_mag_get_z(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int gm = extract32(s->crb, 5, 3);

	/* Convert to uT where 1000 = 1 uT. Conversion factor depends on gain. */
	int64_t value = muldiv64(s->z, 100000, z_gain[gm]);
	visit_type_int(v, name, &value, errp);
	}

	static void lsm303dlhc_mag_set_x(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int64_t value;
	int64_t reg;
	int gm = extract32(s->crb, 5, 3);

	if (!visit_type_int(v, name, &value, errp)) {
	return;
	}

	reg = muldiv64(value, xy_gain[gm], 100000);

	/* Make sure we are within a 12-bit limit. */
	if (reg > 2047 \|\| reg < -2048) {
	error_setg(errp, "value %" PRId64 " out of register's range", value);
	return;
	}

	s->x = (int16_t)reg;
	}

	static void lsm303dlhc_mag_set_y(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int64_t value;
	int64_t reg;
	int gm = extract32(s->crb, 5, 3);

	if (!visit_type_int(v, name, &value, errp)) {
	return;
	}

	reg = muldiv64(value, xy_gain[gm], 100000);

	/* Make sure we are within a 12-bit limit. */
	if (reg > 2047 \|\| reg < -2048) {
	error_setg(errp, "value %" PRId64 " out of register's range", value);
	return;
	}

	s->y = (int16_t)reg;
	}

	static void lsm303dlhc_mag_set_z(Object obj, Visitor v, const char *name,
	void opaque, Error *errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int64_t value;
	int64_t reg;
	int gm = extract32(s->crb, 5, 3);

	if (!visit_type_int(v, name, &value, errp)) {
	return;
	}

	reg = muldiv64(value, z_gain[gm], 100000);

	/* Make sure we are within a 12-bit limit. */
	if (reg > 2047 \|\| reg < -2048) {
	error_setg(errp, "value %" PRId64 " out of register's range", value);
	return;
	}

	s->z = (int16_t)reg;
	}

	/*
	* Get handler for the temperature property.
	*/
	static void lsm303dlhc_mag_get_temperature(Object obj, Visitor v,
	const char name, void opaque,
	Error **errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int64_t value;

	/* Convert to 1 lsb = 0.125 C to 1 = 0.001 C for 'temperature' property. */
	value = s->temperature * 125;

	visit_type_int(v, name, &value, errp);
	}

	/*
	* Set handler for the temperature property.
	*/
	static void lsm303dlhc_mag_set_temperature(Object obj, Visitor v,
	const char name, void opaque,
	Error **errp)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(obj);
	int64_t value;

	if (!visit_type_int(v, name, &value, errp)) {
	return;
	}

	/* Input temperature is in 0.001 C units. Convert to 1 lsb = 0.125 C. */
	value /= 125;

	if (value > 2047 \|\| value < -2048) {
	error_setg(errp, "value %" PRId64 " lsb is out of range", value);
	return;
	}

	s->temperature = (int16_t)value;
	}

	/*
	* Callback handler whenever a 'I2C_START_RECV' (read) event is received.
	*/
	static void lsm303dlhc_mag_read(LSM303DLHCMagState *s)
	{
	/*
	* Set the LOCK bit whenever a new read attempt is made. This will be
	* cleared in I2C_FINISH. Note that DRDY is always set to 1 in this driver.
	*/
	s->sr = 0x3;

	/*
	* Copy the current X/Y/Z and temp. values into the locked registers so
	* that 'mag-x', 'mag-y', 'mag-z' and 'temperature' can continue to be
	* updated via QOM, etc., without corrupting the current read event.
	*/
	s->x_lock = s->x;
	s->z_lock = s->z;
	s->y_lock = s->y;
	s->temperature_lock = s->temperature;
	}

	/*
	* Callback handler whenever a 'I2C_FINISH' event is received.
	*/
	static void lsm303dlhc_mag_finish(LSM303DLHCMagState *s)
	{
	/*
	* Clear the LOCK bit when the read attempt terminates.
	* This bit is initially set in the I2C_START_RECV handler.
	*/
	s->sr = 0x1;
	}

	/*
	* Callback handler when a device attempts to write to a register.
	*/
	static void lsm303dlhc_mag_write(LSM303DLHCMagState *s)
	{
	switch (s->pointer) {
	case LSM303DLHC_MAG_REG_CRA:
	s->cra = s->buf;
	break;
	case LSM303DLHC_MAG_REG_CRB:
	/* Make sure gain is at least 1, falling back to 1 on an error. */
	if (s->buf >> 5 == 0) {
	s->buf = 1 << 5;
	}
	s->crb = s->buf;
	break;
	case LSM303DLHC_MAG_REG_MR:
	s->mr = s->buf;
	break;
	case LSM303DLHC_MAG_REG_SR:
	s->sr = s->buf;
	break;
	case LSM303DLHC_MAG_REG_IRA:
	s->ira = s->buf;
	break;
	case LSM303DLHC_MAG_REG_IRB:
	s->irb = s->buf;
	break;
	case LSM303DLHC_MAG_REG_IRC:
	s->irc = s->buf;
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR, "reg is read-only: 0x%02X", s->buf);
	break;
	}
	}

	/*
	* Low-level master-to-slave transaction handler.
	*/
	static int lsm303dlhc_mag_send(I2CSlave *i2c, uint8_t data)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

	if (s->len == 0) {
	/* First byte is the reg pointer */
	s->pointer = data;
	s->len++;
	} else if (s->len == 1) {
	/* Second byte is the new register value. */
	s->buf = data;
	lsm303dlhc_mag_write(s);
	} else {
	g_assert_not_reached();
	}

	return 0;
	}

	/*
	* Low-level slave-to-master transaction handler (read attempts).
	*/
	static uint8_t lsm303dlhc_mag_recv(I2CSlave *i2c)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);
	uint8_t resp;

	switch (s->pointer) {
	case LSM303DLHC_MAG_REG_CRA:
	resp = s->cra;
	break;
	case LSM303DLHC_MAG_REG_CRB:
	resp = s->crb;
	break;
	case LSM303DLHC_MAG_REG_MR:
	resp = s->mr;
	break;
	case LSM303DLHC_MAG_REG_OUT_X_H:
	resp = (uint8_t)(s->x_lock >> 8);
	break;
	case LSM303DLHC_MAG_REG_OUT_X_L:
	resp = (uint8_t)(s->x_lock);
	break;
	case LSM303DLHC_MAG_REG_OUT_Z_H:
	resp = (uint8_t)(s->z_lock >> 8);
	break;
	case LSM303DLHC_MAG_REG_OUT_Z_L:
	resp = (uint8_t)(s->z_lock);
	break;
	case LSM303DLHC_MAG_REG_OUT_Y_H:
	resp = (uint8_t)(s->y_lock >> 8);
	break;
	case LSM303DLHC_MAG_REG_OUT_Y_L:
	resp = (uint8_t)(s->y_lock);
	break;
	case LSM303DLHC_MAG_REG_SR:
	resp = s->sr;
	break;
	case LSM303DLHC_MAG_REG_IRA:
	resp = s->ira;
	break;
	case LSM303DLHC_MAG_REG_IRB:
	resp = s->irb;
	break;
	case LSM303DLHC_MAG_REG_IRC:
	resp = s->irc;
	break;
	case LSM303DLHC_MAG_REG_TEMP_OUT_H:
	/* Check if the temperature sensor is enabled or not (CRA & 0x80). */
	if (s->cra & 0x80) {
	resp = (uint8_t)(s->temperature_lock >> 8);
	} else {
	resp = 0;
	}
	break;
	case LSM303DLHC_MAG_REG_TEMP_OUT_L:
	if (s->cra & 0x80) {
	resp = (uint8_t)(s->temperature_lock & 0xff);
	} else {
	resp = 0;
	}
	break;
	default:
	resp = 0;
	break;
	}

	/*
	* The address pointer on the LSM303DLHC auto-increments whenever a byte
	* is read, without the master device having to request the next address.
	*
	* The auto-increment process has the following logic:
	*
	* - if (s->pointer == 8) then s->pointer = 3
	* - else: if (s->pointer == 12) then s->pointer = 0
	* - else: s->pointer += 1
	*
	* Reading an invalid address return 0.
	*/
	if (s->pointer == LSM303DLHC_MAG_REG_OUT_Y_L) {
	s->pointer = LSM303DLHC_MAG_REG_OUT_X_H;
	} else if (s->pointer == LSM303DLHC_MAG_REG_IRC) {
	s->pointer = LSM303DLHC_MAG_REG_CRA;
	} else {
	s->pointer++;
	}

	return resp;
	}

	/*
	* Bus state change handler.
	*/
	static int lsm303dlhc_mag_event(I2CSlave *i2c, enum i2c_event event)
	{
	LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

	switch (event) {
	case I2C_START_SEND:
	break;
	case I2C_START_RECV:
	lsm303dlhc_mag_read(s);
	break;
	case I2C_FINISH:
	lsm303dlhc_mag_finish(s);
	break;
	case I2C_NACK:
	break;
	default:
	return -1;
	}

	s->len = 0;
	return 0;
	}

	/*
	* Device data description using VMSTATE macros.
	*/
	static const VMStateDescription vmstate_lsm303dlhc_mag = {
	.name = "LSM303DLHC_MAG",
	.version_id = 0,
	.minimum_version_id = 0,
	.fields = (const VMStateField[]) {

	VMSTATE_I2C_SLAVE(parent_obj, LSM303DLHCMagState),
	VMSTATE_UINT8(len, LSM303DLHCMagState),
	VMSTATE_UINT8(buf, LSM303DLHCMagState),
	VMSTATE_UINT8(pointer, LSM303DLHCMagState),
	VMSTATE_UINT8(cra, LSM303DLHCMagState),
	VMSTATE_UINT8(crb, LSM303DLHCMagState),
	VMSTATE_UINT8(mr, LSM303DLHCMagState),
	VMSTATE_INT16(x, LSM303DLHCMagState),
	VMSTATE_INT16(z, LSM303DLHCMagState),
	VMSTATE_INT16(y, LSM303DLHCMagState),
	VMSTATE_INT16(x_lock, LSM303DLHCMagState),
	VMSTATE_INT16(z_lock, LSM303DLHCMagState),
	VMSTATE_INT16(y_lock, LSM303DLHCMagState),
	VMSTATE_UINT8(sr, LSM303DLHCMagState),
	VMSTATE_UINT8(ira, LSM303DLHCMagState),
	VMSTATE_UINT8(irb, LSM303DLHCMagState),
	VMSTATE_UINT8(irc, LSM303DLHCMagState),
	VMSTATE_INT16(temperature, LSM303DLHCMagState),
	VMSTATE_INT16(temperature_lock, LSM303DLHCMagState),
	VMSTATE_END_OF_LIST()
	}
	};

	/*
	* Put the device into post-reset default state.
	*/
	static void lsm303dlhc_mag_default_cfg(LSM303DLHCMagState *s)
	{
	/* Set the device into is default reset state. */
	s->len = 0;
	s->pointer = 0; /* Current register. */
	s->buf = 0; /* Shared buffer. */
	s->cra = 0x10; /* Temp Enabled = 0, Data Rate = 15.0 Hz. */
	s->crb = 0x20; /* Gain = +/- 1.3 Gauss. */
	s->mr = 0x3; /* Operating Mode = Sleep. */
	s->x = 0;
	s->z = 0;
	s->y = 0;
	s->x_lock = 0;
	s->z_lock = 0;
	s->y_lock = 0;
	s->sr = 0x1; /* DRDY = 1. */
	s->ira = 0x48;
	s->irb = 0x34;
	s->irc = 0x33;
	s->temperature = 0; /* Default to 0 degrees C (0/8 lsb = 0 C). */
	s->temperature_lock = 0;
	}

	/*
	* Callback handler when DeviceState 'reset' is set to true.
	*/
	static void lsm303dlhc_mag_reset(DeviceState *dev)
	{
	I2CSlave *i2c = I2C_SLAVE(dev);
	LSM303DLHCMagState *s = LSM303DLHC_MAG(i2c);

	/* Set the device into its default reset state. */
	lsm303dlhc_mag_default_cfg(s);
	}

	/*
	* Initialisation of any public properties.
	*/
	static void lsm303dlhc_mag_initfn(Object *obj)
	{
	object_property_add(obj, "mag-x", "int",
	lsm303dlhc_mag_get_x,
	lsm303dlhc_mag_set_x, NULL, NULL);

	object_property_add(obj, "mag-y", "int",
	lsm303dlhc_mag_get_y,
	lsm303dlhc_mag_set_y, NULL, NULL);

	object_property_add(obj, "mag-z", "int",
	lsm303dlhc_mag_get_z,
	lsm303dlhc_mag_set_z, NULL, NULL);

	object_property_add(obj, "temperature", "int",
	lsm303dlhc_mag_get_temperature,
	lsm303dlhc_mag_set_temperature, NULL, NULL);
	}

	/*
	* Set the virtual method pointers (bus state change, tx/rx, etc.).
	*/
	static void lsm303dlhc_mag_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);
	I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);

	dc->reset = lsm303dlhc_mag_reset;
	dc->vmsd = &vmstate_lsm303dlhc_mag;
	k->event = lsm303dlhc_mag_event;
	k->recv = lsm303dlhc_mag_recv;
	k->send = lsm303dlhc_mag_send;
	}

	static const TypeInfo lsm303dlhc_mag_info = {
	.name = TYPE_LSM303DLHC_MAG,
	.parent = TYPE_I2C_SLAVE,
	.instance_size = sizeof(LSM303DLHCMagState),
	.instance_init = lsm303dlhc_mag_initfn,
	.class_init = lsm303dlhc_mag_class_init,
	};

	static void lsm303dlhc_mag_register_types(void)
	{
	type_register_static(&lsm303dlhc_mag_info);
	}

	type_init(lsm303dlhc_mag_register_types)