Create a generic battery driver infrastructure

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@4322 7fd9a85b-ad96-42d3-883c-3090e2eb8679

nuttx/ChangeLog

@@ -2391,4 +2391,6 @@
 	* drivers/power:  Rename the drivers/pm directory to power
 	* drivers/power/max1704x.c:  Add a skeleton file that will eventually become
 	  the MAX17040x battery driver.
-
+	* include/power/battery.h and drivers/battery.c:  Add the interface definitions
+	  for an upper and lower half battery driver.  Add the implementation of the
+	  common upper half battery driver.

nuttx/drivers/power/Make.defs

@@ -33,26 +33,53 @@
 #
 ############################################################################
 
-# Has power management support been initialized?
+POWER_DEPPATH =
-
+POWER_VPATH =
-ifeq ($(CONFIG_PM),y)
+POWER_CFLAGS =
 
 # Include power management sources
 
+ifeq ($(CONFIG_PM),y)
+
 CSRCS += pm_activity.c pm_changestate.c pm_checkstate.c pm_initialize.c pm_register.c pm_update.c
 
-# Add I2C devices
+# Include power management in the build
+
+POWER_DEPPATH := --dep-path power
+POWER_VPATH := :power
+POWER_CFLAGS := ${shell $(TOPDIR)/tools/incdir.sh $(INCDIROPT) "$(CC)" $(TOPDIR)/drivers/power}
+
+endif
+
+# Add battery drivers
+
+ifeq ($(CONFIG_BATTERY),y)
+
+CSRCS += battery.c
+
+# Add I2C-based battery drivers
 
 ifeq ($(CONFIG_I2C),y)
+
+# Add the MAX1704x I2C-based battery driver
+
 ifeq ($(CONFIG_I2C_MAX1704X),y)
 CSRCS += max1704x.c
 endif
+
+endif
+
+# Include battery suport in the build
+
+POWER_DEPPATH := --dep-path power
+POWER_VPATH := :power
+POWER_CFLAGS := ${shell $(TOPDIR)/tools/incdir.sh $(INCDIROPT) "$(CC)" $(TOPDIR)/drivers/power}
+
 endif
 
 # Include power management in the build
 
-DEPPATH += --dep-path power
+DEPPATH += $(POWER_DEPPATH)
-VPATH += :power
+VPATH += $(POWER_VPATH)
-CFLAGS += ${shell $(TOPDIR)/tools/incdir.sh $(INCDIROPT) "$(CC)" $(TOPDIR)/drivers/power}
+CFLAGS += $(POWER_CFLAGS);
-endif
 

nuttx/drivers/power/battery.c

@@ -0,0 +1,255 @@
+/****************************************************************************
+ * drivers/power/battery.c
+ * Upper-half, character driver for batteries.
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/power/battery.h>
+
+/* This driver requires:
+ *
+ * CONFIG_BATTERY - Upper half battery driver support
+ */
+
+#if defined(CONFIG_BATTERY)
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private
+ ****************************************************************************/
+
+struct bat_dev_s
+{
+  FAR struct battery_lower_s *lower; /* The lower half battery driver */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Character driver methods */
+
+static int     bat_open(FAR struct file *filep);
+static int     bat_close(FAR struct file *filep);
+static ssize_t bat_read(FAR struct file *, FAR char *, size_t);
+static ssize_t bat_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
+static int     bat_ioctl(FAR struct file *filep,int cmd,unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct battery_operations_s g_max1704xfopg =
+{
+  bat_open,
+  bat_close,
+  bat_read,
+  bat_write,
+  0,
+  bat_ioctl
+#ifndef CONFIG_DISABLE_POLL
+  , 0
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+/****************************************************************************
+ * Name: bat_open
+ *
+ * Description:
+ *   This function is called whenever theMAX1704x device is opened.
+ *
+ ****************************************************************************/
+
+static int bat_open(FAR struct file *filep)
+{
+  return OK;
+}
+
+/****************************************************************************
+ * Name: bat_close
+ *
+ * Description:
+ *   This routine is called when theMAX1704x device is closed.
+ *
+ ****************************************************************************/
+
+static int bat_close(FAR struct file *filep)
+{
+  return OK;
+}
+
+/****************************************************************************
+ * Name: bat_read
+ ****************************************************************************/
+
+static ssize_t bat_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
+{
+  return 0;
+}
+
+/****************************************************************************
+ * Name: bat_write
+ ****************************************************************************/
+
+static ssize_t bat_write(FAR struct file *filep, FAR const char *buffer,
+                          size_t buflen)
+{
+  return -EACCESS;
+}
+
+/****************************************************************************
+ * Name: bat_ioctl
+ ****************************************************************************/
+
+static int bat_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
+{
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct bat_dev_s *upper  = inode->i_private;
+  int ret   = -EINVAL;
+
+  switch (cmd)
+    {
+      case BATIOC_STATE:
+        {
+          FAR int *ptr = (FAR int *)((uintptr_t)arg));
+          if (ptr)
+            {
+              *ptr = upper->state(priv->lower);
+              ret = OK;
+            }
+        }
+        break;
+
+      case BATIOC_ONLINE:
+          FAR bool *ptr = (FAR bool *)((uintptr_t)arg));
+          if (ptr)
+            {
+              *ptr = upper->online(priv->lower);
+              ret = OK;
+            }
+        break;
+
+      case BATIOC_VOLTAGE:
+        {
+          FAR int *ptr = (FAR int *)((uintptr_t)arg));
+          if (ptr)
+            {
+              *ptr = upper->voltage(priv->lower);
+              ret = OK;
+            }
+        }
+        break;
+
+      case BATIOC_CAPACITY:
+        {
+          FAR int *ptr = (FAR int *)((uintptr_t)arg));
+          if (ptr)
+            {
+              *ptr = upper->capacity(priv->lower);
+              ret = OK;
+            }
+        }
+        break;
+
+      default:
+        i2cdbg("Unrecognized cmd: %d\n", cmd);
+        ret = -ENOTTY;
+        break;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: battery_register
+ *
+ * Description:
+ *   Register a lower half battery driver with the common, upper-half
+ *   battery driver.
+ *
+ * Input parameters:
+ *   devpath - The location in the pseudo-filesystem to create the driver.
+ *     Recommended standard is "/dev/bat0", "/dev/bat1", etc.
+ *   lower - The lower half battery state.
+ *
+ * Returned value:
+ *    Zero on success or a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int battery_register(FAR const char *devpath, FAR struct battery_lower_s *lower)
+{
+  FAR struct bat_dev_s *upper;
+  int ret;
+
+  /* Initialize theMAX1704x device structure */
+
+  upper = (FAR struct bat_dev_s *)kzalloc(sizeof(struct bat_dev_s));
+  if (!upper)
+    {
+      i2cdbg("Failed to allocate instance\n");
+      return -ENOMEM;
+    }
+
+  upper->lower = lower;
+
+  /* Register the character driver */
+
+  ret = register_driver(devpath, &g_max1704xfopg, 0555, upper);
+  if (ret < 0)
+    {
+      i2cdbg("Failed to register driver: %d\n", ret);
+      free(upper);
+    }
+  return ret;
+}
+#endif /* CONFIG_BATTERY */

nuttx/drivers/power/max1704x.c

@@ -1,6 +1,6 @@
 /****************************************************************************
  * drivers/power/max1704x.c
- * Character driver for the STMicroMAX1704x Temperature Sensor
+ * Lower half driver for MAX1704x battery charger
  *
  *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
@@ -43,7 +43,16 @@
 #include <errno.h>
 #include <debug.h>
 
-#if defined(CONFIG_I2C) && defined(CONFIG_I2C_MAX1704X)
+#include <nuttx/power/battery.h>
+
+/* This driver requires:
+ *
+ * CONFIG_BATTERY - Upper half battery driver support
+ * CONFIG_I2C - I2C support
+ * CONFIG_I2C_MAX1704X - And the driver must be explictly selected.
+ */
+
+#if defined(CONFIG_BATTERY) && defined(CONFIG_I2C) && defined(CONFIG_I2C_MAX1704X)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -55,6 +64,12 @@
 
 struct max1704x_dev_s
 {
+  /* The common part of the battery driver visible to the upper-half driver */
+
+  FAR const struct battery_operations_s *ops; /* Battery operations */
+
+  /* Data fields specific to the lower half MAX1704x driver follow */
+
   FAR struct i2c_dev_s *i2c; /* I2C interface */
   uint8_t addr;              /* I2C address */
 };
@@ -62,100 +77,84 @@ struct max1704x_dev_s
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
-/* I2C Helpers */
 
-/* Character driver methods */
+/* Battery driver lower half methods */
 
-static int     max1704x_open(FAR struct file *filep);
+static enum battery_status_e mx1704x_state(struct battery_lower_s *lower);
-static int     max1704x_close(FAR struct file *filep);
+static bool mx1704x_online(struct battery_lower_s *lower);
-static ssize_t max1704x_read(FAR struct file *, FAR char *, size_t);
+static int mx1704x_voltage(struct battery_lower_s *lower);
-static ssize_t max1704x_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
+static int mx1704x_capacity(struct battery_lower_s *lower);
-static int     max1704x_ioctl(FAR struct file *filep,int cmd,unsigned long arg);
 
 /****************************************************************************
  * Private Data
  ****************************************************************************/
 
-static const struct file_operations g_max1704xfopg =
+static const struct battery_operations_s g_max1704xfopg =
 {
-  max1704x_open,
+  mx1704x_state,
-  max1704x_close,
+  mx1704x_online,
-  max1704x_read,
+  mx1704x_voltage,
-  max1704x_write,
+  mx1704x_capacity,
-  0,
-  max1704x_ioctl
-#ifndef CONFIG_DISABLE_POLL
-  , 0
-#endif
 };
 
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
+
 /****************************************************************************
  * Name: max1704x_open
  *
  * Description:
- *   This function is called whenever theMAX1704x device is opened.
+ *   Return the current battery state
  *
  ****************************************************************************/
 
-static int max1704x_open(FAR struct file *filep)
+static enum battery_status_e state(struct battery_lower_s *lower)
 {
-  return OK;
+#warning "Missing logic"
+  return BATTERY_UNKNOWN;
 }
 
 /****************************************************************************
- * Name: max1704x_close
+ * Name: max1704x_open
  *
  * Description:
- *   This routine is called when theMAX1704x device is closed.
+ *   Return true if the batter is online
  *
  ****************************************************************************/
 
-static int max1704x_close(FAR struct file *filep)
+static bool online(struct battery_lower_s *lower)
 {
-  return OK;
+#warning "Missing logic"
+  return false;
 }
 
 /****************************************************************************
- * Name: max1704x_read
+ * Name: max1704x_open
+ *
+ * Description:
+ *   Current battery voltage
+ *
  ****************************************************************************/
 
-static ssize_t max1704x_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
+static int voltage(struct battery_lower_s *lower);
 {
-  retrun 0;
+#warning "Missing logic"
+  return 0;
 }
 
 /****************************************************************************
- * Name: max1704x_write
+ * Name: max1704x_open
+ *
+ * Description:
+ *   Battery capacity
+ *
  ****************************************************************************/
 
-static ssize_t max1704x_write(FAR struct file *filep, FAR const char *buffer,
+static int capacity(struct battery_lower_s *lower);
-                          size_t buflen)
 {
-  return -EACCESS;
+#warning "Missing logic"
-}
+  return 0;
-
-/****************************************************************************
- * Name: max1704x_ioctl
- ****************************************************************************/
-
-static int max1704x_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
-{
-  FAR struct inode *inode = filep->f_inode;
-  FAR struct max1704x_dev_s *priv  = inode->i_private;
-  int ret   = OK;
-
-  switch (cmd)
-    {
-      default:
-        i2cdbg("Unrecognized cmd: %d\n", cmd);
-        ret = -ENOTTY;
-        break;
-    }
-
-  return ret;
 }
 
 /****************************************************************************
@@ -163,22 +162,30 @@ static int max1704x_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
  ****************************************************************************/
 
 /****************************************************************************
- * Name: max1704x_register
+ * Name: max1704x_initialize
  *
  * Description:
- *   Register theMAX1704x character device as 'devpath'
+ *   Initialize the MAX1704x battery driver and return an instance of the
+ *   lower_half interface that may be used with battery_register();
+ *
+ *   This driver requires:
+ *
+ *   CONFIG_BATTERY - Upper half battery driver support
+ *   CONFIG_I2C - I2C support
+ *   CONFIG_I2C_MAX1704X - And the driver must be explictly selected.
  *
  * Input Parameters:
- *   devpath - The full path to the driver to register. E.g., "/dev/temp0"
  *   i2c - An instance of the I2C interface to use to communicate with the MAX1704x
  *   addr - The I2C address of the MAX1704x.
  *
  * Returned Value:
- *   Zero (OK) on success; a negated errno value on failure.
+ *   A pointer to the intialized lower-half driver instance.  A NULL pointer
+ *   is returned on a failure to initialize the MAX1704x lower half.
  *
  ****************************************************************************/
 
-int max1704x_register(FAR const char *devpath, FAR struct i2c_dev_s *i2c, uint8_t addr)
+FAR struct battery_lower_s *max1704x_initialize(FAR struct i2c_dev_s *i2c,
+                            uint8_t addr)
 {
   FAR struct max1704x_dev_s *priv;
   int ret;
@@ -186,23 +193,13 @@ int max1704x_register(FAR const char *devpath, FAR struct i2c_dev_s *i2c, uint8_
   /* Initialize theMAX1704x device structure */
 
   priv = (FAR struct max1704x_dev_s *)kzalloc(sizeof(struct max1704x_dev_s));
-  if (!priv)
+  if (priv)
     {
-      i2cdbg("Failed to allocate instance\n");
+      priv->ops   = &g_max1704xfopg;
-      return -ENOMEM;
-    }
-
       priv->i2c   = i2c;
       priv->addr  = addr;
-
-  /* Register the character driver */
-
-  ret = register_driver(devpath, &g_max1704xfopg, 0555, priv);
-  if (ret < 0)
-    {
-      i2cdbg("Failed to register driver: %d\n", ret);
-      free(priv);
     }
-  return ret;
+  return (FAR struct battery_lower_s *)priv;
 }
-#endif /* CONFIG_I2C && CONFIG_I2C_MAX1704X */
+
+#endif /* CONFIG_BATTERY && CONFIG_I2C && CONFIG_I2C_MAX1704X */

nuttx/include/nuttx/ioctl.h

@@ -64,6 +64,7 @@
 #define _ANIOCBASE      (0x0b00) /* Analog (DAC/ADC) ioctl commands */
 #define _PWMIOCBASE     (0x0c00) /* PWM ioctl commands */
 #define _CAIOCBASE      (0x0d00) /* CDC/ACM ioctl commands */
+#define _BATIOCBASE     (0x0e00) /* Battery driver ioctl commands */
 
 /* Macros used to manage ioctl commands */
 
@@ -186,6 +187,12 @@
 #define _CAIOCVALID(c)    (_IOC_TYPE(c)==_CAIOCBASE)
 #define _CAIOC(nr)        _IOC(_CAIOCBASE,nr)
 
+/* NuttX USB CDC/ACM serial driver ioctl definitions ************************/
+/* (see nuttx/power/battery.h) */
+
+#define _BATIOCVALID(c)   (_IOC_TYPE(c)==_BATIOCBASE)
+#define _BATIOC(nr)       _IOC(_BATIOCBASE,nr)
+
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/

nuttx/include/nuttx/power/battery.h

@@ -0,0 +1,202 @@
+/****************************************************************************
+ * include/nuttx/power/battery.h
+ * NuttX Battery Interfaces
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_POWER_BATTERY_H
+#define __INCLUDE_NUTTX_POWER_BATTERY_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/ioctl.h>
+
+#ifdef CONFIG_BATTERY
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+/* CONFIG_BATTERY - Upper half battery driver support
+ *
+ * Specific, lower-half drivers will have other configuration requirements
+ * such as:
+ *
+ *   CONFIG_I2C - I2C support *may* be needed
+ *   CONFIG_I2C_MAX1704X - The MAX1704x driver must be explictly selected.
+ */
+
+/* IOCTL Commands ***********************************************************/
+/* The upper-half battery driver provides a character driver "wrapper"
+ * around the lower-half battery driver that does all of the real work.
+ * Since there is no real data transfer to/or from a battery, all of the
+ * driver interaction is through IOCTIL commands.  The IOCTL commands
+ * supported by the upper-half driver simply provide calls into the the
+ * lower half as summarized below:
+ *
+ * BATIOC_STATE - Return the current state of the battery (see
+ *   enum battery_status_e).
+ *   Input value:  A pointer to type int.
+ * BATIOC_ONLINE - Return 1 if the battery is online; 0 if offline.
+ *   Input value:  A pointer to type bool.
+ * BATIOC_VOLTAGE - Return the current battery voltage.
+ *   Input value:  A pointer to type int.
+ * BATIOC_CAPACITY - Return the current battery capacity.
+ *   Input value:  A pointer to type int.
+ */
+
+#define BATIOC_STATE    _BATIOC(0x0001)
+#define BATIOC_ONLINE   _BATIOC(0x0001)
+#define BATIOC_VOLTAGE  _BATIOC(0x0001)
+#define BATIOC_CAPACITY _BATIOC(0x0001)
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+/* Battery status */
+
+enum battery_status_e
+{
+  BATTERY_UNKNOWN = 0, /* Battery state is not known */
+  BATTERY_IDLE,        /* Not full, not charging, not discharging */
+  BATTERY_FULL,        /* Full, not discharging */
+  BATTERY_CHARGING,    /* Not full, charging */
+  BATTERY_DISCHARGING  /* Probably not full, discharging */
+};
+
+ /* This structure defines the lower half battery interface */
+
+struct battery_lower_s;
+struct battery_operations_s
+{
+  /* Return the current battery state */
+
+  enum battery_status_e state(struct battery_lower_s *lower);
+
+  /* Return true if the batter is online */
+
+  bool online(struct battery_lower_s *lower);
+
+  /* Current battery voltage */
+
+  int voltage(struct battery_lower_s *lower);
+
+  /* Battery capacity */
+
+  int capacity(struct battery_lower_s *lower);
+};
+
+/* This structure defines the lower half battery driver state structure */
+
+struct battery_lower_s
+{
+  FAR const struct battery_operations_s *ops; /* Battery operations */
+
+  /* Data fields specific to the lower half driver may follow */
+};
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C" {
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+/****************************************************************************
+ * Name: battery_register
+ *
+ * Description:
+ *   Register a lower half battery driver with the common, upper-half
+ *   battery driver.
+ *
+ * Input parameters:
+ *   devpath - The location in the pseudo-filesystem to create the driver.
+ *     Recommended standard is "/dev/bat0", "/dev/bat1", etc.
+ *   lower - The lower half battery state.
+ *
+ * Returned value:
+ *    Zero on success or a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+EXTERN int battery_register(FAR const char *devpath,
+                            FAR struct battery_lower_s *lower);
+
+/****************************************************************************
+ * Name: max1704x_initialize
+ *
+ * Description:
+ *   Initialize the MAX1704x battery driver and return an instance of the
+ *   lower_half interface that may be used with battery_register();
+ *
+ *   This driver requires:
+ *
+ *   CONFIG_BATTERY - Upper half battery driver support
+ *   CONFIG_I2C - I2C support
+ *   CONFIG_I2C_MAX1704X - And the driver must be explictly selected.
+ *
+ * Input Parameters:
+ *   i2c - An instance of the I2C interface to use to communicate with the MAX1704x
+ *   addr - The I2C address of the MAX1704x.
+ *
+ * Returned Value:
+ *   A pointer to the intialized lower-half driver instance.  A NULL pointer
+ *   is returned on a failure to initialize the MAX1704x lower half.
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_I2C) && defined(CONFIG_I2C_MAX1704X)
+EXTERN FAR struct battery_lower_s *
+  max1704x_initialize(FAR struct i2c_dev_s *i2c, uint8_t addr);
+#endif
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* CONFIG_BATTERY */
+#endif /* __INCLUDE_NUTTX_POWER_BATTERY_H */