maximal_driver.c

This example is discussed in Writing a new device driver

/******************************************************************************
 *
 * This is a demo of how to implement a driver-device plugin.
 * 
 * The idea is to use every single feature of the API.
 *
 * Yes, the debugging output is excessive.
 *
 *******************************************************************************/

#include <stdlib.h>
#include <devbot/core/driver.h>
#include <devbot/distance.h>


#define _DEBUG_TRACE(...) g_debug(__VA_ARGS__)


/*******************************************************************************
 * Driver implementation
 *******************************************************************************/

static gboolean initialize_driver(void)
{
  _DEBUG_TRACE("initialize_driver");
  /* Perform initialization here e.g. registering with other drivers, initializing other libraries */
  return TRUE;
}

static gboolean free_driver(void)
{
  _DEBUG_TRACE("free_driver");
  /* Perform any cleanups necessitated by initialization process */
  return TRUE;
}

struct _privateDeviceData
{
  int call_count;
};

typedef struct _privateDeviceData privateDeviceData;

static gboolean initialize_device_data (gpointer *data, 
                             BotDeviceConfiguration *configuration)
{
  _DEBUG_TRACE("create_device_data");

  /* 1. Allocate space for our private data */
  privateDeviceData *my_data = g_new0(privateDeviceData, 1);
  if (my_data == NULL) goto creation_failed;

  /* 2. Use configuration to populate it */
  gchar *value;
  gchar *tmp;

  _DEBUG_TRACE(" -> Configuring device");
  
  if (configuration == NULL)
  {
    g_warning("debug devices require configuration");
    goto creation_failed;
  }

  /* 2a. A required configuration value */
  _DEBUG_TRACE(" -> Looking for Required_value");
  value = bot_configuration_get_value(configuration, "Required_value");
  if (value == NULL)
  {
    g_warning("debug devices must specify a value for the 'Required_value' option");
    goto creation_failed;
  }

  _DEBUG_TRACE(" -> Looking for Initial_call_count");
  /* 2b. An optional configuration value */
  value = bot_configuration_get_value(configuration, "Initial_call_count");
  if (value != NULL)
  {
    my_data->call_count = (int) strtol(value, &tmp, 0);
    _DEBUG_TRACE("call_count set to %d by configuration", my_data->call_count);
  }

  /* 3. Set the device data pointer to our newly constructed data */
  *data = my_data;
  _DEBUG_TRACE(" -> Initalization complete");
  return TRUE;

creation_failed:
  _DEBUG_TRACE("Failed to create debug device (see above for reason)");
  g_free(my_data);
  return FALSE;

}

static gboolean free_device_data (gpointer data)
{
    _DEBUG_TRACE("free_device_data");
    g_free(data);

    return 0;
}

static gpointer get_interface (BotDevice *device, BotInterface *type);

BOT_DRIVER_BOILERPLATE("debug",
                       "A maximal driver, demonstrating all the features of the driver API",
                       "1.0",
                       &initialize_driver,
                       &free_driver,
                       &initialize_device_data,
                       &free_device_data,
                       &get_interface);

/*******************************************************************************
 * Interface definitions
 *******************************************************************************/

/* Forward declarations of supported interfaces */
BotDistance _distanceInterface;

/* Return an interface structure of the specified type or NULL if not available */
static gpointer get_interface(BotDevice *device, BotInterface *type)
{
  _DEBUG_TRACE("get_interface (%s)", type->name);
  if (BotDistanceInterface == type) return &_distanceInterface;
  return NULL;
}

/*******************************************************************************
 *
 * Rangefinder implementation
 *
 *******************************************************************************/

static double get_metre(BotDevice *device)
{
  _DEBUG_TRACE("get_distance");
  return ((privateDeviceData *) bot_device_get_data(device))->call_count++;
}

BotDistance _distanceInterface = 
{
  .get_metre = &get_metre
};

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