/*--------------------*/
/*board-dm646x-evm.c*/
int your_cpld_action()
{
  Use global cpld_reg0_client and cpld_client to calls to I2C library.
}

/*--------------------*/
/* your_driver.c*/
static int your_open(...)
{
}

static int your_ioctl(..., args)
{
  your_cpld_action()
}

static int your_close(...)
{
}

struct file_operations your_ops=
{
  .open = your_open,
  .unlocked_ioctl = your_ioctl,
  .release = your_close,
}

MODULE_DESCRIPTION("CPLD Device Driver")
static int __init Init(void)
{
  class_create(...)
  alloc_chrdev_region(...)
  device_create(..., "cpld") <--- "/dev/cpld" created here
  cdev_init(..., your_ops) <--- your ops registered here
}
module_init(init);

static int __exit cleanup(void)
{
  cdev_del()
  device_destory(...)
  unregister_chrdev_region(...)
  class_destroy(...)
}
module_init(init);

/*--------------------*/
/* your_app.c */
int main(...)
{
  int fd;
  fd = open("/dev/cpld")
  ioctl(fd, args);
  close(fd);
}

Example above is derived from "drivers/usb/gadget/printer.c".