MAX_PINS
rc = alloc_chrdev_region(&devid, 0, MAX_PINS, "scx200_gpio");
cdev_add(&scx200_gpio_cdev, devid, MAX_PINS);
unregister_chrdev_region(MKDEV(major, 0), MAX_PINS);
if (m >= MAX_PINS)
rc = register_chrdev_region(devid, MAX_PINS, "scx200_gpio");
struct lola_pin pins[MAX_PINS];