CEC_NUM_DEVICES
int ret = alloc_chrdev_region(&cec_dev_t, 0, CEC_NUM_DEVICES, CEC_NAME);
unregister_chrdev_region(cec_dev_t, CEC_NUM_DEVICES);
unregister_chrdev_region(cec_dev_t, CEC_NUM_DEVICES);
static DECLARE_BITMAP(cec_devnode_nums, CEC_NUM_DEVICES);
minor = find_first_zero_bit(cec_devnode_nums, CEC_NUM_DEVICES);
if (minor == CEC_NUM_DEVICES) {