The commonly used io buttons and USB keyboards obtain the button status by reading /dev/input/eventX; but maybe after you configure the USB keyboard driver and IO driver, there is no device node under /dev/;
At this point, check whether the kernel is configured with the Event interface
Add event keys,
device/support in the kernel
【*】Event interface
After the node appears, you can view related information
cat /proc/bus/input/devices
You can also read the key value with the following command:
cat /dev/input/event0 | hexdump