change keyboard operation in linux

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Linux

I have a trouble with studying linux kernel
I want to change the kernel that it prints 'x pressed' for each key pressing, where x is the scan code of the key
I tried to add printk(" pressed\n") in
'static irqreturn_t atkbd_interrupt()' function at drivers/input/keyboard/atkbd.c
but when I press key, it printed
pressed
a pressed
pressed
b pressed
...
I don't know why it prints twice

and want to change scan code when type 'u', the monitor display 'i'
but I couldn't find the location where scan code defined.

Need your help