Keyboard

Description

The keyboard driver is used to add a first form of input in k. It just detects when a key is pressed by configuring the keyboard controller to trigger interrupt when a key is pressed. You have to implement the non-blocking syscall getkey(). The chip managing the keyboard on the IBM PC is the Intel 8042.

Syscall interface

NAME
    getkey - handle the keyboard
SYNOPSIS
    int getkey(void);
DESCRIPTION
    getkey() returns the last pressed key. It does not support simultaneous key strikes.
RETURN VALUE
    getkey() returns the key code, or -1 if no key was pressed.
SEE ALSO
    Useful constants for scan codes are defined in k/kstd.h.

Recommended methodology

• Ensure that the event manager is working
• Initialize the driver:
  • Add the keyboard interrupt gate to the IDT
  • Update the PIC to unmask the IRQ line 1
• Write a very simple keyboard handler:
  • Read scancodes from I/O port 0x60
  • Extra features such as modifier keys or simultaneous key strikes support are not mandatory
• Implement getkey() as described previously
• You might implement a queue for the keyboard buffer
• You don’t have to push released keys in the buffer

Possible bug causes

• Execution context may be corrupted. Check twice whether the context is correctly restored and whether the stack is well adjusted before returning from interrupt handler
• Hardware interrupts may have been disabled with cli or may not have been enabled with sti
• The keyboard interrupt may be masked in the PIC