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 readkey(). The chip managing the keyboard on the IBM PC is the Intel 8042.

Syscall interface

NAME
    readkey - handle the keyboard
SYNOPSIS
    int readkey(struct key_event *event);
DESCRIPTION
    readkey() returns the key events as a FIFO.

    The `event` argument is a `struct key_event` (as specified in `<kstd.h>`):

        struct key_event {
            int state; /* KEY_PRESSED or KEY_RELEASED */
            int key;   /* scan code */
        }

RETURN VALUE
    readkey() returns 0 in case of success.
ERRORS
    -EAGAIN no key event since last call.
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 readkey() as described previously
• You should implement a queue for the keyboard 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