nt-lite/code/drivers/input/ps2/ps2_i8042.c

// ps2_i8042.c - 8042 controller and device command helpers.
#include "ps2.h"

void Ps2Pause(void) {
    _mm_pause();
}

void Ps2WaitInput(void) {
    int timeout = 100000;
    while ((__inbyte(PS2_STAT) & PS2_STAT_IN_FULL) && --timeout) {
        Ps2Pause();
    }
}

bool Ps2WaitOutput(void) {
    int timeout = 5000000;
    while (!(__inbyte(PS2_STAT) & PS2_STAT_OUT_FULL) && --timeout) {
        Ps2Pause();
    }
    return timeout != 0;
}

void Ps2FlushOutput(void) {
    int timeout = 100000;
    while ((__inbyte(PS2_STAT) & PS2_STAT_OUT_FULL) && --timeout) {
        (void)__inbyte(PS2_DATA);
    }
}

uint8_t Ps2ReadData(void) {
    if (!Ps2WaitOutput()) return 0xFFu;
    return __inbyte(PS2_DATA);
}

void Ps2WriteCommand(uint8_t command) {
    Ps2WaitInput();
    __outbyte(PS2_CMD, command);
}

void Ps2WriteData(uint8_t data) {
    Ps2WaitInput();
    __outbyte(PS2_DATA, data);
}

uint8_t Ps2ReadCommandByte(void) {
    Ps2WriteCommand(0x20u);
    return Ps2ReadData();
}

void Ps2WriteCommandByte(uint8_t commandByte) {
    Ps2WriteCommand(0x60u);
    Ps2WriteData(commandByte);
}

bool Ps2SendKeyboard(uint8_t byte) {
    Ps2WriteData(byte);
    return Ps2ReadData() == 0xFAu;
}

bool Ps2SendMouse(uint8_t byte) {
    Ps2WriteCommand(0xD4u);
    Ps2WriteData(byte);
    return Ps2ReadData() == 0xFAu;
}