Espresso/drivers/ps2_keyboard.c

#include <stdio.h>
#include <port_io.h>
#include <tty.h>
#include <stdlib.h>

#include <drivers/ps2_keyboard.h>


/*
  PS/2 Controller IO Ports

  The PS/2 Controller itself uses 2 IO ports (IO ports 0x60 and 0x64). Like many IO ports, reads and writes may access different internal registers.

  Historical note: The PC-XT PPI had used port 0x61 to reset the keyboard interrupt request signal (among other unrelated functions). Port 0x61 has no keyboard related functions on AT and PS/2 compatibles.
  IO Port  Access Type  Purpose
  0x60 	 Read/Write   Data Port
  0x64 	 Read 	     Status Register
  0x64 	 Write 	     Command Register
*/

/*
  Note:
   The interrupt number for keyboard input in 1.
*/

#define PS2_DATA_PORT   0x60
#define PS2_STATUS_PORT 0x64

#define KEYBOARD_IRQ    1

bool ps2keyboard_initialized = false;

/* State for shift key */
static bool shift_pressed = false;

/* State for caps-lock key */
static bool capslock_pressed = false;

volatile char current_char;
volatile char* current_string = NULL;
volatile int32_t current_length = 0;
volatile int32_t capacity = 0;


static const char scancode_map[128] = {
  0,  27, '1','2','3','4','5','6','7','8','9','0','-','=','\b', /* Backspace */
  '\t', // Tab
  'q','w','e','r','t','y','u','i','o','p','[',']','\n', /* Enter */
  0, /* Control */
  'a','s','d','f','g','h','j','k','l',';','\'','`',
  0, /* Left shift */
  '\\','z','x','c','v','b','n','m',',','.','/',
  0, /* Right shift */
  '*',
  0, /* Alt */
  ' ', /* Spacebar */
  0, /* Caps lock */
  /* The rest are function and control keys */
};


void keyboard_init(void)
{
  outb(0x64, 0xAE); /* Enable keyboard interface (often optional, but here for safety) */
  ps2keyboard_initialized = true;
}

char get_char(void)
{
  return current_char;
}

char* get_string(void)
{
  return current_string;
}

static void append_char(char c)
{
  if (current_length + 1 >= capacity)
  {
    /* Need more space (+1 for the null zero) */
    int new_capacity = (capacity == 0) ? 16 : capacity * 2;

    char* new_str = (char*)malloc(new_capacity);
    if (!new_str) {
      return;
    }

    if (current_string)
    {
      memcpy(new_str, current_string, current_length);
      free(current_string);
    }
    
    if (!current_string)
    {
      return;
    }

    current_string = new_str;
    capacity = new_capacity;
  }

  current_string[current_length] = c;
  current_length++;
  current_string[current_length] = '\0';  /* Maintain null terminator */
}

static void free_current_string(void)
{
  if (current_string)
  {
    free(current_string);
    current_string = NULL;
    current_length = 0;
    capacity = 0;
  }
}

void keyboard_handler(void) {
  uint8_t scancode = inb(PS2_DATA_PORT);

  /* Handle shift press/release */
  if (scancode == 0x2A || scancode == 0x36)
  {
    shift_pressed = true;
    return;
  }
  else if (scancode == 0xAA || scancode == 0xB6)
  {
    shift_pressed = false;
    return;
  }
  else if (scancode == 0x3A)
  {
    capslock_pressed = !capslock_pressed;
    return;
  }


  if (scancode & 0x80)
  {
    /* Key release event, ignore for now */
  } else
  {
    char c = scancode_map[scancode];
    if ((shift_pressed ^ capslock_pressed) && c >= 'a' && c <= 'z') {
      c -= 32; /* Convert to uppercase */
    }
    else if (shift_pressed)
    {
      c = (char) terminal_get_shifted((unsigned char) c);
    }
    
    if (scancode == 0x1C) {
      printf("\n");
      return;
    }


    if (c)
    {
      current_char = c;
      
      if (c == '\n')
      {
        free_current_string();
      }
      else
      {
        append_char(c);
        printf("%c", c);
      }
    }
  }
}