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1 /*
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2 DOS interrupt-based keyboard driver.
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3 Copyright (C) 2013 John Tsiombikas <nuclear@member.fsf.org>
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4
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5 This program is free software: you can redistribute it and/or modify
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6 it under the terms of the GNU General Public License as published by
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7 the Free Software Foundation, either version 3 of the License, or
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8 (at your option) any later version.
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9
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10 This program is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 You should have received a copy of the GNU General Public License
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16 along with the program. If not, see <http://www.gnu.org/licenses/>
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17 */
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18 #define KEYB_C_
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19
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20 #include <stdio.h>
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21 #include <stdlib.h>
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22 #include <string.h>
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23 #include <conio.h>
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24 #include <dos.h>
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25 #include <i86.h>
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26 #include "keyb.h"
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27 #include "scancode.h"
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28
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29 #define KB_INTR 0x9
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30 #define KB_PORT 0x60
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31
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32 #define PIC1_CMD_PORT 0x20
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33 #define OCW2_EOI (1 << 5)
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34
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35 #define DONE_INIT (prev_handler)
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36
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37 static void __interrupt __far kbintr();
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38
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39 static void (__interrupt __far *prev_handler)();
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40
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41 static int *buffer;
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42 static int buffer_size, buf_ridx, buf_widx;
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43 static int last_key;
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44
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45 static unsigned char keystate[256];
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46
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47 #define ADVANCE(x) ((x) = ((x) + 1) % buffer_size)
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48
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49 int kb_init(int bufsz)
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50 {
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51 if(DONE_INIT) {
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52 fprintf(stderr, "keyboard driver already initialized!\n");
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53 return 0;
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54 }
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55
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56 buffer_size = bufsz;
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57 if(buffer_size && !(buffer = malloc(buffer_size * sizeof *buffer))) {
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58 fprintf(stderr, "failed to allocate input buffer, continuing without\n");
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59 buffer_size = 0;
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60 }
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61 buf_ridx = buf_widx = 0;
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62 last_key = -1;
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63
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64 memset(keystate, 0, sizeof keystate);
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65
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66 /* set our interrupt handler */
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67 _disable();
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68 prev_handler = _dos_getvect(KB_INTR);
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69 _dos_setvect(KB_INTR, kbintr);
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70 _enable();
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71
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72 return 0;
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73 }
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74
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75 void kb_shutdown(void)
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76 {
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77 if(!DONE_INIT) {
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78 return;
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79 }
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80
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81 /* restore the original interrupt handler */
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82 _disable();
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83 _dos_setvect(KB_INTR, prev_handler);
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84 _enable();
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85
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86 free(buffer);
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87 }
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88
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89 int kb_isdown(int key)
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90 {
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91 return (int)keystate[key];
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92 }
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93
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94 void kb_wait(void)
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95 {
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96 int key;
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97 while((key = kb_getkey()) == -1) {
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98 /* put the processor to sleep while waiting for keypresses, but first
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99 * make sure interrupts are enabled, or we'll sleep forever
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100 */
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101 __asm {
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102 sti
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103 hlt
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104 }
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105 }
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106 kb_putback(key);
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107 }
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108
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109 int kb_getkey(void)
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110 {
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111 int res;
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112
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113 if(buffer) {
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114 if(buf_ridx == buf_widx) {
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115 return -1;
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116 }
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117 res = buffer[buf_ridx];
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118 ADVANCE(buf_ridx);
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119 } else {
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120 res = last_key;
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121 last_key = -1;
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122 }
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123 return res;
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124 }
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125
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126 void kb_putback(int key)
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127 {
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128 if(buffer) {
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129 /* go back a place */
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130 if(--buf_ridx < 0) {
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131 buf_ridx += buffer_size;
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132 }
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133
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134 /* if the write end hasn't caught up with us, go back one place
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135 * and put it there, otherwise just overwrite the oldest key which
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136 * is right where we were.
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137 */
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138 if(buf_ridx == buf_widx) {
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139 ADVANCE(buf_ridx);
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140 }
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141
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142 buffer[buf_ridx] = key;
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143 } else {
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144 last_key = key;
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145 }
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146 }
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147
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148 static void __interrupt __far kbintr()
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149 {
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150 unsigned char code;
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151 int key, press;
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152
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153 code = inp(KB_PORT);
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154
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155 if(code >= 128) {
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156 press = 0;
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157 code -= 128;
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158 } else {
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159 press = 1;
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160 }
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161
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162 key = scantbl[code];
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163
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164 if(press) {
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165 /* append to buffer */
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166 last_key = key;
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167 if(buffer_size > 0) {
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168 buffer[buf_widx] = key;
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169 ADVANCE(buf_widx);
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170 /* if the write end overtook the read end, advance the read end
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171 * too, to discard the oldest keypress from the buffer
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172 */
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173 if(buf_widx == buf_ridx) {
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174 ADVANCE(buf_ridx);
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175 }
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176 }
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177 }
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178
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179 /* and update keystate table */
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180 keystate[key] = press;
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181
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182 outp(PIC1_CMD_PORT, OCW2_EOI); /* send end-of-interrupt */
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183 }
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