arch/x86/boot/tty.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright (C) 1991, 1992 Linus Torvalds
   4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5  *   Copyright 2009 Intel Corporation; author H. Peter Anvin
   6  *
   7  *   This file is part of the Linux kernel, and is made available under
   8  *   the terms of the GNU General Public License version 2.
   9  *
  10  * ----------------------------------------------------------------------- */
  11
  12 /*
  13  * Very simple screen I/O
  14  * XXX: Probably should add very simple serial I/O?
  15  */
  16
  17 #include "boot.h"
  18
  19 /*
  20  * These functions are in .inittext so they can be used to signal
  21  * error during initialization.
  22  */
  23
  24 void __attribute__((section(".inittext"))) putchar(int ch)
  25 {
  26         struct biosregs ireg;
  27
  28         if (ch == '\n')
  29                 putchar('\r');  /* \n -> \r\n */
  30
  31         initregs(&ireg);
  32         ireg.bx = 0x0007;
  33         ireg.cx = 0x0001;
  34         ireg.ah = 0x0e;
  35         ireg.al = ch;
  36         intcall(0x10, &ireg, NULL);
  37 }
  38
  39 void __attribute__((section(".inittext"))) puts(const char *str)
  40 {
  41         while (*str)
  42                 putchar(*str++);
  43 }
  44
  45 /*
  46  * Read the CMOS clock through the BIOS, and return the
  47  * seconds in BCD.
  48  */
  49
  50 static u8 gettime(void)
  51 {
  52         struct biosregs ireg, oreg;
  53
  54         initregs(&ireg);
  55         ireg.ah = 0x02;
  56         intcall(0x1a, &ireg, &oreg);
  57
  58         return oreg.dh;
  59 }
  60
  61 /*
  62  * Read from the keyboard
  63  */
  64 int getchar(void)
  65 {
  66         struct biosregs ireg, oreg;
  67
  68         initregs(&ireg);
  69         /* ireg.ah = 0x00; */
  70         intcall(0x16, &ireg, &oreg);
  71
  72         return oreg.al;
  73 }
  74
  75 static int kbd_pending(void)
  76 {
  77         struct biosregs ireg, oreg;
  78
  79         initregs(&ireg);
  80         ireg.ah = 0x01;
  81         intcall(0x16, &ireg, &oreg);
  82
  83         return !(oreg.eflags & X86_EFLAGS_ZF);
  84 }
  85
  86 void kbd_flush(void)
  87 {
  88         for (;;) {
  89                 if (!kbd_pending())
  90                         break;
  91                 getchar();
  92         }
  93 }
  94
  95 int getchar_timeout(void)
  96 {
  97         int cnt = 30;
  98         int t0, t1;
  99
 100         t0 = gettime();
 101
 102         while (cnt) {
 103                 if (kbd_pending())
 104                         return getchar();
 105
 106                 t1 = gettime();
 107                 if (t0 != t1) {
 108                         cnt--;
 109                         t0 = t1;
 110                 }
 111         }
 112
 113         return 0;               /* Timeout! */
 114 }