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 and serial I/O
  14  */
  15
  16 #include "boot.h"
  17
  18 int early_serial_base;
  19
  20 #define XMTRDY          0x20
  21
  22 #define TXR             0       /*  Transmit register (WRITE) */
  23 #define LSR             5       /*  Line Status               */
  24
  25 /*
  26  * These functions are in .inittext so they can be used to signal
  27  * error during initialization.
  28  */
  29
  30 static void __attribute__((section(".inittext"))) serial_putchar(int ch)
  31 {
  32         unsigned timeout = 0xffff;
  33
  34         while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
  35                 cpu_relax();
  36
  37         outb(ch, early_serial_base + TXR);
  38 }
  39
  40 static void __attribute__((section(".inittext"))) bios_putchar(int ch)
  41 {
  42         struct biosregs ireg;
  43
  44         initregs(&ireg);
  45         ireg.bx = 0x0007;
  46         ireg.cx = 0x0001;
  47         ireg.ah = 0x0e;
  48         ireg.al = ch;
  49         intcall(0x10, &ireg, NULL);
  50 }
  51
  52 void __attribute__((section(".inittext"))) putchar(int ch)
  53 {
  54         if (ch == '\n')
  55                 putchar('\r');  /* \n -> \r\n */
  56
  57         bios_putchar(ch);
  58
  59         if (early_serial_base != 0)
  60                 serial_putchar(ch);
  61 }
  62
  63 void __attribute__((section(".inittext"))) puts(const char *str)
  64 {
  65         while (*str)
  66                 putchar(*str++);
  67 }
  68
  69 /*
  70  * Read the CMOS clock through the BIOS, and return the
  71  * seconds in BCD.
  72  */
  73
  74 static u8 gettime(void)
  75 {
  76         struct biosregs ireg, oreg;
  77
  78         initregs(&ireg);
  79         ireg.ah = 0x02;
  80         intcall(0x1a, &ireg, &oreg);
  81
  82         return oreg.dh;
  83 }
  84
  85 /*
  86  * Read from the keyboard
  87  */
  88 int getchar(void)
  89 {
  90         struct biosregs ireg, oreg;
  91
  92         initregs(&ireg);
  93         /* ireg.ah = 0x00; */
  94         intcall(0x16, &ireg, &oreg);
  95
  96         return oreg.al;
  97 }
  98
  99 static int kbd_pending(void)
 100 {
 101         struct biosregs ireg, oreg;
 102
 103         initregs(&ireg);
 104         ireg.ah = 0x01;
 105         intcall(0x16, &ireg, &oreg);
 106
 107         return !(oreg.eflags & X86_EFLAGS_ZF);
 108 }
 109
 110 void kbd_flush(void)
 111 {
 112         for (;;) {
 113                 if (!kbd_pending())
 114                         break;
 115                 getchar();
 116         }
 117 }
 118
 119 int getchar_timeout(void)
 120 {
 121         int cnt = 30;
 122         int t0, t1;
 123
 124         t0 = gettime();
 125
 126         while (cnt) {
 127                 if (kbd_pending())
 128                         return getchar();
 129
 130                 t1 = gettime();
 131                 if (t0 != t1) {
 132                         cnt--;
 133                         t0 = t1;
 134                 }
 135         }
 136
 137         return 0;               /* Timeout! */
 138 }
 139