arch/x86/boot/tty.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* -*- linux-c -*- ------------------------------------------------------- *
   3  *
   4  *   Copyright (C) 1991, 1992 Linus Torvalds
   5  *   Copyright 2007 rPath, Inc. - All Rights Reserved
   6  *   Copyright 2009 Intel Corporation; author H. Peter Anvin
   7  *
   8  * ----------------------------------------------------------------------- */
   9
  10 /*
  11  * Very simple screen and serial I/O
  12  */
  13
  14 #include "boot.h"
  15
  16 int early_serial_base;
  17
  18 #define XMTRDY          0x20
  19
  20 #define TXR             0       /*  Transmit register (WRITE) */
  21 #define LSR             5       /*  Line Status               */
  22
  23 /*
  24  * These functions are in .inittext so they can be used to signal
  25  * error during initialization.
  26  */
  27
  28 static void __section(".inittext") serial_putchar(int ch)
  29 {
  30         unsigned timeout = 0xffff;
  31
  32         while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
  33                 cpu_relax();
  34
  35         outb(ch, early_serial_base + TXR);
  36 }
  37
  38 static void __section(".inittext") bios_putchar(int ch)
  39 {
  40         struct biosregs ireg;
  41
  42         initregs(&ireg);
  43         ireg.bx = 0x0007;
  44         ireg.cx = 0x0001;
  45         ireg.ah = 0x0e;
  46         ireg.al = ch;
  47         intcall(0x10, &ireg, NULL);
  48 }
  49
  50 void __section(".inittext") putchar(int ch)
  51 {
  52         if (ch == '\n')
  53                 putchar('\r');  /* \n -> \r\n */
  54
  55         bios_putchar(ch);
  56
  57         if (early_serial_base != 0)
  58                 serial_putchar(ch);
  59 }
  60
  61 void __section(".inittext") puts(const char *str)
  62 {
  63         while (*str)
  64                 putchar(*str++);
  65 }
  66
  67 /*
  68  * Read the CMOS clock through the BIOS, and return the
  69  * seconds in BCD.
  70  */
  71
  72 static u8 gettime(void)
  73 {
  74         struct biosregs ireg, oreg;
  75
  76         initregs(&ireg);
  77         ireg.ah = 0x02;
  78         intcall(0x1a, &ireg, &oreg);
  79
  80         return oreg.dh;
  81 }
  82
  83 /*
  84  * Read from the keyboard
  85  */
  86 int getchar(void)
  87 {
  88         struct biosregs ireg, oreg;
  89
  90         initregs(&ireg);
  91         /* ireg.ah = 0x00; */
  92         intcall(0x16, &ireg, &oreg);
  93
  94         return oreg.al;
  95 }
  96
  97 static int kbd_pending(void)
  98 {
  99         struct biosregs ireg, oreg;
 100
 101         initregs(&ireg);
 102         ireg.ah = 0x01;
 103         intcall(0x16, &ireg, &oreg);
 104
 105         return !(oreg.eflags & X86_EFLAGS_ZF);
 106 }
 107
 108 void kbd_flush(void)
 109 {
 110         for (;;) {
 111                 if (!kbd_pending())
 112                         break;
 113                 getchar();
 114         }
 115 }
 116
 117 int getchar_timeout(void)
 118 {
 119         int cnt = 30;
 120         int t0, t1;
 121
 122         t0 = gettime();
 123
 124         while (cnt) {
 125                 if (kbd_pending())
 126                         return getchar();
 127
 128                 t1 = gettime();
 129                 if (t0 != t1) {
 130                         cnt--;
 131                         t0 = t1;
 132                 }
 133         }
 134
 135         return 0;               /* Timeout! */
 136 }
 137