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
serial_putchar(int ch)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
bios_putchar(int ch)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
putchar(int ch)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
puts(const char * str)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
gettime(void)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 */
getchar(void)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
kbd_pending(void)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
kbd_flush(void)110 void kbd_flush(void)
111 {
112 for (;;) {
113 if (!kbd_pending())
114 break;
115 getchar();
116 }
117 }
118
getchar_timeout(void)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
140