tty.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * Very simple screen and serial I/O
 */

#include "boot.h"

int early_serial_base;

#define XMTRDY          0x20

#define TXR             0       /*  Transmit register (WRITE) */
#define LSR             5       /*  Line Status               */

/*
 * These functions are in .inittext so they can be used to signal
 * error during initialization.
 */

static void __attribute__((section(".inittext"))) serial_putchar(int ch)
{
    unsigned timeout = 0xffff;

    while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
        cpu_relax();

    outb(ch, early_serial_base + TXR);
}

static void __attribute__((section(".inittext"))) bios_putchar(int ch)
{
    struct biosregs ireg;

    initregs(&ireg);
    ireg.bx = 0x0007;
    ireg.cx = 0x0001;
    ireg.ah = 0x0e;
    ireg.al = ch;
    intcall(0x10, &ireg, NULL);
}

void __attribute__((section(".inittext"))) putchar(int ch)
{
    if (ch == '\n')
        putchar('\r');  /* \n -> \r\n */

    bios_putchar(ch);

    if (early_serial_base != 0)
        serial_putchar(ch);
}

void __attribute__((section(".inittext"))) puts(const char *str)
{
    while (*str)
        putchar(*str++);
}

/*
 * Read the CMOS clock through the BIOS, and return the
 * seconds in BCD.
 */

static u8 gettime(void)
{
    struct biosregs ireg, oreg;

    initregs(&ireg);
    ireg.ah = 0x02;
    intcall(0x1a, &ireg, &oreg);

    return oreg.dh;
}

/*
 * Read from the keyboard
 */
int getchar(void)
{
    struct biosregs ireg, oreg;

    initregs(&ireg);
    /* ireg.ah = 0x00; */
    intcall(0x16, &ireg, &oreg);

    return oreg.al;
}

static int kbd_pending(void)
{
    struct biosregs ireg, oreg;

    initregs(&ireg);
    ireg.ah = 0x01;
    intcall(0x16, &ireg, &oreg);

    return !(oreg.eflags & X86_EFLAGS_ZF);
}

void kbd_flush(void)
{
    for (;;) {
        if (!kbd_pending())
            break;
        getchar();
    }
}

int getchar_timeout(void)
{
    int cnt = 30;
    int t0, t1;

    t0 = gettime();

    while (cnt) {
        if (kbd_pending())
            return getchar();

        t1 = gettime();
        if (t0 != t1) {
            cnt--;
            t0 = t1;
        }
    }

    return 0;       /* Timeout! */
}