video-bios.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.
 *
 * ----------------------------------------------------------------------- */

/*
 * Standard video BIOS modes
 *
 * We have two options for this; silent and scanned.
 */

#include "boot.h"
#include "video.h"

static __videocard video_bios;

/* Set a conventional BIOS mode */
static int set_bios_mode(u8 mode);

static int bios_set_mode(struct mode_info *mi)
{
    return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
}

static int set_bios_mode(u8 mode)
{
    struct biosregs ireg, oreg;
    u8 new_mode;

    initregs(&ireg);
    ireg.al = mode;     /* AH=0x00 Set Video Mode */
    intcall(0x10, &ireg, NULL);

    ireg.ah = 0x0f;     /* Get Current Video Mode */
    intcall(0x10, &ireg, &oreg);

    do_restore = 1;     /* Assume video contents were lost */

    /* Not all BIOSes are clean with the top bit */
    new_mode = oreg.al & 0x7f;

    if (new_mode == mode)
        return 0;   /* Mode change OK */

#ifndef _WAKEUP
    if (new_mode != boot_params.screen_info.orig_video_mode) {
        /* Mode setting failed, but we didn't end up where we
           started.  That's bad.  Try to revert to the original
           video mode. */
        ireg.ax = boot_params.screen_info.orig_video_mode;
        intcall(0x10, &ireg, NULL);
    }
#endif
    return -1;
}

static int bios_probe(void)
{
    u8 mode;
#ifdef _WAKEUP
    u8 saved_mode = 0x03;
#else
    u8 saved_mode = boot_params.screen_info.orig_video_mode;
#endif
    u16 crtc;
    struct mode_info *mi;
    int nmodes = 0;

    if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
        return 0;

    set_fs(0);
    crtc = vga_crtc();

    video_bios.modes = GET_HEAP(struct mode_info, 0);

    for (mode = 0x14; mode <= 0x7f; mode++) {
        if (!heap_free(sizeof(struct mode_info)))
            break;

        if (mode_defined(VIDEO_FIRST_BIOS+mode))
            continue;

        if (set_bios_mode(mode))
            continue;

        /* Try to verify that it's a text mode. */

        /* Attribute Controller: make graphics controller disabled */
        if (in_idx(0x3c0, 0x10) & 0x01)
            continue;

        /* Graphics Controller: verify Alpha addressing enabled */
        if (in_idx(0x3ce, 0x06) & 0x01)
            continue;

        /* CRTC cursor location low should be zero(?) */
        if (in_idx(crtc, 0x0f))
            continue;

        mi = GET_HEAP(struct mode_info, 1);
        mi->mode = VIDEO_FIRST_BIOS+mode;
        mi->depth = 0;  /* text */
        mi->x = rdfs16(0x44a);
        mi->y = rdfs8(0x484)+1;
        nmodes++;
    }

    set_bios_mode(saved_mode);

    return nmodes;
}

static __videocard video_bios =
{
    .card_name  = "BIOS",
    .probe      = bios_probe,
    .set_mode   = bios_set_mode,
    .unsafe     = 1,
    .xmode_first    = VIDEO_FIRST_BIOS,
    .xmode_n    = 0x80,
};