video-mode.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007-2008 rPath, Inc. - All Rights Reserved
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * arch/i386/boot/video-mode.c
 *
 * Set the video mode.  This is separated out into a different
 * file in order to be shared with the ACPI wakeup code.
 */

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

/*
 * Common variables
 */
int adapter;            /* 0=CGA/MDA/HGC, 1=EGA, 2=VGA+ */
u16 video_segment;
int force_x, force_y;   /* Don't query the BIOS for cols/rows */

int do_restore;     /* Screen contents changed during mode flip */
int graphic_mode;   /* Graphic mode with linear frame buffer */

/* Probe the video drivers and have them generate their mode lists. */
void probe_cards(int unsafe)
{
    struct card_info *card;
    static u8 probed[2];

    if (probed[unsafe])
        return;

    probed[unsafe] = 1;

    for (card = video_cards; card < video_cards_end; card++) {
        if (card->unsafe == unsafe) {
            if (card->probe)
                card->nmodes = card->probe();
            else
                card->nmodes = 0;
        }
    }
}

/* Test if a mode is defined */
int mode_defined(u16 mode)
{
    struct card_info *card;
    struct mode_info *mi;
    int i;

    for (card = video_cards; card < video_cards_end; card++) {
        mi = card->modes;
        for (i = 0; i < card->nmodes; i++, mi++) {
            if (mi->mode == mode)
                return 1;
        }
    }

    return 0;
}

/* Set mode (without recalc) */
static int raw_set_mode(u16 mode, u16 *real_mode)
{
    int nmode, i;
    struct card_info *card;
    struct mode_info *mi;

    /* Drop the recalc bit if set */
    mode &= ~VIDEO_RECALC;

    /* Scan for mode based on fixed ID, position, or resolution */
    nmode = 0;
    for (card = video_cards; card < video_cards_end; card++) {
        mi = card->modes;
        for (i = 0; i < card->nmodes; i++, mi++) {
            int visible = mi->x || mi->y;

            if ((mode == nmode && visible) ||
                mode == mi->mode ||
                mode == (mi->y << 8)+mi->x) {
                *real_mode = mi->mode;
                return card->set_mode(mi);
            }

            if (visible)
                nmode++;
        }
    }

    /* Nothing found?  Is it an "exceptional" (unprobed) mode? */
    for (card = video_cards; card < video_cards_end; card++) {
        if (mode >= card->xmode_first &&
            mode < card->xmode_first+card->xmode_n) {
            struct mode_info mix;
            *real_mode = mix.mode = mode;
            mix.x = mix.y = 0;
            return card->set_mode(&mix);
        }
    }

    /* Otherwise, failure... */
    return -1;
}

/*
 * Recalculate the vertical video cutoff (hack!)
 */
static void vga_recalc_vertical(void)
{
    unsigned int font_size, rows;
    u16 crtc;
    u8 pt, ov;

    set_fs(0);
    font_size = rdfs8(0x485); /* BIOS: font size (pixels) */
    rows = force_y ? force_y : rdfs8(0x484)+1; /* Text rows */

    rows *= font_size;  /* Visible scan lines */
    rows--;         /* ... minus one */

    crtc = vga_crtc();

    pt = in_idx(crtc, 0x11);
    pt &= ~0x80;        /* Unlock CR0-7 */
    out_idx(pt, crtc, 0x11);

    out_idx((u8)rows, crtc, 0x12); /* Lower height register */

    ov = in_idx(crtc, 0x07); /* Overflow register */
    ov &= 0xbd;
    ov |= (rows >> (8-1)) & 0x02;
    ov |= (rows >> (9-6)) & 0x40;
    out_idx(ov, crtc, 0x07);
}

/* Set mode (with recalc if specified) */
int set_mode(u16 mode)
{
    int rv;
    u16 real_mode;

    /* Very special mode numbers... */
    if (mode == VIDEO_CURRENT_MODE)
        return 0;   /* Nothing to do... */
    else if (mode == NORMAL_VGA)
        mode = VIDEO_80x25;
    else if (mode == EXTENDED_VGA)
        mode = VIDEO_8POINT;

    rv = raw_set_mode(mode, &real_mode);
    if (rv)
        return rv;

    if (mode & VIDEO_RECALC)
        vga_recalc_vertical();

    /* Save the canonical mode number for the kernel, not
       an alias, size specification or menu position */
#ifndef _WAKEUP
    boot_params.hdr.vid_mode = real_mode;
#endif
    return 0;
}