root/arch/x86/boot/video-mode.c

DEFINITIONS

1. probe_cards
2. mode_defined
3. raw_set_mode
4. vga_recalc_vertical
5. set_mode

/* -*- 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;
}