/*-
 * Copyright (c) 2005 Marcel Moolenaar
 * All rights reserved.
 *
 * Copyright (c) 2009 The FreeBSD Foundation
 * All rights reserved.
 *
 * Portions of this software were developed by Ed Schouten
 * under sponsorship from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "opt_acpi.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/module.h>
#include <sys/rman.h>

#include <dev/vt/vt.h>
#include <dev/vt/colors/vt_termcolors.h>
#include <dev/vt/hw/vga/vt_vga_reg.h>
#include <dev/pci/pcivar.h>

#include <machine/bus.h>
#if defined(__amd64__) || defined(__i386__)
#include <contrib/dev/acpica/include/acpi.h>
#include <machine/md_var.h>
#endif

struct vga_softc {
        bus_space_tag_t          vga_fb_tag;
        bus_space_handle_t       vga_fb_handle;
        bus_space_tag_t          vga_reg_tag;
        bus_space_handle_t       vga_reg_handle;
        int                      vga_wmode;
        term_color_t             vga_curfg, vga_curbg;
        boolean_t                vga_enabled;
};

/* Convenience macros. */
#define MEM_READ1(sc, ofs) \
        bus_space_read_1(sc->vga_fb_tag, sc->vga_fb_handle, ofs)
#define MEM_WRITE1(sc, ofs, val) \
        bus_space_write_1(sc->vga_fb_tag, sc->vga_fb_handle, ofs, val)
#define MEM_WRITE2(sc, ofs, val) \
        bus_space_write_2(sc->vga_fb_tag, sc->vga_fb_handle, ofs, val)
#define REG_READ1(sc, reg) \
        bus_space_read_1(sc->vga_reg_tag, sc->vga_reg_handle, reg)
#define REG_WRITE1(sc, reg, val) \
        bus_space_write_1(sc->vga_reg_tag, sc->vga_reg_handle, reg, val)

#define VT_VGA_WIDTH    640
#define VT_VGA_HEIGHT   480
#define VT_VGA_MEMSIZE  (VT_VGA_WIDTH * VT_VGA_HEIGHT / 8)

/*
 * VGA is designed to handle 8 pixels at a time (8 pixels in one byte of
 * memory).
 */
#define VT_VGA_PIXELS_BLOCK     8

/*
 * We use an off-screen addresses to:
 *     o  store the background color;
 *     o  store pixels pattern.
 * Those addresses are then loaded in the latches once.
 */
#define VT_VGA_BGCOLOR_OFFSET   VT_VGA_MEMSIZE

static vd_probe_t       vga_probe;
static vd_init_t        vga_init;
static vd_blank_t       vga_blank;
static vd_bitblt_text_t vga_bitblt_text;
static vd_invalidate_text_t     vga_invalidate_text;
static vd_bitblt_bmp_t  vga_bitblt_bitmap;
static vd_bitblt_argb_t vga_bitblt_argb;
static vd_drawrect_t    vga_drawrect;
static vd_setpixel_t    vga_setpixel;
static vd_postswitch_t  vga_postswitch;

static const struct vt_driver vt_vga_driver = {
        .vd_name        = "vga",
        .vd_probe       = vga_probe,
        .vd_init        = vga_init,
        .vd_blank       = vga_blank,
        .vd_bitblt_text = vga_bitblt_text,
        .vd_invalidate_text = vga_invalidate_text,
        .vd_bitblt_bmp  = vga_bitblt_bitmap,
        .vd_bitblt_argb = vga_bitblt_argb,
        .vd_drawrect    = vga_drawrect,
        .vd_setpixel    = vga_setpixel,
        .vd_postswitch  = vga_postswitch,
        .vd_priority    = VD_PRIORITY_GENERIC,
};

/*
 * Driver supports both text mode and graphics mode.  Make sure the
 * buffer is always big enough to support both.
 */
static struct vga_softc vga_conssoftc;
VT_DRIVER_DECLARE(vt_vga, vt_vga_driver);

static inline void
vga_setwmode(struct vt_device *vd, int wmode)
{
        struct vga_softc *sc = vd->vd_softc;

        if (sc->vga_wmode == wmode)
                return;

        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);
        REG_WRITE1(sc, VGA_GC_DATA, wmode);
        sc->vga_wmode = wmode;

        switch (wmode) {
        case 3:
                /* Re-enable all planes. */
                REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_MAP_MASK);
                REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_MM_EM3 | VGA_SEQ_MM_EM2 |
                    VGA_SEQ_MM_EM1 | VGA_SEQ_MM_EM0);
                break;
        }
}

static inline void
vga_setfg(struct vt_device *vd, term_color_t color)
{
        struct vga_softc *sc = vd->vd_softc;

        vga_setwmode(vd, 3);

        if (sc->vga_curfg == color)
                return;

        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_SET_RESET);
        REG_WRITE1(sc, VGA_GC_DATA, cons_to_vga_colors[color]);
        sc->vga_curfg = color;
}

static inline void
vga_setbg(struct vt_device *vd, term_color_t color)
{
        struct vga_softc *sc = vd->vd_softc;

        vga_setwmode(vd, 3);

        if (sc->vga_curbg == color)
                return;

        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_SET_RESET);
        REG_WRITE1(sc, VGA_GC_DATA, cons_to_vga_colors[color]);

        /*
         * Write 8 pixels using the background color to an off-screen
         * byte in the video memory.
         */
        MEM_WRITE1(sc, VT_VGA_BGCOLOR_OFFSET, 0xff);

        /*
         * Read those 8 pixels back to load the background color in the
         * latches register.
         */
        MEM_READ1(sc, VT_VGA_BGCOLOR_OFFSET);

        sc->vga_curbg = color;

        /*
         * The Set/Reset register doesn't contain the fg color anymore,
         * store an invalid color.
         */
        sc->vga_curfg = 0xff;
}

/*
 * Binary searchable table for Unicode to CP437 conversion.
 */

struct unicp437 {
        uint16_t        unicode_base;
        uint8_t         cp437_base;
        uint8_t         length;
};

static const struct unicp437 cp437table[] = {
        { 0x0020, 0x20, 0x5e }, { 0x00a0, 0x20, 0x00 },
        { 0x00a1, 0xad, 0x00 }, { 0x00a2, 0x9b, 0x00 },
        { 0x00a3, 0x9c, 0x00 }, { 0x00a5, 0x9d, 0x00 },
        { 0x00a6, 0x7c, 0x00 },
        { 0x00a7, 0x15, 0x00 }, { 0x00aa, 0xa6, 0x00 },
        { 0x00ab, 0xae, 0x00 }, { 0x00ac, 0xaa, 0x00 },
        { 0x00b0, 0xf8, 0x00 }, { 0x00b1, 0xf1, 0x00 },
        { 0x00b2, 0xfd, 0x00 }, { 0x00b5, 0xe6, 0x00 },
        { 0x00b6, 0x14, 0x00 }, { 0x00b7, 0xfa, 0x00 },
        { 0x00ba, 0xa7, 0x00 }, { 0x00bb, 0xaf, 0x00 },
        { 0x00bc, 0xac, 0x00 }, { 0x00bd, 0xab, 0x00 },
        { 0x00bf, 0xa8, 0x00 }, { 0x00c4, 0x8e, 0x01 },
        { 0x00c6, 0x92, 0x00 }, { 0x00c7, 0x80, 0x00 },
        { 0x00c9, 0x90, 0x00 }, { 0x00d1, 0xa5, 0x00 },
        { 0x00d6, 0x99, 0x00 }, { 0x00dc, 0x9a, 0x00 },
        { 0x00df, 0xe1, 0x00 }, { 0x00e0, 0x85, 0x00 },
        { 0x00e1, 0xa0, 0x00 }, { 0x00e2, 0x83, 0x00 },
        { 0x00e4, 0x84, 0x00 }, { 0x00e5, 0x86, 0x00 },
        { 0x00e6, 0x91, 0x00 }, { 0x00e7, 0x87, 0x00 },
        { 0x00e8, 0x8a, 0x00 }, { 0x00e9, 0x82, 0x00 },
        { 0x00ea, 0x88, 0x01 }, { 0x00ec, 0x8d, 0x00 },
        { 0x00ed, 0xa1, 0x00 }, { 0x00ee, 0x8c, 0x00 },
        { 0x00ef, 0x8b, 0x00 }, { 0x00f0, 0xeb, 0x00 },
        { 0x00f1, 0xa4, 0x00 }, { 0x00f2, 0x95, 0x00 },
        { 0x00f3, 0xa2, 0x00 }, { 0x00f4, 0x93, 0x00 },
        { 0x00f6, 0x94, 0x00 }, { 0x00f7, 0xf6, 0x00 },
        { 0x00f8, 0xed, 0x00 }, { 0x00f9, 0x97, 0x00 },
        { 0x00fa, 0xa3, 0x00 }, { 0x00fb, 0x96, 0x00 },
        { 0x00fc, 0x81, 0x00 }, { 0x00ff, 0x98, 0x00 },
        { 0x0192, 0x9f, 0x00 }, { 0x0393, 0xe2, 0x00 },
        { 0x0398, 0xe9, 0x00 }, { 0x03a3, 0xe4, 0x00 },
        { 0x03a6, 0xe8, 0x00 }, { 0x03a9, 0xea, 0x00 },
        { 0x03b1, 0xe0, 0x01 }, { 0x03b4, 0xeb, 0x00 },
        { 0x03b5, 0xee, 0x00 }, { 0x03bc, 0xe6, 0x00 },
        { 0x03c0, 0xe3, 0x00 }, { 0x03c3, 0xe5, 0x00 },
        { 0x03c4, 0xe7, 0x00 }, { 0x03c6, 0xed, 0x00 },
        { 0x03d5, 0xed, 0x00 }, { 0x2010, 0x2d, 0x00 },
        { 0x2013, 0x2d, 0x00 },
        { 0x2014, 0x2d, 0x00 }, { 0x2018, 0x60, 0x00 },
        { 0x2019, 0x27, 0x00 }, { 0x201c, 0x22, 0x00 },
        { 0x201d, 0x22, 0x00 }, { 0x2022, 0x07, 0x00 },
        { 0x203c, 0x13, 0x00 }, { 0x207f, 0xfc, 0x00 },
        { 0x20a7, 0x9e, 0x00 }, { 0x20ac, 0xee, 0x00 },
        { 0x2126, 0xea, 0x00 }, { 0x2190, 0x1b, 0x00 },
        { 0x2191, 0x18, 0x00 }, { 0x2192, 0x1a, 0x00 },
        { 0x2193, 0x19, 0x00 }, { 0x2194, 0x1d, 0x00 },
        { 0x2195, 0x12, 0x00 }, { 0x21a8, 0x17, 0x00 },
        { 0x2202, 0xeb, 0x00 }, { 0x2208, 0xee, 0x00 },
        { 0x2211, 0xe4, 0x00 }, { 0x2212, 0x2d, 0x00 },
        { 0x2219, 0xf9, 0x00 }, { 0x221a, 0xfb, 0x00 },
        { 0x221e, 0xec, 0x00 }, { 0x221f, 0x1c, 0x00 },
        { 0x2229, 0xef, 0x00 }, { 0x2248, 0xf7, 0x00 },
        { 0x2261, 0xf0, 0x00 }, { 0x2264, 0xf3, 0x00 },
        { 0x2265, 0xf2, 0x00 }, { 0x2302, 0x7f, 0x00 },
        { 0x2310, 0xa9, 0x00 }, { 0x2320, 0xf4, 0x00 },
        { 0x2321, 0xf5, 0x00 }, { 0x2500, 0xc4, 0x00 },
        { 0x2502, 0xb3, 0x00 }, { 0x250c, 0xda, 0x00 },
        { 0x2510, 0xbf, 0x00 }, { 0x2514, 0xc0, 0x00 },
        { 0x2518, 0xd9, 0x00 }, { 0x251c, 0xc3, 0x00 },
        { 0x2524, 0xb4, 0x00 }, { 0x252c, 0xc2, 0x00 },
        { 0x2534, 0xc1, 0x00 }, { 0x253c, 0xc5, 0x00 },
        { 0x2550, 0xcd, 0x00 }, { 0x2551, 0xba, 0x00 },
        { 0x2552, 0xd5, 0x00 }, { 0x2553, 0xd6, 0x00 },
        { 0x2554, 0xc9, 0x00 }, { 0x2555, 0xb8, 0x00 },
        { 0x2556, 0xb7, 0x00 }, { 0x2557, 0xbb, 0x00 },
        { 0x2558, 0xd4, 0x00 }, { 0x2559, 0xd3, 0x00 },
        { 0x255a, 0xc8, 0x00 }, { 0x255b, 0xbe, 0x00 },
        { 0x255c, 0xbd, 0x00 }, { 0x255d, 0xbc, 0x00 },
        { 0x255e, 0xc6, 0x01 }, { 0x2560, 0xcc, 0x00 },
        { 0x2561, 0xb5, 0x00 }, { 0x2562, 0xb6, 0x00 },
        { 0x2563, 0xb9, 0x00 }, { 0x2564, 0xd1, 0x01 },
        { 0x2566, 0xcb, 0x00 }, { 0x2567, 0xcf, 0x00 },
        { 0x2568, 0xd0, 0x00 }, { 0x2569, 0xca, 0x00 },
        { 0x256a, 0xd8, 0x00 }, { 0x256b, 0xd7, 0x00 },
        { 0x256c, 0xce, 0x00 }, { 0x2580, 0xdf, 0x00 },
        { 0x2584, 0xdc, 0x00 }, { 0x2588, 0xdb, 0x00 },
        { 0x258c, 0xdd, 0x00 }, { 0x2590, 0xde, 0x00 },
        { 0x2591, 0xb0, 0x02 }, { 0x25a0, 0xfe, 0x00 },
        { 0x25ac, 0x16, 0x00 }, { 0x25b2, 0x1e, 0x00 },
        { 0x25ba, 0x10, 0x00 }, { 0x25bc, 0x1f, 0x00 },
        { 0x25c4, 0x11, 0x00 }, { 0x25cb, 0x09, 0x00 },
        { 0x25d8, 0x08, 0x00 }, { 0x25d9, 0x0a, 0x00 },
        { 0x263a, 0x01, 0x01 }, { 0x263c, 0x0f, 0x00 },
        { 0x2640, 0x0c, 0x00 }, { 0x2642, 0x0b, 0x00 },
        { 0x2660, 0x06, 0x00 }, { 0x2663, 0x05, 0x00 },
        { 0x2665, 0x03, 0x01 }, { 0x266a, 0x0d, 0x00 },
        { 0x266c, 0x0e, 0x00 }, { 0x2713, 0xfb, 0x00 },
        { 0x27e8, 0x3c, 0x00 }, { 0x27e9, 0x3e, 0x00 },
};

static uint8_t
vga_get_cp437(term_char_t c)
{
        int min, mid, max;

        min = 0;
        max = nitems(cp437table) - 1;

        if (c < cp437table[0].unicode_base ||
            c > cp437table[max].unicode_base + cp437table[max].length)
                return '?';

        while (max >= min) {
                mid = (min + max) / 2;
                if (c < cp437table[mid].unicode_base)
                        max = mid - 1;
                else if (c > cp437table[mid].unicode_base +
                    cp437table[mid].length)
                        min = mid + 1;
                else
                        return (c - cp437table[mid].unicode_base +
                            cp437table[mid].cp437_base);
        }

        return '?';
}

static void
vga_blank(struct vt_device *vd, term_color_t color)
{
        struct vga_softc *sc = vd->vd_softc;
        u_int ofs;

        vga_setfg(vd, color);
        for (ofs = 0; ofs < VT_VGA_MEMSIZE; ofs++)
                MEM_WRITE1(sc, ofs, 0xff);
}

static inline void
vga_bitblt_put(struct vt_device *vd, u_long dst, term_color_t color,
    uint8_t v)
{
        struct vga_softc *sc = vd->vd_softc;

        /* Skip empty writes, in order to avoid palette changes. */
        if (v != 0x00) {
                vga_setfg(vd, color);
                /*
                 * When this MEM_READ1() gets disabled, all sorts of
                 * artifacts occur.  This is because this read loads the
                 * set of 8 pixels that are about to be changed.  There
                 * is one scenario where we can avoid the read, namely
                 * if all pixels are about to be overwritten anyway.
                 */
                if (v != 0xff) {
                        MEM_READ1(sc, dst);

                        /* The bg color was trashed by the reads. */
                        sc->vga_curbg = 0xff;
                }
                MEM_WRITE1(sc, dst, v);
        }
}

static void
vga_setpixel(struct vt_device *vd, int x, int y, term_color_t color)
{

        if (vd->vd_flags & VDF_TEXTMODE)
                return;

        vga_bitblt_put(vd, (y * VT_VGA_WIDTH / 8) + (x / 8), color,
            0x80 >> (x % 8));
}

static void
vga_drawrect(struct vt_device *vd, int x1, int y1, int x2, int y2, int fill,
    term_color_t color)
{
        int x, y;

        if (vd->vd_flags & VDF_TEXTMODE)
                return;

        for (y = y1; y <= y2; y++) {
                if (fill || (y == y1) || (y == y2)) {
                        for (x = x1; x <= x2; x++)
                                vga_setpixel(vd, x, y, color);
                } else {
                        vga_setpixel(vd, x1, y, color);
                        vga_setpixel(vd, x2, y, color);
                }
        }
}

static void
vga_compute_shifted_pattern(const uint8_t *src, unsigned int bytes,
    unsigned int src_x, unsigned int x_count, unsigned int dst_x,
    uint8_t *pattern, uint8_t *mask)
{
        unsigned int n;

        n = src_x / 8;

        /*
         * This mask has bits set, where a pixel (ether 0 or 1)
         * comes from the source bitmap.
         */
        if (mask != NULL) {
                *mask = (0xff
                    >> (8 - x_count))
                    << (8 - x_count - dst_x);
        }

        if (n == (src_x + x_count - 1) / 8) {
                /* All the pixels we want are in the same byte. */
                *pattern = src[n];
                if (dst_x >= src_x)
                        *pattern >>= (dst_x - src_x % 8);
                else
                        *pattern <<= (src_x % 8 - dst_x);
        } else {
                /* The pixels we want are split into two bytes. */
                if (dst_x >= src_x % 8) {
                        *pattern =
                            src[n] << (8 - dst_x - src_x % 8) |
                            src[n + 1] >> (dst_x - src_x % 8);
                } else {
                        *pattern =
                            src[n] << (src_x % 8 - dst_x) |
                            src[n + 1] >> (8 - src_x % 8 - dst_x);
                }
        }
}

static void
vga_copy_bitmap_portion(uint8_t *pattern_2colors, uint8_t *pattern_ncolors,
    const uint8_t *src, const uint8_t *src_mask, unsigned int src_width,
    unsigned int src_x, unsigned int dst_x, unsigned int x_count,
    unsigned int src_y, unsigned int dst_y, unsigned int y_count,
    term_color_t fg, term_color_t bg, int overwrite)
{
        unsigned int i, bytes;
        uint8_t pattern, relevant_bits, mask;

        bytes = (src_width + 7) / 8;

        for (i = 0; i < y_count; ++i) {
                vga_compute_shifted_pattern(src + (src_y + i) * bytes,
                    bytes, src_x, x_count, dst_x, &pattern, &relevant_bits);

                if (src_mask == NULL) {
                        /*
                         * No src mask. Consider that all wanted bits
                         * from the source are "authoritative".
                         */
                        mask = relevant_bits;
                } else {
                        /*
                         * There's an src mask. We shift it the same way
                         * we shifted the source pattern.
                         */
                        vga_compute_shifted_pattern(
                            src_mask + (src_y + i) * bytes,
                            bytes, src_x, x_count, dst_x,
                            &mask, NULL);

                        /* Now, only keep the wanted bits among them. */
                        mask &= relevant_bits;
                }

                /*
                 * Clear bits from the pattern which must be
                 * transparent, according to the source mask.
                 */
                pattern &= mask;

                /* Set the bits in the 2-colors array. */
                if (overwrite)
                        pattern_2colors[dst_y + i] &= ~mask;
                pattern_2colors[dst_y + i] |= pattern;

                if (pattern_ncolors == NULL)
                        continue;

                /*
                 * Set the same bits in the n-colors array. This one
                 * supports transparency, when a given bit is cleared in
                 * all colors.
                 */
                if (overwrite) {
                        /*
                         * Ensure that the pixels used by this bitmap are
                         * cleared in other colors.
                         */
                        for (int j = 0; j < 16; ++j)
                                pattern_ncolors[(dst_y + i) * 16 + j] &=
                                    ~mask;
                }
                pattern_ncolors[(dst_y + i) * 16 + fg] |= pattern;
                pattern_ncolors[(dst_y + i) * 16 + bg] |= (~pattern & mask);
        }
}

static void
vga_bitblt_pixels_block_2colors(struct vt_device *vd, const uint8_t *masks,
    term_color_t fg, term_color_t bg,
    unsigned int x, unsigned int y, unsigned int height)
{
        unsigned int i, offset;
        struct vga_softc *sc;

        /*
         * The great advantage of Write Mode 3 is that we just need
         * to load the foreground in the Set/Reset register, load the
         * background color in the latches register (this is done
         * through a write in offscreen memory followed by a read of
         * that data), then write the pattern to video memory. This
         * pattern indicates if the pixel should use the foreground
         * color (bit set) or the background color (bit cleared).
         */

        vga_setbg(vd, bg);
        vga_setfg(vd, fg);

        sc = vd->vd_softc;
        offset = (VT_VGA_WIDTH * y + x) / 8;

        for (i = 0; i < height; ++i, offset += VT_VGA_WIDTH / 8) {
                MEM_WRITE1(sc, offset, masks[i]);
        }
}

static void
vga_bitblt_pixels_block_ncolors(struct vt_device *vd, const uint8_t *masks,
    unsigned int x, unsigned int y, unsigned int height)
{
        unsigned int i, j, plane, color, offset;
        struct vga_softc *sc;
        uint8_t mask, planes[height * 4];

        sc = vd->vd_softc;

        memset(planes, 0, sizeof(planes));

        /*
         * To write a group of pixels using 3 or more colors, we select
         * Write Mode 0 and write one byte to each plane separately.
         */

        /*
         * We first compute each byte: each plane contains one bit of the
         * color code for each of the 8 pixels.
         *
         * For example, if the 8 pixels are like this:
         *     GBBBBBBY
         * where:
         *     G (gray)   = 0b0111
         *     B (black)  = 0b0000
         *     Y (yellow) = 0b0011
         *
         * The corresponding for bytes are:
         *             GBBBBBBY
         *    Plane 0: 10000001 = 0x81
         *    Plane 1: 10000001 = 0x81
         *    Plane 2: 10000000 = 0x80
         *    Plane 3: 00000000 = 0x00
         *             |  |   |
         *             |  |   +-> 0b0011 (Y)
         *             |  +-----> 0b0000 (B)
         *             +--------> 0b0111 (G)
         */

        for (i = 0; i < height; ++i) {
                for (color = 0; color < 16; ++color) {
                        mask = masks[i * 16 + color];
                        if (mask == 0x00)
                                continue;

                        for (j = 0; j < 8; ++j) {
                                if (!((mask >> (7 - j)) & 0x1))
                                        continue;

                                /* The pixel "j" uses color "color". */
                                for (plane = 0; plane < 4; ++plane)
                                        planes[i * 4 + plane] |=
                                            ((cons_to_vga_colors[color] >>
                                            plane) & 0x1) << (7 - j);
                        }
                }
        }

        /*
         * The bytes are ready: we now switch to Write Mode 0 and write
         * all bytes, one plane at a time.
         */
        vga_setwmode(vd, 0);

        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_MAP_MASK);
        for (plane = 0; plane < 4; ++plane) {
                /* Select plane. */
                REG_WRITE1(sc, VGA_SEQ_DATA, 1 << plane);

                /* Write all bytes for this plane, from Y to Y+height. */
                for (i = 0; i < height; ++i) {
                        offset = (VT_VGA_WIDTH * (y + i) + x) / 8;
                        MEM_WRITE1(sc, offset, planes[i * 4 + plane]);
                }
        }
}

static void
vga_bitblt_one_text_pixels_block(struct vt_device *vd,
    const struct vt_window *vw, unsigned int x, unsigned int y)
{
        const struct vt_buf *vb;
        const struct vt_font *vf;
        unsigned int i, col, row, src_x, x_count;
        unsigned int used_colors_list[16], used_colors;
        uint8_t pattern_2colors[vw->vw_font->vf_height];
        uint8_t pattern_ncolors[vw->vw_font->vf_height * 16];
        term_char_t c;
        term_color_t fg, bg;
        const uint8_t *src;

        vb = &vw->vw_buf;
        vf = vw->vw_font;

        /*
         * The current pixels block.
         *
         * We fill it with portions of characters, because both "grids"
         * may not match.
         *
         * i is the index in this pixels block.
         */

        i = x;
        used_colors = 0;
        memset(used_colors_list, 0, sizeof(used_colors_list));
        memset(pattern_2colors, 0, sizeof(pattern_2colors));
        memset(pattern_ncolors, 0, sizeof(pattern_ncolors));

        if (i < vw->vw_draw_area.tr_begin.tp_col) {
                /*
                 * i is in the margin used to center the text area on
                 * the screen.
                 */

                i = vw->vw_draw_area.tr_begin.tp_col;
        }

        while (i < x + VT_VGA_PIXELS_BLOCK &&
            i < vw->vw_draw_area.tr_end.tp_col) {
                /*
                 * Find which character is drawn on this pixel in the
                 * pixels block.
                 *
                 * While here, record what colors it uses.
                 */

                col = (i - vw->vw_draw_area.tr_begin.tp_col) / vf->vf_width;
                row = (y - vw->vw_draw_area.tr_begin.tp_row) / vf->vf_height;

                c = VTBUF_GET_FIELD(vb, row, col);
                src = vtfont_lookup(vf, c);

                vt_determine_colors(c, VTBUF_ISCURSOR(vb, row, col), &fg, &bg);
                if ((used_colors_list[fg] & 0x1) != 0x1)
                        used_colors++;
                if ((used_colors_list[bg] & 0x2) != 0x2)
                        used_colors++;
                used_colors_list[fg] |= 0x1;
                used_colors_list[bg] |= 0x2;

                /*
                 * Compute the portion of the character we want to draw,
                 * because the pixels block may start in the middle of a
                 * character.
                 *
                 * The first pixel to draw in the character is
                 *     the current position -
                 *     the start position of the character
                 *
                 * The last pixel to draw is either
                 *     - the last pixel of the character, or
                 *     - the pixel of the character matching the end of
                 *       the pixels block
                 * whichever comes first. This position is then
                 * changed to be relative to the start position of the
                 * character.
                 */

                src_x = i -
                    (col * vf->vf_width + vw->vw_draw_area.tr_begin.tp_col);
                x_count = min(min(
                    (col + 1) * vf->vf_width +
                    vw->vw_draw_area.tr_begin.tp_col,
                    x + VT_VGA_PIXELS_BLOCK),
                    vw->vw_draw_area.tr_end.tp_col);
                x_count -= col * vf->vf_width +
                    vw->vw_draw_area.tr_begin.tp_col;
                x_count -= src_x;

                /* Copy a portion of the character. */
                vga_copy_bitmap_portion(pattern_2colors, pattern_ncolors,
                    src, NULL, vf->vf_width,
                    src_x, i % VT_VGA_PIXELS_BLOCK, x_count,
                    0, 0, vf->vf_height, fg, bg, 0);

                /* We move to the next portion. */
                i += x_count;
        }

#ifndef SC_NO_CUTPASTE
        /*
         * Copy the mouse pointer bitmap if it's over the current pixels
         * block.
         *
         * We use the saved cursor position (saved in vt_flush()), because
         * the current position could be different than the one used
         * to mark the area dirty.
         */
        term_rect_t drawn_area;

        drawn_area.tr_begin.tp_col = x;
        drawn_area.tr_begin.tp_row = y;
        drawn_area.tr_end.tp_col = x + VT_VGA_PIXELS_BLOCK;
        drawn_area.tr_end.tp_row = y + vf->vf_height;
        if (vd->vd_mshown && vt_is_cursor_in_area(vd, &drawn_area)) {
                struct vt_mouse_cursor *cursor;
                unsigned int mx, my;
                unsigned int dst_x, src_y, dst_y, y_count;

                cursor = vd->vd_mcursor;
                mx = vd->vd_mx_drawn + vw->vw_draw_area.tr_begin.tp_col;
                my = vd->vd_my_drawn + vw->vw_draw_area.tr_begin.tp_row;

                /* Compute the portion of the cursor we want to copy. */
                src_x = x > mx ? x - mx : 0;
                dst_x = mx > x ? mx - x : 0;
                x_count = min(min(min(
                    cursor->width - src_x,
                    x + VT_VGA_PIXELS_BLOCK - mx),
                    vw->vw_draw_area.tr_end.tp_col - mx),
                    VT_VGA_PIXELS_BLOCK);

                /*
                 * The cursor isn't aligned on the Y-axis with
                 * characters, so we need to compute the vertical
                 * start/count.
                 */
                src_y = y > my ? y - my : 0;
                dst_y = my > y ? my - y : 0;
                y_count = min(
                    min(cursor->height - src_y, y + vf->vf_height - my),
                    vf->vf_height);

                /* Copy the cursor portion. */
                vga_copy_bitmap_portion(pattern_2colors, pattern_ncolors,
                    cursor->map, cursor->mask, cursor->width,
                    src_x, dst_x, x_count, src_y, dst_y, y_count,
                    vd->vd_mcursor_fg, vd->vd_mcursor_bg, 1);

                if ((used_colors_list[vd->vd_mcursor_fg] & 0x1) != 0x1)
                        used_colors++;
                if ((used_colors_list[vd->vd_mcursor_bg] & 0x2) != 0x2)
                        used_colors++;
        }
#endif

        /*
         * The pixels block is completed, we can now draw it on the
         * screen.
         */
        if (used_colors == 2)
                vga_bitblt_pixels_block_2colors(vd, pattern_2colors, fg, bg,
                    x, y, vf->vf_height);
        else
                vga_bitblt_pixels_block_ncolors(vd, pattern_ncolors,
                    x, y, vf->vf_height);
}

static void
vga_bitblt_text_gfxmode(struct vt_device *vd, const struct vt_window *vw,
    const term_rect_t *area)
{
        const struct vt_font *vf;
        unsigned int col, row;
        unsigned int x1, y1, x2, y2, x, y;

        vf = vw->vw_font;

        /*
         * Compute the top-left pixel position aligned with the video
         * adapter pixels block size.
         *
         * This is calculated from the top-left column of te dirty area:
         *
         *     1. Compute the top-left pixel of the character:
         *        col * font width + x offset
         *
         *        NOTE: x offset is used to center the text area on the
         *        screen. It's expressed in pixels, not in characters
         *        col/row!
         *
         *     2. Find the pixel further on the left marking the start of
         *        an aligned pixels block (eg. chunk of 8 pixels):
         *        character's x / blocksize * blocksize
         *
         *        The division, being made on integers, achieves the
         *        alignment.
         *
         * For the Y-axis, we need to compute the character's y
         * coordinate, but we don't need to align it.
         */

        col = area->tr_begin.tp_col;
        row = area->tr_begin.tp_row;
        x1 = (int)((col * vf->vf_width + vw->vw_draw_area.tr_begin.tp_col)
             / VT_VGA_PIXELS_BLOCK)
            * VT_VGA_PIXELS_BLOCK;
        y1 = row * vf->vf_height + vw->vw_draw_area.tr_begin.tp_row;

        /*
         * Compute the bottom right pixel position, again, aligned with
         * the pixels block size.
         *
         * The same rules apply, we just add 1 to base the computation
         * on the "right border" of the dirty area.
         */

        col = area->tr_end.tp_col;
        row = area->tr_end.tp_row;
        x2 = (int)howmany(col * vf->vf_width + vw->vw_draw_area.tr_begin.tp_col,
            VT_VGA_PIXELS_BLOCK)
            * VT_VGA_PIXELS_BLOCK;
        y2 = row * vf->vf_height + vw->vw_draw_area.tr_begin.tp_row;

        /* Clip the area to the screen size. */
        x2 = min(x2, vw->vw_draw_area.tr_end.tp_col);
        y2 = min(y2, vw->vw_draw_area.tr_end.tp_row);

        /*
         * Now, we take care of N pixels line at a time (the first for
         * loop, N = font height), and for these lines, draw one pixels
         * block at a time (the second for loop), not a character at a
         * time.
         *
         * Therefore, on the X-axis, characters my be drawn partially if
         * they are not aligned on 8-pixels boundary.
         *
         * However, the operation is repeated for the full height of the
         * font before moving to the next character, because it allows
         * to keep the color settings and write mode, before perhaps
         * changing them with the next one.
         */

        for (y = y1; y < y2; y += vf->vf_height) {
                for (x = x1; x < x2; x += VT_VGA_PIXELS_BLOCK) {
                        vga_bitblt_one_text_pixels_block(vd, vw, x, y);
                }
        }
}

static void
vga_bitblt_text_txtmode(struct vt_device *vd, const struct vt_window *vw,
    const term_rect_t *area)
{
        struct vga_softc *sc;
        const struct vt_buf *vb;
        unsigned int col, row;
        term_char_t c;
        term_color_t fg, bg;
        uint8_t ch, attr;
        size_t z;

        sc = vd->vd_softc;
        vb = &vw->vw_buf;

        for (row = area->tr_begin.tp_row; row < area->tr_end.tp_row; ++row) {
                for (col = area->tr_begin.tp_col;
                    col < area->tr_end.tp_col;
                    ++col) {
                        /*
                         * Get next character and its associated fg/bg
                         * colors.
                         */
                        c = VTBUF_GET_FIELD(vb, row, col);
                        vt_determine_colors(c, VTBUF_ISCURSOR(vb, row, col),
                            &fg, &bg);

                        z = row * PIXEL_WIDTH(VT_FB_MAX_WIDTH) + col;
                        if (z >= PIXEL_HEIGHT(VT_FB_MAX_HEIGHT) *
                            PIXEL_WIDTH(VT_FB_MAX_WIDTH))
                                continue;
                        if (vd->vd_drawn && (vd->vd_drawn[z] == c) &&
                            vd->vd_drawnfg && (vd->vd_drawnfg[z] == fg) &&
                            vd->vd_drawnbg && (vd->vd_drawnbg[z] == bg))
                                continue;

                        /*
                         * Convert character to CP437, which is the
                         * character set used by the VGA hardware by
                         * default.
                         */
                        ch = vga_get_cp437(TCHAR_CHARACTER(c));

                        /* Convert colors to VGA attributes. */
                        attr =
                            cons_to_vga_colors[bg] << 4 |
                            cons_to_vga_colors[fg];

                        MEM_WRITE2(sc, (row * 80 + col) * 2 + 0,
                            ch + ((uint16_t)(attr) << 8));

                        if (vd->vd_drawn)
                                vd->vd_drawn[z] = c;
                        if (vd->vd_drawnfg)
                                vd->vd_drawnfg[z] = fg;
                        if (vd->vd_drawnbg)
                                vd->vd_drawnbg[z] = bg;
                }
        }
}

static void
vga_bitblt_text(struct vt_device *vd, const struct vt_window *vw,
    const term_rect_t *area)
{

        if (!(vd->vd_flags & VDF_TEXTMODE)) {
                vga_bitblt_text_gfxmode(vd, vw, area);
        } else {
                vga_bitblt_text_txtmode(vd, vw, area);
        }
}

void
vga_invalidate_text(struct vt_device *vd, const term_rect_t *area)
{
        unsigned int col, row;
        size_t z;

        for (row = area->tr_begin.tp_row; row < area->tr_end.tp_row; ++row) {
                for (col = area->tr_begin.tp_col;
                    col < area->tr_end.tp_col;
                    ++col) {
                        z = row * PIXEL_WIDTH(VT_FB_MAX_WIDTH) + col;
                        if (z >= PIXEL_HEIGHT(VT_FB_MAX_HEIGHT) *
                            PIXEL_WIDTH(VT_FB_MAX_WIDTH))
                                continue;
                        if (vd->vd_drawn)
                                vd->vd_drawn[z] = 0;
                        if (vd->vd_drawnfg)
                                vd->vd_drawnfg[z] = 0;
                        if (vd->vd_drawnbg)
                                vd->vd_drawnbg[z] = 0;
                }
        }
}

static void
vga_bitblt_bitmap(struct vt_device *vd, const struct vt_window *vw,
    const uint8_t *pattern, const uint8_t *mask,
    unsigned int width, unsigned int height,
    unsigned int x, unsigned int y, term_color_t fg, term_color_t bg)
{
        unsigned int x1, y1, x2, y2, i, j, src_x, dst_x, x_count;
        uint8_t pattern_2colors;

        /* Align coordinates with the 8-pxels grid. */
        x1 = rounddown(x, VT_VGA_PIXELS_BLOCK);
        y1 = y;

        x2 = roundup(x + width, VT_VGA_PIXELS_BLOCK);
        y2 = y + height;
        x2 = min(x2, vd->vd_width - 1);
        y2 = min(y2, vd->vd_height - 1);

        for (j = y1; j < y2; ++j) {
                src_x = 0;
                dst_x = x - x1;
                x_count = VT_VGA_PIXELS_BLOCK - dst_x;

                for (i = x1; i < x2; i += VT_VGA_PIXELS_BLOCK) {
                        pattern_2colors = 0;

                        vga_copy_bitmap_portion(
                            &pattern_2colors, NULL,
                            pattern, mask, width,
                            src_x, dst_x, x_count,
                            j - y1, 0, 1, fg, bg, 0);

                        vga_bitblt_pixels_block_2colors(vd,
                            &pattern_2colors, fg, bg,
                            i, j, 1);

                        src_x += x_count;
                        dst_x = (dst_x + x_count) % VT_VGA_PIXELS_BLOCK;
                        x_count = min(width - src_x, VT_VGA_PIXELS_BLOCK);
                }
        }
}

static int
vga_bitblt_argb(struct vt_device *vd, const struct vt_window *vw,
    const uint8_t *argb,
    unsigned int width, unsigned int height,
    unsigned int x, unsigned int y)
{

        return (EOPNOTSUPP);
}

static void
vga_initialize_graphics(struct vt_device *vd)
{
        struct vga_softc *sc = vd->vd_softc;

        /* Clock select. */
        REG_WRITE1(sc, VGA_GEN_MISC_OUTPUT_W, VGA_GEN_MO_VSP | VGA_GEN_MO_HSP |
            VGA_GEN_MO_PB | VGA_GEN_MO_ER | VGA_GEN_MO_IOA);
        /* Set sequencer clocking and memory mode. */
        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_CLOCKING_MODE);
        REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_CM_89);
        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_MEMORY_MODE);
        REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_MM_OE | VGA_SEQ_MM_EM);

        /* Set the graphics controller in graphics mode. */
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MISCELLANEOUS);
        REG_WRITE1(sc, VGA_GC_DATA, 0x04 + VGA_GC_MISC_GA);
        /* Program the CRT controller. */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_HORIZ_TOTAL);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x5f);                    /* 760 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_HORIZ_DISP_END);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x4f);                    /* 640 - 8 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_START_HORIZ_BLANK);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x50);                    /* 640 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_END_HORIZ_BLANK);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_EHB_CR + 2);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_START_HORIZ_RETRACE);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x54);                    /* 672 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_END_HORIZ_RETRACE);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_EHR_EHB + 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_VERT_TOTAL);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x0b);                    /* 523 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_OVERFLOW);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_OF_VT9 | VGA_CRTC_OF_LC8 |
            VGA_CRTC_OF_VBS8 | VGA_CRTC_OF_VRS8 | VGA_CRTC_OF_VDE8);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_MAX_SCAN_LINE);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_MSL_LC9);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_VERT_RETRACE_START);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0xea);                    /* 480 + 10 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_VERT_RETRACE_END);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x0c);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_VERT_DISPLAY_END);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0xdf);                    /* 480 - 1*/
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_OFFSET);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x28);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_START_VERT_BLANK);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0xe7);                    /* 480 + 7 */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_END_VERT_BLANK);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x04);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_MODE_CONTROL);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_MC_WB | VGA_CRTC_MC_AW |
            VGA_CRTC_MC_SRS | VGA_CRTC_MC_CMS);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_LINE_COMPARE);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0xff);                    /* 480 + 31 */

        REG_WRITE1(sc, VGA_GEN_FEATURE_CTRL_W, 0);

        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_MAP_MASK);
        REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_MM_EM3 | VGA_SEQ_MM_EM2 |
            VGA_SEQ_MM_EM1 | VGA_SEQ_MM_EM0);
        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_CHAR_MAP_SELECT);
        REG_WRITE1(sc, VGA_SEQ_DATA, 0);

        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_SET_RESET);
        REG_WRITE1(sc, VGA_GC_DATA, 0);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_ENABLE_SET_RESET);
        REG_WRITE1(sc, VGA_GC_DATA, 0x0f);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_COLOR_COMPARE);
        REG_WRITE1(sc, VGA_GC_DATA, 0);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_DATA_ROTATE);
        REG_WRITE1(sc, VGA_GC_DATA, 0);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_READ_MAP_SELECT);
        REG_WRITE1(sc, VGA_GC_DATA, 0);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);
        REG_WRITE1(sc, VGA_GC_DATA, 0);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_COLOR_DONT_CARE);
        REG_WRITE1(sc, VGA_GC_DATA, 0x0f);
        REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_BIT_MASK);
        REG_WRITE1(sc, VGA_GC_DATA, 0xff);
}

static int
vga_initialize(struct vt_device *vd, int textmode)
{
        struct vga_softc *sc = vd->vd_softc;
        uint8_t x;
        int timeout;

        /* Make sure the VGA adapter is not in monochrome emulation mode. */
        x = REG_READ1(sc, VGA_GEN_MISC_OUTPUT_R);
        REG_WRITE1(sc, VGA_GEN_MISC_OUTPUT_W, x | VGA_GEN_MO_IOA);

        /* Unprotect CRTC registers 0-7. */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_VERT_RETRACE_END);
        x = REG_READ1(sc, VGA_CRTC_DATA);
        REG_WRITE1(sc, VGA_CRTC_DATA, x & ~VGA_CRTC_VRE_PR);

        /*
         * Wait for the vertical retrace.
         * NOTE: this code reads the VGA_GEN_INPUT_STAT_1 register, which has
         * the side-effect of clearing the internal flip-flip of the attribute
         * controller's write register. This means that because this code is
         * here, we know for sure that the first write to the attribute
         * controller will be a write to the address register. Removing this
         * code therefore also removes that guarantee and appropriate measures
         * need to be taken.
         */
        timeout = 10000;
        do {
                DELAY(10);
                x = REG_READ1(sc, VGA_GEN_INPUT_STAT_1);
                x &= VGA_GEN_IS1_VR | VGA_GEN_IS1_DE;
        } while (x != (VGA_GEN_IS1_VR | VGA_GEN_IS1_DE) && --timeout != 0);
        if (timeout == 0) {
                printf("Timeout initializing vt_vga\n");
                return (ENXIO);
        }

        /* Now, disable the sync. signals. */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_MODE_CONTROL);
        x = REG_READ1(sc, VGA_CRTC_DATA);
        REG_WRITE1(sc, VGA_CRTC_DATA, x & ~VGA_CRTC_MC_HR);

        /* Asynchronous sequencer reset. */
        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_RESET);
        REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_RST_SR);

        if (!textmode)
                vga_initialize_graphics(vd);

        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_PRESET_ROW_SCAN);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_CURSOR_START);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_CS_COO);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_CURSOR_END);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_START_ADDR_HIGH);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_START_ADDR_LOW);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_CURSOR_LOC_HIGH);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_CURSOR_LOC_LOW);
        REG_WRITE1(sc, VGA_CRTC_DATA, 0x59);
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_UNDERLINE_LOC);
        REG_WRITE1(sc, VGA_CRTC_DATA, VGA_CRTC_UL_UL);

        if (textmode) {
                /* Set the attribute controller to blink disable. */
                REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_MODE_CONTROL);
                REG_WRITE1(sc, VGA_AC_WRITE, 0);
        } else {
                /* Set the attribute controller in graphics mode. */
                REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_MODE_CONTROL);
                REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_MC_GA);
                REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_HORIZ_PIXEL_PANNING);
                REG_WRITE1(sc, VGA_AC_WRITE, 0);
        }
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(0));
        REG_WRITE1(sc, VGA_AC_WRITE, 0);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(1));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(2));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_G);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(3));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_G | VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(4));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_R);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(5));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_R | VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(6));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SG | VGA_AC_PAL_R);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(7));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_R | VGA_AC_PAL_G | VGA_AC_PAL_B);

        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(8));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(9));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(10));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_G);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(11));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_G | VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(12));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_R);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(13));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_R | VGA_AC_PAL_B);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(14));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_R | VGA_AC_PAL_G);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PALETTE(15));
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_PAL_SR | VGA_AC_PAL_SG |
            VGA_AC_PAL_SB | VGA_AC_PAL_R | VGA_AC_PAL_G | VGA_AC_PAL_B);

        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_OVERSCAN_COLOR);
        REG_WRITE1(sc, VGA_AC_WRITE, 0);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_COLOR_PLANE_ENABLE);
        REG_WRITE1(sc, VGA_AC_WRITE, 0x0f);
        REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_COLOR_SELECT);
        REG_WRITE1(sc, VGA_AC_WRITE, 0);

        if (!textmode) {
                u_int ofs;

                /*
                 * Done.  Clear the frame buffer.  All bit planes are
                 * enabled, so a single-paged loop should clear all
                 * planes.
                 */
                for (ofs = 0; ofs < VT_VGA_MEMSIZE; ofs++) {
                        MEM_WRITE1(sc, ofs, 0);
                }
        }

        /* Re-enable the sequencer. */
        REG_WRITE1(sc, VGA_SEQ_ADDRESS, VGA_SEQ_RESET);
        REG_WRITE1(sc, VGA_SEQ_DATA, VGA_SEQ_RST_SR | VGA_SEQ_RST_NAR);
        /* Re-enable the sync signals. */
        REG_WRITE1(sc, VGA_CRTC_ADDRESS, VGA_CRTC_MODE_CONTROL);
        x = REG_READ1(sc, VGA_CRTC_DATA);
        REG_WRITE1(sc, VGA_CRTC_DATA, x | VGA_CRTC_MC_HR);

        if (!textmode) {
                /* Switch to write mode 3, because we'll mainly do bitblt. */
                REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);
                REG_WRITE1(sc, VGA_GC_DATA, 3);
                sc->vga_wmode = 3;

                /*
                 * In Write Mode 3, Enable Set/Reset is ignored, but we
                 * use Write Mode 0 to write a group of 8 pixels using
                 * 3 or more colors. In this case, we want to disable
                 * Set/Reset: set Enable Set/Reset to 0.
                 */
                REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_ENABLE_SET_RESET);
                REG_WRITE1(sc, VGA_GC_DATA, 0x00);

                /*
                 * Clear the colors we think are loaded into Set/Reset or
                 * the latches.
                 */
                sc->vga_curfg = sc->vga_curbg = 0xff;
        }

        return (0);
}

static bool
vga_acpi_disabled(void)
{
#if defined(__amd64__) || defined(__i386__)
        uint16_t flags;
        int ignore;

        /*
         * Ignore the flag on real hardware: there's a lot of buggy firmware
         * that will wrongly set it.
         */
        ignore = (vm_guest == VM_GUEST_NO);
        TUNABLE_INT_FETCH("hw.vga.acpi_ignore_no_vga", &ignore);
        if (ignore || !acpi_get_fadt_bootflags(&flags))
                return (false);
        return ((flags & ACPI_FADT_NO_VGA) != 0);
#else
        return (false);
#endif
}

static int
vga_probe(struct vt_device *vd)
{

        return (vga_acpi_disabled() ? CN_DEAD : CN_INTERNAL);
}

static int
vga_init(struct vt_device *vd)
{
        struct vga_softc *sc;
        int textmode;

        if (vd->vd_softc == NULL)
                vd->vd_softc = (void *)&vga_conssoftc;
        sc = vd->vd_softc;

        if (vd->vd_flags & VDF_DOWNGRADE && vd->vd_video_dev != NULL)
                vga_pci_repost(vd->vd_video_dev);

#if defined(__amd64__) || defined(__i386__)
        sc->vga_fb_tag = X86_BUS_SPACE_MEM;
        sc->vga_reg_tag = X86_BUS_SPACE_IO;
#else
# error "Architecture not yet supported!"
#endif

        bus_space_map(sc->vga_reg_tag, VGA_REG_BASE, VGA_REG_SIZE, 0,
            &sc->vga_reg_handle);

        /*
         * If "hw.vga.textmode" is not set and we're running on hypervisor,
         * we use text mode by default, this is because when we're on
         * hypervisor, vt(4) is usually much slower in graphics mode than
         * in text mode, especially when we're on Hyper-V.
         */
        textmode = vm_guest != VM_GUEST_NO;
        TUNABLE_INT_FETCH("hw.vga.textmode", &textmode);
        if (textmode) {
                vd->vd_flags |= VDF_TEXTMODE;
                vd->vd_width = 80;
                vd->vd_height = 25;
                bus_space_map(sc->vga_fb_tag, VGA_TXT_BASE, VGA_TXT_SIZE, 0,
                    &sc->vga_fb_handle);
        } else {
                vd->vd_width = VT_VGA_WIDTH;
                vd->vd_height = VT_VGA_HEIGHT;
                bus_space_map(sc->vga_fb_tag, VGA_MEM_BASE, VGA_MEM_SIZE, 0,
                    &sc->vga_fb_handle);
        }
        if (vga_initialize(vd, textmode) != 0)
                return (CN_DEAD);
        sc->vga_enabled = true;

        return (CN_INTERNAL);
}

static void
vga_postswitch(struct vt_device *vd)
{

        /* Reinit VGA mode, to restore view after app which change mode. */
        vga_initialize(vd, (vd->vd_flags & VDF_TEXTMODE));
        /* Ask vt(4) to update chars on visible area. */
        vd->vd_flags |= VDF_INVALID;
}

/* Dummy NewBus functions to reserve the resources used by the vt_vga driver */
static void
vtvga_identify(driver_t *driver, device_t parent)
{

        if (!vga_conssoftc.vga_enabled)
                return;

        if (BUS_ADD_CHILD(parent, 0, driver->name, 0) == NULL)
                panic("Unable to attach vt_vga console");
}

static int
vtvga_probe(device_t dev)
{

        device_set_desc(dev, "VT VGA driver");

        return (BUS_PROBE_NOWILDCARD);
}

static int
vtvga_attach(device_t dev)
{
        struct resource *pseudo_phys_res;
        int res_id;

        res_id = 0;
        pseudo_phys_res = bus_alloc_resource(dev, SYS_RES_MEMORY,
            &res_id, VGA_MEM_BASE, VGA_MEM_BASE + VGA_MEM_SIZE - 1,
            VGA_MEM_SIZE, RF_ACTIVE);
        if (pseudo_phys_res == NULL)
                panic("Unable to reserve vt_vga memory");
        return (0);
}

/*-------------------- Private Device Attachment Data  -----------------------*/
static device_method_t vtvga_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,      vtvga_identify),
        DEVMETHOD(device_probe,         vtvga_probe),
        DEVMETHOD(device_attach,        vtvga_attach),

        DEVMETHOD_END
};

DEFINE_CLASS_0(vtvga, vtvga_driver, vtvga_methods, 0);

DRIVER_MODULE(vtvga, nexus, vtvga_driver, NULL, NULL);