src/devices/dev_vga.c

/*
 *  Copyright (C) 2004-2006  Anders Gavare.  All rights reserved.
 *
 *  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.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  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.
 *   
 *
 *  $Id: dev_vga.c,v 1.95 2006/01/01 13:17:18 debug Exp $
 *
 *  VGA charcell and graphics device.
 *
 *  It should work with 80x25 and 40x25 text modes, and with a few graphics
 *  modes as long as no fancy VGA features are used.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "console.h"
#include "cpu.h"
#include "devices.h"
#include "machine.h"
#include "memory.h"
#include "misc.h"

#include "vga.h"

/*  These are generated from binary font files:  */
#include "fonts/font8x8.c"
#include "fonts/font8x10.c"
#include "fonts/font8x16.c"


/*  For videomem -> framebuffer updates:  */
#define VGA_TICK_SHIFT          18

#define MAX_RETRACE_SCANLINES   420
#define N_IS1_READ_THRESHOLD    50

#define GFX_ADDR_WINDOW         0x18000

#define VGA_FB_ADDR     0x1c00000000ULL

#define MODE_CHARCELL           1
#define MODE_GRAPHICS           2

#define GRAPHICS_MODE_8BIT      1
#define GRAPHICS_MODE_4BIT      2

struct vga_data {
        uint64_t        videomem_base;
        uint64_t        control_base;

        struct vfb_data *fb;
        uint32_t        fb_size;

        int             fb_max_x;               /*  pixels  */
        int             fb_max_y;               /*  pixels  */
        int             max_x;                  /*  charcells or pixels  */
        int             max_y;                  /*  charcells or pixels  */

        /*  Selects charcell mode or graphics mode:  */
        int             cur_mode;

        /*  Common for text and graphics modes:  */
        int             pixel_repx, pixel_repy;

        /*  Textmode:  */
        int             font_width;
        int             font_height;
        unsigned char   *font;
        size_t          charcells_size;
        unsigned char   *charcells;             /*  2 bytes per char  */
        unsigned char   *charcells_outputed;    /*  text  */
        unsigned char   *charcells_drawn;       /*  framebuffer  */

        /*  Graphics:  */
        int             graphics_mode;
        int             bits_per_pixel;
        unsigned char   *gfx_mem;
        uint32_t        gfx_mem_size;

        /*  Registers:  */
        int             attribute_state;        /*  0 or 1  */
        unsigned char   attribute_reg_select;
        unsigned char   attribute_reg[256];

        unsigned char   misc_output_reg;

        unsigned char   sequencer_reg_select;
        unsigned char   sequencer_reg[256];

        unsigned char   graphcontr_reg_select;
        unsigned char   graphcontr_reg[256];

        unsigned char   crtc_reg_select;
        unsigned char   crtc_reg[256];

        unsigned char   palette_read_index;
        char            palette_read_subindex;
        unsigned char   palette_write_index;
        char            palette_write_subindex;

        int             current_retrace_line;
        int             input_status_1;

        /*  Palette per scanline during retrace:  */
        unsigned char   *retrace_palette;
        int             use_palette_per_line;
        int64_t         n_is1_reads;

        /*  Misc.:  */
        int             console_handle;

        int             cursor_x;
        int             cursor_y;

        int             modified;
        int             palette_modified;
        int             update_x1;
        int             update_y1;
        int             update_x2;
        int             update_y2;
};


/*
 *  recalc_cursor_position():
 *
 *  Should be called whenever the cursor location _or_ the display
 *  base has been changed.
 */
static void recalc_cursor_position(struct vga_data *d)
{
        int base = (d->crtc_reg[VGA_CRTC_START_ADDR_HIGH] << 8)
            + d->crtc_reg[VGA_CRTC_START_ADDR_LOW];
        int ofs = d->crtc_reg[VGA_CRTC_CURSOR_LOCATION_HIGH] * 256 +
            d->crtc_reg[VGA_CRTC_CURSOR_LOCATION_LOW];
        ofs -= base;
        d->cursor_x = ofs % d->max_x;
        d->cursor_y = ofs / d->max_x;
}


/*
 *  register_reset():
 *
 *  Resets many registers to sane values.
 */
static void register_reset(struct vga_data *d)
{
        /*  Home cursor and start at the top:  */
        d->crtc_reg[VGA_CRTC_CURSOR_LOCATION_HIGH] =
            d->crtc_reg[VGA_CRTC_CURSOR_LOCATION_LOW] = 0;
        d->crtc_reg[VGA_CRTC_START_ADDR_HIGH] =
            d->crtc_reg[VGA_CRTC_START_ADDR_LOW] = 0;

        recalc_cursor_position(d);

        /*  Reset cursor scanline stuff:  */
        d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_START] = d->font_height - 2;
        d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_END] = d->font_height - 1;

        d->sequencer_reg[VGA_SEQ_MAP_MASK] = 0x0f;
        d->graphcontr_reg[VGA_GRAPHCONTR_MASK] = 0xff;

        d->misc_output_reg = VGA_MISC_OUTPUT_IOAS;
        d->n_is1_reads = 0;
}


static void c_putstr(struct vga_data *d, char *s)
{
        while (*s)
                console_putchar(d->console_handle, *s++);
}


/*
 *  reset_palette():
 */
static void reset_palette(struct vga_data *d, int grayscale)
{
        int i, r, g, b;

        /*  TODO: default values for entry 16..255?  */
        for (i=16; i<256; i++)
                d->fb->rgb_palette[i*3 + 0] = d->fb->rgb_palette[i*3 + 1] =
                    d->fb->rgb_palette[i*3 + 2] = (i & 15) * 4;
        d->palette_modified = 1;
        i = 0;

        if (grayscale) {
                for (r=0; r<2; r++)
                    for (g=0; g<2; g++)
                        for (b=0; b<2; b++) {
                                d->fb->rgb_palette[i + 0] =
                                    d->fb->rgb_palette[i + 1] =
                                    d->fb->rgb_palette[i + 2] =
                                    (r+g+b) * 0xaa / 3;
                                d->fb->rgb_palette[i + 8*3 + 0] =
                                    d->fb->rgb_palette[i + 8*3 + 1] =
                                    d->fb->rgb_palette[i + 8*3 + 2] =
                                    (r+g+b) * 0xaa / 3 + 0x55;
                                i+=3;
                        }
                return;
        }

        for (r=0; r<2; r++)
                for (g=0; g<2; g++)
                        for (b=0; b<2; b++) {
                                d->fb->rgb_palette[i + 0] = r * 0xaa;
                                d->fb->rgb_palette[i + 1] = g * 0xaa;
                                d->fb->rgb_palette[i + 2] = b * 0xaa;
                                i+=3;
                        }
        for (r=0; r<2; r++)
                for (g=0; g<2; g++)
                        for (b=0; b<2; b++) {
                                d->fb->rgb_palette[i + 0] = r * 0xaa + 0x55;
                                d->fb->rgb_palette[i + 1] = g * 0xaa + 0x55;
                                d->fb->rgb_palette[i + 2] = b * 0xaa + 0x55;
                                i+=3;
                        }
}


/*
 *  vga_update_textmode():
 *
 *  Called from vga_update() when use_x11 is false. This causes modified
 *  character cells to be "simulated" by outputing ANSI escape sequences
 *  that draw the characters in a terminal window instead.
 */
static void vga_update_textmode(struct machine *machine,
        struct vga_data *d, int base, int start, int end)
{
        char s[50];
        int i, oldcolor = -1, printed_last = 0;

        for (i=start; i<=end; i+=2) {
                unsigned char ch = d->charcells[base+i];
                int fg = d->charcells[base+i+1] & 15;
                int bg = (d->charcells[base+i+1] >> 4) & 15;
                        /*  top bit of bg = blink  */
                int x = (i/2) % d->max_x;
                int y = (i/2) / d->max_x;

                if (d->charcells[base+i] == d->charcells_outputed[i] &&
                    d->charcells[base+i+1] == d->charcells_outputed[i+1]) {
                        printed_last = 0;
                        continue;
                }

                d->charcells_outputed[i] = d->charcells[base+i];
                d->charcells_outputed[i+1] = d->charcells[base+i+1];

                if (!printed_last || x == 0) {
                        snprintf(s, sizeof(s), "\033[%i;%iH", y + 1, x + 1);
                        c_putstr(d, s);
                }
                if (oldcolor < 0 || (bg<<4)+fg != oldcolor || !printed_last) {
                        snprintf(s, sizeof(s), "\033[0;"); c_putstr(d, s);

                        switch (fg & 7) {
                        case 0: c_putstr(d, "30"); break;
                        case 1: c_putstr(d, "34"); break;
                        case 2: c_putstr(d, "32"); break;
                        case 3: c_putstr(d, "36"); break;
                        case 4: c_putstr(d, "31"); break;
                        case 5: c_putstr(d, "35"); break;
                        case 6: c_putstr(d, "33"); break;
                        case 7: c_putstr(d, "37"); break;
                        }
                        if (fg & 8)
                                c_putstr(d, ";1");
                        c_putstr(d, ";");
                        switch (bg & 7) {
                        case 0: c_putstr(d, "40"); break;
                        case 1: c_putstr(d, "44"); break;
                        case 2: c_putstr(d, "42"); break;
                        case 3: c_putstr(d, "46"); break;
                        case 4: c_putstr(d, "41"); break;
                        case 5: c_putstr(d, "45"); break;
                        case 6: c_putstr(d, "43"); break;
                        case 7: c_putstr(d, "47"); break;
                        }
                        /*  TODO: blink  */
                        c_putstr(d, "m");
                }

                if (ch >= 0x20 && ch != 127)
                        console_putchar(d->console_handle, ch);

                oldcolor = (bg << 4) + fg;
                printed_last = 1;
        }

        /*  Restore the terminal's cursor position:  */
        snprintf(s, sizeof(s), "\033[%i;%iH", d->cursor_y + 1, d->cursor_x + 1);
        c_putstr(d, s);
}


/*
 *  vga_update_graphics():
 *
 *  This function should be called whenever any part of d->gfx_mem[] has
 *  been written to. It will redraw all pixels within the range x1,y1
 *  .. x2,y2 using the right palette.
 */
static void vga_update_graphics(struct machine *machine, struct vga_data *d,
        int x1, int y1, int x2, int y2)
{
        int x, y, ix, iy, c, rx = d->pixel_repx, ry = d->pixel_repy;
        unsigned char pixel[3];

        for (y=y1; y<=y2; y++)
                for (x=x1; x<=x2; x++) {
                        /*  addr is where to read from VGA memory, addr2 is
                            where to write on the 24-bit framebuffer device  */
                        int addr = (y * d->max_x + x) * d->bits_per_pixel;
                        switch (d->bits_per_pixel) {
                        case 8: addr >>= 3;
                                c = d->gfx_mem[addr];
                                pixel[0] = d->fb->rgb_palette[c*3+0];
                                pixel[1] = d->fb->rgb_palette[c*3+1];
                                pixel[2] = d->fb->rgb_palette[c*3+2];
                                break;
                        case 4: addr >>= 2;
                                if (addr & 1)
                                        c = d->gfx_mem[addr >> 1] >> 4;
                                else
                                        c = d->gfx_mem[addr >> 1] & 0xf;
                                pixel[0] = d->fb->rgb_palette[c*3+0];
                                pixel[1] = d->fb->rgb_palette[c*3+1];
                                pixel[2] = d->fb->rgb_palette[c*3+2];
                                break;
                        }
                        for (iy=y*ry; iy<(y+1)*ry; iy++)
                                for (ix=x*rx; ix<(x+1)*rx; ix++) {
                                        uint32_t addr2 = (d->fb_max_x * iy
                                            + ix) * 3;
                                        if (addr2 < d->fb_size)
                                                dev_fb_access(machine->cpus[0],
                                                    machine->memory, addr2,
                                                    pixel, sizeof(pixel),
                                                    MEM_WRITE, d->fb);
                                }
                }
}


/*
 *  vga_update_text():
 *
 *  This function should be called whenever any part of d->charcells[] has
 *  been written to. It will redraw all characters within the range x1,y1
 *  .. x2,y2 using the right palette.
 */
static void vga_update_text(struct machine *machine, struct vga_data *d,
        int x1, int y1, int x2, int y2)
{
        int fg, bg, x,y, subx, line;
        size_t i, start, end, base;
        int font_size = d->font_height;
        int font_width = d->font_width;
        unsigned char *pal = d->fb->rgb_palette;

        if (d->pixel_repx * font_width > 8*8) {
                fatal("[ too large font ]\n");
                return;
        }

        /*  Hm... I'm still using the old start..end code:  */
        start = (d->max_x * y1 + x1) * 2;
        end   = (d->max_x * y2 + x2) * 2;

        start &= ~1;
        end |= 1;

        if (end >= d->charcells_size)
                end = d->charcells_size - 1;

        base = ((d->crtc_reg[VGA_CRTC_START_ADDR_HIGH] << 8)
            + d->crtc_reg[VGA_CRTC_START_ADDR_LOW]) * 2;

        if (!machine->use_x11)
                vga_update_textmode(machine, d, base, start, end);

        for (i=start; i<=end; i+=2) {
                unsigned char ch = d->charcells[i + base];

                if (!d->palette_modified && d->charcells_drawn[i] == ch &&
                    d->charcells_drawn[i+1] == d->charcells[i+base+1])
                        continue;

                d->charcells_drawn[i] = ch;
                d->charcells_drawn[i+1] = d->charcells[i + base + 1];

                fg = d->charcells[i+base + 1] & 15;
                bg = (d->charcells[i+base + 1] >> 4) & 7;

                /*  Blink is hard to do :-), but inversion might be ok too:  */
                if (d->charcells[i+base + 1] & 128) {
                        int tmp = fg; fg = bg; bg = tmp;
                }

                x = (i/2) % d->max_x; x *= font_width;
                y = (i/2) / d->max_x; y *= font_size;

                /*  Draw the character:  */
                for (line = 0; line < font_size; line++) {
                        /*  hardcoded for max 8 scaleup... :-)  */
                        unsigned char rgb_line[3 * 8 * 8];
                        int iy;

                        for (subx = 0; subx < font_width; subx++) {
                                int ix, color_index;

                                if (d->use_palette_per_line) {
                                        int sline = d->pixel_repy * (line+y);
                                        if (sline < MAX_RETRACE_SCANLINES)
                                                pal = d->retrace_palette
                                                    + sline * 256*3;
                                        else
                                                pal = d->fb->rgb_palette;
                                }

                                if (d->font[ch * font_size + line] &
                                    (128 >> subx))
                                        color_index = fg;
                                else
                                        color_index = bg;

                                for (ix=0; ix<d->pixel_repx; ix++)
                                        memcpy(rgb_line + (subx*d->pixel_repx +
                                            ix) * 3, &pal[color_index * 3], 3);
                        }

                        for (iy=0; iy<d->pixel_repy; iy++) {
                                uint32_t addr = (d->fb_max_x * (d->pixel_repy *
                                    (line+y) + iy) + x * d->pixel_repx) * 3;
                                if (addr >= d->fb_size)
                                        continue;
                                dev_fb_access(machine->cpus[0],
                                    machine->memory, addr, rgb_line,
                                    3 * font_width, MEM_WRITE, d->fb);
                        }
                }
        }
}


/*
 *  vga_update_cursor():
 */
static void vga_update_cursor(struct machine *machine, struct vga_data *d)
{
        int onoff = 1, height = d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_END]
            - d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_START] + 1;

        if (d->cur_mode != MODE_CHARCELL)
                onoff = 0;

        if (d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_START] >
            d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_END]) {
                onoff = 0;
                height = 1;
        }

        if (d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_START] >= d->font_height)
                onoff = 0;

        dev_fb_setcursor(d->fb,
            d->cursor_x * d->font_width * d->pixel_repx, (d->cursor_y *
            d->font_height + d->crtc_reg[VGA_CRTC_CURSOR_SCANLINE_START]) *
            d->pixel_repy, onoff, d->font_width * d->pixel_repx, height *
            d->pixel_repy);
}


/*
 *  dev_vga_tick():
 */
void dev_vga_tick(struct cpu *cpu, void *extra)
{
        struct vga_data *d = extra;
        int64_t low = -1, high;

        vga_update_cursor(cpu->machine, d);

        /*  TODO: text vs graphics tick?  */
        memory_device_dyntrans_access(cpu, cpu->mem, extra,
            (uint64_t *) &low, (uint64_t *) &high);

        if (low != -1) {
                int base = ((d->crtc_reg[VGA_CRTC_START_ADDR_HIGH] << 8)
                    + d->crtc_reg[VGA_CRTC_START_ADDR_LOW]) * 2;
                int new_u_y1, new_u_y2;
                debug("[ dev_vga_tick: dyntrans access, %llx .. %llx ]\n",
                    (long long)low, (long long)high);
                low -= base;
                high -= base;
                d->update_x1 = 0;
                d->update_x2 = d->max_x - 1;
                new_u_y1 = (low/2) / d->max_x;
                new_u_y2 = ((high/2) / d->max_x) + 1;
                if (new_u_y1 < d->update_y1)
                        d->update_y1 = new_u_y1;
                if (new_u_y2 > d->update_y2)
                        d->update_y2 = new_u_y2;
                if (d->update_y1 < 0)
                        d->update_y1 = 0;
                if (d->update_y2 >= d->max_y)
                        d->update_y2 = d->max_y - 1;
                d->modified = 1;
        }

        if (d->n_is1_reads > N_IS1_READ_THRESHOLD &&
            d->retrace_palette != NULL) {
                d->use_palette_per_line = 1;
                d->update_x1 = 0;
                d->update_x2 = d->max_x - 1;
                d->update_y1 = 0;
                d->update_y2 = d->max_y - 1;
                d->modified = 1;
        } else {
                if (d->use_palette_per_line) {
                        d->use_palette_per_line = 0;
                        d->update_x1 = 0;
                        d->update_x2 = d->max_x - 1;
                        d->update_y1 = 0;
                        d->update_y2 = d->max_y - 1;
                        d->modified = 1;
                }
        }

        if (!cpu->machine->use_x11) {
                /*  NOTE: 2 > 0, so this only updates the cursor, no
                    character cells.  */
                vga_update_textmode(cpu->machine, d, 0, 2, 0);
        }

        if (d->modified) {
                if (d->cur_mode == MODE_CHARCELL)
                        vga_update_text(cpu->machine, d, d->update_x1,
                            d->update_y1, d->update_x2, d->update_y2);
                else
                        vga_update_graphics(cpu->machine, d, d->update_x1,
                            d->update_y1, d->update_x2, d->update_y2);

                d->palette_modified = 0;
                d->modified = 0;
                d->update_x1 = 999999;
                d->update_x2 = -1;
                d->update_y1 = 999999;
                d->update_y2 = -1;
        }

        if (d->n_is1_reads > N_IS1_READ_THRESHOLD)
                d->n_is1_reads = 0;
}


/*
 *  vga_graphics_access():
 *
 *  Reads and writes to the VGA video memory (pixels).
 */
DEVICE_ACCESS(vga_graphics)
{
        struct vga_data *d = extra;
        int j, x=0, y=0, x2=0, y2=0, modified = 0;
        size_t i;

        if (relative_addr + len >= GFX_ADDR_WINDOW)
                return 0;

        if (d->cur_mode != MODE_GRAPHICS)
                return 1;

        switch (d->graphics_mode) {
        case GRAPHICS_MODE_8BIT:
                y = relative_addr / d->max_x;
                x = relative_addr % d->max_x;
                y2 = (relative_addr+len-1) / d->max_x;
                x2 = (relative_addr+len-1) % d->max_x;

                if (writeflag == MEM_WRITE) {
                        memcpy(d->gfx_mem + relative_addr, data, len);
                        modified = 1;
                } else
                        memcpy(data, d->gfx_mem + relative_addr, len);
                break;
        case GRAPHICS_MODE_4BIT:
                y = relative_addr * 8 / d->max_x;
                x = relative_addr * 8 % d->max_x;
                y2 = ((relative_addr+len)*8-1) / d->max_x;
                x2 = ((relative_addr+len)*8-1) % d->max_x;
                /*  TODO: color stuff  */

                /*  Read/write d->gfx_mem in 4-bit color:  */
                if (writeflag == MEM_WRITE) {
                        /*  i is byte index to write, j is bit index  */
                        for (i=0; i<len; i++)
                                for (j=0; j<8; j++) {
                                        int pixelmask = 1 << (7-j);
                                        int b = data[i] & pixelmask;
                                        int m = d->sequencer_reg[
                                            VGA_SEQ_MAP_MASK] & 0x0f;
                                        uint32_t addr = (y * d->max_x + x +
                                            i*8 + j) * d->bits_per_pixel / 8;
                                        unsigned char byte;
                                        if (!(d->graphcontr_reg[
                                            VGA_GRAPHCONTR_MASK] & pixelmask))
                                                continue;
                                        if (addr >= d->gfx_mem_size)
                                                continue;
                                        byte = d->gfx_mem[addr];
                                        if (b && j&1)
                                                byte |= m << 4;
                                        if (b && !(j&1))
                                                byte |= m;
                                        if (!b && j&1)
                                                byte &= ~(m << 4);
                                        if (!b && !(j&1))
                                                byte &= ~m;
                                        d->gfx_mem[addr] = byte;
                                }
                        modified = 1;
                } else {
                        fatal("TODO: 4 bit graphics read, mask=0x%02x\n",
                            d->sequencer_reg[VGA_SEQ_MAP_MASK]);
                        for (i=0; i<len; i++)
                                data[i] = random();
                }
                break;
        default:fatal("dev_vga: Unimplemented graphics mode %i\n",
                    d->graphics_mode);
                cpu->running = 0;
        }

        if (modified) {
                d->modified = 1;
                if (x < d->update_x1)  d->update_x1 = x;
                if (x > d->update_x2)  d->update_x2 = x;
                if (y < d->update_y1)  d->update_y1 = y;
                if (y > d->update_y2)  d->update_y2 = y;
                if (x2 < d->update_x1)  d->update_x1 = x2;
                if (x2 > d->update_x2)  d->update_x2 = x2;
                if (y2 < d->update_y1)  d->update_y1 = y2;
                if (y2 > d->update_y2)  d->update_y2 = y2;
                if (y != y2) {
                        d->update_x1 = 0;
                        d->update_x2 = d->max_x - 1;
                }
        }
        return 1;
}


/*
 *  dev_vga_access():
 *
 *  Reads and writes to the VGA video memory (charcells).
 */
DEVICE_ACCESS(vga)
{
        struct vga_data *d = extra;
        uint64_t idata = 0, odata = 0;
        int x, y, x2, y2, r, base;
        size_t i;

        if (writeflag == MEM_WRITE)
                idata = memory_readmax64(cpu, data, len);

        base = ((d->crtc_reg[VGA_CRTC_START_ADDR_HIGH] << 8)
            + d->crtc_reg[VGA_CRTC_START_ADDR_LOW]) * 2;
        r = relative_addr - base;
        y = r / (d->max_x * 2);
        x = (r/2) % d->max_x;
        y2 = (r+len-1) / (d->max_x * 2);
        x2 = ((r+len-1)/2) % d->max_x;

        if (relative_addr + len - 1 < d->charcells_size) {
                if (writeflag == MEM_WRITE) {
                        for (i=0; i<len; i++) {
                                int old = d->charcells[relative_addr + i];
                                if (old != data[i]) {
                                        d->charcells[relative_addr + i] =
                                            data[i];
                                        d->modified = 1;
                                }
                        }

                        if (d->modified) {
                                if (x < d->update_x1)  d->update_x1 = x;
                                if (x > d->update_x2)  d->update_x2 = x;
                                if (y < d->update_y1)  d->update_y1 = y;
                                if (y > d->update_y2)  d->update_y2 = y;
                                if (x2 < d->update_x1)  d->update_x1 = x2;
                                if (x2 > d->update_x2)  d->update_x2 = x2;
                                if (y2 < d->update_y1)  d->update_y1 = y2;
                                if (y2 > d->update_y2)  d->update_y2 = y2;

                                if (y != y2) {
                                        d->update_x1 = 0;
                                        d->update_x2 = d->max_x - 1;
                                }
                        }
                } else
                        memcpy(data, d->charcells + relative_addr, len);
                return 1;
        }

        switch (relative_addr) {
        default:
                if (writeflag==MEM_READ) {
                        debug("[ vga: read from 0x%08lx ]\n",
                            (long)relative_addr);
                } else {
                        debug("[ vga: write to  0x%08lx: 0x%08x ]\n",
                            (long)relative_addr, idata);
                }
        }

        if (writeflag == MEM_READ)
                memory_writemax64(cpu, data, len, odata);

        return 1;
}


/*
 *  vga_crtc_reg_write():
 *
 *  Writes to VGA CRTC registers.
 */
static void vga_crtc_reg_write(struct machine *machine, struct vga_data *d,
        int regnr, int idata)
{
        int grayscale;

        switch (regnr) {
        case VGA_CRTC_CURSOR_SCANLINE_START:            /*  0x0a  */
        case VGA_CRTC_CURSOR_SCANLINE_END:              /*  0x0b  */
                break;
        case VGA_CRTC_START_ADDR_HIGH:                  /*  0x0c  */
        case VGA_CRTC_START_ADDR_LOW:                   /*  0x0d  */
                d->update_x1 = 0;
                d->update_x2 = d->max_x - 1;
                d->update_y1 = 0;
                d->update_y2 = d->max_y - 1;
                d->modified = 1;
                recalc_cursor_position(d);
                break;
        case VGA_CRTC_CURSOR_LOCATION_HIGH:             /*  0x0e  */
        case VGA_CRTC_CURSOR_LOCATION_LOW:              /*  0x0f  */
                recalc_cursor_position(d);
                break;
        case 0xff:
                grayscale = 0;
                switch (d->crtc_reg[0xff]) {
                case 0x00:
                        grayscale = 1;
                case 0x01:
                        d->cur_mode = MODE_CHARCELL;
                        d->max_x = 40; d->max_y = 25;
                        d->pixel_repx = machine->x11_scaleup * 2;
                        d->pixel_repy = machine->x11_scaleup;
                        d->font_width = 8;
                        d->font_height = 16;
                        d->font = font8x16;
                        break;
                case 0x02:
                        grayscale = 1;
                case 0x03:
                        d->cur_mode = MODE_CHARCELL;
                        d->max_x = 80; d->max_y = 25;
                        d->pixel_repx = d->pixel_repy = machine->x11_scaleup;
                        d->font_width = 8;
                        d->font_height = 16;
                        d->font = font8x16;
                        break;
                case 0x08:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 160; d->max_y = 200;
                        d->graphics_mode = GRAPHICS_MODE_4BIT;
                        d->bits_per_pixel = 4;
                        d->pixel_repx = 4 * machine->x11_scaleup;
                        d->pixel_repy = 2 * machine->x11_scaleup;
                        break;
                case 0x09:
                case 0x0d:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 320; d->max_y = 200;
                        d->graphics_mode = GRAPHICS_MODE_4BIT;
                        d->bits_per_pixel = 4;
                        d->pixel_repx = d->pixel_repy =
                            2 * machine->x11_scaleup;
                        break;
                case 0x0e:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 640; d->max_y = 200;
                        d->graphics_mode = GRAPHICS_MODE_4BIT;
                        d->bits_per_pixel = 4;
                        d->pixel_repx = machine->x11_scaleup;
                        d->pixel_repy = machine->x11_scaleup * 2;
                        break;
                case 0x10:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 640; d->max_y = 350;
                        d->graphics_mode = GRAPHICS_MODE_4BIT;
                        d->bits_per_pixel = 4;
                        d->pixel_repx = d->pixel_repy = machine->x11_scaleup;
                        break;
                case 0x12:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 640; d->max_y = 480;
                        d->graphics_mode = GRAPHICS_MODE_4BIT;
                        d->bits_per_pixel = 4;
                        d->pixel_repx = d->pixel_repy = machine->x11_scaleup;
                        break;
                case 0x13:
                        d->cur_mode = MODE_GRAPHICS;
                        d->max_x = 320; d->max_y = 200;
                        d->graphics_mode = GRAPHICS_MODE_8BIT;
                        d->bits_per_pixel = 8;
                        d->pixel_repx = d->pixel_repy =
                            2 * machine->x11_scaleup;
                        break;
                default:
                        fatal("TODO! video mode change hack (mode 0x%02x)\n",
                            d->crtc_reg[0xff]);
                        exit(1);
                }

                if (d->cur_mode == MODE_CHARCELL) {
                        dev_fb_resize(d->fb, d->max_x * d->font_width *
                            d->pixel_repx, d->max_y * d->font_height *
                            d->pixel_repy);
                        d->fb_size = d->max_x * d->pixel_repx * d->font_width *
                             d->max_y * d->pixel_repy * d->font_height * 3;
                } else {
                        dev_fb_resize(d->fb, d->max_x * d->pixel_repx,
                            d->max_y * d->pixel_repy);
                        d->fb_size = d->max_x * d->pixel_repx *
                             d->max_y * d->pixel_repy * 3;
                }

                if (d->gfx_mem != NULL)
                        free(d->gfx_mem);
                d->gfx_mem_size = 1;
                if (d->cur_mode == MODE_GRAPHICS)
                        d->gfx_mem_size = d->max_x * d->max_y /
                            (d->graphics_mode == GRAPHICS_MODE_8BIT? 1 : 2);
                d->gfx_mem = malloc(d->gfx_mem_size);

                /*  Clear screen and reset the palette:  */
                memset(d->charcells_outputed, 0, d->charcells_size);
                memset(d->charcells_drawn, 0, d->charcells_size);
                memset(d->gfx_mem, 0, d->gfx_mem_size);
                d->update_x1 = 0;
                d->update_x2 = d->max_x - 1;
                d->update_y1 = 0;
                d->update_y2 = d->max_y - 1;
                d->modified = 1;
                reset_palette(d, grayscale);
                register_reset(d);
                break;
        default:fatal("[ vga_crtc_reg_write: regnr=0x%02x idata=0x%02x ]\n",
                    regnr, idata);
        }
}


/*
 *  vga_sequencer_reg_write():
 *
 *  Writes to VGA Sequencer registers.
 */
static void vga_sequencer_reg_write(struct machine *machine, struct vga_data *d,
        int regnr, int idata)
{
        switch (regnr) {
        case VGA_SEQ_RESET:
        case VGA_SEQ_MAP_MASK:
        case VGA_SEQ_SEQUENCER_MEMORY_MODE:
                debug("[ vga_sequencer_reg_write: select %i: TODO ]\n", regnr);
                break;
        default:fatal("[ vga_sequencer_reg_write: select %i ]\n", regnr);
                /*  cpu->running = 0;  */
        }
}


/*
 *  vga_graphcontr_reg_write():
 *
 *  Writes to VGA Graphics Controller registers.
 */
static void vga_graphcontr_reg_write(struct machine *machine,
        struct vga_data *d, int regnr, int idata)
{
        switch (regnr) {
        case VGA_GRAPHCONTR_READMAPSELECT:
        case VGA_GRAPHCONTR_GRAPHICSMODE:
        case VGA_GRAPHCONTR_MISC:
        case VGA_GRAPHCONTR_MASK:
                debug("[ vga_graphcontr_reg_write: select %i: TODO ]\n", regnr);
                break;
        default:fatal("[ vga_graphcontr_reg_write: select %i ]\n", regnr);
                /*  cpu->running = 0;  */
        }
}


/*
 *  vga_attribute_reg_write():
 *
 *  Writes to VGA Attribute registers.
 */
static void vga_attribute_reg_write(struct machine *machine, struct vga_data *d,
        int regnr, int idata)
{
        /*  0-15 are palette registers: TODO  */
        if (regnr >= 0 && regnr <= 0xf)
                return;

        switch (regnr) {
        default:fatal("[ vga_attribute_reg_write: select %i ]\n", regnr);
                /*  cpu->running = 0;  */
        }
}


/*
 *  dev_vga_ctrl_access():
 *
 *  Reads and writes of the VGA control registers.
 */
DEVICE_ACCESS(vga_ctrl)
{
        struct vga_data *d = extra;
        size_t i;
        uint64_t idata = 0, odata = 0;

        for (i=0; i<len; i++) {
                idata = data[i];

                /*  0x3C0 + relative_addr...  */

                switch (relative_addr) {

                case VGA_ATTRIBUTE_ADDR:                /*  0x00  */
                        switch (d->attribute_state) {
                        case 0: if (writeflag == MEM_READ)
                                        odata = d->attribute_reg_select;
                                else {
                                        d->attribute_reg_select = 1;
                                        d->attribute_state = 1;
                                }
                                break;
                        case 1: d->attribute_state = 0;
                                d->attribute_reg[d->attribute_reg_select] =
                                    idata;
                                vga_attribute_reg_write(cpu->machine, d,
                                    d->attribute_reg_select, idata);
                                break;
                        }
                        break;
                case VGA_ATTRIBUTE_DATA_READ:           /*  0x01  */
                        if (writeflag == MEM_WRITE)
                                fatal("[ dev_vga: WARNING: Write to "
                                    "VGA_ATTRIBUTE_DATA_READ? ]\n");
                        else {
                                if (d->attribute_state == 0)
                                        fatal("[ dev_vga: WARNING: Read from "
                                            "VGA_ATTRIBUTE_DATA_READ, but no"
                                            " register selected? ]\n");
                                else
                                        odata = d->attribute_reg[
                                            d->attribute_reg_select];
                        }
                        break;

                case VGA_MISC_OUTPUT_W:                 /*  0x02  */
                        if (writeflag == MEM_WRITE)
                                d->misc_output_reg = idata;
                        else {
                                /*  Reads: Input Status 0  */
                                odata = 0x00;
                        }
                        break;

                case VGA_SEQUENCER_ADDR:                /*  0x04  */
                        if (writeflag == MEM_READ)
                                odata = d->sequencer_reg_select;
                        else
                                d->sequencer_reg_select = idata;
                        break;
                case VGA_SEQUENCER_DATA:                /*  0x05  */
                        if (writeflag == MEM_READ)
                                odata = d->sequencer_reg[
                                    d->sequencer_reg_select];
                        else {
                                d->sequencer_reg[d->
                                    sequencer_reg_select] = idata;
                                vga_sequencer_reg_write(cpu->machine, d,
                                    d->sequencer_reg_select, idata);
                        }
                        break;

                case VGA_DAC_ADDR_READ:                 /*  0x07  */
                        if (writeflag == MEM_WRITE) {
                                d->palette_read_index = idata;
                                d->palette_read_subindex = 0;
                        } else {
                                debug("[ dev_vga: WARNING: Read from "
                                    "VGA_DAC_ADDR_READ? TODO ]\n");
                                /*  TODO  */
                        }
                        break;
                case VGA_DAC_ADDR_WRITE:                /*  0x08  */
                        if (writeflag == MEM_WRITE) {
                                d->palette_write_index = idata;
                                d->palette_write_subindex = 0;

                                /*  TODO: Is this correct?  */
                                d->palette_read_index = idata;
                                d->palette_read_subindex = 0;
                        } else {
                                fatal("[ dev_vga: WARNING: Read from "
                                    "VGA_DAC_ADDR_WRITE? ]\n");
                                odata = d->palette_write_index;
                        }
                        break;
                case VGA_DAC_DATA:                      /*  0x09  */
                        if (writeflag == MEM_WRITE) {
                                int new = (idata & 63) << 2;
                                int old = d->fb->rgb_palette[d->
                                    palette_write_index*3+d->
                                    palette_write_subindex];
                                d->fb->rgb_palette[d->palette_write_index * 3 +
                                    d->palette_write_subindex] = new;
                                /*  Redraw whole screen, if the
                                    palette changed:  */
                                if (new != old) {
                                        d->modified = 1;
                                        d->palette_modified = 1;
                                        d->update_x1 = d->update_y1 = 0;
                                        d->update_x2 = d->max_x - 1;
                                        d->update_y2 = d->max_y - 1;
                                }
                                d->palette_write_subindex ++;
                                if (d->palette_write_subindex == 3) {
                                        d->palette_write_index ++;
                                        d->palette_write_subindex = 0;
                                }
                        } else {
                                odata = (d->fb->rgb_palette[d->
                                    palette_read_index * 3 +
                                    d->palette_read_subindex] >> 2) & 63;
                                d->palette_read_subindex ++;
                                if (d->palette_read_subindex == 3) {
                                        d->palette_read_index ++;
                                        d->palette_read_subindex = 0;
                                }
                        }
                        break;

                case VGA_MISC_OUTPUT_R:
                        odata = d->misc_output_reg;
                        break;

                case VGA_GRAPHCONTR_ADDR:               /*  0x0e  */
                        if (writeflag == MEM_READ)
                                odata = d->graphcontr_reg_select;
                        else
                                d->graphcontr_reg_select = idata;
                        break;
                case VGA_GRAPHCONTR_DATA:               /*  0x0f  */
                        if (writeflag == MEM_READ)
                                odata = d->graphcontr_reg[
                                    d->graphcontr_reg_select];
                        else {
                                d->graphcontr_reg[d->
                                    graphcontr_reg_select] = idata;
                                vga_graphcontr_reg_write(cpu->machine, d,
                                    d->graphcontr_reg_select, idata);
                        }
                        break;

                case VGA_CRTC_ADDR:                     /*  0x14  */
                        if (writeflag == MEM_READ)
                                odata = d->crtc_reg_select;
                        else
                                d->crtc_reg_select = idata;
                        break;
                case VGA_CRTC_DATA:                     /*  0x15  */
                        if (writeflag == MEM_READ)
                                odata = d->crtc_reg[d->crtc_reg_select];
                        else {
                                d->crtc_reg[d->crtc_reg_select] = idata;
                                vga_crtc_reg_write(cpu->machine, d,
                                    d->crtc_reg_select, idata);
                        }
                        break;

                case VGA_INPUT_STATUS_1:        /*  0x1A  */
                        odata = 0;
                        d->n_is1_reads ++;
                        d->current_retrace_line ++;
                        d->current_retrace_line %= (MAX_RETRACE_SCANLINES * 8);
                        /*  Whenever we are "inside" a scan line, copy the
                            current palette into retrace_palette[][]:  */
                        if ((d->current_retrace_line & 7) == 7) {
                                if (d->retrace_palette == NULL &&
                                    d->n_is1_reads > N_IS1_READ_THRESHOLD) {
                                        d->retrace_palette = malloc(
                                            MAX_RETRACE_SCANLINES * 256*3);
                                        if (d->retrace_palette == NULL) {
                                                fatal("out of memory\n");
                                                exit(1);
                                        }
                                }
                                if (d->retrace_palette != NULL)
                                        memcpy(d->retrace_palette + (d->
                                            current_retrace_line >> 3) * 256*3,
                                            d->fb->rgb_palette, d->cur_mode ==
                                            MODE_CHARCELL? (16*3) : (256*3));
                        }
                        /*  These need to go on and off, to fake the
                            real vertical and horizontal retrace info.  */
                        if (d->current_retrace_line < 20*8)
                                odata |= VGA_IS1_DISPLAY_VRETRACE;
                        else {
                                if ((d->current_retrace_line & 7) == 0)
                                        odata = VGA_IS1_DISPLAY_DISPLAY_DISABLE;
                        }
                        break;

                default:
                        if (writeflag==MEM_READ) {
                                debug("[ vga_ctrl: read from 0x%08lx ]\n",
                                    (long)relative_addr);
                        } else {
                                debug("[ vga_ctrl: write to  0x%08lx: 0x%08x"
                                    " ]\n", (long)relative_addr, (int)idata);
                        }
                }

                if (writeflag == MEM_READ)
                        data[i] = odata;

                /*  For multi-byte accesses:  */
                relative_addr ++;
        }

        return 1;
}


/*
 *  dev_vga_init():
 *
 *  Register a VGA text console device. max_x and max_y could be something
 *  like 80 and 25, respectively.
 */
void dev_vga_init(struct machine *machine, struct memory *mem,
        uint64_t videomem_base, uint64_t control_base, char *name)
{
        struct vga_data *d;
        size_t i;
        size_t allocsize;

        d = malloc(sizeof(struct vga_data));
        if (d == NULL) {
                fprintf(stderr, "out of memory\n");
                exit(1);
        }
        memset(d, 0, sizeof(struct vga_data));

        d->console_handle = console_start_slave(machine, "vga",
            CONSOLE_OUTPUT_ONLY);

        d->videomem_base  = videomem_base;
        d->control_base   = control_base;
        d->max_x          = 80;
        d->max_y          = 25;
        d->cur_mode       = MODE_CHARCELL;
        d->crtc_reg[0xff] = 0x03;
        d->charcells_size = 0x8000;
        d->gfx_mem_size   = 1;  /*  Nothing, as we start in text mode  */
        d->pixel_repx = d->pixel_repy = machine->x11_scaleup;

        /*  Allocate in full pages, to make it possible to use bintrans:  */
        allocsize = ((d->charcells_size-1) | (machine->arch_pagesize-1)) + 1;
        d->charcells = malloc(d->charcells_size);
        d->charcells_outputed = malloc(d->charcells_size);
        d->charcells_drawn = malloc(d->charcells_size);
        d->gfx_mem = malloc(d->gfx_mem_size);
        if (d->charcells == NULL || d->charcells_outputed == NULL ||
            d->charcells_drawn == NULL || d->gfx_mem == NULL) {
                fprintf(stderr, "out of memory in dev_vga_init()\n");
                exit(1);
        }

        memset(d->charcells_drawn, 0, d->charcells_size);

        for (i=0; i<d->charcells_size; i+=2) {
                d->charcells[i] = ' ';
                d->charcells[i+1] = 0x07;  /*  Default color  */
                d->charcells_drawn[i] = ' ';
                d->charcells_drawn[i+1] = 0x07;
        }

        memset(d->charcells_outputed, 0, d->charcells_size);
        memset(d->gfx_mem, 0, d->gfx_mem_size);

        d->font = font8x16;
        d->font_width  = 8;
        d->font_height = 16;

        d->fb_max_x = d->pixel_repx * d->max_x;
        d->fb_max_y = d->pixel_repy * d->max_y;
        if (d->cur_mode == MODE_CHARCELL) {
                d->fb_max_x *= d->font_width;
                d->fb_max_y *= d->font_height;
        }

        memory_device_register(mem, "vga_charcells", videomem_base + 0x18000,
            allocsize, dev_vga_access, d, DM_DYNTRANS_OK |
            DM_DYNTRANS_WRITE_OK | DM_READS_HAVE_NO_SIDE_EFFECTS,
            d->charcells);
        memory_device_register(mem, "vga_gfx", videomem_base, GFX_ADDR_WINDOW,
            dev_vga_graphics_access, d, DM_DEFAULT |
            DM_READS_HAVE_NO_SIDE_EFFECTS, d->gfx_mem);
        memory_device_register(mem, "vga_ctrl", control_base,
            32, dev_vga_ctrl_access, d, DM_DEFAULT, NULL);

        d->fb = dev_fb_init(machine, mem, VGA_FB_ADDR, VFB_GENERIC,
            d->fb_max_x, d->fb_max_y, d->fb_max_x, d->fb_max_y, 24, "VGA");
        d->fb_size = d->fb_max_x * d->fb_max_y * 3;

        reset_palette(d, 0);

        /*  This will force an initial redraw/resynch:  */
        d->update_x1 = 0;
        d->update_x2 = d->max_x - 1;
        d->update_y1 = 0;
        d->update_y2 = d->max_y - 1;
        d->modified = 1;

        machine_add_tickfunction(machine, dev_vga_tick, d, VGA_TICK_SHIFT);

        register_reset(d);

        vga_update_cursor(machine, d);
}
