86Box/src/video/vid_sc1148x_ramdac.c

/*
 * 86Box	A hypervisor and IBM PC system emulator that specializes in
 *		running old operating systems and software designed for IBM
 *		PC systems and compatibles from 1981 through fairly recent
 *		system designs based on the PCI bus.
 *
 *		This file is part of the 86Box distribution.
 *
 *		Emulation of Sierra SC1148x RAMDACs and clones (e.g.: Winbond).
 *
 *		Used by the S3 911 and 924 chips.
 *
 *
 *
 * Authors:	TheCollector1995, <mariogplayer90@gmail.com>
 *
 *		Copyright 2020 TheCollector1995.
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include <86box/86box.h>
#include <86box/device.h>
#include <86box/mem.h>
#include <86box/timer.h>
#include <86box/video.h>
#include <86box/vid_svga.h>


typedef struct
{
    int type;
    int state;
	int rs2;
    uint8_t ctrl;
} sc1148x_ramdac_t;


void
sc1148x_ramdac_out(uint16_t addr, int rs2, uint8_t val, void *p, svga_t *svga)
{
    sc1148x_ramdac_t *ramdac = (sc1148x_ramdac_t *) p;
    uint8_t rs = (addr & 0x03);
    rs |= ((!!rs2) << 2);
	int oldbpp = 0;

    switch (addr) {
	case 0x3c6:
		switch (ramdac->state) {
			case 4:
				ramdac->state = 0;
				if (val == 0xff)
					break;
				ramdac->ctrl = val;
				ramdac->ctrl = (ramdac->ctrl & ~1) | ((((val >> 2) ^ val) & (val & 0x20)) >> 5);
				oldbpp = svga->bpp;
				switch (ramdac->type) {
					case 0: /* Sierra Mark 2 (11483)*/
					case 2:	/* Sierra Mark 2 (11484)*/
					case 3:	/* Sierra Mark 1 (11486)*/
						if (val & 0xa0) {
							svga->bpp = 15;
						} else if (val == 0x00)
							svga->bpp = 8;
						break;
					case 1: /* Sierra Mark 3 (11487)*/
						if (val & 0xa0) {
							if (val & 0x40)
								svga->bpp = 16;
							else
								svga->bpp = 15;
						} else if (val == 0x00)
							svga->bpp = 8;
						break;
				}
				if (oldbpp != svga->bpp)
					svga_recalctimings(svga);
				return;
			default:
				svga_out(addr, val, svga);
				break;
		}
		break;

	case 0x3c7: case 0x3c8:
	case 0x3c9:
		ramdac->state = 0;
		svga_out(addr, val, svga);
		break;
    }
}


uint8_t
sc1148x_ramdac_in(uint16_t addr, int rs2, void *p, svga_t *svga)
{
    sc1148x_ramdac_t *ramdac = (sc1148x_ramdac_t *) p;
    uint8_t ret = 0xff;
    uint8_t rs = (addr & 0x03);
    rs |= ((!!rs2) << 2);    

    switch (addr) {
	case 0x3c6:
		switch (ramdac->state) {
			case 1:
			case 2: case 3:
				ret = 0x00;
				ramdac->state++;
				break;
			case 4:
				ret = ramdac->ctrl;
				ret = (ret & ~0x18) | (svga->dac_mask & 0x18);
				break;
			default:
				ret = svga_in(addr, svga);
				ramdac->state++;
				break;
		}
		break;

	case 0x3c7: case 0x3c8:
	case 0x3c9:
		ret = svga_in(addr, svga);
		ramdac->state = 0;
		break;
    }

    return ret;
}


static void *
sc1148x_ramdac_init(const device_t *info)
{
    sc1148x_ramdac_t *ramdac = (sc1148x_ramdac_t *) malloc(sizeof(sc1148x_ramdac_t));
    memset(ramdac, 0, sizeof(sc1148x_ramdac_t));

    ramdac->type = info->local;

    return ramdac;
}


static void
sc1148x_ramdac_close(void *priv)
{
    sc1148x_ramdac_t *ramdac = (sc1148x_ramdac_t *) priv;

    if (ramdac)
	free(ramdac);
}

const device_t sc11483_ramdac_device =
{
        "Sierra SC11483 RAMDAC",
        0, 0,
        sc1148x_ramdac_init, sc1148x_ramdac_close,
	NULL, { NULL }, NULL, NULL
};

const device_t sc11487_ramdac_device =
{
        "Sierra SC11487 RAMDAC",
        0, 1,
        sc1148x_ramdac_init, sc1148x_ramdac_close,
	NULL, { NULL }, NULL, NULL
};

const device_t sc11484_nors2_ramdac_device =
{
        "Sierra SC11484 RAMDAC (no RS2 signal)",
        0, 2,
        sc1148x_ramdac_init, sc1148x_ramdac_close,
	NULL, { NULL }, NULL, NULL
};

const device_t sc11486_ramdac_device =
{
        "Sierra SC11486 RAMDAC",
        0, 3,
        sc1148x_ramdac_init, sc1148x_ramdac_close,
	NULL, { NULL }, NULL, NULL
};