// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 * ----------------------------------------------------------------------- */

/*
 * Standard video BIOS modes
 *
 * We have two options for this; silent and scanned.
 */

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

static __videocard video_bios;

/* Set a conventional BIOS mode */
static int set_bios_mode(u8 mode);

static int bios_set_mode(struct mode_info *mi)
{
        return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
}

static int set_bios_mode(u8 mode)
{
        struct biosregs ireg, oreg;
        u8 new_mode;

        initregs(&ireg);
        ireg.al = mode;         /* AH=0x00 Set Video Mode */
        intcall(0x10, &ireg, NULL);

        ireg.ah = 0x0f;         /* Get Current Video Mode */
        intcall(0x10, &ireg, &oreg);

        do_restore = 1;         /* Assume video contents were lost */

        /* Not all BIOSes are clean with the top bit */
        new_mode = oreg.al & 0x7f;

        if (new_mode == mode)
                return 0;       /* Mode change OK */

#ifndef _WAKEUP
        if (new_mode != boot_params.screen_info.orig_video_mode) {
                /* Mode setting failed, but we didn't end up where we
                   started.  That's bad.  Try to revert to the original
                   video mode. */
                ireg.ax = boot_params.screen_info.orig_video_mode;
                intcall(0x10, &ireg, NULL);
        }
#endif
        return -1;
}

static int bios_probe(void)
{
        u8 mode;
#ifdef _WAKEUP
        u8 saved_mode = 0x03;
#else
        u8 saved_mode = boot_params.screen_info.orig_video_mode;
#endif
        u16 crtc;
        struct mode_info *mi;
        int nmodes = 0;

        if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
                return 0;

        set_fs(0);
        crtc = vga_crtc();

        video_bios.modes = GET_HEAP(struct mode_info, 0);

        for (mode = 0x14; mode <= 0x7f; mode++) {
                if (!heap_free(sizeof(struct mode_info)))
                        break;

                if (mode_defined(VIDEO_FIRST_BIOS+mode))
                        continue;

                if (set_bios_mode(mode))
                        continue;

                /* Try to verify that it's a text mode. */

                /* Attribute Controller: make graphics controller disabled */
                if (in_idx(0x3c0, 0x10) & 0x01)
                        continue;

                /* Graphics Controller: verify Alpha addressing enabled */
                if (in_idx(0x3ce, 0x06) & 0x01)
                        continue;

                /* CRTC cursor location low should be zero(?) */
                if (in_idx(crtc, 0x0f))
                        continue;

                mi = GET_HEAP(struct mode_info, 1);
                mi->mode = VIDEO_FIRST_BIOS+mode;
                mi->depth = 0;  /* text */
                mi->x = rdfs16(0x44a);
                mi->y = rdfs8(0x484)+1;
                nmodes++;
        }

        set_bios_mode(saved_mode);

        return nmodes;
}

static __videocard video_bios =
{
        .card_name      = "BIOS",
        .probe          = bios_probe,
        .set_mode       = bios_set_mode,
        .unsafe         = 1,
        .xmode_first    = VIDEO_FIRST_BIOS,
        .xmode_n        = 0x80,
};