LXR linux/arch/x86/boot/video-bios.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* -*- linux-c -*- ------------------------------------------------------- *
   3 *
   4 *   Copyright (C) 1991, 1992 Linus Torvalds
   5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
   6 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
   7 *
   8 * ----------------------------------------------------------------------- */
   9
  10/*
  11 * Standard video BIOS modes
  12 *
  13 * We have two options for this; silent and scanned.
  14 */
  15
  16#include "boot.h"
  17#include "video.h"
  18
  19static __videocard video_bios;
  20
  21/* Set a conventional BIOS mode */
  22static int set_bios_mode(u8 mode);
  23
  24static int bios_set_mode(struct mode_info *mi)
  25{
  26        return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
  27}
  28
  29static int set_bios_mode(u8 mode)
  30{
  31        struct biosregs ireg, oreg;
  32        u8 new_mode;
  33
  34        initregs(&ireg);
  35        ireg.al = mode;         /* AH=0x00 Set Video Mode */
  36        intcall(0x10, &ireg, NULL);
  37
  38        ireg.ah = 0x0f;         /* Get Current Video Mode */
  39        intcall(0x10, &ireg, &oreg);
  40
  41        do_restore = 1;         /* Assume video contents were lost */
  42
  43        /* Not all BIOSes are clean with the top bit */
  44        new_mode = oreg.al & 0x7f;
  45
  46        if (new_mode == mode)
  47                return 0;       /* Mode change OK */
  48
  49#ifndef _WAKEUP
  50        if (new_mode != boot_params.screen_info.orig_video_mode) {
  51                /* Mode setting failed, but we didn't end up where we
  52                   started.  That's bad.  Try to revert to the original
  53                   video mode. */
  54                ireg.ax = boot_params.screen_info.orig_video_mode;
  55                intcall(0x10, &ireg, NULL);
  56        }
  57#endif
  58        return -1;
  59}
  60
  61static int bios_probe(void)
  62{
  63        u8 mode;
  64#ifdef _WAKEUP
  65        u8 saved_mode = 0x03;
  66#else
  67        u8 saved_mode = boot_params.screen_info.orig_video_mode;
  68#endif
  69        u16 crtc;
  70        struct mode_info *mi;
  71        int nmodes = 0;
  72
  73        if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
  74                return 0;
  75
  76        set_fs(0);
  77        crtc = vga_crtc();
  78
  79        video_bios.modes = GET_HEAP(struct mode_info, 0);
  80
  81        for (mode = 0x14; mode <= 0x7f; mode++) {
  82                if (!heap_free(sizeof(struct mode_info)))
  83                        break;
  84
  85                if (mode_defined(VIDEO_FIRST_BIOS+mode))
  86                        continue;
  87
  88                if (set_bios_mode(mode))
  89                        continue;
  90
  91                /* Try to verify that it's a text mode. */
  92
  93                /* Attribute Controller: make graphics controller disabled */
  94                if (in_idx(0x3c0, 0x10) & 0x01)
  95                        continue;
  96
  97                /* Graphics Controller: verify Alpha addressing enabled */
  98                if (in_idx(0x3ce, 0x06) & 0x01)
  99                        continue;
 100
 101                /* CRTC cursor location low should be zero(?) */
 102                if (in_idx(crtc, 0x0f))
 103                        continue;
 104
 105                mi = GET_HEAP(struct mode_info, 1);
 106                mi->mode = VIDEO_FIRST_BIOS+mode;
 107                mi->depth = 0;  /* text */
 108                mi->x = rdfs16(0x44a);
 109                mi->y = rdfs8(0x484)+1;
 110                nmodes++;
 111        }
 112
 113        set_bios_mode(saved_mode);
 114
 115        return nmodes;
 116}
 117
 118static __videocard video_bios =
 119{
 120        .card_name      = "BIOS",
 121        .probe          = bios_probe,
 122        .set_mode       = bios_set_mode,
 123        .unsafe         = 1,
 124        .xmode_first    = VIDEO_FIRST_BIOS,
 125        .xmode_n        = 0x80,
 126};
 127