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

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* -*- linux-c -*- ------------------------------------------------------- *
   3 *
   4 *   Copyright (C) 1991, 1992 Linus Torvalds
   5 *   Copyright 2007-2008 rPath, Inc. - All Rights Reserved
   6 *
   7 * ----------------------------------------------------------------------- */
   8
   9/*
  10 * arch/i386/boot/video-mode.c
  11 *
  12 * Set the video mode.  This is separated out into a different
  13 * file in order to be shared with the ACPI wakeup code.
  14 */
  15
  16#include "boot.h"
  17#include "video.h"
  18#include "vesa.h"
  19
  20#include <uapi/asm/boot.h>
  21
  22/*
  23 * Common variables
  24 */
  25int adapter;            /* 0=CGA/MDA/HGC, 1=EGA, 2=VGA+ */
  26int force_x, force_y;   /* Don't query the BIOS for cols/rows */
  27int do_restore;         /* Screen contents changed during mode flip */
  28int graphic_mode;       /* Graphic mode with linear frame buffer */
  29
  30/* Probe the video drivers and have them generate their mode lists. */
  31void probe_cards(int unsafe)
  32{
  33        struct card_info *card;
  34        static u8 probed[2];
  35
  36        if (probed[unsafe])
  37                return;
  38
  39        probed[unsafe] = 1;
  40
  41        for (card = video_cards; card < video_cards_end; card++) {
  42                if (card->unsafe == unsafe) {
  43                        if (card->probe)
  44                                card->nmodes = card->probe();
  45                        else
  46                                card->nmodes = 0;
  47                }
  48        }
  49}
  50
  51/* Test if a mode is defined */
  52int mode_defined(u16 mode)
  53{
  54        struct card_info *card;
  55        struct mode_info *mi;
  56        int i;
  57
  58        for (card = video_cards; card < video_cards_end; card++) {
  59                mi = card->modes;
  60                for (i = 0; i < card->nmodes; i++, mi++) {
  61                        if (mi->mode == mode)
  62                                return 1;
  63                }
  64        }
  65
  66        return 0;
  67}
  68
  69/* Set mode (without recalc) */
  70static int raw_set_mode(u16 mode, u16 *real_mode)
  71{
  72        int nmode, i;
  73        struct card_info *card;
  74        struct mode_info *mi;
  75
  76        /* Drop the recalc bit if set */
  77        mode &= ~VIDEO_RECALC;
  78
  79        /* Scan for mode based on fixed ID, position, or resolution */
  80        nmode = 0;
  81        for (card = video_cards; card < video_cards_end; card++) {
  82                mi = card->modes;
  83                for (i = 0; i < card->nmodes; i++, mi++) {
  84                        int visible = mi->x || mi->y;
  85
  86                        if ((mode == nmode && visible) ||
  87                            mode == mi->mode ||
  88                            mode == (mi->y << 8)+mi->x) {
  89                                *real_mode = mi->mode;
  90                                return card->set_mode(mi);
  91                        }
  92
  93                        if (visible)
  94                                nmode++;
  95                }
  96        }
  97
  98        /* Nothing found?  Is it an "exceptional" (unprobed) mode? */
  99        for (card = video_cards; card < video_cards_end; card++) {
 100                if (mode >= card->xmode_first &&
 101                    mode < card->xmode_first+card->xmode_n) {
 102                        struct mode_info mix;
 103                        *real_mode = mix.mode = mode;
 104                        mix.x = mix.y = 0;
 105                        return card->set_mode(&mix);
 106                }
 107        }
 108
 109        /* Otherwise, failure... */
 110        return -1;
 111}
 112
 113/*
 114 * Recalculate the vertical video cutoff (hack!)
 115 */
 116static void vga_recalc_vertical(void)
 117{
 118        unsigned int font_size, rows;
 119        u16 crtc;
 120        u8 pt, ov;
 121
 122        set_fs(0);
 123        font_size = rdfs8(0x485); /* BIOS: font size (pixels) */
 124        rows = force_y ? force_y : rdfs8(0x484)+1; /* Text rows */
 125
 126        rows *= font_size;      /* Visible scan lines */
 127        rows--;                 /* ... minus one */
 128
 129        crtc = vga_crtc();
 130
 131        pt = in_idx(crtc, 0x11);
 132        pt &= ~0x80;            /* Unlock CR0-7 */
 133        out_idx(pt, crtc, 0x11);
 134
 135        out_idx((u8)rows, crtc, 0x12); /* Lower height register */
 136
 137        ov = in_idx(crtc, 0x07); /* Overflow register */
 138        ov &= 0xbd;
 139        ov |= (rows >> (8-1)) & 0x02;
 140        ov |= (rows >> (9-6)) & 0x40;
 141        out_idx(ov, crtc, 0x07);
 142}
 143
 144/* Set mode (with recalc if specified) */
 145int set_mode(u16 mode)
 146{
 147        int rv;
 148        u16 real_mode;
 149
 150        /* Very special mode numbers... */
 151        if (mode == VIDEO_CURRENT_MODE)
 152                return 0;       /* Nothing to do... */
 153        else if (mode == NORMAL_VGA)
 154                mode = VIDEO_80x25;
 155        else if (mode == EXTENDED_VGA)
 156                mode = VIDEO_8POINT;
 157
 158        rv = raw_set_mode(mode, &real_mode);
 159        if (rv)
 160                return rv;
 161
 162        if (mode & VIDEO_RECALC)
 163                vga_recalc_vertical();
 164
 165        /* Save the canonical mode number for the kernel, not
 166           an alias, size specification or menu position */
 167#ifndef _WAKEUP
 168        boot_params.hdr.vid_mode = real_mode;
 169#endif
 170        return 0;
 171}
 172