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
  19 static __videocard video_bios;
  20
  21 /* Set a conventional BIOS mode */
  22 static int set_bios_mode(u8 mode);
  23
  24 static int bios_set_mode(struct mode_info *mi)
  25 {
  26         return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
  27 }
  28
  29 static 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
  61 static 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
 118 static __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 };