arch/x86/boot/video-bios.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright (C) 1991, 1992 Linus Torvalds
   4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5  *   Copyright 2009 Intel Corporation; author H. Peter Anvin
   6  *
   7  *   This file is part of the Linux kernel, and is made available under
   8  *   the terms of the GNU General Public License version 2.
   9  *
  10  * ----------------------------------------------------------------------- */
  11
  12 /*
  13  * Standard video BIOS modes
  14  *
  15  * We have two options for this; silent and scanned.
  16  */
  17
  18 #include "boot.h"
  19 #include "video.h"
  20
  21 static __videocard video_bios;
  22
  23 /* Set a conventional BIOS mode */
  24 static int set_bios_mode(u8 mode);
  25
  26 static int bios_set_mode(struct mode_info *mi)
  27 {
  28         return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
  29 }
  30
  31 static int set_bios_mode(u8 mode)
  32 {
  33         struct biosregs ireg, oreg;
  34         u8 new_mode;
  35
  36         initregs(&ireg);
  37         ireg.al = mode;         /* AH=0x00 Set Video Mode */
  38         intcall(0x10, &ireg, NULL);
  39
  40
  41         ireg.ah = 0x0f;         /* Get Current Video Mode */
  42         intcall(0x10, &ireg, &oreg);
  43
  44         do_restore = 1;         /* Assume video contents were lost */
  45
  46         /* Not all BIOSes are clean with the top bit */
  47         new_mode = ireg.al & 0x7f;
  48
  49         if (new_mode == mode)
  50                 return 0;       /* Mode change OK */
  51
  52 #ifndef _WAKEUP
  53         if (new_mode != boot_params.screen_info.orig_video_mode) {
  54                 /* Mode setting failed, but we didn't end up where we
  55                    started.  That's bad.  Try to revert to the original
  56                    video mode. */
  57                 ireg.ax = boot_params.screen_info.orig_video_mode;
  58                 intcall(0x10, &ireg, NULL);
  59         }
  60 #endif
  61         return -1;
  62 }
  63
  64 static int bios_probe(void)
  65 {
  66         u8 mode;
  67 #ifdef _WAKEUP
  68         u8 saved_mode = 0x03;
  69 #else
  70         u8 saved_mode = boot_params.screen_info.orig_video_mode;
  71 #endif
  72         u16 crtc;
  73         struct mode_info *mi;
  74         int nmodes = 0;
  75
  76         if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
  77                 return 0;
  78
  79         set_fs(0);
  80         crtc = vga_crtc();
  81
  82         video_bios.modes = GET_HEAP(struct mode_info, 0);
  83
  84         for (mode = 0x14; mode <= 0x7f; mode++) {
  85                 if (!heap_free(sizeof(struct mode_info)))
  86                         break;
  87
  88                 if (mode_defined(VIDEO_FIRST_BIOS+mode))
  89                         continue;
  90
  91                 if (set_bios_mode(mode))
  92                         continue;
  93
  94                 /* Try to verify that it's a text mode. */
  95
  96                 /* Attribute Controller: make graphics controller disabled */
  97                 if (in_idx(0x3c0, 0x10) & 0x01)
  98                         continue;
  99
 100                 /* Graphics Controller: verify Alpha addressing enabled */
 101                 if (in_idx(0x3ce, 0x06) & 0x01)
 102                         continue;
 103
 104                 /* CRTC cursor location low should be zero(?) */
 105                 if (in_idx(crtc, 0x0f))
 106                         continue;
 107
 108                 mi = GET_HEAP(struct mode_info, 1);
 109                 mi->mode = VIDEO_FIRST_BIOS+mode;
 110                 mi->depth = 0;  /* text */
 111                 mi->x = rdfs16(0x44a);
 112                 mi->y = rdfs8(0x484)+1;
 113                 nmodes++;
 114         }
 115
 116         set_bios_mode(saved_mode);
 117
 118         return nmodes;
 119 }
 120
 121 static __videocard video_bios =
 122 {
 123         .card_name      = "BIOS",
 124         .probe          = bios_probe,
 125         .set_mode       = bios_set_mode,
 126         .unsafe         = 1,
 127         .xmode_first    = VIDEO_FIRST_BIOS,
 128         .xmode_n        = 0x80,
 129 };