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         ireg.ah = 0x0f;         /* Get Current Video Mode */
  41         intcall(0x10, &ireg, &oreg);
  42
  43         do_restore = 1;         /* Assume video contents were lost */
  44
  45         /* Not all BIOSes are clean with the top bit */
  46         new_mode = oreg.al & 0x7f;
  47
  48         if (new_mode == mode)
  49                 return 0;       /* Mode change OK */
  50
  51 #ifndef _WAKEUP
  52         if (new_mode != boot_params.screen_info.orig_video_mode) {
  53                 /* Mode setting failed, but we didn't end up where we
  54                    started.  That's bad.  Try to revert to the original
  55                    video mode. */
  56                 ireg.ax = boot_params.screen_info.orig_video_mode;
  57                 intcall(0x10, &ireg, NULL);
  58         }
  59 #endif
  60         return -1;
  61 }
  62
  63 static int bios_probe(void)
  64 {
  65         u8 mode;
  66 #ifdef _WAKEUP
  67         u8 saved_mode = 0x03;
  68 #else
  69         u8 saved_mode = boot_params.screen_info.orig_video_mode;
  70 #endif
  71         u16 crtc;
  72         struct mode_info *mi;
  73         int nmodes = 0;
  74
  75         if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
  76                 return 0;
  77
  78         set_fs(0);
  79         crtc = vga_crtc();
  80
  81         video_bios.modes = GET_HEAP(struct mode_info, 0);
  82
  83         for (mode = 0x14; mode <= 0x7f; mode++) {
  84                 if (!heap_free(sizeof(struct mode_info)))
  85                         break;
  86
  87                 if (mode_defined(VIDEO_FIRST_BIOS+mode))
  88                         continue;
  89
  90                 if (set_bios_mode(mode))
  91                         continue;
  92
  93                 /* Try to verify that it's a text mode. */
  94
  95                 /* Attribute Controller: make graphics controller disabled */
  96                 if (in_idx(0x3c0, 0x10) & 0x01)
  97                         continue;
  98
  99                 /* Graphics Controller: verify Alpha addressing enabled */
 100                 if (in_idx(0x3ce, 0x06) & 0x01)
 101                         continue;
 102
 103                 /* CRTC cursor location low should be zero(?) */
 104                 if (in_idx(crtc, 0x0f))
 105                         continue;
 106
 107                 mi = GET_HEAP(struct mode_info, 1);
 108                 mi->mode = VIDEO_FIRST_BIOS+mode;
 109                 mi->depth = 0;  /* text */
 110                 mi->x = rdfs16(0x44a);
 111                 mi->y = rdfs8(0x484)+1;
 112                 nmodes++;
 113         }
 114
 115         set_bios_mode(saved_mode);
 116
 117         return nmodes;
 118 }
 119
 120 static __videocard video_bios =
 121 {
 122         .card_name      = "BIOS",
 123         .probe          = bios_probe,
 124         .set_mode       = bios_set_mode,
 125         .unsafe         = 1,
 126         .xmode_first    = VIDEO_FIRST_BIOS,
 127         .xmode_n        = 0x80,
 128 };