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  *
   6  *   This file is part of the Linux kernel, and is made available under
   7  *   the terms of the GNU General Public License version 2.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * arch/i386/boot/video-bios.c
  13  *
  14  * Standard video BIOS modes
  15  *
  16  * We have two options for this; silent and scanned.
  17  */
  18
  19 #include "boot.h"
  20 #include "video.h"
  21
  22 __videocard video_bios;
  23
  24 /* Set a conventional BIOS mode */
  25 static int set_bios_mode(u8 mode);
  26
  27 static int bios_set_mode(struct mode_info *mi)
  28 {
  29         return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
  30 }
  31
  32 static int set_bios_mode(u8 mode)
  33 {
  34         u16 ax;
  35         u8 new_mode;
  36
  37         ax = mode;              /* AH=0x00 Set Video Mode */
  38         asm volatile(INT10
  39                      : "+a" (ax)
  40                      : : "ebx", "ecx", "edx", "esi", "edi");
  41
  42         ax = 0x0f00;            /* Get Current Video Mode */
  43         asm volatile(INT10
  44                      : "+a" (ax)
  45                      : : "ebx", "ecx", "edx", "esi", "edi");
  46
  47         do_restore = 1;         /* Assume video contents were lost */
  48         new_mode = ax & 0x7f;   /* Not all BIOSes are clean with the top bit */
  49
  50         if (new_mode == mode)
  51                 return 0;       /* Mode change OK */
  52
  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                 ax = boot_params.screen_info.orig_video_mode;
  58                 asm volatile(INT10
  59                              : "+a" (ax)
  60                              : : "ebx", "ecx", "edx", "esi", "edi");
  61         }
  62         return -1;
  63 }
  64
  65 static int bios_probe(void)
  66 {
  67         u8 mode;
  68         u8 saved_mode = boot_params.screen_info.orig_video_mode;
  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 __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 };