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  * Standard video BIOS modes
  13  *
  14  * We have two options for this; silent and scanned.
  15  */
  16
  17 #include "boot.h"
  18 #include "video.h"
  19
  20 static __videocard video_bios;
  21
  22 /* Set a conventional BIOS mode */
  23 static int set_bios_mode(u8 mode);
  24
  25 static int bios_set_mode(struct mode_info *mi)
  26 {
  27         return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
  28 }
  29
  30 static int set_bios_mode(u8 mode)
  31 {
  32         u16 ax;
  33         u8 new_mode;
  34
  35         ax = mode;              /* AH=0x00 Set Video Mode */
  36         asm volatile(INT10
  37                      : "+a" (ax)
  38                      : : "ebx", "ecx", "edx", "esi", "edi");
  39
  40         ax = 0x0f00;            /* Get Current Video Mode */
  41         asm volatile(INT10
  42                      : "+a" (ax)
  43                      : : "ebx", "ecx", "edx", "esi", "edi");
  44
  45         do_restore = 1;         /* Assume video contents were lost */
  46         new_mode = ax & 0x7f;   /* Not all BIOSes are clean with the top bit */
  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                 ax = boot_params.screen_info.orig_video_mode;
  57                 asm volatile(INT10
  58                              : "+a" (ax)
  59                              : : "ebx", "ecx", "edx", "esi", "edi");
  60         }
  61 #endif
  62         return -1;
  63 }
  64
  65 static int bios_probe(void)
  66 {
  67         u8 mode;
  68 #ifdef _WAKEUP
  69         u8 saved_mode = 0x03;
  70 #else
  71         u8 saved_mode = boot_params.screen_info.orig_video_mode;
  72 #endif
  73         u16 crtc;
  74         struct mode_info *mi;
  75         int nmodes = 0;
  76
  77         if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
  78                 return 0;
  79
  80         set_fs(0);
  81         crtc = vga_crtc();
  82
  83         video_bios.modes = GET_HEAP(struct mode_info, 0);
  84
  85         for (mode = 0x14; mode <= 0x7f; mode++) {
  86                 if (!heap_free(sizeof(struct mode_info)))
  87                         break;
  88
  89                 if (mode_defined(VIDEO_FIRST_BIOS+mode))
  90                         continue;
  91
  92                 if (set_bios_mode(mode))
  93                         continue;
  94
  95                 /* Try to verify that it's a text mode. */
  96
  97                 /* Attribute Controller: make graphics controller disabled */
  98                 if (in_idx(0x3c0, 0x10) & 0x01)
  99                         continue;
 100
 101                 /* Graphics Controller: verify Alpha addressing enabled */
 102                 if (in_idx(0x3ce, 0x06) & 0x01)
 103                         continue;
 104
 105                 /* CRTC cursor location low should be zero(?) */
 106                 if (in_idx(crtc, 0x0f))
 107                         continue;
 108
 109                 mi = GET_HEAP(struct mode_info, 1);
 110                 mi->mode = VIDEO_FIRST_BIOS+mode;
 111                 mi->depth = 0;  /* text */
 112                 mi->x = rdfs16(0x44a);
 113                 mi->y = rdfs8(0x484)+1;
 114                 nmodes++;
 115         }
 116
 117         set_bios_mode(saved_mode);
 118
 119         return nmodes;
 120 }
 121
 122 static __videocard video_bios =
 123 {
 124         .card_name      = "BIOS",
 125         .probe          = bios_probe,
 126         .set_mode       = bios_set_mode,
 127         .unsafe         = 1,
 128         .xmode_first    = VIDEO_FIRST_BIOS,
 129         .xmode_n        = 0x80,
 130 };