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 };
127
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