1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 * Copyright 2009 Intel Corporation; author H. Peter Anvin
7 *
8 * ----------------------------------------------------------------------- */
9
10 /*
11 * Standard video BIOS modes
12 *
13 * We have two options for this; silent and scanned.
14 */
15
16 #include "boot.h"
17 #include "video.h"
18
19 static __videocard video_bios;
20
21 /* Set a conventional BIOS mode */
22 static int set_bios_mode(u8 mode);
23
24 static int bios_set_mode(struct mode_info *mi)
25 {
26 return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
27 }
28
29 static int set_bios_mode(u8 mode)
30 {
31 struct biosregs ireg, oreg;
32 u8 new_mode;
33
34 initregs(&ireg);
35 ireg.al = mode; /* AH=0x00 Set Video Mode */
36 intcall(0x10, &ireg, NULL);
37
38 ireg.ah = 0x0f; /* Get Current Video Mode */
39 intcall(0x10, &ireg, &oreg);
40
41 do_restore = 1; /* Assume video contents were lost */
42
43 /* Not all BIOSes are clean with the top bit */
44 new_mode = oreg.al & 0x7f;
45
46 if (new_mode == mode)
47 return 0; /* Mode change OK */
48
49 #ifndef _WAKEUP
50 if (new_mode != boot_params.screen_info.orig_video_mode) {
51 /* Mode setting failed, but we didn't end up where we
52 started. That's bad. Try to revert to the original
53 video mode. */
54 ireg.ax = boot_params.screen_info.orig_video_mode;
55 intcall(0x10, &ireg, NULL);
56 }
57 #endif
58 return -1;
59 }
60
61 static int bios_probe(void)
62 {
63 u8 mode;
64 #ifdef _WAKEUP
65 u8 saved_mode = 0x03;
66 #else
67 u8 saved_mode = boot_params.screen_info.orig_video_mode;
68 #endif
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 static __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
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.