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 
bios_set_mode(struct mode_info * mi)24 static int bios_set_mode(struct mode_info *mi)
25 {
26 	return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
27 }
28 
set_bios_mode(u8 mode)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 
bios_probe(void)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