1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- linux-c -*- ------------------------------------------------------- *
3  *
4  *   Copyright (C) 1991, 1992 Linus Torvalds
5  *   Copyright 2007-2008 rPath, Inc. - All Rights Reserved
6  *
7  * ----------------------------------------------------------------------- */
8 
9 /*
10  * arch/i386/boot/video-mode.c
11  *
12  * Set the video mode.  This is separated out into a different
13  * file in order to be shared with the ACPI wakeup code.
14  */
15 
16 #include "boot.h"
17 #include "video.h"
18 #include "vesa.h"
19 
20 #include <uapi/asm/boot.h>
21 
22 /*
23  * Common variables
24  */
25 int adapter;		/* 0=CGA/MDA/HGC, 1=EGA, 2=VGA+ */
26 int force_x, force_y;	/* Don't query the BIOS for cols/rows */
27 int do_restore;		/* Screen contents changed during mode flip */
28 int graphic_mode;	/* Graphic mode with linear frame buffer */
29 
30 /* Probe the video drivers and have them generate their mode lists. */
probe_cards(int unsafe)31 void probe_cards(int unsafe)
32 {
33 	struct card_info *card;
34 	static u8 probed[2];
35 
36 	if (probed[unsafe])
37 		return;
38 
39 	probed[unsafe] = 1;
40 
41 	for (card = video_cards; card < video_cards_end; card++) {
42 		if (card->unsafe == unsafe) {
43 			if (card->probe)
44 				card->nmodes = card->probe();
45 			else
46 				card->nmodes = 0;
47 		}
48 	}
49 }
50 
51 /* Test if a mode is defined */
mode_defined(u16 mode)52 int mode_defined(u16 mode)
53 {
54 	struct card_info *card;
55 	struct mode_info *mi;
56 	int i;
57 
58 	for (card = video_cards; card < video_cards_end; card++) {
59 		mi = card->modes;
60 		for (i = 0; i < card->nmodes; i++, mi++) {
61 			if (mi->mode == mode)
62 				return 1;
63 		}
64 	}
65 
66 	return 0;
67 }
68 
69 /* Set mode (without recalc) */
raw_set_mode(u16 mode,u16 * real_mode)70 static int raw_set_mode(u16 mode, u16 *real_mode)
71 {
72 	int nmode, i;
73 	struct card_info *card;
74 	struct mode_info *mi;
75 
76 	/* Drop the recalc bit if set */
77 	mode &= ~VIDEO_RECALC;
78 
79 	/* Scan for mode based on fixed ID, position, or resolution */
80 	nmode = 0;
81 	for (card = video_cards; card < video_cards_end; card++) {
82 		mi = card->modes;
83 		for (i = 0; i < card->nmodes; i++, mi++) {
84 			int visible = mi->x || mi->y;
85 
86 			if ((mode == nmode && visible) ||
87 			    mode == mi->mode ||
88 			    mode == (mi->y << 8)+mi->x) {
89 				*real_mode = mi->mode;
90 				return card->set_mode(mi);
91 			}
92 
93 			if (visible)
94 				nmode++;
95 		}
96 	}
97 
98 	/* Nothing found?  Is it an "exceptional" (unprobed) mode? */
99 	for (card = video_cards; card < video_cards_end; card++) {
100 		if (mode >= card->xmode_first &&
101 		    mode < card->xmode_first+card->xmode_n) {
102 			struct mode_info mix;
103 			*real_mode = mix.mode = mode;
104 			mix.x = mix.y = 0;
105 			return card->set_mode(&mix);
106 		}
107 	}
108 
109 	/* Otherwise, failure... */
110 	return -1;
111 }
112 
113 /*
114  * Recalculate the vertical video cutoff (hack!)
115  */
vga_recalc_vertical(void)116 static void vga_recalc_vertical(void)
117 {
118 	unsigned int font_size, rows;
119 	u16 crtc;
120 	u8 pt, ov;
121 
122 	set_fs(0);
123 	font_size = rdfs8(0x485); /* BIOS: font size (pixels) */
124 	rows = force_y ? force_y : rdfs8(0x484)+1; /* Text rows */
125 
126 	rows *= font_size;	/* Visible scan lines */
127 	rows--;			/* ... minus one */
128 
129 	crtc = vga_crtc();
130 
131 	pt = in_idx(crtc, 0x11);
132 	pt &= ~0x80;		/* Unlock CR0-7 */
133 	out_idx(pt, crtc, 0x11);
134 
135 	out_idx((u8)rows, crtc, 0x12); /* Lower height register */
136 
137 	ov = in_idx(crtc, 0x07); /* Overflow register */
138 	ov &= 0xbd;
139 	ov |= (rows >> (8-1)) & 0x02;
140 	ov |= (rows >> (9-6)) & 0x40;
141 	out_idx(ov, crtc, 0x07);
142 }
143 
144 /* Set mode (with recalc if specified) */
set_mode(u16 mode)145 int set_mode(u16 mode)
146 {
147 	int rv;
148 	u16 real_mode;
149 
150 	/* Very special mode numbers... */
151 	if (mode == VIDEO_CURRENT_MODE)
152 		return 0;	/* Nothing to do... */
153 	else if (mode == NORMAL_VGA)
154 		mode = VIDEO_80x25;
155 	else if (mode == EXTENDED_VGA)
156 		mode = VIDEO_8POINT;
157 
158 	rv = raw_set_mode(mode, &real_mode);
159 	if (rv)
160 		return rv;
161 
162 	if (mode & VIDEO_RECALC)
163 		vga_recalc_vertical();
164 
165 	/* Save the canonical mode number for the kernel, not
166 	   an alias, size specification or menu position */
167 #ifndef _WAKEUP
168 	boot_params.hdr.vid_mode = real_mode;
169 #endif
170 	return 0;
171 }
172