1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  linux/drivers/video/dummycon.c -- A dummy console driver
4 *
5 *  To be used if there's no other console driver (e.g. for plain VGA text)
6 *  available, usually until fbcon takes console over.
7 */
8
9#include <linux/types.h>
10#include <linux/kdev_t.h>
11#include <linux/console.h>
12#include <linux/vt_kern.h>
13#include <linux/screen_info.h>
14#include <linux/init.h>
15#include <linux/module.h>
16
17/*
18 *  Dummy console driver
19 */
20
21#if defined(__arm__)
22#define DUMMY_COLUMNS	screen_info.orig_video_cols
23#define DUMMY_ROWS	screen_info.orig_video_lines
24#else
25/* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */
26#define DUMMY_COLUMNS	CONFIG_DUMMY_CONSOLE_COLUMNS
27#define DUMMY_ROWS	CONFIG_DUMMY_CONSOLE_ROWS
28#endif
29
30#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
31/* These are both protected by the console_lock */
32static RAW_NOTIFIER_HEAD(dummycon_output_nh);
33static bool dummycon_putc_called;
34
35void dummycon_register_output_notifier(struct notifier_block *nb)
36{
37	WARN_CONSOLE_UNLOCKED();
38
39	raw_notifier_chain_register(&dummycon_output_nh, nb);
40
41	if (dummycon_putc_called)
42		nb->notifier_call(nb, 0, NULL);
43}
44
45void dummycon_unregister_output_notifier(struct notifier_block *nb)
46{
47	WARN_CONSOLE_UNLOCKED();
48
49	raw_notifier_chain_unregister(&dummycon_output_nh, nb);
50}
51
52static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
53{
54	WARN_CONSOLE_UNLOCKED();
55
56	dummycon_putc_called = true;
57	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
58}
59
60static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
61			   int count, int ypos, int xpos)
62{
63	int i;
64
65	if (!dummycon_putc_called) {
66		/* Ignore erases */
67		for (i = 0 ; i < count; i++) {
68			if (s[i] != vc->vc_video_erase_char)
69				break;
70		}
71		if (i == count)
72			return;
73
74		dummycon_putc_called = true;
75	}
76
77	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
78}
79
80static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
81{
82	/* Redraw, so that we get putc(s) for output done while blanked */
83	return 1;
84}
85#else
86static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
87static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
88			   int count, int ypos, int xpos) { }
89static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
90{
91	return 0;
92}
93#endif
94
95static const char *dummycon_startup(void)
96{
97    return "dummy device";
98}
99
100static void dummycon_init(struct vc_data *vc, int init)
101{
102    vc->vc_can_do_color = 1;
103    if (init) {
104	vc->vc_cols = DUMMY_COLUMNS;
105	vc->vc_rows = DUMMY_ROWS;
106    } else
107	vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
108}
109
110static void dummycon_deinit(struct vc_data *vc) { }
111static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
112			   int width) { }
113static void dummycon_cursor(struct vc_data *vc, int mode) { }
114
115static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
116			    unsigned int bottom, enum con_scroll dir,
117			    unsigned int lines)
118{
119	return false;
120}
121
122static int dummycon_switch(struct vc_data *vc)
123{
124	return 0;
125}
126
127/*
128 *  The console `switch' structure for the dummy console
129 *
130 *  Most of the operations are dummies.
131 */
132
133const struct consw dummy_con = {
134	.owner =		THIS_MODULE,
135	.con_startup =	dummycon_startup,
136	.con_init =		dummycon_init,
137	.con_deinit =	dummycon_deinit,
138	.con_clear =	dummycon_clear,
139	.con_putc =		dummycon_putc,
140	.con_putcs =	dummycon_putcs,
141	.con_cursor =	dummycon_cursor,
142	.con_scroll =	dummycon_scroll,
143	.con_switch =	dummycon_switch,
144	.con_blank =	dummycon_blank,
145};
146EXPORT_SYMBOL_GPL(dummy_con);
147