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(CONFIG_ARCH_FOOTBRIDGE) && defined(CONFIG_VGA_CONSOLE)
22#include <asm/vga.h>
23#define DUMMY_COLUMNS vgacon_screen_info.orig_video_cols
24#define DUMMY_ROWS vgacon_screen_info.orig_video_lines
25#else
26/* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */
27#define DUMMY_COLUMNS CONFIG_DUMMY_CONSOLE_COLUMNS
28#define DUMMY_ROWS CONFIG_DUMMY_CONSOLE_ROWS
29#endif
30
31#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
32/* These are both protected by the console_lock */
33static RAW_NOTIFIER_HEAD(dummycon_output_nh);
34static bool dummycon_putc_called;
35
36void dummycon_register_output_notifier(struct notifier_block *nb)
37{
38 WARN_CONSOLE_UNLOCKED();
39
40 raw_notifier_chain_register(&dummycon_output_nh, nb);
41
42 if (dummycon_putc_called)
43 nb->notifier_call(nb, 0, NULL);
44}
45
46void dummycon_unregister_output_notifier(struct notifier_block *nb)
47{
48 WARN_CONSOLE_UNLOCKED();
49
50 raw_notifier_chain_unregister(&dummycon_output_nh, nb);
51}
52
53static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y,
54 unsigned int x)
55{
56 WARN_CONSOLE_UNLOCKED();
57
58 dummycon_putc_called = true;
59 raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
60}
61
62static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
63 unsigned int ypos, unsigned int xpos)
64{
65 unsigned int i;
66
67 if (!dummycon_putc_called) {
68 /* Ignore erases */
69 for (i = 0 ; i < count; i++) {
70 if (s[i] != vc->vc_video_erase_char)
71 break;
72 }
73 if (i == count)
74 return;
75
76 dummycon_putc_called = true;
77 }
78
79 raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
80}
81
82static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
83 bool mode_switch)
84{
85 /* Redraw, so that we get putc(s) for output done while blanked */
86 return true;
87}
88
89static bool dummycon_switch(struct vc_data *vc)
90{
91 /*
92 * Redraw, so that we get putc(s) for output done while switched
93 * away. Informs deferred consoles to take over the display.
94 */
95 return true;
96}
97#else
98static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y,
99 unsigned int x) { }
100static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
101 unsigned int ypos, unsigned int xpos) { }
102static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
103 bool mode_switch)
104{
105 return false;
106}
107static bool dummycon_switch(struct vc_data *vc)
108{
109 return false;
110}
111#endif
112
113static const char *dummycon_startup(void)
114{
115 return "dummy device";
116}
117
118static void dummycon_init(struct vc_data *vc, bool init)
119{
120 vc->vc_can_do_color = 1;
121 if (init) {
122 vc->vc_cols = DUMMY_COLUMNS;
123 vc->vc_rows = DUMMY_ROWS;
124 } else
125 vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
126}
127
128static void dummycon_deinit(struct vc_data *vc) { }
129static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
130 unsigned int width) { }
131static void dummycon_cursor(struct vc_data *vc, bool enable) { }
132
133static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
134 unsigned int bottom, enum con_scroll dir,
135 unsigned int lines)
136{
137 return false;
138}
139
140/*
141 * The console `switch' structure for the dummy console
142 *
143 * Most of the operations are dummies.
144 */
145
146const struct consw dummy_con = {
147 .owner = THIS_MODULE,
148 .con_startup = dummycon_startup,
149 .con_init = dummycon_init,
150 .con_deinit = dummycon_deinit,
151 .con_clear = dummycon_clear,
152 .con_putc = dummycon_putc,
153 .con_putcs = dummycon_putcs,
154 .con_cursor = dummycon_cursor,
155 .con_scroll = dummycon_scroll,
156 .con_switch = dummycon_switch,
157 .con_blank = dummycon_blank,
158};
159EXPORT_SYMBOL_GPL(dummy_con);
160