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 */
32 static RAW_NOTIFIER_HEAD(dummycon_output_nh);
33 static bool dummycon_putc_called;
34
dummycon_register_output_notifier(struct notifier_block * nb)35 void 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
dummycon_unregister_output_notifier(struct notifier_block * nb)45 void 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
dummycon_putc(struct vc_data * vc,int c,int ypos,int xpos)52 static 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
dummycon_putcs(struct vc_data * vc,const unsigned short * s,int count,int ypos,int xpos)60 static 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
dummycon_blank(struct vc_data * vc,int blank,int mode_switch)80 static 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
dummycon_putc(struct vc_data * vc,int c,int ypos,int xpos)86 static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
dummycon_putcs(struct vc_data * vc,const unsigned short * s,int count,int ypos,int xpos)87 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
88 int count, int ypos, int xpos) { }
dummycon_blank(struct vc_data * vc,int blank,int mode_switch)89 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
90 {
91 return 0;
92 }
93 #endif
94
dummycon_startup(void)95 static const char *dummycon_startup(void)
96 {
97 return "dummy device";
98 }
99
dummycon_init(struct vc_data * vc,int init)100 static 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
dummycon_deinit(struct vc_data * vc)110 static void dummycon_deinit(struct vc_data *vc) { }
dummycon_clear(struct vc_data * vc,int sy,int sx,int height,int width)111 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
112 int width) { }
dummycon_cursor(struct vc_data * vc,int mode)113 static void dummycon_cursor(struct vc_data *vc, int mode) { }
114
dummycon_scroll(struct vc_data * vc,unsigned int top,unsigned int bottom,enum con_scroll dir,unsigned int lines)115 static 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
dummycon_switch(struct vc_data * vc)122 static 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
133 const 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 };
146 EXPORT_SYMBOL_GPL(dummy_con);
147