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 */
33 static RAW_NOTIFIER_HEAD(dummycon_output_nh);
34 static bool dummycon_putc_called;
35
dummycon_register_output_notifier(struct notifier_block * nb)36 void 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
dummycon_unregister_output_notifier(struct notifier_block * nb)46 void 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
dummycon_putc(struct vc_data * vc,int c,int ypos,int xpos)53 static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
54 {
55 WARN_CONSOLE_UNLOCKED();
56
57 dummycon_putc_called = true;
58 raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
59 }
60
dummycon_putcs(struct vc_data * vc,const unsigned short * s,int count,int ypos,int xpos)61 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
62 int count, int ypos, int xpos)
63 {
64 int i;
65
66 if (!dummycon_putc_called) {
67 /* Ignore erases */
68 for (i = 0 ; i < count; i++) {
69 if (s[i] != vc->vc_video_erase_char)
70 break;
71 }
72 if (i == count)
73 return;
74
75 dummycon_putc_called = true;
76 }
77
78 raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
79 }
80
dummycon_blank(struct vc_data * vc,int blank,int mode_switch)81 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
82 {
83 /* Redraw, so that we get putc(s) for output done while blanked */
84 return 1;
85 }
86 #else
dummycon_putc(struct vc_data * vc,int c,int ypos,int xpos)87 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)88 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
89 int count, int ypos, int xpos) { }
dummycon_blank(struct vc_data * vc,int blank,int mode_switch)90 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
91 {
92 return 0;
93 }
94 #endif
95
dummycon_startup(void)96 static const char *dummycon_startup(void)
97 {
98 return "dummy device";
99 }
100
dummycon_init(struct vc_data * vc,int init)101 static void dummycon_init(struct vc_data *vc, int init)
102 {
103 vc->vc_can_do_color = 1;
104 if (init) {
105 vc->vc_cols = DUMMY_COLUMNS;
106 vc->vc_rows = DUMMY_ROWS;
107 } else
108 vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
109 }
110
dummycon_deinit(struct vc_data * vc)111 static void dummycon_deinit(struct vc_data *vc) { }
dummycon_clear(struct vc_data * vc,int sy,int sx,int height,int width)112 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
113 int width) { }
dummycon_cursor(struct vc_data * vc,int mode)114 static void dummycon_cursor(struct vc_data *vc, int mode) { }
115
dummycon_scroll(struct vc_data * vc,unsigned int top,unsigned int bottom,enum con_scroll dir,unsigned int lines)116 static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
117 unsigned int bottom, enum con_scroll dir,
118 unsigned int lines)
119 {
120 return false;
121 }
122
dummycon_switch(struct vc_data * vc)123 static int dummycon_switch(struct vc_data *vc)
124 {
125 return 0;
126 }
127
128 /*
129 * The console `switch' structure for the dummy console
130 *
131 * Most of the operations are dummies.
132 */
133
134 const struct consw dummy_con = {
135 .owner = THIS_MODULE,
136 .con_startup = dummycon_startup,
137 .con_init = dummycon_init,
138 .con_deinit = dummycon_deinit,
139 .con_clear = dummycon_clear,
140 .con_putc = dummycon_putc,
141 .con_putcs = dummycon_putcs,
142 .con_cursor = dummycon_cursor,
143 .con_scroll = dummycon_scroll,
144 .con_switch = dummycon_switch,
145 .con_blank = dummycon_blank,
146 };
147 EXPORT_SYMBOL_GPL(dummy_con);
148