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 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 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 53 static 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 62 static 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 82 static 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 #else 89 static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y, 90 unsigned int x) { } 91 static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, 92 unsigned int ypos, unsigned int xpos) { } 93 static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank, 94 bool mode_switch) 95 { 96 return false; 97 } 98 #endif 99 100 static const char *dummycon_startup(void) 101 { 102 return "dummy device"; 103 } 104 105 static void dummycon_init(struct vc_data *vc, bool init) 106 { 107 vc->vc_can_do_color = 1; 108 if (init) { 109 vc->vc_cols = DUMMY_COLUMNS; 110 vc->vc_rows = DUMMY_ROWS; 111 } else 112 vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS); 113 } 114 115 static void dummycon_deinit(struct vc_data *vc) { } 116 static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx, 117 unsigned int width) { } 118 static void dummycon_cursor(struct vc_data *vc, bool enable) { } 119 120 static bool dummycon_scroll(struct vc_data *vc, unsigned int top, 121 unsigned int bottom, enum con_scroll dir, 122 unsigned int lines) 123 { 124 return false; 125 } 126 127 static bool dummycon_switch(struct vc_data *vc) 128 { 129 return false; 130 } 131 132 /* 133 * The console `switch' structure for the dummy console 134 * 135 * Most of the operations are dummies. 136 */ 137 138 const struct consw dummy_con = { 139 .owner = THIS_MODULE, 140 .con_startup = dummycon_startup, 141 .con_init = dummycon_init, 142 .con_deinit = dummycon_deinit, 143 .con_clear = dummycon_clear, 144 .con_putc = dummycon_putc, 145 .con_putcs = dummycon_putcs, 146 .con_cursor = dummycon_cursor, 147 .con_scroll = dummycon_scroll, 148 .con_switch = dummycon_switch, 149 .con_blank = dummycon_blank, 150 }; 151 EXPORT_SYMBOL_GPL(dummy_con); 152