drivers/video/console/dummycon.c

   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);