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(__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
  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
  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
  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
  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
  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
  86 static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
  87 static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
  88                            int count, int ypos, int xpos) { }
  89 static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
  90 {
  91         return 0;
  92 }
  93 #endif
  94
  95 static const char *dummycon_startup(void)
  96 {
  97     return "dummy device";
  98 }
  99
 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
 110 static void dummycon_deinit(struct vc_data *vc) { }
 111 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
 112                            int width) { }
 113 static void dummycon_cursor(struct vc_data *vc, int mode) { }
 114
 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
 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);