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