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 */
 33static RAW_NOTIFIER_HEAD(dummycon_output_nh);
 34static bool dummycon_putc_called;
 35
 36void 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
 46void 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
 53static 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
 62static 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
 82static 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
 89static bool dummycon_switch(struct vc_data *vc)
 90{
 91	/*
 92	 * Redraw, so that we get putc(s) for output done while switched
 93	 * away. Informs deferred consoles to take over the display.
 94	 */
 95	return true;
 96}
 97#else
 98static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y,
 99			  unsigned int x) { }
100static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
101			   unsigned int ypos, unsigned int xpos) { }
102static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
103			   bool mode_switch)
104{
105	return false;
106}
107static bool dummycon_switch(struct vc_data *vc)
108{
109	return false;
110}
111#endif
112
113static const char *dummycon_startup(void)
114{
115    return "dummy device";
116}
117
118static void dummycon_init(struct vc_data *vc, bool init)
119{
120    vc->vc_can_do_color = 1;
121    if (init) {
122	vc->vc_cols = DUMMY_COLUMNS;
123	vc->vc_rows = DUMMY_ROWS;
124    } else
125	vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS);
126}
127
128static void dummycon_deinit(struct vc_data *vc) { }
129static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
130			   unsigned int width) { }
131static void dummycon_cursor(struct vc_data *vc, bool enable) { }
132
133static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
134			    unsigned int bottom, enum con_scroll dir,
135			    unsigned int lines)
136{
137	return false;
138}
139
140/*
141 *  The console `switch' structure for the dummy console
142 *
143 *  Most of the operations are dummies.
144 */
145
146const struct consw dummy_con = {
147	.owner =		THIS_MODULE,
148	.con_startup =	dummycon_startup,
149	.con_init =		dummycon_init,
150	.con_deinit =	dummycon_deinit,
151	.con_clear =	dummycon_clear,
152	.con_putc =		dummycon_putc,
153	.con_putcs =	dummycon_putcs,
154	.con_cursor =	dummycon_cursor,
155	.con_scroll =	dummycon_scroll,
156	.con_switch =	dummycon_switch,
157	.con_blank =	dummycon_blank,
158};
159EXPORT_SYMBOL_GPL(dummy_con);