linux/drivers/video/console/dummycon.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/drivers/video/dummycon.c -- A dummy console driver
 *
 *  To be used if there's no other console driver (e.g. for plain VGA text)
 *  available, usually until fbcon takes console over.
 */

#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/console.h>
#include <linux/vt_kern.h>
#include <linux/screen_info.h>
#include <linux/init.h>
#include <linux/module.h>

/*
 *  Dummy console driver
 */

#if defined(CONFIG_ARCH_FOOTBRIDGE) && defined(CONFIG_VGA_CONSOLE)
#include <asm/vga.h>
#define DUMMY_COLUMNS …
#define DUMMY_ROWS …
#else
/* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */
#define DUMMY_COLUMNS …
#define DUMMY_ROWS …
#endif

#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
/* These are both protected by the console_lock */
static RAW_NOTIFIER_HEAD(dummycon_output_nh);
static bool dummycon_putc_called;

void dummycon_register_output_notifier(struct notifier_block *nb)
{ … }

void dummycon_unregister_output_notifier(struct notifier_block *nb)
{ … }

static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y,
                          unsigned int x)
{ … }

static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
			   unsigned int ypos, unsigned int xpos)
{ … }

static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
			   bool mode_switch)
{ … }
#else
static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y,
			  unsigned int x) { }
static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
			   unsigned int ypos, unsigned int xpos) { }
static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
			   bool mode_switch)
{
	return false;
}
#endif

static const char *dummycon_startup(void)
{ … }

static void dummycon_init(struct vc_data *vc, bool init)
{ … }

static void dummycon_deinit(struct vc_data *vc) { … }
static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
			   unsigned int width) { … }
static void dummycon_cursor(struct vc_data *vc, bool enable) { … }

static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
			    unsigned int bottom, enum con_scroll dir,
			    unsigned int lines)
{ … }

static bool dummycon_switch(struct vc_data *vc)
{ … }

/*
 *  The console `switch' structure for the dummy console
 *
 *  Most of the operations are dummies.
 */

const struct consw dummy_con = …;
EXPORT_SYMBOL_GPL(…);