/* * drivers/power/process.c - Functions for saving/restoring console. * * Originally from swsusp. */ #include <linux/vt_kern.h>#include <linux/kbd_kern.h>#include <linux/console.h>#include <linux/module.h>#include "power.h" #if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)#define SUSPEND_CONSOLE	(MAX_NR_CONSOLES-1) static int orig_fgconsole, orig_kmsg;static int disable_vt_switch; /* * Normally during a suspend, we allocate a new console and switch to it. * When we resume, we switch back to the original console.  This switch * can be slow, so on systems where the framebuffer can handle restoration * of video registers anyways, there's little point in doing the console * switch.  This function allows you to disable it by passing it '0'. */void pm_set_vt_switch(int do_switch){	acquire_console_sem();	disable_vt_switch = !do_switch;	release_console_sem();}EXPORT_SYMBOL(pm_set_vt_switch); int pm_prepare_console(void){	acquire_console_sem(); 	if (disable_vt_switch) {		release_console_sem();		return 0;	} 	orig_fgconsole = fg_console; 	if (vc_allocate(SUSPEND_CONSOLE)) {	  /* we can't have a free VC for now. Too bad,	   * we don't want to mess the screen for now. */		release_console_sem();		return 1;	} 	if (set_console(SUSPEND_CONSOLE)) {		/*		 * We're unable to switch to the SUSPEND_CONSOLE.		 * Let the calling function know so it can decide		 * what to do.		 */		release_console_sem();		return 1;	}	release_console_sem(); 	if (vt_waitactive(SUSPEND_CONSOLE)) {		pr_debug("Suspend: Can't switch VCs.");		return 1;	}	orig_kmsg = kmsg_redirect;	kmsg_redirect = SUSPEND_CONSOLE;	return 0;} void pm_restore_console(void){	acquire_console_sem();	if (disable_vt_switch) {		release_console_sem();		return;	}	set_console(orig_fgconsole);	release_console_sem();	kmsg_redirect = orig_kmsg;}#endif