root/kernel/power/console.c

DEFINITIONS

1. pm_set_vt_switch
2. pm_prepare_console
3. pm_restore_console

/*
 * 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