kernel/power/console.c

   1 /*
   2  * drivers/power/process.c - Functions for saving/restoring console.
   3  *
   4  * Originally from swsusp.
   5  */
   6
   7 #include <linux/vt_kern.h>
   8 #include <linux/kbd_kern.h>
   9 #include <linux/console.h>
  10 #include <linux/module.h>
  11 #include "power.h"
  12
  13 #if defined(CONFIG_VT) && defined(CONFIG_VT_CONSOLE)
  14 #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)
  15
  16 static int orig_fgconsole, orig_kmsg;
  17 static int disable_vt_switch;
  18
  19 /*
  20  * Normally during a suspend, we allocate a new console and switch to it.
  21  * When we resume, we switch back to the original console.  This switch
  22  * can be slow, so on systems where the framebuffer can handle restoration
  23  * of video registers anyways, there's little point in doing the console
  24  * switch.  This function allows you to disable it by passing it '0'.
  25  */
  26 void pm_set_vt_switch(int do_switch)
  27 {
  28         acquire_console_sem();
  29         disable_vt_switch = !do_switch;
  30         release_console_sem();
  31 }
  32 EXPORT_SYMBOL(pm_set_vt_switch);
  33
  34 int pm_prepare_console(void)
  35 {
  36         acquire_console_sem();
  37
  38         if (disable_vt_switch) {
  39                 release_console_sem();
  40                 return 0;
  41         }
  42
  43         orig_fgconsole = fg_console;
  44
  45         if (vc_allocate(SUSPEND_CONSOLE)) {
  46           /* we can't have a free VC for now. Too bad,
  47            * we don't want to mess the screen for now. */
  48                 release_console_sem();
  49                 return 1;
  50         }
  51
  52         if (set_console(SUSPEND_CONSOLE)) {
  53                 /*
  54                  * We're unable to switch to the SUSPEND_CONSOLE.
  55                  * Let the calling function know so it can decide
  56                  * what to do.
  57                  */
  58                 release_console_sem();
  59                 return 1;
  60         }
  61         release_console_sem();
  62
  63         if (vt_waitactive(SUSPEND_CONSOLE)) {
  64                 pr_debug("Suspend: Can't switch VCs.");
  65                 return 1;
  66         }
  67         orig_kmsg = kmsg_redirect;
  68         kmsg_redirect = SUSPEND_CONSOLE;
  69         return 0;
  70 }
  71
  72 void pm_restore_console(void)
  73 {
  74         acquire_console_sem();
  75         if (disable_vt_switch) {
  76                 release_console_sem();
  77                 return;
  78         }
  79         set_console(orig_fgconsole);
  80         release_console_sem();
  81
  82         if (vt_waitactive(orig_fgconsole)) {
  83                 pr_debug("Resume: Can't switch VCs.");
  84                 return;
  85         }
  86
  87         kmsg_redirect = orig_kmsg;
  88 }
  89 #endif