kernel/power/console.c

   1 /*
   2  * Functions for saving/restoring console.
   3  *
   4  * Originally from swsusp.
   5  */
   6
   7 #include <linux/console.h>
   8 #include <linux/vt_kern.h>
   9 #include <linux/kbd_kern.h>
  10 #include <linux/vt.h>
  11 #include <linux/module.h>
  12 #include "power.h"
  13
  14 #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)
  15
  16 static int orig_fgconsole, orig_kmsg;
  17
  18 static DEFINE_MUTEX(vt_switch_mutex);
  19
  20 struct pm_vt_switch {
  21         struct list_head head;
  22         struct device *dev;
  23         bool required;
  24 };
  25
  26 static LIST_HEAD(pm_vt_switch_list);
  27
  28
  29 /**
  30  * pm_vt_switch_required - indicate VT switch at suspend requirements
  31  * @dev: device
  32  * @required: if true, caller needs VT switch at suspend/resume time
  33  *
  34  * The different console drivers may or may not require VT switches across
  35  * suspend/resume, depending on how they handle restoring video state and
  36  * what may be running.
  37  *
  38  * Drivers can indicate support for switchless suspend/resume, which can
  39  * save time and flicker, by using this routine and passing 'false' as
  40  * the argument.  If any loaded driver needs VT switching, or the
  41  * no_console_suspend argument has been passed on the command line, VT
  42  * switches will occur.
  43  */
  44 void pm_vt_switch_required(struct device *dev, bool required)
  45 {
  46         struct pm_vt_switch *entry, *tmp;
  47
  48         mutex_lock(&vt_switch_mutex);
  49         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
  50                 if (tmp->dev == dev) {
  51                         /* already registered, update requirement */
  52                         tmp->required = required;
  53                         goto out;
  54                 }
  55         }
  56
  57         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  58         if (!entry)
  59                 goto out;
  60
  61         entry->required = required;
  62         entry->dev = dev;
  63
  64         list_add(&entry->head, &pm_vt_switch_list);
  65 out:
  66         mutex_unlock(&vt_switch_mutex);
  67 }
  68 EXPORT_SYMBOL(pm_vt_switch_required);
  69
  70 /**
  71  * pm_vt_switch_unregister - stop tracking a device's VT switching needs
  72  * @dev: device
  73  *
  74  * Remove @dev from the vt switch list.
  75  */
  76 void pm_vt_switch_unregister(struct device *dev)
  77 {
  78         struct pm_vt_switch *tmp;
  79
  80         mutex_lock(&vt_switch_mutex);
  81         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
  82                 if (tmp->dev == dev) {
  83                         list_del(&tmp->head);
  84                         kfree(tmp);
  85                         break;
  86                 }
  87         }
  88         mutex_unlock(&vt_switch_mutex);
  89 }
  90 EXPORT_SYMBOL(pm_vt_switch_unregister);
  91
  92 /*
  93  * There are three cases when a VT switch on suspend/resume are required:
  94  *   1) no driver has indicated a requirement one way or another, so preserve
  95  *      the old behavior
  96  *   2) console suspend is disabled, we want to see debug messages across
  97  *      suspend/resume
  98  *   3) any registered driver indicates it needs a VT switch
  99  *
 100  * If none of these conditions is present, meaning we have at least one driver
 101  * that doesn't need the switch, and none that do, we can avoid it to make
 102  * resume look a little prettier (and suspend too, but that's usually hidden,
 103  * e.g. when closing the lid on a laptop).
 104  */
 105 static bool pm_vt_switch(void)
 106 {
 107         struct pm_vt_switch *entry;
 108         bool ret = true;
 109
 110         mutex_lock(&vt_switch_mutex);
 111         if (list_empty(&pm_vt_switch_list))
 112                 goto out;
 113
 114         if (!console_suspend_enabled)
 115                 goto out;
 116
 117         list_for_each_entry(entry, &pm_vt_switch_list, head) {
 118                 if (entry->required)
 119                         goto out;
 120         }
 121
 122         ret = false;
 123 out:
 124         mutex_unlock(&vt_switch_mutex);
 125         return ret;
 126 }
 127
 128 int pm_prepare_console(void)
 129 {
 130         if (!pm_vt_switch())
 131                 return 0;
 132
 133         orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
 134         if (orig_fgconsole < 0)
 135                 return 1;
 136
 137         orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
 138         return 0;
 139 }
 140
 141 void pm_restore_console(void)
 142 {
 143         if (!pm_vt_switch())
 144                 return;
 145
 146         if (orig_fgconsole >= 0) {
 147                 vt_move_to_console(orig_fgconsole, 0);
 148                 vt_kmsg_redirect(orig_kmsg);
 149         }
 150 }