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 <linux/slab.h>
  13 #include "power.h"
  14
  15 #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)
  16
  17 static int orig_fgconsole, orig_kmsg;
  18
  19 static DEFINE_MUTEX(vt_switch_mutex);
  20
  21 struct pm_vt_switch {
  22         struct list_head head;
  23         struct device *dev;
  24         bool required;
  25 };
  26
  27 static LIST_HEAD(pm_vt_switch_list);
  28
  29
  30 /**
  31  * pm_vt_switch_required - indicate VT switch at suspend requirements
  32  * @dev: device
  33  * @required: if true, caller needs VT switch at suspend/resume time
  34  *
  35  * The different console drivers may or may not require VT switches across
  36  * suspend/resume, depending on how they handle restoring video state and
  37  * what may be running.
  38  *
  39  * Drivers can indicate support for switchless suspend/resume, which can
  40  * save time and flicker, by using this routine and passing 'false' as
  41  * the argument.  If any loaded driver needs VT switching, or the
  42  * no_console_suspend argument has been passed on the command line, VT
  43  * switches will occur.
  44  */
  45 void pm_vt_switch_required(struct device *dev, bool required)
  46 {
  47         struct pm_vt_switch *entry, *tmp;
  48
  49         mutex_lock(&vt_switch_mutex);
  50         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
  51                 if (tmp->dev == dev) {
  52                         /* already registered, update requirement */
  53                         tmp->required = required;
  54                         goto out;
  55                 }
  56         }
  57
  58         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  59         if (!entry)
  60                 goto out;
  61
  62         entry->required = required;
  63         entry->dev = dev;
  64
  65         list_add(&entry->head, &pm_vt_switch_list);
  66 out:
  67         mutex_unlock(&vt_switch_mutex);
  68 }
  69 EXPORT_SYMBOL(pm_vt_switch_required);
  70
  71 /**
  72  * pm_vt_switch_unregister - stop tracking a device's VT switching needs
  73  * @dev: device
  74  *
  75  * Remove @dev from the vt switch list.
  76  */
  77 void pm_vt_switch_unregister(struct device *dev)
  78 {
  79         struct pm_vt_switch *tmp;
  80
  81         mutex_lock(&vt_switch_mutex);
  82         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
  83                 if (tmp->dev == dev) {
  84                         list_del(&tmp->head);
  85                         kfree(tmp);
  86                         break;
  87                 }
  88         }
  89         mutex_unlock(&vt_switch_mutex);
  90 }
  91 EXPORT_SYMBOL(pm_vt_switch_unregister);
  92
  93 /*
  94  * There are three cases when a VT switch on suspend/resume are required:
  95  *   1) no driver has indicated a requirement one way or another, so preserve
  96  *      the old behavior
  97  *   2) console suspend is disabled, we want to see debug messages across
  98  *      suspend/resume
  99  *   3) any registered driver indicates it needs a VT switch
 100  *
 101  * If none of these conditions is present, meaning we have at least one driver
 102  * that doesn't need the switch, and none that do, we can avoid it to make
 103  * resume look a little prettier (and suspend too, but that's usually hidden,
 104  * e.g. when closing the lid on a laptop).
 105  */
 106 static bool pm_vt_switch(void)
 107 {
 108         struct pm_vt_switch *entry;
 109         bool ret = true;
 110
 111         mutex_lock(&vt_switch_mutex);
 112         if (list_empty(&pm_vt_switch_list))
 113                 goto out;
 114
 115         if (!console_suspend_enabled)
 116                 goto out;
 117
 118         list_for_each_entry(entry, &pm_vt_switch_list, head) {
 119                 if (entry->required)
 120                         goto out;
 121         }
 122
 123         ret = false;
 124 out:
 125         mutex_unlock(&vt_switch_mutex);
 126         return ret;
 127 }
 128
 129 void pm_prepare_console(void)
 130 {
 131         if (!pm_vt_switch())
 132                 return;
 133
 134         orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
 135         if (orig_fgconsole < 0)
 136                 return;
 137
 138         orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
 139         return;
 140 }
 141
 142 void pm_restore_console(void)
 143 {
 144         if (!pm_vt_switch())
 145                 return;
 146
 147         if (orig_fgconsole >= 0) {
 148                 vt_move_to_console(orig_fgconsole, 0);
 149                 vt_kmsg_redirect(orig_kmsg);
 150         }
 151 }