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TOMOYO Linux Cross Reference
Linux/kernel/power/console.c

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  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                         break;
 85                 }
 86         }
 87         mutex_unlock(&vt_switch_mutex);
 88 }
 89 EXPORT_SYMBOL(pm_vt_switch_unregister);
 90 
 91 /*
 92  * There are three cases when a VT switch on suspend/resume are required:
 93  *   1) no driver has indicated a requirement one way or another, so preserve
 94  *      the old behavior
 95  *   2) console suspend is disabled, we want to see debug messages across
 96  *      suspend/resume
 97  *   3) any registered driver indicates it needs a VT switch
 98  *
 99  * If none of these conditions is present, meaning we have at least one driver
100  * that doesn't need the switch, and none that do, we can avoid it to make
101  * resume look a little prettier (and suspend too, but that's usually hidden,
102  * e.g. when closing the lid on a laptop).
103  */
104 static bool pm_vt_switch(void)
105 {
106         struct pm_vt_switch *entry;
107         bool ret = true;
108 
109         mutex_lock(&vt_switch_mutex);
110         if (list_empty(&pm_vt_switch_list))
111                 goto out;
112 
113         if (!console_suspend_enabled)
114                 goto out;
115 
116         list_for_each_entry(entry, &pm_vt_switch_list, head) {
117                 if (entry->required)
118                         goto out;
119         }
120 
121         ret = false;
122 out:
123         mutex_unlock(&vt_switch_mutex);
124         return ret;
125 }
126 
127 int pm_prepare_console(void)
128 {
129         if (!pm_vt_switch())
130                 return 0;
131 
132         orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
133         if (orig_fgconsole < 0)
134                 return 1;
135 
136         orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
137         return 0;
138 }
139 
140 void pm_restore_console(void)
141 {
142         if (!pm_vt_switch())
143                 return;
144 
145         if (orig_fgconsole >= 0) {
146                 vt_move_to_console(orig_fgconsole, 0);
147                 vt_kmsg_redirect(orig_kmsg);
148         }
149 }
150 

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