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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 <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 int pm_prepare_console(void)
130 {
131         if (!pm_vt_switch())
132                 return 0;
133 
134         orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
135         if (orig_fgconsole < 0)
136                 return 1;
137 
138         orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
139         return 0;
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 }
152 

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