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

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Functions for saving/restoring console.
  4  *
  5  * Originally from swsusp.
  6  */
  7 
  8 #include <linux/console.h>
  9 #include <linux/vt_kern.h>
 10 #include <linux/kbd_kern.h>
 11 #include <linux/vt.h>
 12 #include <linux/module.h>
 13 #include <linux/slab.h>
 14 #include "power.h"
 15 
 16 #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)
 17 
 18 static int orig_fgconsole, orig_kmsg;
 19 
 20 static DEFINE_MUTEX(vt_switch_mutex);
 21 
 22 struct pm_vt_switch {
 23         struct list_head head;
 24         struct device *dev;
 25         bool required;
 26 };
 27 
 28 static LIST_HEAD(pm_vt_switch_list);
 29 
 30 
 31 /**
 32  * pm_vt_switch_required - indicate VT switch at suspend requirements
 33  * @dev: device
 34  * @required: if true, caller needs VT switch at suspend/resume time
 35  *
 36  * The different console drivers may or may not require VT switches across
 37  * suspend/resume, depending on how they handle restoring video state and
 38  * what may be running.
 39  *
 40  * Drivers can indicate support for switchless suspend/resume, which can
 41  * save time and flicker, by using this routine and passing 'false' as
 42  * the argument.  If any loaded driver needs VT switching, or the
 43  * no_console_suspend argument has been passed on the command line, VT
 44  * switches will occur.
 45  */
 46 void pm_vt_switch_required(struct device *dev, bool required)
 47 {
 48         struct pm_vt_switch *entry, *tmp;
 49 
 50         mutex_lock(&vt_switch_mutex);
 51         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
 52                 if (tmp->dev == dev) {
 53                         /* already registered, update requirement */
 54                         tmp->required = required;
 55                         goto out;
 56                 }
 57         }
 58 
 59         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 60         if (!entry)
 61                 goto out;
 62 
 63         entry->required = required;
 64         entry->dev = dev;
 65 
 66         list_add(&entry->head, &pm_vt_switch_list);
 67 out:
 68         mutex_unlock(&vt_switch_mutex);
 69 }
 70 EXPORT_SYMBOL(pm_vt_switch_required);
 71 
 72 /**
 73  * pm_vt_switch_unregister - stop tracking a device's VT switching needs
 74  * @dev: device
 75  *
 76  * Remove @dev from the vt switch list.
 77  */
 78 void pm_vt_switch_unregister(struct device *dev)
 79 {
 80         struct pm_vt_switch *tmp;
 81 
 82         mutex_lock(&vt_switch_mutex);
 83         list_for_each_entry(tmp, &pm_vt_switch_list, head) {
 84                 if (tmp->dev == dev) {
 85                         list_del(&tmp->head);
 86                         kfree(tmp);
 87                         break;
 88                 }
 89         }
 90         mutex_unlock(&vt_switch_mutex);
 91 }
 92 EXPORT_SYMBOL(pm_vt_switch_unregister);
 93 
 94 /*
 95  * There are three cases when a VT switch on suspend/resume are required:
 96  *   1) no driver has indicated a requirement one way or another, so preserve
 97  *      the old behavior
 98  *   2) console suspend is disabled, we want to see debug messages across
 99  *      suspend/resume
100  *   3) any registered driver indicates it needs a VT switch
101  *
102  * If none of these conditions is present, meaning we have at least one driver
103  * that doesn't need the switch, and none that do, we can avoid it to make
104  * resume look a little prettier (and suspend too, but that's usually hidden,
105  * e.g. when closing the lid on a laptop).
106  */
107 static bool pm_vt_switch(void)
108 {
109         struct pm_vt_switch *entry;
110         bool ret = true;
111 
112         mutex_lock(&vt_switch_mutex);
113         if (list_empty(&pm_vt_switch_list))
114                 goto out;
115 
116         if (!console_suspend_enabled)
117                 goto out;
118 
119         list_for_each_entry(entry, &pm_vt_switch_list, head) {
120                 if (entry->required)
121                         goto out;
122         }
123 
124         ret = false;
125 out:
126         mutex_unlock(&vt_switch_mutex);
127         return ret;
128 }
129 
130 void pm_prepare_console(void)
131 {
132         if (!pm_vt_switch())
133                 return;
134 
135         orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
136         if (orig_fgconsole < 0)
137                 return;
138 
139         orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
140         return;
141 }
142 
143 void pm_restore_console(void)
144 {
145         if (!pm_vt_switch())
146                 return;
147 
148         if (orig_fgconsole >= 0) {
149                 vt_move_to_console(orig_fgconsole, 0);
150                 vt_kmsg_redirect(orig_kmsg);
151         }
152 }
153 

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