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
18static int orig_fgconsole, orig_kmsg;
19static bool vt_switch_done;
20
21static DEFINE_MUTEX(vt_switch_mutex);
22
23struct pm_vt_switch {
24 struct list_head head;
25 struct device *dev;
26 bool required;
27};
28
29static LIST_HEAD(pm_vt_switch_list);
30
31
32/**
33 * pm_vt_switch_required - indicate VT switch at suspend requirements
34 * @dev: device
35 * @required: if true, caller needs VT switch at suspend/resume time
36 *
37 * The different console drivers may or may not require VT switches across
38 * suspend/resume, depending on how they handle restoring video state and
39 * what may be running.
40 *
41 * Drivers can indicate support for switchless suspend/resume, which can
42 * save time and flicker, by using this routine and passing 'false' as
43 * the argument. If any loaded driver needs VT switching, or the
44 * no_console_suspend argument has been passed on the command line, VT
45 * switches will occur.
46 */
47void pm_vt_switch_required(struct device *dev, bool required)
48{
49 struct pm_vt_switch *entry, *tmp;
50
51 mutex_lock(lock: &vt_switch_mutex);
52 list_for_each_entry(tmp, &pm_vt_switch_list, head) {
53 if (tmp->dev == dev) {
54 /* already registered, update requirement */
55 tmp->required = required;
56 goto out;
57 }
58 }
59
60 entry = kmalloc(sizeof(*entry), GFP_KERNEL);
61 if (!entry)
62 goto out;
63
64 entry->required = required;
65 entry->dev = dev;
66
67 list_add(new: &entry->head, head: &pm_vt_switch_list);
68out:
69 mutex_unlock(lock: &vt_switch_mutex);
70}
71EXPORT_SYMBOL(pm_vt_switch_required);
72
73/**
74 * pm_vt_switch_unregister - stop tracking a device's VT switching needs
75 * @dev: device
76 *
77 * Remove @dev from the vt switch list.
78 */
79void pm_vt_switch_unregister(struct device *dev)
80{
81 struct pm_vt_switch *tmp;
82
83 mutex_lock(lock: &vt_switch_mutex);
84 list_for_each_entry(tmp, &pm_vt_switch_list, head) {
85 if (tmp->dev == dev) {
86 list_del(entry: &tmp->head);
87 kfree(objp: tmp);
88 break;
89 }
90 }
91 mutex_unlock(lock: &vt_switch_mutex);
92}
93EXPORT_SYMBOL(pm_vt_switch_unregister);
94
95/*
96 * There are three cases when a VT switch on suspend/resume are required:
97 * 1) no driver has indicated a requirement one way or another, so preserve
98 * the old behavior
99 * 2) console suspend is disabled, we want to see debug messages across
100 * suspend/resume
101 * 3) any registered driver indicates it needs a VT switch
102 *
103 * If none of these conditions is present, meaning we have at least one driver
104 * that doesn't need the switch, and none that do, we can avoid it to make
105 * resume look a little prettier (and suspend too, but that's usually hidden,
106 * e.g. when closing the lid on a laptop).
107 */
108static bool pm_vt_switch(void)
109{
110 struct pm_vt_switch *entry;
111 bool ret = true;
112
113 mutex_lock(lock: &vt_switch_mutex);
114 if (list_empty(head: &pm_vt_switch_list))
115 goto out;
116
117 if (!console_suspend_enabled)
118 goto out;
119
120 list_for_each_entry(entry, &pm_vt_switch_list, head) {
121 if (entry->required)
122 goto out;
123 }
124
125 ret = false;
126out:
127 mutex_unlock(lock: &vt_switch_mutex);
128 return ret;
129}
130
131void pm_prepare_console(void)
132{
133 if (!pm_vt_switch())
134 return;
135
136 orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, alloc: 1);
137 if (orig_fgconsole < 0)
138 return;
139
140 vt_switch_done = true;
141
142 orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
143 return;
144}
145
146void pm_restore_console(void)
147{
148 if (!pm_vt_switch() && !vt_switch_done)
149 return;
150
151 if (orig_fgconsole >= 0) {
152 vt_move_to_console(vt: orig_fgconsole, alloc: 0);
153 vt_kmsg_redirect(new: orig_kmsg);
154 }
155
156 vt_switch_done = false;
157}
158