projects/linux·blob v6.13 · refs

152 lines · 3.5 KiB

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;
19
20static DEFINE_MUTEX(vt_switch_mutex);
21
22struct pm_vt_switch {
23 struct list_head head;
24 struct device *dev;
25 bool required;
26};
27
28static 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 */
46void 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);
67out:
68 mutex_unlock(&vt_switch_mutex);
69}
70EXPORT_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 */
78void 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}
92EXPORT_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 */
107static 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;
125out:
126 mutex_unlock(&vt_switch_mutex);
127 return ret;
128}
129
130void 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
143void 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}