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
17static int orig_fgconsole, orig_kmsg;
18
19static DEFINE_MUTEX(vt_switch_mutex);
20
21struct pm_vt_switch {
22	struct list_head head;
23	struct device *dev;
24	bool required;
25};
26
27static 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 */
45void 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);
66out:
67	mutex_unlock(&vt_switch_mutex);
68}
69EXPORT_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 */
77void 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}
91EXPORT_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 */
106static 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;
124out:
125	mutex_unlock(&vt_switch_mutex);
126	return ret;
127}
128
129int 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
142void 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