console.c

  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 */
 47int pm_vt_switch_required(struct device *dev, bool required)
 48{
 49	struct pm_vt_switch *entry, *tmp;
 50	int ret = 0;
 51
 52	mutex_lock(&vt_switch_mutex);
 53	list_for_each_entry(tmp, &pm_vt_switch_list, head) {
 54		if (tmp->dev == dev) {
 55			/* already registered, update requirement */
 56			tmp->required = required;
 57			goto out;
 58		}
 59	}
 60
 61	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 62	if (!entry) {
 63		ret = -ENOMEM;
 64		goto out;
 65		}
 66
 67	entry->required = required;
 68	entry->dev = dev;
 69
 70	list_add(&entry->head, &pm_vt_switch_list);
 71out:
 72	mutex_unlock(&vt_switch_mutex);
 73	return ret;
 74}
 75EXPORT_SYMBOL(pm_vt_switch_required);
 76
 77/**
 78 * pm_vt_switch_unregister - stop tracking a device's VT switching needs
 79 * @dev: device
 80 *
 81 * Remove @dev from the vt switch list.
 82 */
 83void pm_vt_switch_unregister(struct device *dev)
 84{
 85	struct pm_vt_switch *tmp;
 86
 87	mutex_lock(&vt_switch_mutex);
 88	list_for_each_entry(tmp, &pm_vt_switch_list, head) {
 89		if (tmp->dev == dev) {
 90			list_del(&tmp->head);
 91			kfree(tmp);
 92			break;
 93		}
 94	}
 95	mutex_unlock(&vt_switch_mutex);
 96}
 97EXPORT_SYMBOL(pm_vt_switch_unregister);
 98
 99/*
100 * There are three cases when a VT switch on suspend/resume are required:
101 *   1) no driver has indicated a requirement one way or another, so preserve
102 *      the old behavior
103 *   2) console suspend is disabled, we want to see debug messages across
104 *      suspend/resume
105 *   3) any registered driver indicates it needs a VT switch
106 *
107 * If none of these conditions is present, meaning we have at least one driver
108 * that doesn't need the switch, and none that do, we can avoid it to make
109 * resume look a little prettier (and suspend too, but that's usually hidden,
110 * e.g. when closing the lid on a laptop).
111 */
112static bool pm_vt_switch(void)
113{
114	struct pm_vt_switch *entry;
115	bool ret = true;
116
117	mutex_lock(&vt_switch_mutex);
118	if (list_empty(&pm_vt_switch_list))
119		goto out;
120
121	if (!console_suspend_enabled)
122		goto out;
123
124	list_for_each_entry(entry, &pm_vt_switch_list, head) {
125		if (entry->required)
126			goto out;
127	}
128
129	ret = false;
130out:
131	mutex_unlock(&vt_switch_mutex);
132	return ret;
133}
134
135void pm_prepare_console(void)
136{
137	if (!pm_vt_switch())
138		return;
139
140	orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
141	if (orig_fgconsole < 0)
142		return;
143
144	vt_switch_done = true;
145
146	orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
147	return;
148}
149
150void pm_restore_console(void)
151{
152	if (!pm_vt_switch() && !vt_switch_done)
153		return;
154
155	if (orig_fgconsole >= 0) {
156		vt_move_to_console(orig_fgconsole, 0);
157		vt_kmsg_redirect(orig_kmsg);
158	}
159
160	vt_switch_done = false;
161}