// SPDX-License-Identifier: GPL-2.0
/*
 * Functions for saving/restoring console.
 *
 * Originally from swsusp.
 */

#include <linux/console.h>
#include <linux/vt_kern.h>
#include <linux/kbd_kern.h>
#include <linux/vt.h>
#include <linux/module.h>
#include <linux/slab.h>
#include "power.h"

#define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)

static int orig_fgconsole, orig_kmsg;
static bool vt_switch_done;

static DEFINE_MUTEX(vt_switch_mutex);

struct pm_vt_switch {
        struct list_head head;
        struct device *dev;
        bool required;
};

static LIST_HEAD(pm_vt_switch_list);


/**
 * pm_vt_switch_required - indicate VT switch at suspend requirements
 * @dev: device
 * @required: if true, caller needs VT switch at suspend/resume time
 *
 * The different console drivers may or may not require VT switches across
 * suspend/resume, depending on how they handle restoring video state and
 * what may be running.
 *
 * Drivers can indicate support for switchless suspend/resume, which can
 * save time and flicker, by using this routine and passing 'false' as
 * the argument.  If any loaded driver needs VT switching, or the
 * no_console_suspend argument has been passed on the command line, VT
 * switches will occur.
 */
int pm_vt_switch_required(struct device *dev, bool required)
{
        struct pm_vt_switch *entry, *tmp;
        int ret = 0;

        mutex_lock(&vt_switch_mutex);
        list_for_each_entry(tmp, &pm_vt_switch_list, head) {
                if (tmp->dev == dev) {
                        /* already registered, update requirement */
                        tmp->required = required;
                        goto out;
                }
        }

        entry = kmalloc_obj(*entry);
        if (!entry) {
                ret = -ENOMEM;
                goto out;
                }

        entry->required = required;
        entry->dev = dev;

        list_add(&entry->head, &pm_vt_switch_list);
out:
        mutex_unlock(&vt_switch_mutex);
        return ret;
}
EXPORT_SYMBOL(pm_vt_switch_required);

/**
 * pm_vt_switch_unregister - stop tracking a device's VT switching needs
 * @dev: device
 *
 * Remove @dev from the vt switch list.
 */
void pm_vt_switch_unregister(struct device *dev)
{
        struct pm_vt_switch *tmp;

        mutex_lock(&vt_switch_mutex);
        list_for_each_entry(tmp, &pm_vt_switch_list, head) {
                if (tmp->dev == dev) {
                        list_del(&tmp->head);
                        kfree(tmp);
                        break;
                }
        }
        mutex_unlock(&vt_switch_mutex);
}
EXPORT_SYMBOL(pm_vt_switch_unregister);

/*
 * There are three cases when a VT switch on suspend/resume are required:
 *   1) no driver has indicated a requirement one way or another, so preserve
 *      the old behavior
 *   2) console suspend is disabled, we want to see debug messages across
 *      suspend/resume
 *   3) any registered driver indicates it needs a VT switch
 *
 * If none of these conditions is present, meaning we have at least one driver
 * that doesn't need the switch, and none that do, we can avoid it to make
 * resume look a little prettier (and suspend too, but that's usually hidden,
 * e.g. when closing the lid on a laptop).
 */
static bool pm_vt_switch(void)
{
        struct pm_vt_switch *entry;
        bool ret = true;

        mutex_lock(&vt_switch_mutex);
        if (list_empty(&pm_vt_switch_list))
                goto out;

        if (!console_suspend_enabled)
                goto out;

        list_for_each_entry(entry, &pm_vt_switch_list, head) {
                if (entry->required)
                        goto out;
        }

        ret = false;
out:
        mutex_unlock(&vt_switch_mutex);
        return ret;
}

void pm_prepare_console(void)
{
        if (!pm_vt_switch())
                return;

        orig_fgconsole = vt_move_to_console(SUSPEND_CONSOLE, 1);
        if (orig_fgconsole < 0)
                return;

        vt_switch_done = true;

        orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);
        return;
}

void pm_restore_console(void)
{
        if (!pm_vt_switch() && !vt_switch_done)
                return;

        if (orig_fgconsole >= 0) {
                vt_move_to_console(orig_fgconsole, 0);
                vt_kmsg_redirect(orig_kmsg);
        }

        vt_switch_done = false;
}