text: // SPDX-License-Identifier: GPL-2.0
  /*
   * kernel/power/wakelock.c
   *
   * User space wakeup sources support.
   *
   * Copyright (C) 2012 Rafael J. Wysocki <rjw@sisk.pl>
   *
   * This code is based on the analogous interface allowing user space to
   * manipulate wakelocks on Android.
   */
  
  #include <linux/capability.h>
  #include <linux/ctype.h>
  #include <linux/device.h>
  #include <linux/err.h>
  #include <linux/hrtimer.h>
  #include <linux/list.h>
  #include <linux/rbtree.h>
  #include <linux/slab.h>
  #include <linux/workqueue.h>
  
  #include "power.h"
  
  static DEFINE_MUTEX(wakelocks_lock);
  
  struct wakelock {
  	char			*name;
  	struct rb_node		node;
  	struct wakeup_source	*ws;
  #ifdef CONFIG_PM_WAKELOCKS_GC
  	struct list_head	lru;
  #endif
  };
  
  static struct rb_root wakelocks_tree = RB_ROOT;
  
  ssize_t pm_show_wakelocks(char *buf, bool show_active)
  {
  	struct rb_node *node;
  	struct wakelock *wl;
  	char *str = buf;
  	char *end = buf + PAGE_SIZE;
  
  	mutex_lock(&wakelocks_lock);
  
  	for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
  		wl = rb_entry(node, struct wakelock, node);
  		if (wl->ws->active == show_active)
  			str += scnprintf(str, end - str, "%s ", wl->name);
  	}
  	if (str > buf)
  		str--;
  
  	str += scnprintf(str, end - str, "\n");
  
  	mutex_unlock(&wakelocks_lock);
  	return (str - buf);
  }
  
  #if CONFIG_PM_WAKELOCKS_LIMIT > 0
  static unsigned int number_of_wakelocks;
  
  static inline bool wakelocks_limit_exceeded(void)
  {
  	return number_of_wakelocks > CONFIG_PM_WAKELOCKS_LIMIT;
  }
  
  static inline void increment_wakelocks_number(void)
  {
  	number_of_wakelocks++;
  }
  
  static inline void decrement_wakelocks_number(void)
  {
  	number_of_wakelocks--;
  }
  #else /* CONFIG_PM_WAKELOCKS_LIMIT = 0 */
  static inline bool wakelocks_limit_exceeded(void) { return false; }
  static inline void increment_wakelocks_number(void) {}
  static inline void decrement_wakelocks_number(void) {}
  #endif /* CONFIG_PM_WAKELOCKS_LIMIT */
  
  #ifdef CONFIG_PM_WAKELOCKS_GC
  #define WL_GC_COUNT_MAX	100
  #define WL_GC_TIME_SEC	300
  
  static void __wakelocks_gc(struct work_struct *work);
  static LIST_HEAD(wakelocks_lru_list);
  static DECLARE_WORK(wakelock_work, __wakelocks_gc);
  static unsigned int wakelocks_gc_count;
  
  static inline void wakelocks_lru_add(struct wakelock *wl)
  {
  	list_add(&wl->lru, &wakelocks_lru_list);
  }
  
  static inline void wakelocks_lru_most_recent(struct wakelock *wl)
  {
  	list_move(&wl->lru, &wakelocks_lru_list);
  }
  
  static void __wakelocks_gc(struct work_struct *work)
  {
  	struct wakelock *wl, *aux;
  	ktime_t now;
  
  	mutex_lock(&wakelocks_lock);
  
  	now = ktime_get();
  	list_for_each_entry_safe_reverse(wl, aux, &wakelocks_lru_list, lru) {
  		u64 idle_time_ns;
  		bool active;
  
  		spin_lock_irq(&wl->ws->lock);
  		idle_time_ns = ktime_to_ns(ktime_sub(now, wl->ws->last_time));
  		active = wl->ws->active;
  		spin_unlock_irq(&wl->ws->lock);
  
  		if (idle_time_ns < ((u64)WL_GC_TIME_SEC * NSEC_PER_SEC))
  			break;
  
  		if (!active) {
  			wakeup_source_unregister(wl->ws);
  			rb_erase(&wl->node, &wakelocks_tree);
  			list_del(&wl->lru);
  			kfree(wl->name);
  			kfree(wl);
  			decrement_wakelocks_number();
  		}
  	}
  	wakelocks_gc_count = 0;
  
  	mutex_unlock(&wakelocks_lock);
  }
  
  static void wakelocks_gc(void)
  {
  	if (++wakelocks_gc_count <= WL_GC_COUNT_MAX)
  		return;
  
  	schedule_work(&wakelock_work);
  }
  #else /* !CONFIG_PM_WAKELOCKS_GC */
  static inline void wakelocks_lru_add(struct wakelock *wl) {}
  static inline void wakelocks_lru_most_recent(struct wakelock *wl) {}
  static inline void wakelocks_gc(void) {}
  #endif /* !CONFIG_PM_WAKELOCKS_GC */
  
  static struct wakelock *wakelock_lookup_add(const char *name, size_t len,
  					    bool add_if_not_found)
  {
  	struct rb_node **node = &wakelocks_tree.rb_node;
  	struct rb_node *parent = *node;
  	struct wakelock *wl;
  
  	while (*node) {
  		int diff;
  
  		parent = *node;
  		wl = rb_entry(*node, struct wakelock, node);
  		diff = strncmp(name, wl->name, len);
  		if (diff == 0) {
  			if (wl->name[len])
  				diff = -1;
  			else
  				return wl;
  		}
  		if (diff < 0)
  			node = &(*node)->rb_left;
  		else
  			node = &(*node)->rb_right;
  	}
  	if (!add_if_not_found)
  		return ERR_PTR(-EINVAL);
  
  	if (wakelocks_limit_exceeded())
  		return ERR_PTR(-ENOSPC);
  
  	/* Not found, we have to add a new one. */
  	wl = kzalloc(sizeof(*wl), GFP_KERNEL);
  	if (!wl)
  		return ERR_PTR(-ENOMEM);
  
  	wl->name = kstrndup(name, len, GFP_KERNEL);
  	if (!wl->name) {
  		kfree(wl);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	wl->ws = wakeup_source_register(wl->name);
  	if (!wl->ws) {
  		kfree(wl->name);
  		kfree(wl);
  		return ERR_PTR(-ENOMEM);
  	}
  	wl->ws->last_time = ktime_get();
  
  	rb_link_node(&wl->node, parent, node);
  	rb_insert_color(&wl->node, &wakelocks_tree);
  	wakelocks_lru_add(wl);
  	increment_wakelocks_number();
  	return wl;
  }
  
  int pm_wake_lock(const char *buf)
  {
  	const char *str = buf;
  	struct wakelock *wl;
  	u64 timeout_ns = 0;
  	size_t len;
  	int ret = 0;
  
  	if (!capable(CAP_BLOCK_SUSPEND))
  		return -EPERM;
  
  	while (*str && !isspace(*str))
  		str++;
  
  	len = str - buf;
  	if (!len)
  		return -EINVAL;
  
  	if (*str && *str != '\n') {
  		/* Find out if there's a valid timeout string appended. */
  		ret = kstrtou64(skip_spaces(str), 10, &timeout_ns);
  		if (ret)
  			return -EINVAL;
  	}
  
  	mutex_lock(&wakelocks_lock);
  
  	wl = wakelock_lookup_add(buf, len, true);
  	if (IS_ERR(wl)) {
  		ret = PTR_ERR(wl);
  		goto out;
  	}
  	if (timeout_ns) {
  		u64 timeout_ms = timeout_ns + NSEC_PER_MSEC - 1;
  
  		do_div(timeout_ms, NSEC_PER_MSEC);
  		__pm_wakeup_event(wl->ws, timeout_ms);
  	} else {
  		__pm_stay_awake(wl->ws);
  	}
  
  	wakelocks_lru_most_recent(wl);
  
   out:
  	mutex_unlock(&wakelocks_lock);
  	return ret;
  }
  
  int pm_wake_unlock(const char *buf)
  {
  	struct wakelock *wl;
  	size_t len;
  	int ret = 0;
  
  	if (!capable(CAP_BLOCK_SUSPEND))
  		return -EPERM;
  
  	len = strlen(buf);
  	if (!len)
  		return -EINVAL;
  
  	if (buf[len-1] == '\n')
  		len--;
  
  	if (!len)
  		return -EINVAL;
  
  	mutex_lock(&wakelocks_lock);
  
  	wl = wakelock_lookup_add(buf, len, false);
  	if (IS_ERR(wl)) {
  		ret = PTR_ERR(wl);
  		goto out;
  	}
  	__pm_relax(wl->ws);
  
  	wakelocks_lru_most_recent(wl);
  	wakelocks_gc();
  
   out:
  	mutex_unlock(&wakelocks_lock);
  	return ret;
  }
  