// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2003-2008 Takahiro Hirofuchi
 * Copyright (C) 2015 Nobuo Iwata
 */

#include <linux/kthread.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

#include "usbip_common.h"

struct usbip_event {
	struct list_head node;
	struct usbip_device *ud;
};

static DEFINE_SPINLOCK(event_lock);
static LIST_HEAD(event_list);

static void set_event(struct usbip_device *ud, unsigned long event)
{
	unsigned long flags;

	spin_lock_irqsave(&ud->lock, flags);
	ud->event |= event;
	spin_unlock_irqrestore(&ud->lock, flags);
}

static void unset_event(struct usbip_device *ud, unsigned long event)
{
	unsigned long flags;

	spin_lock_irqsave(&ud->lock, flags);
	ud->event &= ~event;
	spin_unlock_irqrestore(&ud->lock, flags);
}

static struct usbip_device *get_event(void)
{
	struct usbip_event *ue = NULL;
	struct usbip_device *ud = NULL;
	unsigned long flags;

	spin_lock_irqsave(&event_lock, flags);
	if (!list_empty(&event_list)) {
		ue = list_first_entry(&event_list, struct usbip_event, node);
		list_del(&ue->node);
	}
	spin_unlock_irqrestore(&event_lock, flags);

	if (ue) {
		ud = ue->ud;
		kfree(ue);
	}
	return ud;
}

static struct task_struct *worker_context;

static void event_handler(struct work_struct *work)
{
	struct usbip_device *ud;

	if (worker_context == NULL) {
		worker_context = current;
	}

	while ((ud = get_event()) != NULL) {
		usbip_dbg_eh("pending event %lx\n", ud->event);

		mutex_lock(&ud->sysfs_lock);
		/*
		 * NOTE: shutdown must come first.
		 * Shutdown the device.
		 */
		if (ud->event & USBIP_EH_SHUTDOWN) {
			ud->eh_ops.shutdown(ud);
			unset_event(ud, USBIP_EH_SHUTDOWN);
		}

		/* Reset the device. */
		if (ud->event & USBIP_EH_RESET) {
			ud->eh_ops.reset(ud);
			unset_event(ud, USBIP_EH_RESET);
		}

		/* Mark the device as unusable. */
		if (ud->event & USBIP_EH_UNUSABLE) {
			ud->eh_ops.unusable(ud);
			unset_event(ud, USBIP_EH_UNUSABLE);
		}
		mutex_unlock(&ud->sysfs_lock);

		wake_up(&ud->eh_waitq);
	}
}

int usbip_start_eh(struct usbip_device *ud)
{
	init_waitqueue_head(&ud->eh_waitq);
	ud->event = 0;
	return 0;
}
EXPORT_SYMBOL_GPL(usbip_start_eh);

void usbip_stop_eh(struct usbip_device *ud)
{
	unsigned long pending = ud->event & ~USBIP_EH_BYE;

	if (!(ud->event & USBIP_EH_BYE))
		usbip_dbg_eh("usbip_eh stopping but not removed\n");

	if (pending)
		usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending);

	wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
	usbip_dbg_eh("usbip_eh has stopped\n");
}
EXPORT_SYMBOL_GPL(usbip_stop_eh);

#define WORK_QUEUE_NAME "usbip_event"

static struct workqueue_struct *usbip_queue;
static DECLARE_WORK(usbip_work, event_handler);

int usbip_init_eh(void)
{
	usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME);
	if (usbip_queue == NULL) {
		pr_err("failed to create usbip_event\n");
		return -ENOMEM;
	}
	return 0;
}

void usbip_finish_eh(void)
{
	flush_workqueue(usbip_queue);
	destroy_workqueue(usbip_queue);
	usbip_queue = NULL;
}

void usbip_event_add(struct usbip_device *ud, unsigned long event)
{
	struct usbip_event *ue;
	unsigned long flags;

	if (ud->event & USBIP_EH_BYE)
		return;

	set_event(ud, event);

	spin_lock_irqsave(&event_lock, flags);

	list_for_each_entry_reverse(ue, &event_list, node) {
		if (ue->ud == ud)
			goto out;
	}

	ue = kmalloc(sizeof(struct usbip_event), GFP_ATOMIC);
	if (ue == NULL)
		goto out;

	ue->ud = ud;

	list_add_tail(&ue->node, &event_list);
	queue_work(usbip_queue, &usbip_work);

out:
	spin_unlock_irqrestore(&event_lock, flags);
}
EXPORT_SYMBOL_GPL(usbip_event_add);

int usbip_event_happened(struct usbip_device *ud)
{
	int happened = 0;
	unsigned long flags;

	spin_lock_irqsave(&ud->lock, flags);
	if (ud->event != 0)
		happened = 1;
	spin_unlock_irqrestore(&ud->lock, flags);

	return happened;
}
EXPORT_SYMBOL_GPL(usbip_event_happened);

int usbip_in_eh(struct task_struct *task)
{
	if (task == worker_context)
		return 1;

	return 0;
}
EXPORT_SYMBOL_GPL(usbip_in_eh);