// 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)
{
        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_obj(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);