// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2022, STMicroelectronics
 * Copyright (c) 2016, Linaro Ltd.
 * Copyright (c) 2012, Michal Simek <monstr@monstr.eu>
 * Copyright (c) 2012, PetaLogix
 * Copyright (c) 2011, Texas Instruments, Inc.
 * Copyright (c) 2011, Google, Inc.
 *
 * Based on rpmsg performance statistics driver by Michal Simek, which in turn
 * was based on TI & Google OMX rpmsg driver.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/rpmsg.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <uapi/linux/rpmsg.h>

#include "rpmsg_char.h"
#include "rpmsg_internal.h"

#define RPMSG_DEV_MAX   (MINORMASK + 1)

static dev_t rpmsg_major;

static DEFINE_IDA(rpmsg_ept_ida);
static DEFINE_IDA(rpmsg_minor_ida);

#define dev_to_eptdev(dev) container_of(dev, struct rpmsg_eptdev, dev)
#define cdev_to_eptdev(i_cdev) container_of(i_cdev, struct rpmsg_eptdev, cdev)

/**
 * struct rpmsg_eptdev - endpoint device context
 * @dev:        endpoint device
 * @cdev:       cdev for the endpoint device
 * @rpdev:      underlaying rpmsg device
 * @chinfo:     info used to open the endpoint
 * @ept_lock:   synchronization of @ept modifications
 * @ept:        rpmsg endpoint reference, when open
 * @queue_lock: synchronization of @queue operations
 * @queue:      incoming message queue
 * @readq:      wait object for incoming queue
 * @default_ept: set to channel default endpoint if the default endpoint should be re-used
 *              on device open to prevent endpoint address update.
 * @remote_flow_restricted: to indicate if the remote has requested for flow to be limited
 * @remote_flow_updated: to indicate if the flow control has been requested
 */
struct rpmsg_eptdev {
        struct device dev;
        struct cdev cdev;

        struct rpmsg_device *rpdev;
        struct rpmsg_channel_info chinfo;

        struct mutex ept_lock;
        struct rpmsg_endpoint *ept;
        struct rpmsg_endpoint *default_ept;

        spinlock_t queue_lock;
        struct sk_buff_head queue;
        wait_queue_head_t readq;

        bool remote_flow_restricted;
        bool remote_flow_updated;
};

int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
{
        struct rpmsg_eptdev *eptdev = dev_to_eptdev(dev);

        mutex_lock(&eptdev->ept_lock);
        eptdev->rpdev = NULL;
        if (eptdev->ept) {
                /* The default endpoint is released by the rpmsg core */
                if (!eptdev->default_ept)
                        rpmsg_destroy_ept(eptdev->ept);
                eptdev->ept = NULL;
        }
        mutex_unlock(&eptdev->ept_lock);

        /* wake up any blocked readers */
        wake_up_interruptible(&eptdev->readq);

        cdev_device_del(&eptdev->cdev, &eptdev->dev);
        put_device(&eptdev->dev);

        return 0;
}
EXPORT_SYMBOL(rpmsg_chrdev_eptdev_destroy);

static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void *buf, int len,
                        void *priv, u32 addr)
{
        struct rpmsg_eptdev *eptdev = priv;
        struct sk_buff *skb;

        skb = alloc_skb(len, GFP_ATOMIC);
        if (!skb)
                return -ENOMEM;

        skb_put_data(skb, buf, len);

        spin_lock(&eptdev->queue_lock);
        skb_queue_tail(&eptdev->queue, skb);
        spin_unlock(&eptdev->queue_lock);

        /* wake up any blocking processes, waiting for new data */
        wake_up_interruptible(&eptdev->readq);

        return 0;
}

static int rpmsg_ept_flow_cb(struct rpmsg_device *rpdev, void *priv, bool enable)
{
        struct rpmsg_eptdev *eptdev = priv;

        eptdev->remote_flow_restricted = enable;
        eptdev->remote_flow_updated = true;

        wake_up_interruptible(&eptdev->readq);

        return 0;
}

static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
{
        struct rpmsg_eptdev *eptdev = cdev_to_eptdev(inode->i_cdev);
        struct rpmsg_endpoint *ept;
        struct rpmsg_device *rpdev = eptdev->rpdev;
        struct device *dev = &eptdev->dev;

        mutex_lock(&eptdev->ept_lock);
        if (eptdev->ept) {
                mutex_unlock(&eptdev->ept_lock);
                return -EBUSY;
        }

        if (!eptdev->rpdev) {
                mutex_unlock(&eptdev->ept_lock);
                return -ENETRESET;
        }

        get_device(dev);

        /*
         * If the default_ept is set, the rpmsg device default endpoint is used.
         * Else a new endpoint is created on open that will be destroyed on release.
         */
        if (eptdev->default_ept)
                ept = eptdev->default_ept;
        else
                ept = rpmsg_create_ept(rpdev, rpmsg_ept_cb, eptdev, eptdev->chinfo);

        if (!ept) {
                dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
                put_device(dev);
                mutex_unlock(&eptdev->ept_lock);
                return -EINVAL;
        }

        ept->flow_cb = rpmsg_ept_flow_cb;
        eptdev->ept = ept;
        filp->private_data = eptdev;
        mutex_unlock(&eptdev->ept_lock);

        return 0;
}

static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
{
        struct rpmsg_eptdev *eptdev = cdev_to_eptdev(inode->i_cdev);
        struct device *dev = &eptdev->dev;

        /* Close the endpoint, if it's not already destroyed by the parent */
        mutex_lock(&eptdev->ept_lock);
        if (eptdev->ept) {
                if (!eptdev->default_ept)
                        rpmsg_destroy_ept(eptdev->ept);
                eptdev->ept = NULL;
        }
        mutex_unlock(&eptdev->ept_lock);
        eptdev->remote_flow_updated = false;

        /* Discard all SKBs */
        skb_queue_purge(&eptdev->queue);

        put_device(dev);

        return 0;
}

static ssize_t rpmsg_eptdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *filp = iocb->ki_filp;
        struct rpmsg_eptdev *eptdev = filp->private_data;
        unsigned long flags;
        struct sk_buff *skb;
        int use;

        if (!eptdev->ept)
                return -EPIPE;

        spin_lock_irqsave(&eptdev->queue_lock, flags);

        /* Wait for data in the queue */
        if (skb_queue_empty(&eptdev->queue)) {
                spin_unlock_irqrestore(&eptdev->queue_lock, flags);

                if (filp->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                /* Wait until we get data or the endpoint goes away */
                if (wait_event_interruptible(eptdev->readq,
                                             !skb_queue_empty(&eptdev->queue) ||
                                             !eptdev->ept))
                        return -ERESTARTSYS;

                /* We lost the endpoint while waiting */
                if (!eptdev->ept)
                        return -EPIPE;

                spin_lock_irqsave(&eptdev->queue_lock, flags);
        }

        skb = skb_dequeue(&eptdev->queue);
        spin_unlock_irqrestore(&eptdev->queue_lock, flags);
        if (!skb)
                return -EFAULT;

        use = min_t(size_t, iov_iter_count(to), skb->len);
        if (copy_to_iter(skb->data, use, to) != use)
                use = -EFAULT;

        kfree_skb(skb);

        return use;
}

static ssize_t rpmsg_eptdev_write_iter(struct kiocb *iocb,
                                       struct iov_iter *from)
{
        struct file *filp = iocb->ki_filp;
        struct rpmsg_eptdev *eptdev = filp->private_data;
        size_t len = iov_iter_count(from);
        void *kbuf;
        int ret;

        kbuf = kzalloc(len, GFP_KERNEL);
        if (!kbuf)
                return -ENOMEM;

        if (!copy_from_iter_full(kbuf, len, from)) {
                ret = -EFAULT;
                goto free_kbuf;
        }

        if (mutex_lock_interruptible(&eptdev->ept_lock)) {
                ret = -ERESTARTSYS;
                goto free_kbuf;
        }

        if (!eptdev->ept) {
                ret = -EPIPE;
                goto unlock_eptdev;
        }

        if (filp->f_flags & O_NONBLOCK) {
                ret = rpmsg_trysendto(eptdev->ept, kbuf, len, eptdev->chinfo.dst);
                if (ret == -ENOMEM)
                        ret = -EAGAIN;
        } else {
                ret = rpmsg_sendto(eptdev->ept, kbuf, len, eptdev->chinfo.dst);
        }

unlock_eptdev:
        mutex_unlock(&eptdev->ept_lock);

free_kbuf:
        kfree(kbuf);
        return ret < 0 ? ret : len;
}

static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
{
        struct rpmsg_eptdev *eptdev = filp->private_data;
        __poll_t mask = 0;

        if (!eptdev->ept)
                return EPOLLERR;

        poll_wait(filp, &eptdev->readq, wait);

        if (!skb_queue_empty(&eptdev->queue))
                mask |= EPOLLIN | EPOLLRDNORM;

        if (eptdev->remote_flow_updated)
                mask |= EPOLLPRI;

        mutex_lock(&eptdev->ept_lock);
        mask |= rpmsg_poll(eptdev->ept, filp, wait);
        mutex_unlock(&eptdev->ept_lock);

        return mask;
}

static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
                               unsigned long arg)
{
        struct rpmsg_eptdev *eptdev = fp->private_data;

        bool set;
        int ret;

        switch (cmd) {
        case RPMSG_GET_OUTGOING_FLOWCONTROL:
                eptdev->remote_flow_updated = false;
                ret = put_user(eptdev->remote_flow_restricted, (int __user *)arg);
                break;
        case RPMSG_SET_INCOMING_FLOWCONTROL:
                if (arg > 1) {
                        ret = -EINVAL;
                        break;
                }
                set = !!arg;
                ret = rpmsg_set_flow_control(eptdev->ept, set, eptdev->chinfo.dst);
                break;
        case RPMSG_DESTROY_EPT_IOCTL:
                /* Don't allow to destroy a default endpoint. */
                if (eptdev->default_ept) {
                        ret = -EINVAL;
                        break;
                }
                ret = rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
                break;
        default:
                ret = -EINVAL;
        }

        return ret;
}

static const struct file_operations rpmsg_eptdev_fops = {
        .owner = THIS_MODULE,
        .open = rpmsg_eptdev_open,
        .release = rpmsg_eptdev_release,
        .read_iter = rpmsg_eptdev_read_iter,
        .write_iter = rpmsg_eptdev_write_iter,
        .poll = rpmsg_eptdev_poll,
        .unlocked_ioctl = rpmsg_eptdev_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
};

static ssize_t name_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct rpmsg_eptdev *eptdev = dev_get_drvdata(dev);

        return sprintf(buf, "%s\n", eptdev->chinfo.name);
}
static DEVICE_ATTR_RO(name);

static ssize_t src_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct rpmsg_eptdev *eptdev = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", eptdev->chinfo.src);
}
static DEVICE_ATTR_RO(src);

static ssize_t dst_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct rpmsg_eptdev *eptdev = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", eptdev->chinfo.dst);
}
static DEVICE_ATTR_RO(dst);

static struct attribute *rpmsg_eptdev_attrs[] = {
        &dev_attr_name.attr,
        &dev_attr_src.attr,
        &dev_attr_dst.attr,
        NULL
};
ATTRIBUTE_GROUPS(rpmsg_eptdev);

static void rpmsg_eptdev_release_device(struct device *dev)
{
        struct rpmsg_eptdev *eptdev = dev_to_eptdev(dev);

        ida_free(&rpmsg_ept_ida, dev->id);
        ida_free(&rpmsg_minor_ida, MINOR(eptdev->dev.devt));
        kfree(eptdev);
}

static struct rpmsg_eptdev *rpmsg_chrdev_eptdev_alloc(struct rpmsg_device *rpdev,
                                                      struct device *parent)
{
        struct rpmsg_eptdev *eptdev;
        struct device *dev;

        eptdev = kzalloc_obj(*eptdev);
        if (!eptdev)
                return ERR_PTR(-ENOMEM);

        dev = &eptdev->dev;
        eptdev->rpdev = rpdev;

        mutex_init(&eptdev->ept_lock);
        spin_lock_init(&eptdev->queue_lock);
        skb_queue_head_init(&eptdev->queue);
        init_waitqueue_head(&eptdev->readq);

        device_initialize(dev);
        dev->class = &rpmsg_class;
        dev->parent = parent;
        dev->groups = rpmsg_eptdev_groups;
        dev_set_drvdata(dev, eptdev);

        cdev_init(&eptdev->cdev, &rpmsg_eptdev_fops);
        eptdev->cdev.owner = THIS_MODULE;

        return eptdev;
}

static int rpmsg_chrdev_eptdev_add(struct rpmsg_eptdev *eptdev, struct rpmsg_channel_info chinfo)
{
        struct device *dev = &eptdev->dev;
        int ret;

        eptdev->chinfo = chinfo;

        ret = ida_alloc_max(&rpmsg_minor_ida, RPMSG_DEV_MAX - 1, GFP_KERNEL);
        if (ret < 0)
                goto free_eptdev;
        dev->devt = MKDEV(MAJOR(rpmsg_major), ret);

        ret = ida_alloc(&rpmsg_ept_ida, GFP_KERNEL);
        if (ret < 0)
                goto free_minor_ida;
        dev->id = ret;
        dev_set_name(dev, "rpmsg%d", ret);

        ret = cdev_device_add(&eptdev->cdev, &eptdev->dev);
        if (ret)
                goto free_ept_ida;

        /* We can now rely on the release function for cleanup */
        dev->release = rpmsg_eptdev_release_device;

        return ret;

free_ept_ida:
        ida_free(&rpmsg_ept_ida, dev->id);
free_minor_ida:
        ida_free(&rpmsg_minor_ida, MINOR(dev->devt));
free_eptdev:
        put_device(dev);
        kfree(eptdev);

        return ret;
}

int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
                               struct rpmsg_channel_info chinfo)
{
        struct rpmsg_eptdev *eptdev;

        eptdev = rpmsg_chrdev_eptdev_alloc(rpdev, parent);
        if (IS_ERR(eptdev))
                return PTR_ERR(eptdev);

        return rpmsg_chrdev_eptdev_add(eptdev, chinfo);
}
EXPORT_SYMBOL(rpmsg_chrdev_eptdev_create);

static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
{
        struct rpmsg_channel_info chinfo;
        struct rpmsg_eptdev *eptdev;
        struct device *dev = &rpdev->dev;

        memcpy(chinfo.name, rpdev->id.name, RPMSG_NAME_SIZE);
        chinfo.src = rpdev->src;
        chinfo.dst = rpdev->dst;

        eptdev = rpmsg_chrdev_eptdev_alloc(rpdev, dev);
        if (IS_ERR(eptdev))
                return PTR_ERR(eptdev);

        /* Set the default_ept to the rpmsg device endpoint */
        eptdev->default_ept = rpdev->ept;

        /*
         * The rpmsg_ept_cb uses *priv parameter to get its rpmsg_eptdev context.
         * Storedit in default_ept *priv field.
         */
        eptdev->default_ept->priv = eptdev;

        return rpmsg_chrdev_eptdev_add(eptdev, chinfo);
}

static void rpmsg_chrdev_remove(struct rpmsg_device *rpdev)
{
        int ret;

        ret = device_for_each_child(&rpdev->dev, NULL, rpmsg_chrdev_eptdev_destroy);
        if (ret)
                dev_warn(&rpdev->dev, "failed to destroy endpoints: %d\n", ret);
}

static struct rpmsg_device_id rpmsg_chrdev_id_table[] = {
        { .name = "rpmsg-raw" },
        { .name = "rpmsg_chrdev" },
        { },
};
MODULE_DEVICE_TABLE(rpmsg, rpmsg_chrdev_id_table);

static struct rpmsg_driver rpmsg_chrdev_driver = {
        .probe = rpmsg_chrdev_probe,
        .remove = rpmsg_chrdev_remove,
        .callback = rpmsg_ept_cb,
        .id_table = rpmsg_chrdev_id_table,
        .drv.name = "rpmsg_chrdev",
};

static int rpmsg_chrdev_init(void)
{
        int ret;

        ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg_char");
        if (ret < 0) {
                pr_err("failed to allocate char dev region\n");
                return ret;
        }

        ret = register_rpmsg_driver(&rpmsg_chrdev_driver);
        if (ret < 0) {
                pr_err("rpmsg: failed to register rpmsg raw driver\n");
                goto free_region;
        }

        return 0;

free_region:
        unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);

        return ret;
}
postcore_initcall(rpmsg_chrdev_init);

static void rpmsg_chrdev_exit(void)
{
        unregister_rpmsg_driver(&rpmsg_chrdev_driver);
        unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
}
module_exit(rpmsg_chrdev_exit);

MODULE_DESCRIPTION("RPMSG device interface");
MODULE_LICENSE("GPL v2");