// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */

#include <linux/err.h>
#include <linux/errno.h>
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/termios.h>
#include <linux/wwan.h>
#include <net/rtnetlink.h>
#include <uapi/linux/wwan.h>

/* Maximum number of minors in use */
#define WWAN_MAX_MINORS         (1 << MINORBITS)

static DEFINE_MUTEX(wwan_register_lock); /* WWAN device create|remove lock */
static DEFINE_IDA(minors); /* minors for WWAN port chardevs */
static DEFINE_IDA(wwan_dev_ids); /* for unique WWAN device IDs */
static struct class *wwan_class;
static int wwan_major;
static struct dentry *wwan_debugfs_dir;

#define to_wwan_dev(d) container_of(d, struct wwan_device, dev)
#define to_wwan_port(d) container_of(d, struct wwan_port, dev)

/* WWAN port flags */
#define WWAN_PORT_TX_OFF        0

/**
 * struct wwan_device - The structure that defines a WWAN device
 *
 * @id: WWAN device unique ID.
 * @dev: Underlying device.
 * @port_id: Current available port ID to pick.
 * @ops: wwan device ops
 * @ops_ctxt: context to pass to ops
 * @debugfs_dir:  WWAN device debugfs dir
 */
struct wwan_device {
        unsigned int id;
        struct device dev;
        atomic_t port_id;
        const struct wwan_ops *ops;
        void *ops_ctxt;
#ifdef CONFIG_WWAN_DEBUGFS
        struct dentry *debugfs_dir;
#endif
};

/**
 * struct wwan_port - The structure that defines a WWAN port
 * @type: Port type
 * @start_count: Port start counter
 * @flags: Store port state and capabilities
 * @ops: Pointer to WWAN port operations
 * @ops_lock: Protect port ops
 * @dev: Underlying device
 * @rxq: Buffer inbound queue
 * @waitqueue: The waitqueue for port fops (read/write/poll)
 * @data_lock: Port specific data access serialization
 * @at_data: AT port specific data
 */
struct wwan_port {
        enum wwan_port_type type;
        unsigned int start_count;
        unsigned long flags;
        const struct wwan_port_ops *ops;
        struct mutex ops_lock; /* Serialize ops + protect against removal */
        struct device dev;
        struct sk_buff_head rxq;
        wait_queue_head_t waitqueue;
        struct mutex data_lock; /* Port specific data access serialization */
        union {
                struct {
                        struct ktermios termios;
                        int mdmbits;
                } at_data;
        };
};

static ssize_t index_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct wwan_device *wwan = to_wwan_dev(dev);

        return sprintf(buf, "%d\n", wwan->id);
}
static DEVICE_ATTR_RO(index);

static struct attribute *wwan_dev_attrs[] = {
        &dev_attr_index.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wwan_dev);

static void wwan_dev_destroy(struct device *dev)
{
        struct wwan_device *wwandev = to_wwan_dev(dev);

        ida_free(&wwan_dev_ids, wwandev->id);
        kfree(wwandev);
}

static const struct device_type wwan_dev_type = {
        .name    = "wwan_dev",
        .release = wwan_dev_destroy,
        .groups = wwan_dev_groups,
};

static int wwan_dev_parent_match(struct device *dev, const void *parent)
{
        return (dev->type == &wwan_dev_type &&
                (dev->parent == parent || dev == parent));
}

static struct wwan_device *wwan_dev_get_by_parent(struct device *parent)
{
        struct device *dev;

        dev = class_find_device(wwan_class, NULL, parent, wwan_dev_parent_match);
        if (!dev)
                return ERR_PTR(-ENODEV);

        return to_wwan_dev(dev);
}

static int wwan_dev_name_match(struct device *dev, const void *name)
{
        return dev->type == &wwan_dev_type &&
               strcmp(dev_name(dev), name) == 0;
}

static struct wwan_device *wwan_dev_get_by_name(const char *name)
{
        struct device *dev;

        dev = class_find_device(wwan_class, NULL, name, wwan_dev_name_match);
        if (!dev)
                return ERR_PTR(-ENODEV);

        return to_wwan_dev(dev);
}

#ifdef CONFIG_WWAN_DEBUGFS
struct dentry *wwan_get_debugfs_dir(struct device *parent)
{
        struct wwan_device *wwandev;

        wwandev = wwan_dev_get_by_parent(parent);
        if (IS_ERR(wwandev))
                return ERR_CAST(wwandev);

        return wwandev->debugfs_dir;
}
EXPORT_SYMBOL_GPL(wwan_get_debugfs_dir);

static int wwan_dev_debugfs_match(struct device *dev, const void *dir)
{
        struct wwan_device *wwandev;

        if (dev->type != &wwan_dev_type)
                return 0;

        wwandev = to_wwan_dev(dev);

        return wwandev->debugfs_dir == dir;
}

static struct wwan_device *wwan_dev_get_by_debugfs(struct dentry *dir)
{
        struct device *dev;

        dev = class_find_device(wwan_class, NULL, dir, wwan_dev_debugfs_match);
        if (!dev)
                return ERR_PTR(-ENODEV);

        return to_wwan_dev(dev);
}

void wwan_put_debugfs_dir(struct dentry *dir)
{
        struct wwan_device *wwandev = wwan_dev_get_by_debugfs(dir);

        if (WARN_ON(IS_ERR(wwandev)))
                return;

        /* wwan_dev_get_by_debugfs() also got a reference */
        put_device(&wwandev->dev);
        put_device(&wwandev->dev);
}
EXPORT_SYMBOL_GPL(wwan_put_debugfs_dir);
#endif

/* This function allocates and registers a new WWAN device OR if a WWAN device
 * already exist for the given parent, it gets a reference and return it.
 * This function is not exported (for now), it is called indirectly via
 * wwan_create_port().
 */
static struct wwan_device *wwan_create_dev(struct device *parent)
{
        struct wwan_device *wwandev;
        int err, id;

        /* The 'find-alloc-register' operation must be protected against
         * concurrent execution, a WWAN device is possibly shared between
         * multiple callers or concurrently unregistered from wwan_remove_dev().
         */
        mutex_lock(&wwan_register_lock);

        /* If wwandev already exists, return it */
        wwandev = wwan_dev_get_by_parent(parent);
        if (!IS_ERR(wwandev))
                goto done_unlock;

        id = ida_alloc(&wwan_dev_ids, GFP_KERNEL);
        if (id < 0) {
                wwandev = ERR_PTR(id);
                goto done_unlock;
        }

        wwandev = kzalloc(sizeof(*wwandev), GFP_KERNEL);
        if (!wwandev) {
                wwandev = ERR_PTR(-ENOMEM);
                ida_free(&wwan_dev_ids, id);
                goto done_unlock;
        }

        wwandev->dev.parent = parent;
        wwandev->dev.class = wwan_class;
        wwandev->dev.type = &wwan_dev_type;
        wwandev->id = id;
        dev_set_name(&wwandev->dev, "wwan%d", wwandev->id);

        err = device_register(&wwandev->dev);
        if (err) {
                put_device(&wwandev->dev);
                wwandev = ERR_PTR(err);
                goto done_unlock;
        }

#ifdef CONFIG_WWAN_DEBUGFS
        wwandev->debugfs_dir =
                        debugfs_create_dir(kobject_name(&wwandev->dev.kobj),
                                           wwan_debugfs_dir);
#endif

done_unlock:
        mutex_unlock(&wwan_register_lock);

        return wwandev;
}

static int is_wwan_child(struct device *dev, void *data)
{
        return dev->class == wwan_class;
}

static void wwan_remove_dev(struct wwan_device *wwandev)
{
        int ret;

        /* Prevent concurrent picking from wwan_create_dev */
        mutex_lock(&wwan_register_lock);

        /* WWAN device is created and registered (get+add) along with its first
         * child port, and subsequent port registrations only grab a reference
         * (get). The WWAN device must then be unregistered (del+put) along with
         * its last port, and reference simply dropped (put) otherwise. In the
         * same fashion, we must not unregister it when the ops are still there.
         */
        if (wwandev->ops)
                ret = 1;
        else
                ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child);

        if (!ret) {
#ifdef CONFIG_WWAN_DEBUGFS
                debugfs_remove_recursive(wwandev->debugfs_dir);
#endif
                device_unregister(&wwandev->dev);
        } else {
                put_device(&wwandev->dev);
        }

        mutex_unlock(&wwan_register_lock);
}

/* ------- WWAN port management ------- */

static const struct {
        const char * const name;        /* Port type name */
        const char * const devsuf;      /* Port devce name suffix */
} wwan_port_types[WWAN_PORT_MAX + 1] = {
        [WWAN_PORT_AT] = {
                .name = "AT",
                .devsuf = "at",
        },
        [WWAN_PORT_MBIM] = {
                .name = "MBIM",
                .devsuf = "mbim",
        },
        [WWAN_PORT_QMI] = {
                .name = "QMI",
                .devsuf = "qmi",
        },
        [WWAN_PORT_QCDM] = {
                .name = "QCDM",
                .devsuf = "qcdm",
        },
        [WWAN_PORT_FIREHOSE] = {
                .name = "FIREHOSE",
                .devsuf = "firehose",
        },
};

static ssize_t type_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct wwan_port *port = to_wwan_port(dev);

        return sprintf(buf, "%s\n", wwan_port_types[port->type].name);
}
static DEVICE_ATTR_RO(type);

static struct attribute *wwan_port_attrs[] = {
        &dev_attr_type.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wwan_port);

static void wwan_port_destroy(struct device *dev)
{
        struct wwan_port *port = to_wwan_port(dev);

        ida_free(&minors, MINOR(port->dev.devt));
        mutex_destroy(&port->data_lock);
        mutex_destroy(&port->ops_lock);
        kfree(port);
}

static const struct device_type wwan_port_dev_type = {
        .name = "wwan_port",
        .release = wwan_port_destroy,
        .groups = wwan_port_groups,
};

static int wwan_port_minor_match(struct device *dev, const void *minor)
{
        return (dev->type == &wwan_port_dev_type &&
                MINOR(dev->devt) == *(unsigned int *)minor);
}

static struct wwan_port *wwan_port_get_by_minor(unsigned int minor)
{
        struct device *dev;

        dev = class_find_device(wwan_class, NULL, &minor, wwan_port_minor_match);
        if (!dev)
                return ERR_PTR(-ENODEV);

        return to_wwan_port(dev);
}

/* Allocate and set unique name based on passed format
 *
 * Name allocation approach is highly inspired by the __dev_alloc_name()
 * function.
 *
 * To avoid names collision, the caller must prevent the new port device
 * registration as well as concurrent invocation of this function.
 */
static int __wwan_port_dev_assign_name(struct wwan_port *port, const char *fmt)
{
        struct wwan_device *wwandev = to_wwan_dev(port->dev.parent);
        const unsigned int max_ports = PAGE_SIZE * 8;
        struct class_dev_iter iter;
        unsigned long *idmap;
        struct device *dev;
        char buf[0x20];
        int id;

        idmap = (unsigned long *)get_zeroed_page(GFP_KERNEL);
        if (!idmap)
                return -ENOMEM;

        /* Collect ids of same name format ports */
        class_dev_iter_init(&iter, wwan_class, NULL, &wwan_port_dev_type);
        while ((dev = class_dev_iter_next(&iter))) {
                if (dev->parent != &wwandev->dev)
                        continue;
                if (sscanf(dev_name(dev), fmt, &id) != 1)
                        continue;
                if (id < 0 || id >= max_ports)
                        continue;
                set_bit(id, idmap);
        }
        class_dev_iter_exit(&iter);

        /* Allocate unique id */
        id = find_first_zero_bit(idmap, max_ports);
        free_page((unsigned long)idmap);

        snprintf(buf, sizeof(buf), fmt, id);    /* Name generation */

        dev = device_find_child_by_name(&wwandev->dev, buf);
        if (dev) {
                put_device(dev);
                return -ENFILE;
        }

        return dev_set_name(&port->dev, buf);
}

struct wwan_port *wwan_create_port(struct device *parent,
                                   enum wwan_port_type type,
                                   const struct wwan_port_ops *ops,
                                   void *drvdata)
{
        struct wwan_device *wwandev;
        struct wwan_port *port;
        char namefmt[0x20];
        int minor, err;

        if (type > WWAN_PORT_MAX || !ops)
                return ERR_PTR(-EINVAL);

        /* A port is always a child of a WWAN device, retrieve (allocate or
         * pick) the WWAN device based on the provided parent device.
         */
        wwandev = wwan_create_dev(parent);
        if (IS_ERR(wwandev))
                return ERR_CAST(wwandev);

        /* A port is exposed as character device, get a minor */
        minor = ida_alloc_range(&minors, 0, WWAN_MAX_MINORS - 1, GFP_KERNEL);
        if (minor < 0) {
                err = minor;
                goto error_wwandev_remove;
        }

        port = kzalloc(sizeof(*port), GFP_KERNEL);
        if (!port) {
                err = -ENOMEM;
                ida_free(&minors, minor);
                goto error_wwandev_remove;
        }

        port->type = type;
        port->ops = ops;
        mutex_init(&port->ops_lock);
        skb_queue_head_init(&port->rxq);
        init_waitqueue_head(&port->waitqueue);
        mutex_init(&port->data_lock);

        port->dev.parent = &wwandev->dev;
        port->dev.class = wwan_class;
        port->dev.type = &wwan_port_dev_type;
        port->dev.devt = MKDEV(wwan_major, minor);
        dev_set_drvdata(&port->dev, drvdata);

        /* allocate unique name based on wwan device id, port type and number */
        snprintf(namefmt, sizeof(namefmt), "wwan%u%s%%d", wwandev->id,
                 wwan_port_types[port->type].devsuf);

        /* Serialize ports registration */
        mutex_lock(&wwan_register_lock);

        __wwan_port_dev_assign_name(port, namefmt);
        err = device_register(&port->dev);

        mutex_unlock(&wwan_register_lock);

        if (err)
                goto error_put_device;

        return port;

error_put_device:
        put_device(&port->dev);
error_wwandev_remove:
        wwan_remove_dev(wwandev);

        return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(wwan_create_port);

void wwan_remove_port(struct wwan_port *port)
{
        struct wwan_device *wwandev = to_wwan_dev(port->dev.parent);

        mutex_lock(&port->ops_lock);
        if (port->start_count)
                port->ops->stop(port);
        port->ops = NULL; /* Prevent any new port operations (e.g. from fops) */
        mutex_unlock(&port->ops_lock);

        wake_up_interruptible(&port->waitqueue);

        skb_queue_purge(&port->rxq);
        dev_set_drvdata(&port->dev, NULL);
        device_unregister(&port->dev);

        /* Release related wwan device */
        wwan_remove_dev(wwandev);
}
EXPORT_SYMBOL_GPL(wwan_remove_port);

void wwan_port_rx(struct wwan_port *port, struct sk_buff *skb)
{
        skb_queue_tail(&port->rxq, skb);
        wake_up_interruptible(&port->waitqueue);
}
EXPORT_SYMBOL_GPL(wwan_port_rx);

void wwan_port_txon(struct wwan_port *port)
{
        clear_bit(WWAN_PORT_TX_OFF, &port->flags);
        wake_up_interruptible(&port->waitqueue);
}
EXPORT_SYMBOL_GPL(wwan_port_txon);

void wwan_port_txoff(struct wwan_port *port)
{
        set_bit(WWAN_PORT_TX_OFF, &port->flags);
}
EXPORT_SYMBOL_GPL(wwan_port_txoff);

void *wwan_port_get_drvdata(struct wwan_port *port)
{
        return dev_get_drvdata(&port->dev);
}
EXPORT_SYMBOL_GPL(wwan_port_get_drvdata);

static int wwan_port_op_start(struct wwan_port *port)
{
        int ret = 0;

        mutex_lock(&port->ops_lock);
        if (!port->ops) { /* Port got unplugged */
                ret = -ENODEV;
                goto out_unlock;
        }

        /* If port is already started, don't start again */
        if (!port->start_count)
                ret = port->ops->start(port);

        if (!ret)
                port->start_count++;

out_unlock:
        mutex_unlock(&port->ops_lock);

        return ret;
}

static void wwan_port_op_stop(struct wwan_port *port)
{
        mutex_lock(&port->ops_lock);
        port->start_count--;
        if (!port->start_count) {
                if (port->ops)
                        port->ops->stop(port);
                skb_queue_purge(&port->rxq);
        }
        mutex_unlock(&port->ops_lock);
}

static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb,
                           bool nonblock)
{
        int ret;

        mutex_lock(&port->ops_lock);
        if (!port->ops) { /* Port got unplugged */
                ret = -ENODEV;
                goto out_unlock;
        }

        if (nonblock || !port->ops->tx_blocking)
                ret = port->ops->tx(port, skb);
        else
                ret = port->ops->tx_blocking(port, skb);

out_unlock:
        mutex_unlock(&port->ops_lock);

        return ret;
}

static bool is_read_blocked(struct wwan_port *port)
{
        return skb_queue_empty(&port->rxq) && port->ops;
}

static bool is_write_blocked(struct wwan_port *port)
{
        return test_bit(WWAN_PORT_TX_OFF, &port->flags) && port->ops;
}

static int wwan_wait_rx(struct wwan_port *port, bool nonblock)
{
        if (!is_read_blocked(port))
                return 0;

        if (nonblock)
                return -EAGAIN;

        if (wait_event_interruptible(port->waitqueue, !is_read_blocked(port)))
                return -ERESTARTSYS;

        return 0;
}

static int wwan_wait_tx(struct wwan_port *port, bool nonblock)
{
        if (!is_write_blocked(port))
                return 0;

        if (nonblock)
                return -EAGAIN;

        if (wait_event_interruptible(port->waitqueue, !is_write_blocked(port)))
                return -ERESTARTSYS;

        return 0;
}

static int wwan_port_fops_open(struct inode *inode, struct file *file)
{
        struct wwan_port *port;
        int err = 0;

        port = wwan_port_get_by_minor(iminor(inode));
        if (IS_ERR(port))
                return PTR_ERR(port);

        file->private_data = port;
        stream_open(inode, file);

        err = wwan_port_op_start(port);
        if (err)
                put_device(&port->dev);

        return err;
}

static int wwan_port_fops_release(struct inode *inode, struct file *filp)
{
        struct wwan_port *port = filp->private_data;

        wwan_port_op_stop(port);
        put_device(&port->dev);

        return 0;
}

static ssize_t wwan_port_fops_read(struct file *filp, char __user *buf,
                                   size_t count, loff_t *ppos)
{
        struct wwan_port *port = filp->private_data;
        struct sk_buff *skb;
        size_t copied;
        int ret;

        ret = wwan_wait_rx(port, !!(filp->f_flags & O_NONBLOCK));
        if (ret)
                return ret;

        skb = skb_dequeue(&port->rxq);
        if (!skb)
                return -EIO;

        copied = min_t(size_t, count, skb->len);
        if (copy_to_user(buf, skb->data, copied)) {
                kfree_skb(skb);
                return -EFAULT;
        }
        skb_pull(skb, copied);

        /* skb is not fully consumed, keep it in the queue */
        if (skb->len)
                skb_queue_head(&port->rxq, skb);
        else
                consume_skb(skb);

        return copied;
}

static ssize_t wwan_port_fops_write(struct file *filp, const char __user *buf,
                                    size_t count, loff_t *offp)
{
        struct wwan_port *port = filp->private_data;
        struct sk_buff *skb;
        int ret;

        ret = wwan_wait_tx(port, !!(filp->f_flags & O_NONBLOCK));
        if (ret)
                return ret;

        skb = alloc_skb(count, GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        if (copy_from_user(skb_put(skb, count), buf, count)) {
                kfree_skb(skb);
                return -EFAULT;
        }

        ret = wwan_port_op_tx(port, skb, !!(filp->f_flags & O_NONBLOCK));
        if (ret) {
                kfree_skb(skb);
                return ret;
        }

        return count;
}

static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait)
{
        struct wwan_port *port = filp->private_data;
        __poll_t mask = 0;

        poll_wait(filp, &port->waitqueue, wait);

        mutex_lock(&port->ops_lock);
        if (port->ops && port->ops->tx_poll)
                mask |= port->ops->tx_poll(port, filp, wait);
        else if (!is_write_blocked(port))
                mask |= EPOLLOUT | EPOLLWRNORM;
        if (!is_read_blocked(port))
                mask |= EPOLLIN | EPOLLRDNORM;
        if (!port->ops)
                mask |= EPOLLHUP | EPOLLERR;
        mutex_unlock(&port->ops_lock);

        return mask;
}

/* Implements minimalistic stub terminal IOCTLs support */
static long wwan_port_fops_at_ioctl(struct wwan_port *port, unsigned int cmd,
                                    unsigned long arg)
{
        int ret = 0;

        mutex_lock(&port->data_lock);

        switch (cmd) {
        case TCFLSH:
                break;

        case TCGETS:
                if (copy_to_user((void __user *)arg, &port->at_data.termios,
                                 sizeof(struct termios)))
                        ret = -EFAULT;
                break;

        case TCSETS:
        case TCSETSW:
        case TCSETSF:
                if (copy_from_user(&port->at_data.termios, (void __user *)arg,
                                   sizeof(struct termios)))
                        ret = -EFAULT;
                break;

#ifdef TCGETS2
        case TCGETS2:
                if (copy_to_user((void __user *)arg, &port->at_data.termios,
                                 sizeof(struct termios2)))
                        ret = -EFAULT;
                break;

        case TCSETS2:
        case TCSETSW2:
        case TCSETSF2:
                if (copy_from_user(&port->at_data.termios, (void __user *)arg,
                                   sizeof(struct termios2)))
                        ret = -EFAULT;
                break;
#endif

        case TIOCMGET:
                ret = put_user(port->at_data.mdmbits, (int __user *)arg);
                break;

        case TIOCMSET:
        case TIOCMBIC:
        case TIOCMBIS: {
                int mdmbits;

                if (copy_from_user(&mdmbits, (int __user *)arg, sizeof(int))) {
                        ret = -EFAULT;
                        break;
                }
                if (cmd == TIOCMBIC)
                        port->at_data.mdmbits &= ~mdmbits;
                else if (cmd == TIOCMBIS)
                        port->at_data.mdmbits |= mdmbits;
                else
                        port->at_data.mdmbits = mdmbits;
                break;
        }

        default:
                ret = -ENOIOCTLCMD;
        }

        mutex_unlock(&port->data_lock);

        return ret;
}

static long wwan_port_fops_ioctl(struct file *filp, unsigned int cmd,
                                 unsigned long arg)
{
        struct wwan_port *port = filp->private_data;
        int res;

        if (port->type == WWAN_PORT_AT) {       /* AT port specific IOCTLs */
                res = wwan_port_fops_at_ioctl(port, cmd, arg);
                if (res != -ENOIOCTLCMD)
                        return res;
        }

        switch (cmd) {
        case TIOCINQ: { /* aka SIOCINQ aka FIONREAD */
                unsigned long flags;
                struct sk_buff *skb;
                int amount = 0;

                spin_lock_irqsave(&port->rxq.lock, flags);
                skb_queue_walk(&port->rxq, skb)
                        amount += skb->len;
                spin_unlock_irqrestore(&port->rxq.lock, flags);

                return put_user(amount, (int __user *)arg);
        }

        default:
                return -ENOIOCTLCMD;
        }
}

static const struct file_operations wwan_port_fops = {
        .owner = THIS_MODULE,
        .open = wwan_port_fops_open,
        .release = wwan_port_fops_release,
        .read = wwan_port_fops_read,
        .write = wwan_port_fops_write,
        .poll = wwan_port_fops_poll,
        .unlocked_ioctl = wwan_port_fops_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = compat_ptr_ioctl,
#endif
        .llseek = noop_llseek,
};

static int wwan_rtnl_validate(struct nlattr *tb[], struct nlattr *data[],
                              struct netlink_ext_ack *extack)
{
        if (!data)
                return -EINVAL;

        if (!tb[IFLA_PARENT_DEV_NAME])
                return -EINVAL;

        if (!data[IFLA_WWAN_LINK_ID])
                return -EINVAL;

        return 0;
}

static struct device_type wwan_type = { .name = "wwan" };

static struct net_device *wwan_rtnl_alloc(struct nlattr *tb[],
                                          const char *ifname,
                                          unsigned char name_assign_type,
                                          unsigned int num_tx_queues,
                                          unsigned int num_rx_queues)
{
        const char *devname = nla_data(tb[IFLA_PARENT_DEV_NAME]);
        struct wwan_device *wwandev = wwan_dev_get_by_name(devname);
        struct net_device *dev;
        unsigned int priv_size;

        if (IS_ERR(wwandev))
                return ERR_CAST(wwandev);

        /* only supported if ops were registered (not just ports) */
        if (!wwandev->ops) {
                dev = ERR_PTR(-EOPNOTSUPP);
                goto out;
        }

        priv_size = sizeof(struct wwan_netdev_priv) + wwandev->ops->priv_size;
        dev = alloc_netdev_mqs(priv_size, ifname, name_assign_type,
                               wwandev->ops->setup, num_tx_queues, num_rx_queues);

        if (dev) {
                SET_NETDEV_DEV(dev, &wwandev->dev);
                SET_NETDEV_DEVTYPE(dev, &wwan_type);
        }

out:
        /* release the reference */
        put_device(&wwandev->dev);
        return dev;
}

static int wwan_rtnl_newlink(struct net *src_net, struct net_device *dev,
                             struct nlattr *tb[], struct nlattr *data[],
                             struct netlink_ext_ack *extack)
{
        struct wwan_device *wwandev = wwan_dev_get_by_parent(dev->dev.parent);
        u32 link_id = nla_get_u32(data[IFLA_WWAN_LINK_ID]);
        struct wwan_netdev_priv *priv = netdev_priv(dev);
        int ret;

        if (IS_ERR(wwandev))
                return PTR_ERR(wwandev);

        /* shouldn't have a netdev (left) with us as parent so WARN */
        if (WARN_ON(!wwandev->ops)) {
                ret = -EOPNOTSUPP;
                goto out;
        }

        priv->link_id = link_id;
        if (wwandev->ops->newlink)
                ret = wwandev->ops->newlink(wwandev->ops_ctxt, dev,
                                            link_id, extack);
        else
                ret = register_netdevice(dev);

out:
        /* release the reference */
        put_device(&wwandev->dev);
        return ret;
}

static void wwan_rtnl_dellink(struct net_device *dev, struct list_head *head)
{
        struct wwan_device *wwandev = wwan_dev_get_by_parent(dev->dev.parent);

        if (IS_ERR(wwandev))
                return;

        /* shouldn't have a netdev (left) with us as parent so WARN */
        if (WARN_ON(!wwandev->ops))
                goto out;

        if (wwandev->ops->dellink)
                wwandev->ops->dellink(wwandev->ops_ctxt, dev, head);
        else
                unregister_netdevice_queue(dev, head);

out:
        /* release the reference */
        put_device(&wwandev->dev);
}

static size_t wwan_rtnl_get_size(const struct net_device *dev)
{
        return
                nla_total_size(4) +     /* IFLA_WWAN_LINK_ID */
                0;
}

static int wwan_rtnl_fill_info(struct sk_buff *skb,
                               const struct net_device *dev)
{
        struct wwan_netdev_priv *priv = netdev_priv(dev);

        if (nla_put_u32(skb, IFLA_WWAN_LINK_ID, priv->link_id))
                goto nla_put_failure;

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static const struct nla_policy wwan_rtnl_policy[IFLA_WWAN_MAX + 1] = {
        [IFLA_WWAN_LINK_ID] = { .type = NLA_U32 },
};

static struct rtnl_link_ops wwan_rtnl_link_ops __read_mostly = {
        .kind = "wwan",
        .maxtype = __IFLA_WWAN_MAX,
        .alloc = wwan_rtnl_alloc,
        .validate = wwan_rtnl_validate,
        .newlink = wwan_rtnl_newlink,
        .dellink = wwan_rtnl_dellink,

        .get_size = wwan_rtnl_get_size,
        .fill_info = wwan_rtnl_fill_info,
        .policy = wwan_rtnl_policy,
};

static void wwan_create_default_link(struct wwan_device *wwandev,
                                     u32 def_link_id)
{
        struct nlattr *tb[IFLA_MAX + 1], *linkinfo[IFLA_INFO_MAX + 1];
        struct nlattr *data[IFLA_WWAN_MAX + 1];
        struct net_device *dev;
        struct nlmsghdr *nlh;
        struct sk_buff *msg;

        /* Forge attributes required to create a WWAN netdev. We first
         * build a netlink message and then parse it. This looks
         * odd, but such approach is less error prone.
         */
        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (WARN_ON(!msg))
                return;
        nlh = nlmsg_put(msg, 0, 0, RTM_NEWLINK, 0, 0);
        if (WARN_ON(!nlh))
                goto free_attrs;

        if (nla_put_string(msg, IFLA_PARENT_DEV_NAME, dev_name(&wwandev->dev)))
                goto free_attrs;
        tb[IFLA_LINKINFO] = nla_nest_start(msg, IFLA_LINKINFO);
        if (!tb[IFLA_LINKINFO])
                goto free_attrs;
        linkinfo[IFLA_INFO_DATA] = nla_nest_start(msg, IFLA_INFO_DATA);
        if (!linkinfo[IFLA_INFO_DATA])
                goto free_attrs;
        if (nla_put_u32(msg, IFLA_WWAN_LINK_ID, def_link_id))
                goto free_attrs;
        nla_nest_end(msg, linkinfo[IFLA_INFO_DATA]);
        nla_nest_end(msg, tb[IFLA_LINKINFO]);

        nlmsg_end(msg, nlh);

        /* The next three parsing calls can not fail */
        nlmsg_parse_deprecated(nlh, 0, tb, IFLA_MAX, NULL, NULL);
        nla_parse_nested_deprecated(linkinfo, IFLA_INFO_MAX, tb[IFLA_LINKINFO],
                                    NULL, NULL);
        nla_parse_nested_deprecated(data, IFLA_WWAN_MAX,
                                    linkinfo[IFLA_INFO_DATA], NULL, NULL);

        rtnl_lock();

        dev = rtnl_create_link(&init_net, "wwan%d", NET_NAME_ENUM,
                               &wwan_rtnl_link_ops, tb, NULL);
        if (WARN_ON(IS_ERR(dev)))
                goto unlock;

        if (WARN_ON(wwan_rtnl_newlink(&init_net, dev, tb, data, NULL))) {
                free_netdev(dev);
                goto unlock;
        }

        rtnl_configure_link(dev, NULL); /* Link initialized, notify new link */

unlock:
        rtnl_unlock();

free_attrs:
        nlmsg_free(msg);
}

/**
 * wwan_register_ops - register WWAN device ops
 * @parent: Device to use as parent and shared by all WWAN ports and
 *      created netdevs
 * @ops: operations to register
 * @ctxt: context to pass to operations
 * @def_link_id: id of the default link that will be automatically created by
 *      the WWAN core for the WWAN device. The default link will not be created
 *      if the passed value is WWAN_NO_DEFAULT_LINK.
 *
 * Returns: 0 on success, a negative error code on failure
 */
int wwan_register_ops(struct device *parent, const struct wwan_ops *ops,
                      void *ctxt, u32 def_link_id)
{
        struct wwan_device *wwandev;

        if (WARN_ON(!parent || !ops || !ops->setup))
                return -EINVAL;

        wwandev = wwan_create_dev(parent);
        if (IS_ERR(wwandev))
                return PTR_ERR(wwandev);

        if (WARN_ON(wwandev->ops)) {
                wwan_remove_dev(wwandev);
                return -EBUSY;
        }

        wwandev->ops = ops;
        wwandev->ops_ctxt = ctxt;

        /* NB: we do not abort ops registration in case of default link
         * creation failure. Link ops is the management interface, while the
         * default link creation is a service option. And we should not prevent
         * a user from manually creating a link latter if service option failed
         * now.
         */
        if (def_link_id != WWAN_NO_DEFAULT_LINK)
                wwan_create_default_link(wwandev, def_link_id);

        return 0;
}
EXPORT_SYMBOL_GPL(wwan_register_ops);

/* Enqueue child netdev deletion */
static int wwan_child_dellink(struct device *dev, void *data)
{
        struct list_head *kill_list = data;

        if (dev->type == &wwan_type)
                wwan_rtnl_dellink(to_net_dev(dev), kill_list);

        return 0;
}

/**
 * wwan_unregister_ops - remove WWAN device ops
 * @parent: Device to use as parent and shared by all WWAN ports and
 *      created netdevs
 */
void wwan_unregister_ops(struct device *parent)
{
        struct wwan_device *wwandev = wwan_dev_get_by_parent(parent);
        LIST_HEAD(kill_list);

        if (WARN_ON(IS_ERR(wwandev)))
                return;
        if (WARN_ON(!wwandev->ops)) {
                put_device(&wwandev->dev);
                return;
        }

        /* put the reference obtained by wwan_dev_get_by_parent(),
         * we should still have one (that the owner is giving back
         * now) due to the ops being assigned.
         */
        put_device(&wwandev->dev);

        rtnl_lock();    /* Prevent concurent netdev(s) creation/destroying */

        /* Remove all child netdev(s), using batch removing */
        device_for_each_child(&wwandev->dev, &kill_list,
                              wwan_child_dellink);
        unregister_netdevice_many(&kill_list);

        wwandev->ops = NULL;    /* Finally remove ops */

        rtnl_unlock();

        wwandev->ops_ctxt = NULL;
        wwan_remove_dev(wwandev);
}
EXPORT_SYMBOL_GPL(wwan_unregister_ops);

static int __init wwan_init(void)
{
        int err;

        err = rtnl_link_register(&wwan_rtnl_link_ops);
        if (err)
                return err;

        wwan_class = class_create(THIS_MODULE, "wwan");
        if (IS_ERR(wwan_class)) {
                err = PTR_ERR(wwan_class);
                goto unregister;
        }

        /* chrdev used for wwan ports */
        wwan_major = __register_chrdev(0, 0, WWAN_MAX_MINORS, "wwan_port",
                                       &wwan_port_fops);
        if (wwan_major < 0) {
                err = wwan_major;
                goto destroy;
        }

#ifdef CONFIG_WWAN_DEBUGFS
        wwan_debugfs_dir = debugfs_create_dir("wwan", NULL);
#endif

        return 0;

destroy:
        class_destroy(wwan_class);
unregister:
        rtnl_link_unregister(&wwan_rtnl_link_ops);
        return err;
}

static void __exit wwan_exit(void)
{
        debugfs_remove_recursive(wwan_debugfs_dir);
        __unregister_chrdev(wwan_major, 0, WWAN_MAX_MINORS, "wwan_port");
        rtnl_link_unregister(&wwan_rtnl_link_ops);
        class_destroy(wwan_class);
}

module_init(wwan_init);
module_exit(wwan_exit);

MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>");
MODULE_DESCRIPTION("WWAN core");
MODULE_LICENSE("GPL v2");