// SPDX-License-Identifier: GPL-2.0
/*
 * f_phonet.c -- USB CDC Phonet function
 *
 * Copyright (C) 2007-2008 Nokia Corporation. All rights reserved.
 *
 * Author: Rémi Denis-Courmont
 */

#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>

#include <linux/netdevice.h>
#include <linux/if_ether.h>
#include <linux/if_phonet.h>
#include <linux/if_arp.h>

#include <linux/usb/ch9.h>
#include <linux/usb/cdc.h>
#include <linux/usb/composite.h>

#include "u_phonet.h"
#include "u_ether.h"

#define PN_MEDIA_USB    0x1B
#define MAXPACKET       512
#if (PAGE_SIZE % MAXPACKET)
#error MAXPACKET must divide PAGE_SIZE!
#endif

/*-------------------------------------------------------------------------*/

struct phonet_port {
        struct f_phonet                 *usb;
        spinlock_t                      lock;
};

struct f_phonet {
        struct usb_function             function;
        struct {
                struct sk_buff          *skb;
                spinlock_t              lock;
        } rx;
        struct net_device               *dev;
        struct usb_ep                   *in_ep, *out_ep;

        struct usb_request              *in_req;
        struct usb_request              *out_reqv[];
};

static int phonet_rxq_size = 17;

static inline struct f_phonet *func_to_pn(struct usb_function *f)
{
        return container_of(f, struct f_phonet, function);
}

/*-------------------------------------------------------------------------*/

#define USB_CDC_SUBCLASS_PHONET 0xfe
#define USB_CDC_PHONET_TYPE     0xab

static struct usb_interface_descriptor
pn_control_intf_desc = {
        .bLength =              sizeof pn_control_intf_desc,
        .bDescriptorType =      USB_DT_INTERFACE,

        /* .bInterfaceNumber =  DYNAMIC, */
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_PHONET,
};

static const struct usb_cdc_header_desc
pn_header_desc = {
        .bLength =              sizeof pn_header_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,
        .bcdCDC =               cpu_to_le16(0x0110),
};

static const struct usb_cdc_header_desc
pn_phonet_desc = {
        .bLength =              sizeof pn_phonet_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_PHONET_TYPE,
        .bcdCDC =               cpu_to_le16(0x1505), /* ??? */
};

static struct usb_cdc_union_desc
pn_union_desc = {
        .bLength =              sizeof pn_union_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_UNION_TYPE,

        /* .bMasterInterface0 = DYNAMIC, */
        /* .bSlaveInterface0 =  DYNAMIC, */
};

static struct usb_interface_descriptor
pn_data_nop_intf_desc = {
        .bLength =              sizeof pn_data_nop_intf_desc,
        .bDescriptorType =      USB_DT_INTERFACE,

        /* .bInterfaceNumber =  DYNAMIC, */
        .bAlternateSetting =    0,
        .bNumEndpoints =        0,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
};

static struct usb_interface_descriptor
pn_data_intf_desc = {
        .bLength =              sizeof pn_data_intf_desc,
        .bDescriptorType =      USB_DT_INTERFACE,

        /* .bInterfaceNumber =  DYNAMIC, */
        .bAlternateSetting =    1,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
};

static struct usb_endpoint_descriptor
pn_fs_sink_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor
pn_hs_sink_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(MAXPACKET),
};

static struct usb_endpoint_descriptor
pn_fs_source_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor
pn_hs_source_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(512),
};

static struct usb_descriptor_header *fs_pn_function[] = {
        (struct usb_descriptor_header *) &pn_control_intf_desc,
        (struct usb_descriptor_header *) &pn_header_desc,
        (struct usb_descriptor_header *) &pn_phonet_desc,
        (struct usb_descriptor_header *) &pn_union_desc,
        (struct usb_descriptor_header *) &pn_data_nop_intf_desc,
        (struct usb_descriptor_header *) &pn_data_intf_desc,
        (struct usb_descriptor_header *) &pn_fs_sink_desc,
        (struct usb_descriptor_header *) &pn_fs_source_desc,
        NULL,
};

static struct usb_descriptor_header *hs_pn_function[] = {
        (struct usb_descriptor_header *) &pn_control_intf_desc,
        (struct usb_descriptor_header *) &pn_header_desc,
        (struct usb_descriptor_header *) &pn_phonet_desc,
        (struct usb_descriptor_header *) &pn_union_desc,
        (struct usb_descriptor_header *) &pn_data_nop_intf_desc,
        (struct usb_descriptor_header *) &pn_data_intf_desc,
        (struct usb_descriptor_header *) &pn_hs_sink_desc,
        (struct usb_descriptor_header *) &pn_hs_source_desc,
        NULL,
};

/*-------------------------------------------------------------------------*/

static int pn_net_open(struct net_device *dev)
{
        netif_wake_queue(dev);
        return 0;
}

static int pn_net_close(struct net_device *dev)
{
        netif_stop_queue(dev);
        return 0;
}

static void pn_tx_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_phonet *fp = ep->driver_data;
        struct net_device *dev = fp->dev;
        struct sk_buff *skb = req->context;

        switch (req->status) {
        case 0:
                dev->stats.tx_packets++;
                dev->stats.tx_bytes += skb->len;
                break;

        case -ESHUTDOWN: /* disconnected */
        case -ECONNRESET: /* disabled */
                dev->stats.tx_aborted_errors++;
                fallthrough;
        default:
                dev->stats.tx_errors++;
        }

        dev_kfree_skb_any(skb);
        netif_wake_queue(dev);
}

static netdev_tx_t pn_net_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct phonet_port *port = netdev_priv(dev);
        struct f_phonet *fp;
        struct usb_request *req;
        unsigned long flags;

        if (skb->protocol != htons(ETH_P_PHONET))
                goto out;

        spin_lock_irqsave(&port->lock, flags);
        fp = port->usb;
        if (unlikely(!fp)) /* race with carrier loss */
                goto out_unlock;

        req = fp->in_req;
        req->buf = skb->data;
        req->length = skb->len;
        req->complete = pn_tx_complete;
        req->zero = 1;
        req->context = skb;

        if (unlikely(usb_ep_queue(fp->in_ep, req, GFP_ATOMIC)))
                goto out_unlock;

        netif_stop_queue(dev);
        skb = NULL;

out_unlock:
        spin_unlock_irqrestore(&port->lock, flags);
out:
        if (unlikely(skb)) {
                dev_kfree_skb(skb);
                dev->stats.tx_dropped++;
        }
        return NETDEV_TX_OK;
}

static const struct net_device_ops pn_netdev_ops = {
        .ndo_open       = pn_net_open,
        .ndo_stop       = pn_net_close,
        .ndo_start_xmit = pn_net_xmit,
};

static void pn_net_setup(struct net_device *dev)
{
        const u8 addr = PN_MEDIA_USB;

        dev->features           = 0;
        dev->type               = ARPHRD_PHONET;
        dev->flags              = IFF_POINTOPOINT | IFF_NOARP;
        dev->mtu                = PHONET_DEV_MTU;
        dev->min_mtu            = PHONET_MIN_MTU;
        dev->max_mtu            = PHONET_MAX_MTU;
        dev->hard_header_len    = 1;
        dev->addr_len           = 1;
        dev_addr_set(dev, &addr);

        dev->tx_queue_len       = 1;

        dev->netdev_ops         = &pn_netdev_ops;
        dev->needs_free_netdev  = true;
        dev->header_ops         = &phonet_header_ops;
}

/*-------------------------------------------------------------------------*/

/*
 * Queue buffer for data from the host
 */
static int
pn_rx_submit(struct f_phonet *fp, struct usb_request *req, gfp_t gfp_flags)
{
        struct page *page;
        int err;

        page = __dev_alloc_page(gfp_flags | __GFP_NOMEMALLOC);
        if (!page)
                return -ENOMEM;

        req->buf = page_address(page);
        req->length = PAGE_SIZE;
        req->context = page;

        err = usb_ep_queue(fp->out_ep, req, gfp_flags);
        if (unlikely(err))
                put_page(page);
        return err;
}

static void pn_rx_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_phonet *fp = ep->driver_data;
        struct net_device *dev = fp->dev;
        struct page *page = req->context;
        struct sk_buff *skb;
        unsigned long flags;
        int status = req->status;

        switch (status) {
        case 0:
                spin_lock_irqsave(&fp->rx.lock, flags);
                skb = fp->rx.skb;
                if (!skb)
                        skb = fp->rx.skb = netdev_alloc_skb(dev, 12);
                if (req->actual < req->length) /* Last fragment */
                        fp->rx.skb = NULL;
                spin_unlock_irqrestore(&fp->rx.lock, flags);

                if (unlikely(!skb))
                        break;

                if (skb->len == 0) { /* First fragment */
                        skb->protocol = htons(ETH_P_PHONET);
                        skb_reset_mac_header(skb);
                        /* Can't use pskb_pull() on page in IRQ */
                        skb_put_data(skb, page_address(page), 1);
                }

                skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
                                skb->len <= 1, req->actual, PAGE_SIZE);
                page = NULL;

                if (req->actual < req->length) { /* Last fragment */
                        skb->dev = dev;
                        dev->stats.rx_packets++;
                        dev->stats.rx_bytes += skb->len;

                        netif_rx(skb);
                }
                break;

        /* Do not resubmit in these cases: */
        case -ESHUTDOWN: /* disconnect */
        case -ECONNABORTED: /* hw reset */
        case -ECONNRESET: /* dequeued (unlink or netif down) */
                req = NULL;
                break;

        /* Do resubmit in these cases: */
        case -EOVERFLOW: /* request buffer overflow */
                dev->stats.rx_over_errors++;
                fallthrough;
        default:
                dev->stats.rx_errors++;
                break;
        }

        if (page)
                put_page(page);
        if (req)
                pn_rx_submit(fp, req, GFP_ATOMIC);
}

/*-------------------------------------------------------------------------*/

static void __pn_reset(struct usb_function *f)
{
        struct f_phonet *fp = func_to_pn(f);
        struct net_device *dev = fp->dev;
        struct phonet_port *port = netdev_priv(dev);

        netif_carrier_off(dev);
        port->usb = NULL;

        usb_ep_disable(fp->out_ep);
        usb_ep_disable(fp->in_ep);
        if (fp->rx.skb) {
                dev_kfree_skb_irq(fp->rx.skb);
                fp->rx.skb = NULL;
        }
}

static int pn_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_phonet *fp = func_to_pn(f);
        struct usb_gadget *gadget = fp->function.config->cdev->gadget;

        if (intf == pn_control_intf_desc.bInterfaceNumber)
                /* control interface, no altsetting */
                return (alt > 0) ? -EINVAL : 0;

        if (intf == pn_data_intf_desc.bInterfaceNumber) {
                struct net_device *dev = fp->dev;
                struct phonet_port *port = netdev_priv(dev);

                /* data intf (0: inactive, 1: active) */
                if (alt > 1)
                        return -EINVAL;

                spin_lock(&port->lock);

                if (fp->in_ep->enabled)
                        __pn_reset(f);

                if (alt == 1) {
                        int i;

                        if (config_ep_by_speed(gadget, f, fp->in_ep) ||
                            config_ep_by_speed(gadget, f, fp->out_ep)) {
                                fp->in_ep->desc = NULL;
                                fp->out_ep->desc = NULL;
                                spin_unlock(&port->lock);
                                return -EINVAL;
                        }
                        usb_ep_enable(fp->out_ep);
                        usb_ep_enable(fp->in_ep);

                        port->usb = fp;
                        fp->out_ep->driver_data = fp;
                        fp->in_ep->driver_data = fp;

                        netif_carrier_on(dev);
                        for (i = 0; i < phonet_rxq_size; i++)
                                pn_rx_submit(fp, fp->out_reqv[i], GFP_ATOMIC);
                }
                spin_unlock(&port->lock);
                return 0;
        }

        return -EINVAL;
}

static int pn_get_alt(struct usb_function *f, unsigned intf)
{
        struct f_phonet *fp = func_to_pn(f);

        if (intf == pn_control_intf_desc.bInterfaceNumber)
                return 0;

        if (intf == pn_data_intf_desc.bInterfaceNumber) {
                struct phonet_port *port = netdev_priv(fp->dev);
                u8 alt;

                spin_lock(&port->lock);
                alt = port->usb != NULL;
                spin_unlock(&port->lock);
                return alt;
        }

        return -EINVAL;
}

static void pn_disconnect(struct usb_function *f)
{
        struct f_phonet *fp = func_to_pn(f);
        struct phonet_port *port = netdev_priv(fp->dev);
        unsigned long flags;

        /* remain disabled until set_alt */
        spin_lock_irqsave(&port->lock, flags);
        __pn_reset(f);
        spin_unlock_irqrestore(&port->lock, flags);
}

/*-------------------------------------------------------------------------*/

static int pn_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct usb_gadget *gadget = cdev->gadget;
        struct f_phonet *fp = func_to_pn(f);
        struct usb_ep *ep;
        int status, i;

        struct f_phonet_opts *phonet_opts;

        phonet_opts = container_of(f->fi, struct f_phonet_opts, func_inst);

        /*
         * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
         * configurations are bound in sequence with list_for_each_entry,
         * in each configuration its functions are bound in sequence
         * with list_for_each_entry, so we assume no race condition
         * with regard to phonet_opts->bound access
         */
        if (!phonet_opts->bound) {
                gphonet_set_gadget(phonet_opts->net, gadget);
                status = gphonet_register_netdev(phonet_opts->net);
                if (status)
                        return status;
                phonet_opts->bound = true;
        }

        /* Reserve interface IDs */
        status = usb_interface_id(c, f);
        if (status < 0)
                goto err;
        pn_control_intf_desc.bInterfaceNumber = status;
        pn_union_desc.bMasterInterface0 = status;

        status = usb_interface_id(c, f);
        if (status < 0)
                goto err;
        pn_data_nop_intf_desc.bInterfaceNumber = status;
        pn_data_intf_desc.bInterfaceNumber = status;
        pn_union_desc.bSlaveInterface0 = status;

        /* Reserve endpoints */
        status = -ENODEV;
        ep = usb_ep_autoconfig(gadget, &pn_fs_sink_desc);
        if (!ep)
                goto err;
        fp->out_ep = ep;

        ep = usb_ep_autoconfig(gadget, &pn_fs_source_desc);
        if (!ep)
                goto err;
        fp->in_ep = ep;

        pn_hs_sink_desc.bEndpointAddress = pn_fs_sink_desc.bEndpointAddress;
        pn_hs_source_desc.bEndpointAddress = pn_fs_source_desc.bEndpointAddress;

        /* Do not try to bind Phonet twice... */
        status = usb_assign_descriptors(f, fs_pn_function, hs_pn_function,
                        NULL, NULL);
        if (status)
                goto err;

        /* Incoming USB requests */
        status = -ENOMEM;
        for (i = 0; i < phonet_rxq_size; i++) {
                struct usb_request *req;

                req = usb_ep_alloc_request(fp->out_ep, GFP_KERNEL);
                if (!req)
                        goto err_req;

                req->complete = pn_rx_complete;
                fp->out_reqv[i] = req;
        }

        /* Outgoing USB requests */
        fp->in_req = usb_ep_alloc_request(fp->in_ep, GFP_KERNEL);
        if (!fp->in_req)
                goto err_req;

        INFO(cdev, "USB CDC Phonet function\n");
        INFO(cdev, "using %s, OUT %s, IN %s\n", cdev->gadget->name,
                fp->out_ep->name, fp->in_ep->name);
        return 0;

err_req:
        for (i = 0; i < phonet_rxq_size && fp->out_reqv[i]; i++)
                usb_ep_free_request(fp->out_ep, fp->out_reqv[i]);
        usb_free_all_descriptors(f);
err:
        ERROR(cdev, "USB CDC Phonet: cannot autoconfigure\n");
        return status;
}

static inline struct f_phonet_opts *to_f_phonet_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct f_phonet_opts,
                        func_inst.group);
}

static void phonet_attr_release(struct config_item *item)
{
        struct f_phonet_opts *opts = to_f_phonet_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static const struct configfs_item_operations phonet_item_ops = {
        .release                = phonet_attr_release,
};

static ssize_t f_phonet_ifname_show(struct config_item *item, char *page)
{
        return gether_get_ifname(to_f_phonet_opts(item)->net, page, PAGE_SIZE);
}

CONFIGFS_ATTR_RO(f_phonet_, ifname);

static struct configfs_attribute *phonet_attrs[] = {
        &f_phonet_attr_ifname,
        NULL,
};

static const struct config_item_type phonet_func_type = {
        .ct_item_ops    = &phonet_item_ops,
        .ct_attrs       = phonet_attrs,
        .ct_owner       = THIS_MODULE,
};

static void phonet_free_inst(struct usb_function_instance *f)
{
        struct f_phonet_opts *opts;

        opts = container_of(f, struct f_phonet_opts, func_inst);
        if (opts->bound)
                gphonet_cleanup(opts->net);
        else
                free_netdev(opts->net);
        kfree(opts);
}

static struct usb_function_instance *phonet_alloc_inst(void)
{
        struct f_phonet_opts *opts;

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

        opts->func_inst.free_func_inst = phonet_free_inst;
        opts->net = gphonet_setup_default();
        if (IS_ERR(opts->net)) {
                struct net_device *net = opts->net;
                kfree(opts);
                return ERR_CAST(net);
        }

        config_group_init_type_name(&opts->func_inst.group, "",
                        &phonet_func_type);

        return &opts->func_inst;
}

static void phonet_free(struct usb_function *f)
{
        struct f_phonet *phonet;

        phonet = func_to_pn(f);
        kfree(phonet);
}

static void pn_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_phonet *fp = func_to_pn(f);
        int i;

        /* We are already disconnected */
        if (fp->in_req)
                usb_ep_free_request(fp->in_ep, fp->in_req);
        for (i = 0; i < phonet_rxq_size; i++)
                if (fp->out_reqv[i])
                        usb_ep_free_request(fp->out_ep, fp->out_reqv[i]);

        usb_free_all_descriptors(f);
}

static struct usb_function *phonet_alloc(struct usb_function_instance *fi)
{
        struct f_phonet *fp;
        struct f_phonet_opts *opts;

        fp = kzalloc_flex(*fp, out_reqv, phonet_rxq_size);
        if (!fp)
                return ERR_PTR(-ENOMEM);

        opts = container_of(fi, struct f_phonet_opts, func_inst);

        fp->dev = opts->net;
        fp->function.name = "phonet";
        fp->function.bind = pn_bind;
        fp->function.unbind = pn_unbind;
        fp->function.set_alt = pn_set_alt;
        fp->function.get_alt = pn_get_alt;
        fp->function.disable = pn_disconnect;
        fp->function.free_func = phonet_free;
        spin_lock_init(&fp->rx.lock);

        return &fp->function;
}

struct net_device *gphonet_setup_default(void)
{
        struct net_device *dev;
        struct phonet_port *port;

        /* Create net device */
        dev = alloc_netdev(sizeof(*port), "upnlink%d", NET_NAME_UNKNOWN,
                           pn_net_setup);
        if (!dev)
                return ERR_PTR(-ENOMEM);

        port = netdev_priv(dev);
        spin_lock_init(&port->lock);
        netif_carrier_off(dev);

        return dev;
}

void gphonet_set_gadget(struct net_device *net, struct usb_gadget *g)
{
        SET_NETDEV_DEV(net, &g->dev);
}

int gphonet_register_netdev(struct net_device *net)
{
        int status;

        status = register_netdev(net);
        if (status)
                free_netdev(net);

        return status;
}

void gphonet_cleanup(struct net_device *dev)
{
        unregister_netdev(dev);
}

DECLARE_USB_FUNCTION_INIT(phonet, phonet_alloc_inst, phonet_alloc);
MODULE_AUTHOR("Rémi Denis-Courmont");
MODULE_DESCRIPTION("USB CDC Phonet function");
MODULE_LICENSE("GPL");