// SPDX-License-Identifier: GPL-2.0+
/*
 * f_eem.c -- USB CDC Ethernet (EEM) link function driver
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2008 Nokia Corporation
 * Copyright (C) 2009 EF Johnson Technologies
 */

#include <linux/cleanup.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/etherdevice.h>
#include <linux/crc32.h>
#include <linux/slab.h>

#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_eem.h"

#define EEM_HLEN 2

/*
 * This function is a "CDC Ethernet Emulation Model" (CDC EEM)
 * Ethernet link.
 */

struct f_eem {
        struct gether                   port;
        u8                              ctrl_id;
};

struct in_context {
        struct sk_buff  *skb;
        struct usb_ep   *ep;
};

static inline struct f_eem *func_to_eem(struct usb_function *f)
{
        return container_of(f, struct f_eem, port.func);
}

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

/* interface descriptor: */

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

        /* .bInterfaceNumber = DYNAMIC */
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_EEM,
        .bInterfaceProtocol =   USB_CDC_PROTO_EEM,
        /* .iInterface = DYNAMIC */
};

/* full speed support: */

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

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

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

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

static struct usb_descriptor_header *eem_fs_function[] = {
        /* CDC EEM control descriptors */
        (struct usb_descriptor_header *) &eem_intf,
        (struct usb_descriptor_header *) &eem_fs_in_desc,
        (struct usb_descriptor_header *) &eem_fs_out_desc,
        NULL,
};

/* high speed support: */

static struct usb_endpoint_descriptor eem_hs_in_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_endpoint_descriptor eem_hs_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

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

static struct usb_descriptor_header *eem_hs_function[] = {
        /* CDC EEM control descriptors */
        (struct usb_descriptor_header *) &eem_intf,
        (struct usb_descriptor_header *) &eem_hs_in_desc,
        (struct usb_descriptor_header *) &eem_hs_out_desc,
        NULL,
};

/* super speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

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

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor eem_ss_bulk_comp_desc = {
        .bLength =              sizeof eem_ss_bulk_comp_desc,
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,

        /* the following 2 values can be tweaked if necessary */
        /* .bMaxBurst =         0, */
        /* .bmAttributes =      0, */
};

static struct usb_descriptor_header *eem_ss_function[] = {
        /* CDC EEM control descriptors */
        (struct usb_descriptor_header *) &eem_intf,
        (struct usb_descriptor_header *) &eem_ss_in_desc,
        (struct usb_descriptor_header *) &eem_ss_bulk_comp_desc,
        (struct usb_descriptor_header *) &eem_ss_out_desc,
        (struct usb_descriptor_header *) &eem_ss_bulk_comp_desc,
        NULL,
};

/* string descriptors: */

static struct usb_string eem_string_defs[] = {
        [0].s = "CDC Ethernet Emulation Model (EEM)",
        {  } /* end of list */
};

static struct usb_gadget_strings eem_string_table = {
        .language =             0x0409, /* en-us */
        .strings =              eem_string_defs,
};

static struct usb_gadget_strings *eem_strings[] = {
        &eem_string_table,
        NULL,
};

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

static int eem_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
        struct usb_composite_dev *cdev = f->config->cdev;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        DBG(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
                ctrl->bRequestType, ctrl->bRequest,
                w_value, w_index, w_length);

        /* device either stalls (value < 0) or reports success */
        return -EOPNOTSUPP;
}


static int eem_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_eem            *eem = func_to_eem(f);
        struct usb_composite_dev *cdev = f->config->cdev;
        struct net_device       *net;

        /* we know alt == 0, so this is an activation or a reset */
        if (alt != 0)
                goto fail;

        if (intf == eem->ctrl_id) {
                DBG(cdev, "reset eem\n");
                gether_disconnect(&eem->port);

                if (!eem->port.in_ep->desc || !eem->port.out_ep->desc) {
                        DBG(cdev, "init eem\n");
                        if (config_ep_by_speed(cdev->gadget, f,
                                               eem->port.in_ep) ||
                            config_ep_by_speed(cdev->gadget, f,
                                               eem->port.out_ep)) {
                                eem->port.in_ep->desc = NULL;
                                eem->port.out_ep->desc = NULL;
                                goto fail;
                        }
                }

                /* zlps should not occur because zero-length EEM packets
                 * will be inserted in those cases where they would occur
                 */
                eem->port.is_zlp_ok = 1;
                eem->port.cdc_filter = DEFAULT_FILTER;
                DBG(cdev, "activate eem\n");
                net = gether_connect(&eem->port);
                if (IS_ERR(net))
                        return PTR_ERR(net);
        } else
                goto fail;

        return 0;
fail:
        return -EINVAL;
}

static void eem_disable(struct usb_function *f)
{
        struct f_eem            *eem = func_to_eem(f);
        struct usb_composite_dev *cdev = f->config->cdev;

        DBG(cdev, "eem deactivated\n");

        if (eem->port.in_ep->enabled)
                gether_disconnect(&eem->port);
}

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

/* EEM function driver setup/binding */

static int eem_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct f_eem            *eem = func_to_eem(f);
        struct usb_string       *us;
        int                     status;
        struct usb_ep           *ep;

        struct f_eem_opts       *eem_opts;
        struct net_device       *net __free(detach_gadget) = NULL;

        eem_opts = container_of(f->fi, struct f_eem_opts, func_inst);

        scoped_guard(mutex, &eem_opts->lock)
                if (eem_opts->bind_count == 0 && !eem_opts->bound) {
                        if (!device_is_registered(&eem_opts->net->dev)) {
                                gether_set_gadget(eem_opts->net, cdev->gadget);
                                status = gether_register_netdev(eem_opts->net);
                        } else
                                status = gether_attach_gadget(eem_opts->net, cdev->gadget);

                        if (status)
                                return status;
                        net = eem_opts->net;
                }

        us = usb_gstrings_attach(cdev, eem_strings,
                                 ARRAY_SIZE(eem_string_defs));
        if (IS_ERR(us))
                return PTR_ERR(us);
        eem_intf.iInterface = us[0].id;

        /* allocate instance-specific interface IDs */
        status = usb_interface_id(c, f);
        if (status < 0)
                return status;
        eem->ctrl_id = status;
        eem_intf.bInterfaceNumber = status;

        /* allocate instance-specific endpoints */
        ep = usb_ep_autoconfig(cdev->gadget, &eem_fs_in_desc);
        if (!ep)
                return -ENODEV;
        eem->port.in_ep = ep;

        ep = usb_ep_autoconfig(cdev->gadget, &eem_fs_out_desc);
        if (!ep)
                return -ENODEV;
        eem->port.out_ep = ep;

        /* support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
         * both speeds
         */
        eem_hs_in_desc.bEndpointAddress = eem_fs_in_desc.bEndpointAddress;
        eem_hs_out_desc.bEndpointAddress = eem_fs_out_desc.bEndpointAddress;

        eem_ss_in_desc.bEndpointAddress = eem_fs_in_desc.bEndpointAddress;
        eem_ss_out_desc.bEndpointAddress = eem_fs_out_desc.bEndpointAddress;

        status = usb_assign_descriptors(f, eem_fs_function, eem_hs_function,
                        eem_ss_function, eem_ss_function);
        if (status)
                return status;

        eem_opts->bind_count++;
        retain_and_null_ptr(net);

        DBG(cdev, "CDC Ethernet (EEM): IN/%s OUT/%s\n",
                        eem->port.in_ep->name, eem->port.out_ep->name);
        return 0;
}

static void eem_cmd_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct in_context *ctx = req->context;

        dev_kfree_skb_any(ctx->skb);
        kfree(req->buf);
        usb_ep_free_request(ctx->ep, req);
        kfree(ctx);
}

/*
 * Add the EEM header and ethernet checksum.
 * We currently do not attempt to put multiple ethernet frames
 * into a single USB transfer
 */
static struct sk_buff *eem_wrap(struct gether *port, struct sk_buff *skb)
{
        struct sk_buff  *skb2 = NULL;
        struct usb_ep   *in = port->in_ep;
        int             headroom, tailroom, padlen = 0;
        u16             len;

        if (!skb)
                return NULL;

        len = skb->len;
        headroom = skb_headroom(skb);
        tailroom = skb_tailroom(skb);

        /* When (len + EEM_HLEN + ETH_FCS_LEN) % in->maxpacket) is 0,
         * stick two bytes of zero-length EEM packet on the end.
         */
        if (((len + EEM_HLEN + ETH_FCS_LEN) % in->maxpacket) == 0)
                padlen += 2;

        if ((tailroom >= (ETH_FCS_LEN + padlen)) &&
                        (headroom >= EEM_HLEN) && !skb_cloned(skb))
                goto done;

        skb2 = skb_copy_expand(skb, EEM_HLEN, ETH_FCS_LEN + padlen, GFP_ATOMIC);
        dev_kfree_skb_any(skb);
        skb = skb2;
        if (!skb)
                return skb;

done:
        /* use the "no CRC" option */
        put_unaligned_be32(0xdeadbeef, skb_put(skb, 4));

        /* EEM packet header format:
         * b0..13:      length of ethernet frame
         * b14:         bmCRC (0 == sentinel CRC)
         * b15:         bmType (0 == data)
         */
        len = skb->len;
        put_unaligned_le16(len & 0x3FFF, skb_push(skb, 2));

        /* add a zero-length EEM packet, if needed */
        if (padlen)
                put_unaligned_le16(0, skb_put(skb, 2));

        return skb;
}

/*
 * Remove the EEM header.  Note that there can be many EEM packets in a single
 * USB transfer, so we need to break them out and handle them independently.
 */
static int eem_unwrap(struct gether *port,
                        struct sk_buff *skb,
                        struct sk_buff_head *list)
{
        struct usb_composite_dev        *cdev = port->func.config->cdev;
        int                             status = 0;

        do {
                struct sk_buff  *skb2;
                u16             header;
                u16             len = 0;

                if (skb->len < EEM_HLEN) {
                        status = -EINVAL;
                        DBG(cdev, "invalid EEM header\n");
                        goto error;
                }

                /* remove the EEM header */
                header = get_unaligned_le16(skb->data);
                skb_pull(skb, EEM_HLEN);

                /* EEM packet header format:
                 * b0..14:      EEM type dependent (data or command)
                 * b15:         bmType (0 == data, 1 == command)
                 */
                if (header & BIT(15)) {
                        struct usb_request      *req;
                        struct in_context       *ctx;
                        struct usb_ep           *ep;
                        u16                     bmEEMCmd;

                        /* EEM command packet format:
                         * b0..10:      bmEEMCmdParam
                         * b11..13:     bmEEMCmd
                         * b14:         reserved (must be zero)
                         * b15:         bmType (1 == command)
                         */
                        if (header & BIT(14))
                                continue;

                        bmEEMCmd = (header >> 11) & 0x7;
                        switch (bmEEMCmd) {
                        case 0: /* echo */
                                len = header & 0x7FF;
                                if (skb->len < len) {
                                        status = -EOVERFLOW;
                                        goto error;
                                }

                                skb2 = skb_clone(skb, GFP_ATOMIC);
                                if (unlikely(!skb2)) {
                                        DBG(cdev, "EEM echo response error\n");
                                        goto next;
                                }
                                skb_trim(skb2, len);
                                put_unaligned_le16(BIT(15) | BIT(11) | len,
                                                        skb_push(skb2, 2));

                                ep = port->in_ep;
                                req = usb_ep_alloc_request(ep, GFP_ATOMIC);
                                if (!req) {
                                        dev_kfree_skb_any(skb2);
                                        goto next;
                                }

                                req->buf = kmalloc(skb2->len, GFP_KERNEL);
                                if (!req->buf) {
                                        usb_ep_free_request(ep, req);
                                        dev_kfree_skb_any(skb2);
                                        goto next;
                                }

                                ctx = kmalloc_obj(*ctx);
                                if (!ctx) {
                                        kfree(req->buf);
                                        usb_ep_free_request(ep, req);
                                        dev_kfree_skb_any(skb2);
                                        goto next;
                                }
                                ctx->skb = skb2;
                                ctx->ep = ep;

                                skb_copy_bits(skb2, 0, req->buf, skb2->len);
                                req->length = skb2->len;
                                req->complete = eem_cmd_complete;
                                req->zero = 1;
                                req->context = ctx;
                                if (usb_ep_queue(port->in_ep, req, GFP_ATOMIC)) {
                                        DBG(cdev, "echo response queue fail\n");
                                        kfree(ctx);
                                        kfree(req->buf);
                                        usb_ep_free_request(ep, req);
                                        dev_kfree_skb_any(skb2);
                                }
                                break;

                        case 1:  /* echo response */
                        case 2:  /* suspend hint */
                        case 3:  /* response hint */
                        case 4:  /* response complete hint */
                        case 5:  /* tickle */
                        default: /* reserved */
                                continue;
                        }
                } else {
                        u32             crc, crc2;
                        struct sk_buff  *skb3;

                        /* check for zero-length EEM packet */
                        if (header == 0)
                                continue;

                        /* EEM data packet format:
                         * b0..13:      length of ethernet frame
                         * b14:         bmCRC (0 == sentinel, 1 == calculated)
                         * b15:         bmType (0 == data)
                         */
                        len = header & 0x3FFF;
                        if ((skb->len < len)
                                        || (len < (ETH_HLEN + ETH_FCS_LEN))) {
                                status = -EINVAL;
                                goto error;
                        }

                        /* validate CRC */
                        if (header & BIT(14)) {
                                crc = get_unaligned_le32(skb->data + len
                                                        - ETH_FCS_LEN);
                                crc2 = ~crc32_le(~0,
                                                skb->data, len - ETH_FCS_LEN);
                        } else {
                                crc = get_unaligned_be32(skb->data + len
                                                        - ETH_FCS_LEN);
                                crc2 = 0xdeadbeef;
                        }
                        if (crc != crc2) {
                                DBG(cdev, "invalid EEM CRC\n");
                                goto next;
                        }

                        skb2 = skb_clone(skb, GFP_ATOMIC);
                        if (unlikely(!skb2)) {
                                DBG(cdev, "unable to unframe EEM packet\n");
                                goto next;
                        }
                        skb_trim(skb2, len - ETH_FCS_LEN);

                        skb3 = skb_copy_expand(skb2,
                                                NET_IP_ALIGN,
                                                0,
                                                GFP_ATOMIC);
                        if (unlikely(!skb3)) {
                                dev_kfree_skb_any(skb2);
                                goto next;
                        }
                        dev_kfree_skb_any(skb2);
                        skb_queue_tail(list, skb3);
                }
next:
                skb_pull(skb, len);
        } while (skb->len);

error:
        dev_kfree_skb_any(skb);
        return status;
}

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

/* f_eem_item_ops */
USB_ETHERNET_CONFIGFS_ITEM(eem);

/* f_eem_opts_dev_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(eem);

/* f_eem_opts_host_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(eem);

/* f_eem_opts_qmult */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(eem);

/* f_eem_opts_ifname */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(eem);

static struct configfs_attribute *eem_attrs[] = {
        &eem_opts_attr_dev_addr,
        &eem_opts_attr_host_addr,
        &eem_opts_attr_qmult,
        &eem_opts_attr_ifname,
        NULL,
};

static const struct config_item_type eem_func_type = {
        .ct_item_ops    = &eem_item_ops,
        .ct_attrs       = eem_attrs,
        .ct_owner       = THIS_MODULE,
};

static void eem_free_inst(struct usb_function_instance *f)
{
        struct f_eem_opts *opts;

        opts = container_of(f, struct f_eem_opts, func_inst);
        if (device_is_registered(&opts->net->dev))
                gether_cleanup(netdev_priv(opts->net));
        else
                free_netdev(opts->net);
        kfree(opts);
}

static struct usb_function_instance *eem_alloc_inst(void)
{
        struct f_eem_opts *opts;

        opts = kzalloc_obj(*opts);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = eem_free_inst;
        opts->net = gether_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, "", &eem_func_type);

        return &opts->func_inst;
}

static void eem_free(struct usb_function *f)
{
        struct f_eem *eem;
        struct f_eem_opts *opts;

        eem = func_to_eem(f);
        opts = container_of(f->fi, struct f_eem_opts, func_inst);
        kfree(eem);
        mutex_lock(&opts->lock);
        opts->refcnt--;
        mutex_unlock(&opts->lock);
}

static void eem_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_eem_opts *opts;

        DBG(c->cdev, "eem unbind\n");

        opts = container_of(f->fi, struct f_eem_opts, func_inst);

        usb_free_all_descriptors(f);

        opts->bind_count--;
        if (opts->bind_count == 0 && !opts->bound)
                gether_detach_gadget(opts->net);
}

static struct usb_function *eem_alloc(struct usb_function_instance *fi)
{
        struct f_eem    *eem;
        struct f_eem_opts *opts;

        /* allocate and initialize one new instance */
        eem = kzalloc_obj(*eem);
        if (!eem)
                return ERR_PTR(-ENOMEM);

        opts = container_of(fi, struct f_eem_opts, func_inst);
        mutex_lock(&opts->lock);
        opts->refcnt++;

        eem->port.ioport = netdev_priv(opts->net);
        mutex_unlock(&opts->lock);
        eem->port.cdc_filter = DEFAULT_FILTER;

        eem->port.func.name = "cdc_eem";
        /* descriptors are per-instance copies */
        eem->port.func.bind = eem_bind;
        eem->port.func.unbind = eem_unbind;
        eem->port.func.set_alt = eem_set_alt;
        eem->port.func.setup = eem_setup;
        eem->port.func.disable = eem_disable;
        eem->port.func.free_func = eem_free;
        eem->port.wrap = eem_wrap;
        eem->port.unwrap = eem_unwrap;
        eem->port.header_len = EEM_HLEN;

        return &eem->port.func;
}

DECLARE_USB_FUNCTION_INIT(eem, eem_alloc_inst, eem_alloc);
MODULE_DESCRIPTION("USB CDC Ethernet (EEM) link function driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");