/*
 * f_ecm.c -- USB CDC Ethernet (ECM) link function driver
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2008 Nokia Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

/* #define VERBOSE_DEBUG */

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

#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_ecm.h"


/*
 * This function is a "CDC Ethernet Networking Control Model" (CDC ECM)
 * Ethernet link.  The data transfer model is simple (packets sent and
 * received over bulk endpoints using normal short packet termination),
 * and the control model exposes various data and optional notifications.
 *
 * ECM is well standardized and (except for Microsoft) supported by most
 * operating systems with USB host support.  It's the preferred interop
 * solution for Ethernet over USB, at least for firmware based solutions.
 * (Hardware solutions tend to be more minimalist.)  A newer and simpler
 * "Ethernet Emulation Model" (CDC EEM) hasn't yet caught on.
 *
 * Note that ECM requires the use of "alternate settings" for its data
 * interface.  This means that the set_alt() method has real work to do,
 * and also means that a get_alt() method is required.
 */


enum ecm_notify_state {
        ECM_NOTIFY_NONE,                /* don't notify */
        ECM_NOTIFY_CONNECT,             /* issue CONNECT next */
        ECM_NOTIFY_SPEED,               /* issue SPEED_CHANGE next */
};

struct f_ecm {
        struct gether                   port;
        u8                              ctrl_id, data_id;

        char                            ethaddr[14];

        struct usb_ep                   *notify;
        struct usb_request              *notify_req;
        u8                              notify_state;
        bool                            is_open;

        /* FIXME is_open needs some irq-ish locking
         * ... possibly the same as port.ioport
         */
};

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

/* peak (theoretical) bulk transfer rate in bits-per-second */
static inline unsigned ecm_bitrate(struct usb_gadget *g)
{
        if (gadget_is_superspeed(g) && g->speed == USB_SPEED_SUPER)
                return 13 * 1024 * 8 * 1000 * 8;
        else if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
                return 13 * 512 * 8 * 1000 * 8;
        else
                return 19 * 64 * 1 * 1000 * 8;
}

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

/*
 * Include the status endpoint if we can, even though it's optional.
 *
 * Use wMaxPacketSize big enough to fit CDC_NOTIFY_SPEED_CHANGE in one
 * packet, to simplify cancellation; and a big transfer interval, to
 * waste less bandwidth.
 *
 * Some drivers (like Linux 2.4 cdc-ether!) "need" it to exist even
 * if they ignore the connect/disconnect notifications that real aether
 * can provide.  More advanced cdc configurations might want to support
 * encapsulated commands (vendor-specific, using control-OUT).
 */

#define ECM_STATUS_INTERVAL_MS          32
#define ECM_STATUS_BYTECOUNT            16      /* 8 byte header + data */


/* interface descriptor: */

static struct usb_interface_assoc_descriptor
ecm_iad_descriptor = {
        .bLength =              sizeof ecm_iad_descriptor,
        .bDescriptorType =      USB_DT_INTERFACE_ASSOCIATION,

        /* .bFirstInterface =   DYNAMIC, */
        .bInterfaceCount =      2,      /* control + data */
        .bFunctionClass =       USB_CLASS_COMM,
        .bFunctionSubClass =    USB_CDC_SUBCLASS_ETHERNET,
        .bFunctionProtocol =    USB_CDC_PROTO_NONE,
        /* .iFunction =         DYNAMIC */
};


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

        /* .bInterfaceNumber = DYNAMIC */
        /* status endpoint is optional; this could be patched later */
        .bNumEndpoints =        1,
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_ETHERNET,
        .bInterfaceProtocol =   USB_CDC_PROTO_NONE,
        /* .iInterface = DYNAMIC */
};

static struct usb_cdc_header_desc ecm_header_desc = {
        .bLength =              sizeof ecm_header_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,

        .bcdCDC =               cpu_to_le16(0x0110),
};

static struct usb_cdc_union_desc ecm_union_desc = {
        .bLength =              sizeof(ecm_union_desc),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_UNION_TYPE,
        /* .bMasterInterface0 = DYNAMIC */
        /* .bSlaveInterface0 =  DYNAMIC */
};

static struct usb_cdc_ether_desc ecm_desc = {
        .bLength =              sizeof ecm_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_ETHERNET_TYPE,

        /* this descriptor actually adds value, surprise! */
        /* .iMACAddress = DYNAMIC */
        .bmEthernetStatistics = cpu_to_le32(0), /* no statistics */
        .wMaxSegmentSize =      cpu_to_le16(ETH_FRAME_LEN),
        .wNumberMCFilters =     cpu_to_le16(0),
        .bNumberPowerFilters =  0,
};

/* the default data interface has no endpoints ... */

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

        .bInterfaceNumber =     1,
        .bAlternateSetting =    0,
        .bNumEndpoints =        0,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
        .bInterfaceSubClass =   0,
        .bInterfaceProtocol =   0,
        /* .iInterface = DYNAMIC */
};

/* ... but the "real" data interface has two bulk endpoints */

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

        .bInterfaceNumber =     1,
        .bAlternateSetting =    1,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
        .bInterfaceSubClass =   0,
        .bInterfaceProtocol =   0,
        /* .iInterface = DYNAMIC */
};

/* full speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(ECM_STATUS_BYTECOUNT),
        .bInterval =            ECM_STATUS_INTERVAL_MS,
};

static struct usb_endpoint_descriptor fs_ecm_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 fs_ecm_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 *ecm_fs_function[] = {
        /* CDC ECM control descriptors */
        (struct usb_descriptor_header *) &ecm_iad_descriptor,
        (struct usb_descriptor_header *) &ecm_control_intf,
        (struct usb_descriptor_header *) &ecm_header_desc,
        (struct usb_descriptor_header *) &ecm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,

        /* NOTE: status endpoint might need to be removed */
        (struct usb_descriptor_header *) &fs_ecm_notify_desc,

        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ecm_data_nop_intf,
        (struct usb_descriptor_header *) &ecm_data_intf,
        (struct usb_descriptor_header *) &fs_ecm_in_desc,
        (struct usb_descriptor_header *) &fs_ecm_out_desc,
        NULL,
};

/* high speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(ECM_STATUS_BYTECOUNT),
        .bInterval =            USB_MS_TO_HS_INTERVAL(ECM_STATUS_INTERVAL_MS),
};

static struct usb_endpoint_descriptor hs_ecm_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 hs_ecm_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 *ecm_hs_function[] = {
        /* CDC ECM control descriptors */
        (struct usb_descriptor_header *) &ecm_iad_descriptor,
        (struct usb_descriptor_header *) &ecm_control_intf,
        (struct usb_descriptor_header *) &ecm_header_desc,
        (struct usb_descriptor_header *) &ecm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,

        /* NOTE: status endpoint might need to be removed */
        (struct usb_descriptor_header *) &hs_ecm_notify_desc,

        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ecm_data_nop_intf,
        (struct usb_descriptor_header *) &ecm_data_intf,
        (struct usb_descriptor_header *) &hs_ecm_in_desc,
        (struct usb_descriptor_header *) &hs_ecm_out_desc,
        NULL,
};

/* super speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(ECM_STATUS_BYTECOUNT),
        .bInterval =            USB_MS_TO_HS_INTERVAL(ECM_STATUS_INTERVAL_MS),
};

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

        /* the following 3 values can be tweaked if necessary */
        /* .bMaxBurst =         0, */
        /* .bmAttributes =      0, */
        .wBytesPerInterval =    cpu_to_le16(ECM_STATUS_BYTECOUNT),
};

static struct usb_endpoint_descriptor ss_ecm_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 ss_ecm_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 ss_ecm_bulk_comp_desc = {
        .bLength =              sizeof ss_ecm_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 *ecm_ss_function[] = {
        /* CDC ECM control descriptors */
        (struct usb_descriptor_header *) &ecm_iad_descriptor,
        (struct usb_descriptor_header *) &ecm_control_intf,
        (struct usb_descriptor_header *) &ecm_header_desc,
        (struct usb_descriptor_header *) &ecm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,

        /* NOTE: status endpoint might need to be removed */
        (struct usb_descriptor_header *) &ss_ecm_notify_desc,
        (struct usb_descriptor_header *) &ss_ecm_intr_comp_desc,

        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ecm_data_nop_intf,
        (struct usb_descriptor_header *) &ecm_data_intf,
        (struct usb_descriptor_header *) &ss_ecm_in_desc,
        (struct usb_descriptor_header *) &ss_ecm_bulk_comp_desc,
        (struct usb_descriptor_header *) &ss_ecm_out_desc,
        (struct usb_descriptor_header *) &ss_ecm_bulk_comp_desc,
        NULL,
};

/* string descriptors: */

static struct usb_string ecm_string_defs[] = {
        [0].s = "CDC Ethernet Control Model (ECM)",
        [1].s = "",
        [2].s = "CDC Ethernet Data",
        [3].s = "CDC ECM",
        {  } /* end of list */
};

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

static struct usb_gadget_strings *ecm_strings[] = {
        &ecm_string_table,
        NULL,
};

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

static void ecm_do_notify(struct f_ecm *ecm)
{
        struct usb_request              *req = ecm->notify_req;
        struct usb_cdc_notification     *event;
        struct usb_composite_dev        *cdev = ecm->port.func.config->cdev;
        __le32                          *data;
        int                             status;

        /* notification already in flight? */
        if (!req)
                return;

        event = req->buf;
        switch (ecm->notify_state) {
        case ECM_NOTIFY_NONE:
                return;

        case ECM_NOTIFY_CONNECT:
                event->bNotificationType = USB_CDC_NOTIFY_NETWORK_CONNECTION;
                if (ecm->is_open)
                        event->wValue = cpu_to_le16(1);
                else
                        event->wValue = cpu_to_le16(0);
                event->wLength = 0;
                req->length = sizeof *event;

                DBG(cdev, "notify connect %s\n",
                                ecm->is_open ? "true" : "false");
                ecm->notify_state = ECM_NOTIFY_SPEED;
                break;

        case ECM_NOTIFY_SPEED:
                event->bNotificationType = USB_CDC_NOTIFY_SPEED_CHANGE;
                event->wValue = cpu_to_le16(0);
                event->wLength = cpu_to_le16(8);
                req->length = ECM_STATUS_BYTECOUNT;

                /* SPEED_CHANGE data is up/down speeds in bits/sec */
                data = req->buf + sizeof *event;
                data[0] = cpu_to_le32(ecm_bitrate(cdev->gadget));
                data[1] = data[0];

                DBG(cdev, "notify speed %d\n", ecm_bitrate(cdev->gadget));
                ecm->notify_state = ECM_NOTIFY_NONE;
                break;
        }
        event->bmRequestType = 0xA1;
        event->wIndex = cpu_to_le16(ecm->ctrl_id);

        ecm->notify_req = NULL;
        status = usb_ep_queue(ecm->notify, req, GFP_ATOMIC);
        if (status < 0) {
                ecm->notify_req = req;
                DBG(cdev, "notify --> %d\n", status);
        }
}

static void ecm_notify(struct f_ecm *ecm)
{
        /* NOTE on most versions of Linux, host side cdc-ethernet
         * won't listen for notifications until its netdevice opens.
         * The first notification then sits in the FIFO for a long
         * time, and the second one is queued.
         */
        ecm->notify_state = ECM_NOTIFY_CONNECT;
        ecm_do_notify(ecm);
}

static void ecm_notify_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_ecm                    *ecm = req->context;
        struct usb_composite_dev        *cdev = ecm->port.func.config->cdev;
        struct usb_cdc_notification     *event = req->buf;

        switch (req->status) {
        case 0:
                /* no fault */
                break;
        case -ECONNRESET:
        case -ESHUTDOWN:
                ecm->notify_state = ECM_NOTIFY_NONE;
                break;
        default:
                DBG(cdev, "event %02x --> %d\n",
                        event->bNotificationType, req->status);
                break;
        }
        ecm->notify_req = req;
        ecm_do_notify(ecm);
}

static int ecm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
        struct f_ecm            *ecm = func_to_ecm(f);
        struct usb_composite_dev *cdev = f->config->cdev;
        struct usb_request      *req = cdev->req;
        int                     value = -EOPNOTSUPP;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        /* composite driver infrastructure handles everything except
         * CDC class messages; interface activation uses set_alt().
         */
        switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                        | USB_CDC_SET_ETHERNET_PACKET_FILTER:
                /* see 6.2.30: no data, wIndex = interface,
                 * wValue = packet filter bitmap
                 */
                if (w_length != 0 || w_index != ecm->ctrl_id)
                        goto invalid;
                DBG(cdev, "packet filter %02x\n", w_value);
                /* REVISIT locking of cdc_filter.  This assumes the UDC
                 * driver won't have a concurrent packet TX irq running on
                 * another CPU; or that if it does, this write is atomic...
                 */
                ecm->port.cdc_filter = w_value;
                value = 0;
                break;

        /* and optionally:
         * case USB_CDC_SEND_ENCAPSULATED_COMMAND:
         * case USB_CDC_GET_ENCAPSULATED_RESPONSE:
         * case USB_CDC_SET_ETHERNET_MULTICAST_FILTERS:
         * case USB_CDC_SET_ETHERNET_PM_PATTERN_FILTER:
         * case USB_CDC_GET_ETHERNET_PM_PATTERN_FILTER:
         * case USB_CDC_GET_ETHERNET_STATISTIC:
         */

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

        /* respond with data transfer or status phase? */
        if (value >= 0) {
                DBG(cdev, "ecm req%02x.%02x v%04x i%04x l%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        w_value, w_index, w_length);
                req->zero = 0;
                req->length = value;
                value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
                if (value < 0)
                        ERROR(cdev, "ecm req %02x.%02x response err %d\n",
                                        ctrl->bRequestType, ctrl->bRequest,
                                        value);
        }

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


static int ecm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_ecm            *ecm = func_to_ecm(f);
        struct usb_composite_dev *cdev = f->config->cdev;

        /* Control interface has only altsetting 0 */
        if (intf == ecm->ctrl_id) {
                if (alt != 0)
                        goto fail;

                VDBG(cdev, "reset ecm control %d\n", intf);
                usb_ep_disable(ecm->notify);
                if (!(ecm->notify->desc)) {
                        VDBG(cdev, "init ecm ctrl %d\n", intf);
                        if (config_ep_by_speed(cdev->gadget, f, ecm->notify))
                                goto fail;
                }
                usb_ep_enable(ecm->notify);

        /* Data interface has two altsettings, 0 and 1 */
        } else if (intf == ecm->data_id) {
                if (alt > 1)
                        goto fail;

                if (ecm->port.in_ep->enabled) {
                        DBG(cdev, "reset ecm\n");
                        gether_disconnect(&ecm->port);
                }

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

                /* CDC Ethernet only sends data in non-default altsettings.
                 * Changing altsettings resets filters, statistics, etc.
                 */
                if (alt == 1) {
                        struct net_device       *net;

                        /* Enable zlps by default for ECM conformance;
                         * override for musb_hdrc (avoids txdma ovhead).
                         */
                        ecm->port.is_zlp_ok =
                                gadget_is_zlp_supported(cdev->gadget);
                        ecm->port.cdc_filter = DEFAULT_FILTER;
                        DBG(cdev, "activate ecm\n");
                        net = gether_connect(&ecm->port);
                        if (IS_ERR(net))
                                return PTR_ERR(net);
                }

                /* NOTE this can be a minor disagreement with the ECM spec,
                 * which says speed notifications will "always" follow
                 * connection notifications.  But we allow one connect to
                 * follow another (if the first is in flight), and instead
                 * just guarantee that a speed notification is always sent.
                 */
                ecm_notify(ecm);
        } else
                goto fail;

        return 0;
fail:
        return -EINVAL;
}

/* Because the data interface supports multiple altsettings,
 * this ECM function *MUST* implement a get_alt() method.
 */
static int ecm_get_alt(struct usb_function *f, unsigned intf)
{
        struct f_ecm            *ecm = func_to_ecm(f);

        if (intf == ecm->ctrl_id)
                return 0;
        return ecm->port.in_ep->enabled ? 1 : 0;
}

static void ecm_disable(struct usb_function *f)
{
        struct f_ecm            *ecm = func_to_ecm(f);
        struct usb_composite_dev *cdev = f->config->cdev;

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

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

        usb_ep_disable(ecm->notify);
        ecm->notify->desc = NULL;
}

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

/*
 * Callbacks let us notify the host about connect/disconnect when the
 * net device is opened or closed.
 *
 * For testing, note that link states on this side include both opened
 * and closed variants of:
 *
 *   - disconnected/unconfigured
 *   - configured but inactive (data alt 0)
 *   - configured and active (data alt 1)
 *
 * Each needs to be tested with unplug, rmmod, SET_CONFIGURATION, and
 * SET_INTERFACE (altsetting).  Remember also that "configured" doesn't
 * imply the host is actually polling the notification endpoint, and
 * likewise that "active" doesn't imply it's actually using the data
 * endpoints for traffic.
 */

static void ecm_open(struct gether *geth)
{
        struct f_ecm            *ecm = func_to_ecm(&geth->func);

        DBG(ecm->port.func.config->cdev, "%s\n", __func__);

        ecm->is_open = true;
        ecm_notify(ecm);
}

static void ecm_close(struct gether *geth)
{
        struct f_ecm            *ecm = func_to_ecm(&geth->func);

        DBG(ecm->port.func.config->cdev, "%s\n", __func__);

        ecm->is_open = false;
        ecm_notify(ecm);
}

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

/* ethernet function driver setup/binding */

static int
ecm_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct f_ecm            *ecm = func_to_ecm(f);
        struct usb_string       *us;
        int                     status;
        struct usb_ep           *ep;

        struct f_ecm_opts       *ecm_opts;

        if (!can_support_ecm(cdev->gadget))
                return -EINVAL;

        ecm_opts = container_of(f->fi, struct f_ecm_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 ecm_opts->bound access
         */
        if (!ecm_opts->bound) {
                mutex_lock(&ecm_opts->lock);
                gether_set_gadget(ecm_opts->net, cdev->gadget);
                status = gether_register_netdev(ecm_opts->net);
                mutex_unlock(&ecm_opts->lock);
                if (status)
                        return status;
                ecm_opts->bound = true;
        }

        us = usb_gstrings_attach(cdev, ecm_strings,
                                 ARRAY_SIZE(ecm_string_defs));
        if (IS_ERR(us))
                return PTR_ERR(us);
        ecm_control_intf.iInterface = us[0].id;
        ecm_data_intf.iInterface = us[2].id;
        ecm_desc.iMACAddress = us[1].id;
        ecm_iad_descriptor.iFunction = us[3].id;

        /* allocate instance-specific interface IDs */
        status = usb_interface_id(c, f);
        if (status < 0)
                goto fail;
        ecm->ctrl_id = status;
        ecm_iad_descriptor.bFirstInterface = status;

        ecm_control_intf.bInterfaceNumber = status;
        ecm_union_desc.bMasterInterface0 = status;

        status = usb_interface_id(c, f);
        if (status < 0)
                goto fail;
        ecm->data_id = status;

        ecm_data_nop_intf.bInterfaceNumber = status;
        ecm_data_intf.bInterfaceNumber = status;
        ecm_union_desc.bSlaveInterface0 = status;

        status = -ENODEV;

        /* allocate instance-specific endpoints */
        ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_in_desc);
        if (!ep)
                goto fail;
        ecm->port.in_ep = ep;

        ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_out_desc);
        if (!ep)
                goto fail;
        ecm->port.out_ep = ep;

        /* NOTE:  a status/notification endpoint is *OPTIONAL* but we
         * don't treat it that way.  It's simpler, and some newer CDC
         * profiles (wireless handsets) no longer treat it as optional.
         */
        ep = usb_ep_autoconfig(cdev->gadget, &fs_ecm_notify_desc);
        if (!ep)
                goto fail;
        ecm->notify = ep;

        status = -ENOMEM;

        /* allocate notification request and buffer */
        ecm->notify_req = usb_ep_alloc_request(ep, GFP_KERNEL);
        if (!ecm->notify_req)
                goto fail;
        ecm->notify_req->buf = kmalloc(ECM_STATUS_BYTECOUNT, GFP_KERNEL);
        if (!ecm->notify_req->buf)
                goto fail;
        ecm->notify_req->context = ecm;
        ecm->notify_req->complete = ecm_notify_complete;

        /* support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
         * both speeds
         */
        hs_ecm_in_desc.bEndpointAddress = fs_ecm_in_desc.bEndpointAddress;
        hs_ecm_out_desc.bEndpointAddress = fs_ecm_out_desc.bEndpointAddress;
        hs_ecm_notify_desc.bEndpointAddress =
                fs_ecm_notify_desc.bEndpointAddress;

        ss_ecm_in_desc.bEndpointAddress = fs_ecm_in_desc.bEndpointAddress;
        ss_ecm_out_desc.bEndpointAddress = fs_ecm_out_desc.bEndpointAddress;
        ss_ecm_notify_desc.bEndpointAddress =
                fs_ecm_notify_desc.bEndpointAddress;

        status = usb_assign_descriptors(f, ecm_fs_function, ecm_hs_function,
                        ecm_ss_function, NULL);
        if (status)
                goto fail;

        /* NOTE:  all that is done without knowing or caring about
         * the network link ... which is unavailable to this code
         * until we're activated via set_alt().
         */

        ecm->port.open = ecm_open;
        ecm->port.close = ecm_close;

        DBG(cdev, "CDC Ethernet: %s speed IN/%s OUT/%s NOTIFY/%s\n",
                        gadget_is_superspeed(c->cdev->gadget) ? "super" :
                        gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
                        ecm->port.in_ep->name, ecm->port.out_ep->name,
                        ecm->notify->name);
        return 0;

fail:
        if (ecm->notify_req) {
                kfree(ecm->notify_req->buf);
                usb_ep_free_request(ecm->notify, ecm->notify_req);
        }

        ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);

        return status;
}

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

/* f_ecm_item_ops */
USB_ETHERNET_CONFIGFS_ITEM(ecm);

/* f_ecm_opts_dev_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(ecm);

/* f_ecm_opts_host_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(ecm);

/* f_ecm_opts_qmult */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(ecm);

/* f_ecm_opts_ifname */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(ecm);

static struct configfs_attribute *ecm_attrs[] = {
        &ecm_opts_attr_dev_addr,
        &ecm_opts_attr_host_addr,
        &ecm_opts_attr_qmult,
        &ecm_opts_attr_ifname,
        NULL,
};

static struct config_item_type ecm_func_type = {
        .ct_item_ops    = &ecm_item_ops,
        .ct_attrs       = ecm_attrs,
        .ct_owner       = THIS_MODULE,
};

static void ecm_free_inst(struct usb_function_instance *f)
{
        struct f_ecm_opts *opts;

        opts = container_of(f, struct f_ecm_opts, func_inst);
        if (opts->bound)
                gether_cleanup(netdev_priv(opts->net));
        else
                free_netdev(opts->net);
        kfree(opts);
}

static struct usb_function_instance *ecm_alloc_inst(void)
{
        struct f_ecm_opts *opts;

        opts = kzalloc(sizeof(*opts), GFP_KERNEL);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = ecm_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, "", &ecm_func_type);

        return &opts->func_inst;
}

static void ecm_free(struct usb_function *f)
{
        struct f_ecm *ecm;
        struct f_ecm_opts *opts;

        ecm = func_to_ecm(f);
        opts = container_of(f->fi, struct f_ecm_opts, func_inst);
        kfree(ecm);
        mutex_lock(&opts->lock);
        opts->refcnt--;
        mutex_unlock(&opts->lock);
}

static void ecm_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_ecm            *ecm = func_to_ecm(f);

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

        usb_free_all_descriptors(f);

        kfree(ecm->notify_req->buf);
        usb_ep_free_request(ecm->notify, ecm->notify_req);
}

static struct usb_function *ecm_alloc(struct usb_function_instance *fi)
{
        struct f_ecm    *ecm;
        struct f_ecm_opts *opts;
        int status;

        /* allocate and initialize one new instance */
        ecm = kzalloc(sizeof(*ecm), GFP_KERNEL);
        if (!ecm)
                return ERR_PTR(-ENOMEM);

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

        /* export host's Ethernet address in CDC format */
        status = gether_get_host_addr_cdc(opts->net, ecm->ethaddr,
                                          sizeof(ecm->ethaddr));
        if (status < 12) {
                kfree(ecm);
                mutex_unlock(&opts->lock);
                return ERR_PTR(-EINVAL);
        }
        ecm_string_defs[1].s = ecm->ethaddr;

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

        ecm->port.func.name = "cdc_ethernet";
        /* descriptors are per-instance copies */
        ecm->port.func.bind = ecm_bind;
        ecm->port.func.unbind = ecm_unbind;
        ecm->port.func.set_alt = ecm_set_alt;
        ecm->port.func.get_alt = ecm_get_alt;
        ecm->port.func.setup = ecm_setup;
        ecm->port.func.disable = ecm_disable;
        ecm->port.func.free_func = ecm_free;

        return &ecm->port.func;
}

DECLARE_USB_FUNCTION_INIT(ecm, ecm_alloc_inst, ecm_alloc);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");