// SPDX-License-Identifier: GPL-2.0+
/*
 * f_ncm.c -- USB CDC Network (NCM) link function driver
 *
 * Copyright (C) 2010 Nokia Corporation
 * Contact: Yauheni Kaliuta <yauheni.kaliuta@nokia.com>
 *
 * The driver borrows from f_ecm.c which is:
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2008 Nokia Corporation
 */

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

#include <linux/usb/cdc.h>
#include <linux/usb/gadget.h>

#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_ncm.h"
#include "configfs.h"

/*
 * This function is a "CDC Network Control Model" (CDC NCM) Ethernet link.
 * NCM is intended to be used with high-speed network attachments.
 *
 * Note that NCM 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.
 */

/* to trigger crc/non-crc ndp signature */

#define NCM_NDP_HDR_CRC         0x01000000

enum ncm_notify_state {
        NCM_NOTIFY_NONE,                /* don't notify */
        NCM_NOTIFY_CONNECT,             /* issue CONNECT next */
        NCM_NOTIFY_SPEED,               /* issue SPEED_CHANGE next */
};

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

        char                            ethaddr[14];

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

        const struct ndp_parser_opts    *parser_opts;
        bool                            is_crc;
        u32                             ndp_sign;

        /*
         * for notification, it is accessed from both
         * callback and ethernet open/close
         */
        spinlock_t                      lock;

        struct net_device               *netdev;

        /* For multi-frame NDP TX */
        struct sk_buff                  *skb_tx_data;
        struct sk_buff                  *skb_tx_ndp;
        u16                             ndp_dgram_count;
        struct hrtimer                  task_timer;
};

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

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

/*
 * We cannot group frames so use just the minimal size which ok to put
 * one max-size ethernet frame.
 * If the host can group frames, allow it to do that, 16K is selected,
 * because it's used by default by the current linux host driver
 */
#define NTB_DEFAULT_IN_SIZE     16384
#define NTB_OUT_SIZE            16384

/* Allocation for storing the NDP, 32 should suffice for a
 * 16k packet. This allows a maximum of 32 * 507 Byte packets to
 * be transmitted in a single 16kB skb, though when sending full size
 * packets this limit will be plenty.
 * Smaller packets are not likely to be trying to maximize the
 * throughput and will be mstly sending smaller infrequent frames.
 */
#define TX_MAX_NUM_DPE          32

/* Delay for the transmit to wait before sending an unfilled NTB frame. */
#define TX_TIMEOUT_NSECS        300000

/*
 * Although max mtu as dictated by u_ether is 15412 bytes, setting
 * max_segment_size to 15426 would not be efficient. If user chooses segment
 * size to be (>= 8192), then we can't aggregate more than one buffer in each
 * NTB (assuming each packet coming from network layer is >= 8192 bytes) as ep
 * maxpacket limit is 16384. So let max_segment_size be limited to 8000 to allow
 * at least 2 packets to be aggregated reducing wastage of NTB buffer space
 */
#define MAX_DATAGRAM_SIZE       8000

#define FORMATS_SUPPORTED       (USB_CDC_NCM_NTB16_SUPPORTED |  \
                                 USB_CDC_NCM_NTB32_SUPPORTED)

static struct usb_cdc_ncm_ntb_parameters ntb_parameters = {
        .wLength = cpu_to_le16(sizeof(ntb_parameters)),
        .bmNtbFormatsSupported = cpu_to_le16(FORMATS_SUPPORTED),
        .dwNtbInMaxSize = cpu_to_le32(NTB_DEFAULT_IN_SIZE),
        .wNdpInDivisor = cpu_to_le16(4),
        .wNdpInPayloadRemainder = cpu_to_le16(0),
        .wNdpInAlignment = cpu_to_le16(4),

        .dwNtbOutMaxSize = cpu_to_le32(NTB_OUT_SIZE),
        .wNdpOutDivisor = cpu_to_le16(4),
        .wNdpOutPayloadRemainder = cpu_to_le16(0),
        .wNdpOutAlignment = cpu_to_le16(4),
};

/*
 * 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.
 */

#define NCM_STATUS_INTERVAL_MS          32
#define NCM_STATUS_BYTECOUNT            16      /* 8 byte header + data */

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

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

/* interface descriptor: */

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

        /* .bInterfaceNumber = DYNAMIC */
        .bNumEndpoints =        1,
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_NCM,
        .bInterfaceProtocol =   USB_CDC_PROTO_NONE,
        /* .iInterface = DYNAMIC */
};

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

        .bcdCDC =               cpu_to_le16(0x0110),
};

static struct usb_cdc_union_desc ncm_union_desc = {
        .bLength =              sizeof(ncm_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 */
        .wNumberMCFilters =     cpu_to_le16(0),
        .bNumberPowerFilters =  0,
};

#define NCAPS   (USB_CDC_NCM_NCAP_ETH_FILTER | USB_CDC_NCM_NCAP_CRC_MODE)

static struct usb_cdc_ncm_desc ncm_desc = {
        .bLength =              sizeof ncm_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_NCM_TYPE,

        .bcdNcmVersion =        cpu_to_le16(0x0100),
        /* can process SetEthernetPacketFilter */
        .bmNetworkCapabilities = NCAPS,
};

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

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

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

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

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

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

/* full speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(NCM_STATUS_BYTECOUNT),
        .bInterval =            NCM_STATUS_INTERVAL_MS,
};

static struct usb_endpoint_descriptor fs_ncm_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_ncm_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 *ncm_fs_function[] = {
        (struct usb_descriptor_header *) &ncm_iad_desc,
        /* CDC NCM control descriptors */
        (struct usb_descriptor_header *) &ncm_control_intf,
        (struct usb_descriptor_header *) &ncm_header_desc,
        (struct usb_descriptor_header *) &ncm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,
        (struct usb_descriptor_header *) &ncm_desc,
        (struct usb_descriptor_header *) &fs_ncm_notify_desc,
        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ncm_data_nop_intf,
        (struct usb_descriptor_header *) &ncm_data_intf,
        (struct usb_descriptor_header *) &fs_ncm_in_desc,
        (struct usb_descriptor_header *) &fs_ncm_out_desc,
        NULL,
};

/* high speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(NCM_STATUS_BYTECOUNT),
        .bInterval =            USB_MS_TO_HS_INTERVAL(NCM_STATUS_INTERVAL_MS),
};
static struct usb_endpoint_descriptor hs_ncm_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_ncm_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 *ncm_hs_function[] = {
        (struct usb_descriptor_header *) &ncm_iad_desc,
        /* CDC NCM control descriptors */
        (struct usb_descriptor_header *) &ncm_control_intf,
        (struct usb_descriptor_header *) &ncm_header_desc,
        (struct usb_descriptor_header *) &ncm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,
        (struct usb_descriptor_header *) &ncm_desc,
        (struct usb_descriptor_header *) &hs_ncm_notify_desc,
        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ncm_data_nop_intf,
        (struct usb_descriptor_header *) &ncm_data_intf,
        (struct usb_descriptor_header *) &hs_ncm_in_desc,
        (struct usb_descriptor_header *) &hs_ncm_out_desc,
        NULL,
};


/* super speed support: */

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

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       cpu_to_le16(NCM_STATUS_BYTECOUNT),
        .bInterval =            USB_MS_TO_HS_INTERVAL(NCM_STATUS_INTERVAL_MS)
};

static struct usb_ss_ep_comp_descriptor ss_ncm_notify_comp_desc = {
        .bLength =              sizeof(ss_ncm_notify_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(NCM_STATUS_BYTECOUNT),
};

static struct usb_endpoint_descriptor ss_ncm_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_ncm_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_ncm_bulk_comp_desc = {
        .bLength =              sizeof(ss_ncm_bulk_comp_desc),
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,

        /* the following 2 values can be tweaked if necessary */
        .bMaxBurst =            15,
        /* .bmAttributes =      0, */
};

static struct usb_descriptor_header *ncm_ss_function[] = {
        (struct usb_descriptor_header *) &ncm_iad_desc,
        /* CDC NCM control descriptors */
        (struct usb_descriptor_header *) &ncm_control_intf,
        (struct usb_descriptor_header *) &ncm_header_desc,
        (struct usb_descriptor_header *) &ncm_union_desc,
        (struct usb_descriptor_header *) &ecm_desc,
        (struct usb_descriptor_header *) &ncm_desc,
        (struct usb_descriptor_header *) &ss_ncm_notify_desc,
        (struct usb_descriptor_header *) &ss_ncm_notify_comp_desc,
        /* data interface, altsettings 0 and 1 */
        (struct usb_descriptor_header *) &ncm_data_nop_intf,
        (struct usb_descriptor_header *) &ncm_data_intf,
        (struct usb_descriptor_header *) &ss_ncm_in_desc,
        (struct usb_descriptor_header *) &ss_ncm_bulk_comp_desc,
        (struct usb_descriptor_header *) &ss_ncm_out_desc,
        (struct usb_descriptor_header *) &ss_ncm_bulk_comp_desc,
        NULL,
};

/* string descriptors: */

#define STRING_CTRL_IDX 0
#define STRING_MAC_IDX  1
#define STRING_DATA_IDX 2
#define STRING_IAD_IDX  3

static struct usb_string ncm_string_defs[] = {
        [STRING_CTRL_IDX].s = "CDC Network Control Model (NCM)",
        [STRING_MAC_IDX].s = "",
        [STRING_DATA_IDX].s = "CDC Network Data",
        [STRING_IAD_IDX].s = "CDC NCM",
        {  } /* end of list */
};

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

static struct usb_gadget_strings *ncm_strings[] = {
        &ncm_string_table,
        NULL,
};

/*
 * Here are options for NCM Datagram Pointer table (NDP) parser.
 * There are 2 different formats: NDP16 and NDP32 in the spec (ch. 3),
 * in NDP16 offsets and sizes fields are 1 16bit word wide,
 * in NDP32 -- 2 16bit words wide. Also signatures are different.
 * To make the parser code the same, put the differences in the structure,
 * and switch pointers to the structures when the format is changed.
 */

struct ndp_parser_opts {
        u32             nth_sign;
        u32             ndp_sign;
        unsigned        nth_size;
        unsigned        ndp_size;
        unsigned        dpe_size;
        unsigned        ndplen_align;
        /* sizes in u16 units */
        unsigned        dgram_item_len; /* index or length */
        unsigned        block_length;
        unsigned        ndp_index;
        unsigned        reserved1;
        unsigned        reserved2;
        unsigned        next_ndp_index;
};

static const struct ndp_parser_opts ndp16_opts = {
        .nth_sign = USB_CDC_NCM_NTH16_SIGN,
        .ndp_sign = USB_CDC_NCM_NDP16_NOCRC_SIGN,
        .nth_size = sizeof(struct usb_cdc_ncm_nth16),
        .ndp_size = sizeof(struct usb_cdc_ncm_ndp16),
        .dpe_size = sizeof(struct usb_cdc_ncm_dpe16),
        .ndplen_align = 4,
        .dgram_item_len = 1,
        .block_length = 1,
        .ndp_index = 1,
        .reserved1 = 0,
        .reserved2 = 0,
        .next_ndp_index = 1,
};

static const struct ndp_parser_opts ndp32_opts = {
        .nth_sign = USB_CDC_NCM_NTH32_SIGN,
        .ndp_sign = USB_CDC_NCM_NDP32_NOCRC_SIGN,
        .nth_size = sizeof(struct usb_cdc_ncm_nth32),
        .ndp_size = sizeof(struct usb_cdc_ncm_ndp32),
        .dpe_size = sizeof(struct usb_cdc_ncm_dpe32),
        .ndplen_align = 8,
        .dgram_item_len = 2,
        .block_length = 2,
        .ndp_index = 2,
        .reserved1 = 1,
        .reserved2 = 2,
        .next_ndp_index = 2,
};

static inline void put_ncm(__le16 **p, unsigned size, unsigned val)
{
        switch (size) {
        case 1:
                put_unaligned_le16((u16)val, *p);
                break;
        case 2:
                put_unaligned_le32((u32)val, *p);

                break;
        default:
                BUG();
        }

        *p += size;
}

static inline unsigned get_ncm(__le16 **p, unsigned size)
{
        unsigned tmp;

        switch (size) {
        case 1:
                tmp = get_unaligned_le16(*p);
                break;
        case 2:
                tmp = get_unaligned_le32(*p);
                break;
        default:
                BUG();
        }

        *p += size;
        return tmp;
}

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

static inline void ncm_reset_values(struct f_ncm *ncm)
{
        ncm->parser_opts = &ndp16_opts;
        ncm->is_crc = false;
        ncm->ndp_sign = ncm->parser_opts->ndp_sign;
        ncm->port.cdc_filter = DEFAULT_FILTER;

        /* doesn't make sense for ncm, fixed size used */
        ncm->port.header_len = 0;

        ncm->port.fixed_out_len = le32_to_cpu(ntb_parameters.dwNtbOutMaxSize);
        ncm->port.fixed_in_len = NTB_DEFAULT_IN_SIZE;
}

/*
 * Context: ncm->lock held
 */
static void ncm_do_notify(struct f_ncm *ncm)
{
        struct usb_request              *req = ncm->notify_req;
        struct usb_cdc_notification     *event;
        struct usb_composite_dev        *cdev = ncm->port.func.config->cdev;
        __le32                          *data;
        int                             status;

        /* notification already in flight? */
        if (atomic_read(&ncm->notify_count))
                return;

        event = req->buf;
        switch (ncm->notify_state) {
        case NCM_NOTIFY_NONE:
                return;

        case NCM_NOTIFY_CONNECT:
                event->bNotificationType = USB_CDC_NOTIFY_NETWORK_CONNECTION;
                if (ncm->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",
                                str_true_false(ncm->is_open));
                ncm->notify_state = NCM_NOTIFY_NONE;
                break;

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

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

                DBG(cdev, "notify speed %u\n", gether_bitrate(cdev->gadget));
                ncm->notify_state = NCM_NOTIFY_CONNECT;
                break;
        }
        event->bmRequestType = 0xA1;
        event->wIndex = cpu_to_le16(ncm->ctrl_id);

        atomic_inc(&ncm->notify_count);

        /*
         * In double buffering if there is a space in FIFO,
         * completion callback can be called right after the call,
         * so unlocking
         */
        spin_unlock(&ncm->lock);
        status = usb_ep_queue(ncm->notify, req, GFP_ATOMIC);
        spin_lock(&ncm->lock);
        if (status < 0) {
                atomic_dec(&ncm->notify_count);
                DBG(cdev, "notify --> %d\n", status);
        }
}

/*
 * Context: ncm->lock held
 */
static void ncm_notify(struct f_ncm *ncm)
{
        /*
         * 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.
         *
         * If ncm_notify() is called before the second (CONNECT)
         * notification is sent, then it will reset to send the SPEED
         * notificaion again (and again, and again), but it's not a problem
         */
        ncm->notify_state = NCM_NOTIFY_SPEED;
        ncm_do_notify(ncm);
}

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

        spin_lock(&ncm->lock);
        switch (req->status) {
        case 0:
                VDBG(cdev, "Notification %02x sent\n",
                     event->bNotificationType);
                atomic_dec(&ncm->notify_count);
                break;
        case -ECONNRESET:
        case -ESHUTDOWN:
                atomic_set(&ncm->notify_count, 0);
                ncm->notify_state = NCM_NOTIFY_NONE;
                break;
        default:
                DBG(cdev, "event %02x --> %d\n",
                        event->bNotificationType, req->status);
                atomic_dec(&ncm->notify_count);
                break;
        }
        ncm_do_notify(ncm);
        spin_unlock(&ncm->lock);
}

static void ncm_ep0out_complete(struct usb_ep *ep, struct usb_request *req)
{
        /* now for SET_NTB_INPUT_SIZE only */
        unsigned                in_size;
        struct usb_function     *f = req->context;
        struct f_ncm            *ncm = func_to_ncm(f);
        struct usb_composite_dev *cdev = f->config->cdev;

        req->context = NULL;
        if (req->status || req->actual != req->length) {
                DBG(cdev, "Bad control-OUT transfer\n");
                goto invalid;
        }

        in_size = get_unaligned_le32(req->buf);
        if (in_size < USB_CDC_NCM_NTB_MIN_IN_SIZE ||
            in_size > le32_to_cpu(ntb_parameters.dwNtbInMaxSize)) {
                DBG(cdev, "Got wrong INPUT SIZE (%d) from host\n", in_size);
                goto invalid;
        }

        ncm->port.fixed_in_len = in_size;
        VDBG(cdev, "Set NTB INPUT SIZE %d\n", in_size);
        return;

invalid:
        usb_ep_set_halt(ep);
        return;
}

static int ncm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
        struct f_ncm            *ncm = func_to_ncm(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 != ncm->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...
                 */
                ncm->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:
         */

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_GET_NTB_PARAMETERS:

                if (w_length == 0 || w_value != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                value = w_length > sizeof ntb_parameters ?
                        sizeof ntb_parameters : w_length;
                memcpy(req->buf, &ntb_parameters, value);
                VDBG(cdev, "Host asked NTB parameters\n");
                break;

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_GET_NTB_INPUT_SIZE:

                if (w_length < 4 || w_value != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                put_unaligned_le32(ncm->port.fixed_in_len, req->buf);
                value = 4;
                VDBG(cdev, "Host asked INPUT SIZE, sending %d\n",
                     ncm->port.fixed_in_len);
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_SET_NTB_INPUT_SIZE:
        {
                if (w_length != 4 || w_value != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                req->complete = ncm_ep0out_complete;
                req->length = w_length;
                req->context = f;

                value = req->length;
                break;
        }

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_GET_NTB_FORMAT:
        {
                uint16_t format;

                if (w_length < 2 || w_value != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                format = (ncm->parser_opts == &ndp16_opts) ? 0x0000 : 0x0001;
                put_unaligned_le16(format, req->buf);
                value = 2;
                VDBG(cdev, "Host asked NTB FORMAT, sending %d\n", format);
                break;
        }

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_SET_NTB_FORMAT:
        {
                if (w_length != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                switch (w_value) {
                case 0x0000:
                        ncm->parser_opts = &ndp16_opts;
                        DBG(cdev, "NCM16 selected\n");
                        break;
                case 0x0001:
                        ncm->parser_opts = &ndp32_opts;
                        DBG(cdev, "NCM32 selected\n");
                        break;
                default:
                        goto invalid;
                }
                value = 0;
                break;
        }
        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_GET_CRC_MODE:
        {
                uint16_t is_crc;

                if (w_length < 2 || w_value != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                is_crc = ncm->is_crc ? 0x0001 : 0x0000;
                put_unaligned_le16(is_crc, req->buf);
                value = 2;
                VDBG(cdev, "Host asked CRC MODE, sending %d\n", is_crc);
                break;
        }

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
                | USB_CDC_SET_CRC_MODE:
        {
                if (w_length != 0 || w_index != ncm->ctrl_id)
                        goto invalid;
                switch (w_value) {
                case 0x0000:
                        ncm->is_crc = false;
                        DBG(cdev, "non-CRC mode selected\n");
                        break;
                case 0x0001:
                        ncm->is_crc = true;
                        DBG(cdev, "CRC mode selected\n");
                        break;
                default:
                        goto invalid;
                }
                value = 0;
                break;
        }

        /* and disabled in ncm descriptor: */
        /* case USB_CDC_GET_NET_ADDRESS: */
        /* case USB_CDC_SET_NET_ADDRESS: */
        /* case USB_CDC_GET_MAX_DATAGRAM_SIZE: */
        /* case USB_CDC_SET_MAX_DATAGRAM_SIZE: */

        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);
        }
        ncm->ndp_sign = ncm->parser_opts->ndp_sign |
                (ncm->is_crc ? NCM_NDP_HDR_CRC : 0);

        /* respond with data transfer or status phase? */
        if (value >= 0) {
                DBG(cdev, "ncm 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, "ncm req %02x.%02x response err %d\n",
                                        ctrl->bRequestType, ctrl->bRequest,
                                        value);
        }

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


static int ncm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_ncm            *ncm = func_to_ncm(f);
        struct usb_composite_dev *cdev = f->config->cdev;

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

                DBG(cdev, "reset ncm control %d\n", intf);
                usb_ep_disable(ncm->notify);

                if (!(ncm->notify->desc)) {
                        DBG(cdev, "init ncm ctrl %d\n", intf);
                        if (config_ep_by_speed(cdev->gadget, f, ncm->notify))
                                goto fail;
                }
                usb_ep_enable(ncm->notify);

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

                if (ncm->netdev) {
                        DBG(cdev, "reset ncm\n");
                        ncm->netdev = NULL;
                        gether_disconnect(&ncm->port);
                        ncm_reset_values(ncm);
                }

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

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

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

                spin_lock(&ncm->lock);
                ncm_notify(ncm);
                spin_unlock(&ncm->lock);
        } else
                goto fail;

        return 0;
fail:
        return -EINVAL;
}

/*
 * Because the data interface supports multiple altsettings,
 * this NCM function *MUST* implement a get_alt() method.
 */
static int ncm_get_alt(struct usb_function *f, unsigned intf)
{
        struct f_ncm            *ncm = func_to_ncm(f);

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

static struct sk_buff *package_for_tx(struct f_ncm *ncm)
{
        __le16          *ntb_iter;
        struct sk_buff  *skb2 = NULL;
        unsigned        ndp_pad;
        unsigned        ndp_index;
        unsigned        new_len;

        const struct ndp_parser_opts *opts = ncm->parser_opts;
        const int ndp_align = le16_to_cpu(ntb_parameters.wNdpInAlignment);
        const int dgram_idx_len = 2 * 2 * opts->dgram_item_len;

        /* Stop the timer */
        hrtimer_try_to_cancel(&ncm->task_timer);

        ndp_pad = ALIGN(ncm->skb_tx_data->len, ndp_align) -
                        ncm->skb_tx_data->len;
        ndp_index = ncm->skb_tx_data->len + ndp_pad;
        new_len = ndp_index + dgram_idx_len + ncm->skb_tx_ndp->len;

        /* Set the final BlockLength and wNdpIndex */
        ntb_iter = (void *) ncm->skb_tx_data->data;
        /* Increment pointer to BlockLength */
        ntb_iter += 2 + 1 + 1;
        put_ncm(&ntb_iter, opts->block_length, new_len);
        put_ncm(&ntb_iter, opts->ndp_index, ndp_index);

        /* Set the final NDP wLength */
        new_len = opts->ndp_size +
                        (ncm->ndp_dgram_count * dgram_idx_len);
        ncm->ndp_dgram_count = 0;
        /* Increment from start to wLength */
        ntb_iter = (void *) ncm->skb_tx_ndp->data;
        ntb_iter += 2;
        put_unaligned_le16(new_len, ntb_iter);

        /* Merge the skbs */
        swap(skb2, ncm->skb_tx_data);
        if (ncm->skb_tx_data) {
                dev_consume_skb_any(ncm->skb_tx_data);
                ncm->skb_tx_data = NULL;
        }

        /* Insert NDP alignment. */
        skb_put_zero(skb2, ndp_pad);

        /* Copy NTB across. */
        skb_put_data(skb2, ncm->skb_tx_ndp->data, ncm->skb_tx_ndp->len);
        dev_consume_skb_any(ncm->skb_tx_ndp);
        ncm->skb_tx_ndp = NULL;

        /* Insert zero'd datagram. */
        skb_put_zero(skb2, dgram_idx_len);

        return skb2;
}

static struct sk_buff *ncm_wrap_ntb(struct gether *port,
                                    struct sk_buff *skb)
{
        struct f_ncm    *ncm = func_to_ncm(&port->func);
        struct sk_buff  *skb2 = NULL;

        if (skb) {
                int             ncb_len = 0;
                __le16          *ntb_data;
                __le16          *ntb_ndp;
                int             dgram_pad;

                unsigned        max_size = ncm->port.fixed_in_len;
                const struct ndp_parser_opts *opts = ncm->parser_opts;
                const int ndp_align = le16_to_cpu(ntb_parameters.wNdpInAlignment);
                const int div = le16_to_cpu(ntb_parameters.wNdpInDivisor);
                const int rem = le16_to_cpu(ntb_parameters.wNdpInPayloadRemainder);
                const int dgram_idx_len = 2 * 2 * opts->dgram_item_len;

                /* Add the CRC if required up front */
                if (ncm->is_crc) {
                        uint32_t        crc;
                        __le16          *crc_pos;

                        crc = ~crc32_le(~0,
                                        skb->data,
                                        skb->len);
                        crc_pos = skb_put(skb, sizeof(uint32_t));
                        put_unaligned_le32(crc, crc_pos);
                }

                /* If the new skb is too big for the current NCM NTB then
                 * set the current stored skb to be sent now and clear it
                 * ready for new data.
                 * NOTE: Assume maximum align for speed of calculation.
                 */
                if (ncm->skb_tx_data
                    && (ncm->ndp_dgram_count >= TX_MAX_NUM_DPE
                    || (ncm->skb_tx_data->len +
                    div + rem + skb->len +
                    ncm->skb_tx_ndp->len + ndp_align + (2 * dgram_idx_len))
                    > max_size)) {
                        skb2 = package_for_tx(ncm);
                        if (!skb2)
                                goto err;
                }

                if (!ncm->skb_tx_data) {
                        ncb_len = opts->nth_size;
                        dgram_pad = ALIGN(ncb_len, div) + rem - ncb_len;
                        ncb_len += dgram_pad;

                        /* Create a new skb for the NTH and datagrams. */
                        ncm->skb_tx_data = alloc_skb(max_size, GFP_ATOMIC);
                        if (!ncm->skb_tx_data)
                                goto err;

                        ncm->skb_tx_data->dev = ncm->netdev;
                        ntb_data = skb_put_zero(ncm->skb_tx_data, ncb_len);
                        /* dwSignature */
                        put_unaligned_le32(opts->nth_sign, ntb_data);
                        ntb_data += 2;
                        /* wHeaderLength */
                        put_unaligned_le16(opts->nth_size, ntb_data++);

                        /* Allocate an skb for storing the NDP,
                         * TX_MAX_NUM_DPE should easily suffice for a
                         * 16k packet.
                         */
                        ncm->skb_tx_ndp = alloc_skb((int)(opts->ndp_size
                                                    + opts->dpe_size
                                                    * TX_MAX_NUM_DPE),
                                                    GFP_ATOMIC);
                        if (!ncm->skb_tx_ndp)
                                goto err;

                        ncm->skb_tx_ndp->dev = ncm->netdev;
                        ntb_ndp = skb_put(ncm->skb_tx_ndp, opts->ndp_size);
                        memset(ntb_ndp, 0, ncb_len);
                        /* dwSignature */
                        put_unaligned_le32(ncm->ndp_sign, ntb_ndp);
                        ntb_ndp += 2;

                        /* There is always a zeroed entry */
                        ncm->ndp_dgram_count = 1;

                        /* Note: we skip opts->next_ndp_index */

                        /* Start the timer. */
                        hrtimer_start(&ncm->task_timer, TX_TIMEOUT_NSECS,
                                      HRTIMER_MODE_REL_SOFT);
                }

                /* Add the datagram position entries */
                ntb_ndp = skb_put_zero(ncm->skb_tx_ndp, dgram_idx_len);

                ncb_len = ncm->skb_tx_data->len;
                dgram_pad = ALIGN(ncb_len, div) + rem - ncb_len;
                ncb_len += dgram_pad;

                /* (d)wDatagramIndex */
                put_ncm(&ntb_ndp, opts->dgram_item_len, ncb_len);
                /* (d)wDatagramLength */
                put_ncm(&ntb_ndp, opts->dgram_item_len, skb->len);
                ncm->ndp_dgram_count++;

                /* Add the new data to the skb */
                skb_put_zero(ncm->skb_tx_data, dgram_pad);
                skb_put_data(ncm->skb_tx_data, skb->data, skb->len);
                dev_consume_skb_any(skb);
                skb = NULL;

        } else if (ncm->skb_tx_data) {
                /* If we get here ncm_wrap_ntb() was called with NULL skb,
                 * because eth_start_xmit() was called with NULL skb by
                 * ncm_tx_timeout() - hence, this is our signal to flush/send.
                 */
                skb2 = package_for_tx(ncm);
                if (!skb2)
                        goto err;
        }

        return skb2;

err:
        ncm->netdev->stats.tx_dropped++;

        if (skb)
                dev_kfree_skb_any(skb);
        if (ncm->skb_tx_data)
                dev_kfree_skb_any(ncm->skb_tx_data);
        if (ncm->skb_tx_ndp)
                dev_kfree_skb_any(ncm->skb_tx_ndp);

        return NULL;
}

/*
 * The transmit should only be run if no skb data has been sent
 * for a certain duration.
 */
static enum hrtimer_restart ncm_tx_timeout(struct hrtimer *data)
{
        struct f_ncm *ncm = container_of(data, struct f_ncm, task_timer);
        struct net_device *netdev = READ_ONCE(ncm->netdev);

        if (netdev) {
                /* XXX This allowance of a NULL skb argument to ndo_start_xmit
                 * XXX is not sane.  The gadget layer should be redesigned so
                 * XXX that the dev->wrap() invocations to build SKBs is transparent
                 * XXX and performed in some way outside of the ndo_start_xmit
                 * XXX interface.
                 *
                 * This will call directly into u_ether's eth_start_xmit()
                 */
                netdev->netdev_ops->ndo_start_xmit(NULL, netdev);
        }
        return HRTIMER_NORESTART;
}

static int ncm_unwrap_ntb(struct gether *port,
                          struct sk_buff *skb,
                          struct sk_buff_head *list)
{
        struct f_ncm    *ncm = func_to_ncm(&port->func);
        unsigned char   *ntb_ptr = skb->data;
        __le16          *tmp;
        unsigned        index, index2;
        int             ndp_index;
        unsigned        dg_len, dg_len2;
        unsigned        ndp_len;
        unsigned        block_len;
        struct sk_buff  *skb2;
        int             ret = -EINVAL;
        unsigned        ntb_max = le32_to_cpu(ntb_parameters.dwNtbOutMaxSize);
        unsigned        frame_max;
        const struct ndp_parser_opts *opts = ncm->parser_opts;
        unsigned        crc_len = ncm->is_crc ? sizeof(uint32_t) : 0;
        int             dgram_counter;
        int             to_process = skb->len;
        struct f_ncm_opts *ncm_opts;

        ncm_opts = container_of(port->func.fi, struct f_ncm_opts, func_inst);
        frame_max = ncm_opts->max_segment_size;

parse_ntb:
        tmp = (__le16 *)ntb_ptr;

        /* dwSignature */
        if (get_unaligned_le32(tmp) != opts->nth_sign) {
                INFO(port->func.config->cdev, "Wrong NTH SIGN, skblen %d\n",
                        skb->len);
                print_hex_dump(KERN_INFO, "HEAD:", DUMP_PREFIX_ADDRESS, 32, 1,
                               skb->data, 32, false);

                goto err;
        }
        tmp += 2;
        /* wHeaderLength */
        if (get_unaligned_le16(tmp++) != opts->nth_size) {
                INFO(port->func.config->cdev, "Wrong NTB headersize\n");
                goto err;
        }
        tmp++; /* skip wSequence */

        block_len = get_ncm(&tmp, opts->block_length);
        /* (d)wBlockLength */
        if (block_len > ntb_max) {
                INFO(port->func.config->cdev, "OUT size exceeded\n");
                goto err;
        }

        ndp_index = get_ncm(&tmp, opts->ndp_index);

        /* Run through all the NDP's in the NTB */
        do {
                /*
                 * NCM 3.2
                 * dwNdpIndex
                 */
                if (((ndp_index % 4) != 0) ||
                                (ndp_index < opts->nth_size) ||
                                (ndp_index > (block_len -
                                              opts->ndp_size))) {
                        INFO(port->func.config->cdev, "Bad index: %#X\n",
                             ndp_index);
                        goto err;
                }

                /*
                 * walk through NDP
                 * dwSignature
                 */
                tmp = (__le16 *)(ntb_ptr + ndp_index);
                if (get_unaligned_le32(tmp) != ncm->ndp_sign) {
                        INFO(port->func.config->cdev, "Wrong NDP SIGN\n");
                        goto err;
                }
                tmp += 2;

                ndp_len = get_unaligned_le16(tmp++);
                /*
                 * NCM 3.3.1
                 * wLength
                 * entry is 2 items
                 * item size is 16/32 bits, opts->dgram_item_len * 2 bytes
                 * minimal: struct usb_cdc_ncm_ndpX + normal entry + zero entry
                 * Each entry is a dgram index and a dgram length.
                 */
                if ((ndp_len < opts->ndp_size
                                + 2 * 2 * (opts->dgram_item_len * 2)) ||
                                (ndp_len % opts->ndplen_align != 0)) {
                        INFO(port->func.config->cdev, "Bad NDP length: %#X\n",
                             ndp_len);
                        goto err;
                }
                tmp += opts->reserved1;
                /* Check for another NDP (d)wNextNdpIndex */
                ndp_index = get_ncm(&tmp, opts->next_ndp_index);
                tmp += opts->reserved2;

                ndp_len -= opts->ndp_size;
                index2 = get_ncm(&tmp, opts->dgram_item_len);
                dg_len2 = get_ncm(&tmp, opts->dgram_item_len);
                dgram_counter = 0;

                do {
                        index = index2;
                        /* wDatagramIndex[0] */
                        if ((index < opts->nth_size) ||
                                        (index > block_len - opts->dpe_size)) {
                                INFO(port->func.config->cdev,
                                     "Bad index: %#X\n", index);
                                goto err;
                        }

                        dg_len = dg_len2;
                        /*
                         * wDatagramLength[0]
                         * ethernet hdr + crc or larger than max frame size
                         */
                        if ((dg_len < 14 + crc_len) ||
                                        (dg_len > frame_max)) {
                                INFO(port->func.config->cdev,
                                     "Bad dgram length: %#X\n", dg_len);
                                goto err;
                        }
                        if (ncm->is_crc) {
                                uint32_t crc, crc2;

                                crc = get_unaligned_le32(ntb_ptr +
                                                         index + dg_len -
                                                         crc_len);
                                crc2 = ~crc32_le(~0,
                                                 ntb_ptr + index,
                                                 dg_len - crc_len);
                                if (crc != crc2) {
                                        INFO(port->func.config->cdev,
                                             "Bad CRC\n");
                                        goto err;
                                }
                        }

                        index2 = get_ncm(&tmp, opts->dgram_item_len);
                        dg_len2 = get_ncm(&tmp, opts->dgram_item_len);

                        /* wDatagramIndex[1] */
                        if (index2 > block_len - opts->dpe_size) {
                                INFO(port->func.config->cdev,
                                     "Bad index: %#X\n", index2);
                                goto err;
                        }

                        /*
                         * Copy the data into a new skb.
                         * This ensures the truesize is correct
                         */
                        skb2 = netdev_alloc_skb_ip_align(ncm->netdev,
                                                         dg_len - crc_len);
                        if (skb2 == NULL)
                                goto err;
                        skb_put_data(skb2, ntb_ptr + index,
                                     dg_len - crc_len);

                        skb_queue_tail(list, skb2);

                        ndp_len -= 2 * (opts->dgram_item_len * 2);

                        dgram_counter++;
                        if (index2 == 0 || dg_len2 == 0)
                                break;
                } while (ndp_len > 2 * (opts->dgram_item_len * 2));
        } while (ndp_index);

        VDBG(port->func.config->cdev,
             "Parsed NTB with %d frames\n", dgram_counter);

        to_process -= block_len;

        /*
         * Windows NCM driver avoids USB ZLPs by adding a 1-byte
         * zero pad as needed.
         */
        if (to_process == 1 &&
            (*(unsigned char *)(ntb_ptr + block_len) == 0x00)) {
                to_process--;
        } else if ((to_process > 0) && (block_len != 0)) {
                ntb_ptr = (unsigned char *)(ntb_ptr + block_len);
                goto parse_ntb;
        }

        dev_consume_skb_any(skb);

        return 0;
err:
        skb_queue_purge(list);
        dev_kfree_skb_any(skb);
        return ret;
}

static void ncm_disable(struct usb_function *f)
{
        struct f_ncm            *ncm = func_to_ncm(f);
        struct usb_composite_dev *cdev = f->config->cdev;

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

        if (ncm->netdev) {
                ncm->netdev = NULL;
                gether_disconnect(&ncm->port);
        }

        if (ncm->notify->enabled) {
                usb_ep_disable(ncm->notify);
                ncm->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 ncm_open(struct gether *geth)
{
        struct f_ncm            *ncm = func_to_ncm(&geth->func);

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

        spin_lock(&ncm->lock);
        ncm->is_open = true;
        ncm_notify(ncm);
        spin_unlock(&ncm->lock);
}

static void ncm_close(struct gether *geth)
{
        struct f_ncm            *ncm = func_to_ncm(&geth->func);

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

        spin_lock(&ncm->lock);
        ncm->is_open = false;
        ncm_notify(ncm);
        spin_unlock(&ncm->lock);
}

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

/* ethernet function driver setup/binding */

static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct f_ncm            *ncm = func_to_ncm(f);
        struct usb_string       *us;
        int                     status = 0;
        struct usb_ep           *ep;
        struct f_ncm_opts       *ncm_opts;

        struct usb_os_desc_table        *os_desc_table __free(kfree) = NULL;
        struct net_device               *net __free(detach_gadget) = NULL;
        struct usb_request              *request __free(free_usb_request) = NULL;

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

        ncm_opts = container_of(f->fi, struct f_ncm_opts, func_inst);

        if (cdev->use_os_string) {
                os_desc_table = kzalloc(sizeof(*os_desc_table), GFP_KERNEL);
                if (!os_desc_table)
                        return -ENOMEM;
        }

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

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

        ncm_string_defs[1].s = ncm->ethaddr;

        us = usb_gstrings_attach(cdev, ncm_strings,
                                 ARRAY_SIZE(ncm_string_defs));
        if (IS_ERR(us))
                return PTR_ERR(us);

        ncm_control_intf.iInterface = us[STRING_CTRL_IDX].id;
        ncm_data_nop_intf.iInterface = us[STRING_DATA_IDX].id;
        ncm_data_intf.iInterface = us[STRING_DATA_IDX].id;
        ecm_desc.iMACAddress = us[STRING_MAC_IDX].id;
        ncm_iad_desc.iFunction = us[STRING_IAD_IDX].id;

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

        ncm_control_intf.bInterfaceNumber = status;
        ncm_union_desc.bMasterInterface0 = status;

        status = usb_interface_id(c, f);
        if (status < 0)
                return status;
        ncm->data_id = status;

        ncm_data_nop_intf.bInterfaceNumber = status;
        ncm_data_intf.bInterfaceNumber = status;
        ncm_union_desc.bSlaveInterface0 = status;

        ecm_desc.wMaxSegmentSize = cpu_to_le16(ncm_opts->max_segment_size);

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

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

        ep = usb_ep_autoconfig(cdev->gadget, &fs_ncm_notify_desc);
        if (!ep)
                return -ENODEV;
        ncm->notify = ep;

        /* allocate notification request and buffer */
        request = usb_ep_alloc_request(ep, GFP_KERNEL);
        if (!request)
                return -ENOMEM;
        request->buf = kmalloc(NCM_STATUS_BYTECOUNT, GFP_KERNEL);
        if (!request->buf)
                return -ENOMEM;
        request->context = ncm;
        request->complete = ncm_notify_complete;

        /*
         * support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
         * both speeds
         */
        hs_ncm_in_desc.bEndpointAddress = fs_ncm_in_desc.bEndpointAddress;
        hs_ncm_out_desc.bEndpointAddress = fs_ncm_out_desc.bEndpointAddress;
        hs_ncm_notify_desc.bEndpointAddress =
                fs_ncm_notify_desc.bEndpointAddress;

        ss_ncm_in_desc.bEndpointAddress = fs_ncm_in_desc.bEndpointAddress;
        ss_ncm_out_desc.bEndpointAddress = fs_ncm_out_desc.bEndpointAddress;
        ss_ncm_notify_desc.bEndpointAddress =
                fs_ncm_notify_desc.bEndpointAddress;

        status = usb_assign_descriptors(f, ncm_fs_function, ncm_hs_function,
                        ncm_ss_function, ncm_ss_function);
        if (status)
                return status;

        /*
         * 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().
         */

        ncm->port.open = ncm_open;
        ncm->port.close = ncm_close;

        hrtimer_setup(&ncm->task_timer, ncm_tx_timeout, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);

        if (cdev->use_os_string) {
                os_desc_table[0].os_desc = &ncm_opts->ncm_os_desc;
                os_desc_table[0].if_id = ncm_iad_desc.bFirstInterface;
                f->os_desc_table = no_free_ptr(os_desc_table);
                f->os_desc_n = 1;
        }
        ncm->notify_req = no_free_ptr(request);

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

        DBG(cdev, "CDC Network: IN/%s OUT/%s NOTIFY/%s\n",
                        ncm->port.in_ep->name, ncm->port.out_ep->name,
                        ncm->notify->name);
        return 0;
}

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

/* f_ncm_item_ops */
USB_ETHERNET_CONFIGFS_ITEM(ncm);

/* f_ncm_opts_dev_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(ncm);

/* f_ncm_opts_host_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(ncm);

/* f_ncm_opts_qmult */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(ncm);

/* f_ncm_opts_ifname */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(ncm);

static ssize_t ncm_opts_max_segment_size_show(struct config_item *item,
                                              char *page)
{
        struct f_ncm_opts *opts = to_f_ncm_opts(item);
        u16 segment_size;

        mutex_lock(&opts->lock);
        segment_size = opts->max_segment_size;
        mutex_unlock(&opts->lock);

        return sysfs_emit(page, "%u\n", segment_size);
}

static ssize_t ncm_opts_max_segment_size_store(struct config_item *item,
                                               const char *page, size_t len)
{
        struct f_ncm_opts *opts = to_f_ncm_opts(item);
        u16 segment_size;
        int ret;

        mutex_lock(&opts->lock);
        if (opts->refcnt) {
                ret = -EBUSY;
                goto out;
        }

        ret = kstrtou16(page, 0, &segment_size);
        if (ret)
                goto out;

        if (segment_size > MAX_DATAGRAM_SIZE) {
                ret = -EINVAL;
                goto out;
        }

        opts->max_segment_size = segment_size;
        ret = len;
out:
        mutex_unlock(&opts->lock);
        return ret;
}

CONFIGFS_ATTR(ncm_opts_, max_segment_size);

static struct configfs_attribute *ncm_attrs[] = {
        &ncm_opts_attr_dev_addr,
        &ncm_opts_attr_host_addr,
        &ncm_opts_attr_qmult,
        &ncm_opts_attr_ifname,
        &ncm_opts_attr_max_segment_size,
        NULL,
};

static const struct config_item_type ncm_func_type = {
        .ct_item_ops    = &ncm_item_ops,
        .ct_attrs       = ncm_attrs,
        .ct_owner       = THIS_MODULE,
};

static void ncm_free_inst(struct usb_function_instance *f)
{
        struct f_ncm_opts *opts;

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

static struct usb_function_instance *ncm_alloc_inst(void)
{
        struct f_ncm_opts *opts;
        struct usb_os_desc *descs[1];
        char *names[1];
        struct config_group *ncm_interf_group;

        opts = kzalloc_obj(*opts);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        opts->ncm_os_desc.ext_compat_id = opts->ncm_ext_compat_id;

        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = ncm_free_inst;
        opts->net = gether_setup_default();
        if (IS_ERR(opts->net)) {
                struct net_device *net = opts->net;
                kfree(opts);
                return ERR_CAST(net);
        }
        opts->max_segment_size = ETH_FRAME_LEN;
        INIT_LIST_HEAD(&opts->ncm_os_desc.ext_prop);

        descs[0] = &opts->ncm_os_desc;
        names[0] = "ncm";

        config_group_init_type_name(&opts->func_inst.group, "", &ncm_func_type);
        ncm_interf_group =
                usb_os_desc_prepare_interf_dir(&opts->func_inst.group, 1, descs,
                                               names, THIS_MODULE);
        if (IS_ERR(ncm_interf_group)) {
                ncm_free_inst(&opts->func_inst);
                return ERR_CAST(ncm_interf_group);
        }
        opts->ncm_interf_group = ncm_interf_group;

        return &opts->func_inst;
}

static void ncm_free(struct usb_function *f)
{
        struct f_ncm *ncm;
        struct f_ncm_opts *opts;

        ncm = func_to_ncm(f);
        opts = container_of(f->fi, struct f_ncm_opts, func_inst);
        kfree(ncm);
        mutex_lock(&opts->lock);
        opts->refcnt--;
        mutex_unlock(&opts->lock);
}

static void ncm_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_ncm *ncm = func_to_ncm(f);
        struct f_ncm_opts *ncm_opts;

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

        ncm_opts = container_of(f->fi, struct f_ncm_opts, func_inst);

        hrtimer_cancel(&ncm->task_timer);

        kfree(f->os_desc_table);
        f->os_desc_n = 0;

        ncm_string_defs[0].id = 0;
        usb_free_all_descriptors(f);

        if (atomic_read(&ncm->notify_count)) {
                usb_ep_dequeue(ncm->notify, ncm->notify_req);
                atomic_set(&ncm->notify_count, 0);
        }

        kfree(ncm->notify_req->buf);
        usb_ep_free_request(ncm->notify, ncm->notify_req);

        ncm_opts->bind_count--;
        if (ncm_opts->bind_count == 0)
                gether_detach_gadget(ncm_opts->net);
}

static struct usb_function *ncm_alloc(struct usb_function_instance *fi)
{
        struct f_ncm            *ncm;
        struct f_ncm_opts       *opts;
        int status;

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

        opts = container_of(fi, struct f_ncm_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, ncm->ethaddr,
                                      sizeof(ncm->ethaddr));
        if (status < 12) { /* strlen("01234567890a") */
                kfree(ncm);
                mutex_unlock(&opts->lock);
                return ERR_PTR(-EINVAL);
        }

        spin_lock_init(&ncm->lock);
        ncm_reset_values(ncm);
        ncm->port.ioport = netdev_priv(opts->net);
        mutex_unlock(&opts->lock);
        ncm->port.is_fixed = true;
        ncm->port.supports_multi_frame = true;

        ncm->port.func.name = "cdc_network";
        /* descriptors are per-instance copies */
        ncm->port.func.bind = ncm_bind;
        ncm->port.func.unbind = ncm_unbind;
        ncm->port.func.set_alt = ncm_set_alt;
        ncm->port.func.get_alt = ncm_get_alt;
        ncm->port.func.setup = ncm_setup;
        ncm->port.func.disable = ncm_disable;
        ncm->port.func.free_func = ncm_free;

        ncm->port.wrap = ncm_wrap_ntb;
        ncm->port.unwrap = ncm_unwrap_ntb;

        return &ncm->port.func;
}

DECLARE_USB_FUNCTION_INIT(ncm, ncm_alloc_inst, ncm_alloc);
MODULE_DESCRIPTION("USB CDC Network (NCM) link function driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yauheni Kaliuta");