/*
 * hdm_usb.c - Hardware dependent module for USB
 *
 * Copyright (C) 2013-2015 Microchip Technology Germany II GmbH & Co. KG
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * This file is licensed under GPLv2.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/usb.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/sysfs.h>
#include <linux/dma-mapping.h>
#include <linux/etherdevice.h>
#include <linux/uaccess.h>
#include "mostcore.h"
#include "networking.h"

#define USB_MTU                 512
#define NO_ISOCHRONOUS_URB      0
#define AV_PACKETS_PER_XACT     2
#define BUF_CHAIN_SIZE          0xFFFF
#define MAX_NUM_ENDPOINTS       30
#define MAX_SUFFIX_LEN          10
#define MAX_STRING_LEN          80
#define MAX_BUF_SIZE            0xFFFF

#define USB_VENDOR_ID_SMSC      0x0424  /* VID: SMSC */
#define USB_DEV_ID_BRDG         0xC001  /* PID: USB Bridge */
#define USB_DEV_ID_OS81118      0xCF18  /* PID: USB OS81118 */
#define USB_DEV_ID_OS81119      0xCF19  /* PID: USB OS81119 */
#define USB_DEV_ID_OS81210      0xCF30  /* PID: USB OS81210 */
/* DRCI Addresses */
#define DRCI_REG_NI_STATE       0x0100
#define DRCI_REG_PACKET_BW      0x0101
#define DRCI_REG_NODE_ADDR      0x0102
#define DRCI_REG_NODE_POS       0x0103
#define DRCI_REG_MEP_FILTER     0x0140
#define DRCI_REG_HASH_TBL0      0x0141
#define DRCI_REG_HASH_TBL1      0x0142
#define DRCI_REG_HASH_TBL2      0x0143
#define DRCI_REG_HASH_TBL3      0x0144
#define DRCI_REG_HW_ADDR_HI     0x0145
#define DRCI_REG_HW_ADDR_MI     0x0146
#define DRCI_REG_HW_ADDR_LO     0x0147
#define DRCI_REG_BASE           0x1100
#define DRCI_COMMAND            0x02
#define DRCI_READ_REQ           0xA0
#define DRCI_WRITE_REQ          0xA1

/**
 * struct most_dci_obj - Direct Communication Interface
 * @kobj:position in sysfs
 * @usb_device: pointer to the usb device
 * @reg_addr: register address for arbitrary DCI access
 */
struct most_dci_obj {
        struct kobject kobj;
        struct usb_device *usb_device;
        u16 reg_addr;
};

#define to_dci_obj(p) container_of(p, struct most_dci_obj, kobj)

struct most_dev;

struct clear_hold_work {
        struct work_struct ws;
        struct most_dev *mdev;
        unsigned int channel;
        int pipe;
};

#define to_clear_hold_work(w) container_of(w, struct clear_hold_work, ws)

/**
 * struct most_dev - holds all usb interface specific stuff
 * @parent: parent object in sysfs
 * @usb_device: pointer to usb device
 * @iface: hardware interface
 * @cap: channel capabilities
 * @conf: channel configuration
 * @dci: direct communication interface of hardware
 * @ep_address: endpoint address table
 * @description: device description
 * @suffix: suffix for channel name
 * @channel_lock: synchronize channel access
 * @padding_active: indicates channel uses padding
 * @is_channel_healthy: health status table of each channel
 * @busy_urbs: list of anchored items
 * @io_mutex: synchronize I/O with disconnect
 * @link_stat_timer: timer for link status reports
 * @poll_work_obj: work for polling link status
 */
struct most_dev {
        struct kobject *parent;
        struct usb_device *usb_device;
        struct most_interface iface;
        struct most_channel_capability *cap;
        struct most_channel_config *conf;
        struct most_dci_obj *dci;
        u8 *ep_address;
        char description[MAX_STRING_LEN];
        char suffix[MAX_NUM_ENDPOINTS][MAX_SUFFIX_LEN];
        spinlock_t channel_lock[MAX_NUM_ENDPOINTS]; /* sync channel access */
        bool padding_active[MAX_NUM_ENDPOINTS];
        bool is_channel_healthy[MAX_NUM_ENDPOINTS];
        struct clear_hold_work clear_work[MAX_NUM_ENDPOINTS];
        struct usb_anchor *busy_urbs;
        struct mutex io_mutex;
        struct timer_list link_stat_timer;
        struct work_struct poll_work_obj;
};

#define to_mdev(d) container_of(d, struct most_dev, iface)
#define to_mdev_from_work(w) container_of(w, struct most_dev, poll_work_obj)

static void wq_clear_halt(struct work_struct *wq_obj);
static void wq_netinfo(struct work_struct *wq_obj);

/**
 * drci_rd_reg - read a DCI register
 * @dev: usb device
 * @reg: register address
 * @buf: buffer to store data
 *
 * This is reads data from INIC's direct register communication interface
 */
static inline int drci_rd_reg(struct usb_device *dev, u16 reg, u16 *buf)
{
        int retval;
        __le16 *dma_buf = kzalloc(sizeof(*dma_buf), GFP_KERNEL);
        u8 req_type = USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE;

        if (!dma_buf)
                return -ENOMEM;

        retval = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
                                 DRCI_READ_REQ, req_type,
                                 0x0000,
                                 reg, dma_buf, sizeof(*dma_buf), 5 * HZ);
        *buf = le16_to_cpu(*dma_buf);
        kfree(dma_buf);

        return retval;
}

/**
 * drci_wr_reg - write a DCI register
 * @dev: usb device
 * @reg: register address
 * @data: data to write
 *
 * This is writes data to INIC's direct register communication interface
 */
static inline int drci_wr_reg(struct usb_device *dev, u16 reg, u16 data)
{
        return usb_control_msg(dev,
                               usb_sndctrlpipe(dev, 0),
                               DRCI_WRITE_REQ,
                               USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               data,
                               reg,
                               NULL,
                               0,
                               5 * HZ);
}

static inline int start_sync_ep(struct usb_device *usb_dev, u16 ep)
{
        return drci_wr_reg(usb_dev, DRCI_REG_BASE + DRCI_COMMAND + ep * 16, 1);
}

/**
 * get_stream_frame_size - calculate frame size of current configuration
 * @cfg: channel configuration
 */
static unsigned int get_stream_frame_size(struct most_channel_config *cfg)
{
        unsigned int frame_size = 0;
        unsigned int sub_size = cfg->subbuffer_size;

        if (!sub_size) {
                pr_warn("Misconfig: Subbuffer size zero.\n");
                return frame_size;
        }
        switch (cfg->data_type) {
        case MOST_CH_ISOC:
                frame_size = AV_PACKETS_PER_XACT * sub_size;
                break;
        case MOST_CH_SYNC:
                if (cfg->packets_per_xact == 0) {
                        pr_warn("Misconfig: Packets per XACT zero\n");
                        frame_size = 0;
                } else if (cfg->packets_per_xact == 0xFF) {
                        frame_size = (USB_MTU / sub_size) * sub_size;
                } else {
                        frame_size = cfg->packets_per_xact * sub_size;
                }
                break;
        default:
                pr_warn("Query frame size of non-streaming channel\n");
                break;
        }
        return frame_size;
}

/**
 * hdm_poison_channel - mark buffers of this channel as invalid
 * @iface: pointer to the interface
 * @channel: channel ID
 *
 * This unlinks all URBs submitted to the HCD,
 * calls the associated completion function of the core and removes
 * them from the list.
 *
 * Returns 0 on success or error code otherwise.
 */
static int hdm_poison_channel(struct most_interface *iface, int channel)
{
        struct most_dev *mdev = to_mdev(iface);
        unsigned long flags;
        spinlock_t *lock; /* temp. lock */

        if (unlikely(!iface)) {
                dev_warn(&mdev->usb_device->dev, "Poison: Bad interface.\n");
                return -EIO;
        }
        if (unlikely(channel < 0 || channel >= iface->num_channels)) {
                dev_warn(&mdev->usb_device->dev, "Channel ID out of range.\n");
                return -ECHRNG;
        }

        lock = mdev->channel_lock + channel;
        spin_lock_irqsave(lock, flags);
        mdev->is_channel_healthy[channel] = false;
        spin_unlock_irqrestore(lock, flags);

        cancel_work_sync(&mdev->clear_work[channel].ws);

        mutex_lock(&mdev->io_mutex);
        usb_kill_anchored_urbs(&mdev->busy_urbs[channel]);
        if (mdev->padding_active[channel])
                mdev->padding_active[channel] = false;

        if (mdev->conf[channel].data_type == MOST_CH_ASYNC) {
                del_timer_sync(&mdev->link_stat_timer);
                cancel_work_sync(&mdev->poll_work_obj);
        }
        mutex_unlock(&mdev->io_mutex);
        return 0;
}

/**
 * hdm_add_padding - add padding bytes
 * @mdev: most device
 * @channel: channel ID
 * @mbo: buffer object
 *
 * This inserts the INIC hardware specific padding bytes into a streaming
 * channel's buffer
 */
static int hdm_add_padding(struct most_dev *mdev, int channel, struct mbo *mbo)
{
        struct most_channel_config *conf = &mdev->conf[channel];
        unsigned int frame_size = get_stream_frame_size(conf);
        unsigned int j, num_frames;
        u16 rd_addr, wr_addr;

        if (!frame_size)
                return -EIO;
        num_frames = mbo->buffer_length / frame_size;

        if (num_frames < 1) {
                dev_err(&mdev->usb_device->dev,
                        "Missed minimal transfer unit.\n");
                return -EIO;
        }

        for (j = 1; j < num_frames; j++) {
                wr_addr = (num_frames - j) * USB_MTU;
                rd_addr = (num_frames - j) * frame_size;
                memmove(mbo->virt_address + wr_addr,
                        mbo->virt_address + rd_addr,
                        frame_size);
        }
        mbo->buffer_length = num_frames * USB_MTU;
        return 0;
}

/**
 * hdm_remove_padding - remove padding bytes
 * @mdev: most device
 * @channel: channel ID
 * @mbo: buffer object
 *
 * This takes the INIC hardware specific padding bytes off a streaming
 * channel's buffer.
 */
static int hdm_remove_padding(struct most_dev *mdev, int channel,
                              struct mbo *mbo)
{
        struct most_channel_config *const conf = &mdev->conf[channel];
        unsigned int frame_size = get_stream_frame_size(conf);
        unsigned int j, num_frames;

        if (!frame_size)
                return -EIO;
        num_frames = mbo->processed_length / USB_MTU;

        for (j = 1; j < num_frames; j++)
                memmove(mbo->virt_address + frame_size * j,
                        mbo->virt_address + USB_MTU * j,
                        frame_size);

        mbo->processed_length = frame_size * num_frames;
        return 0;
}

/**
 * hdm_write_completion - completion function for submitted Tx URBs
 * @urb: the URB that has been completed
 *
 * This checks the status of the completed URB. In case the URB has been
 * unlinked before, it is immediately freed. On any other error the MBO
 * transfer flag is set. On success it frees allocated resources and calls
 * the completion function.
 *
 * Context: interrupt!
 */
static void hdm_write_completion(struct urb *urb)
{
        struct mbo *mbo = urb->context;
        struct most_dev *mdev = to_mdev(mbo->ifp);
        unsigned int channel = mbo->hdm_channel_id;
        struct device *dev = &mdev->usb_device->dev;
        spinlock_t *lock = mdev->channel_lock + channel;
        unsigned long flags;

        spin_lock_irqsave(lock, flags);

        mbo->processed_length = 0;
        mbo->status = MBO_E_INVAL;
        if (likely(mdev->is_channel_healthy[channel])) {
                switch (urb->status) {
                case 0:
                case -ESHUTDOWN:
                        mbo->processed_length = urb->actual_length;
                        mbo->status = MBO_SUCCESS;
                        break;
                case -EPIPE:
                        dev_warn(dev, "Broken OUT pipe detected\n");
                        mdev->is_channel_healthy[channel] = false;
                        mdev->clear_work[channel].pipe = urb->pipe;
                        schedule_work(&mdev->clear_work[channel].ws);
                        break;
                case -ENODEV:
                case -EPROTO:
                        mbo->status = MBO_E_CLOSE;
                        break;
                }
        }

        spin_unlock_irqrestore(lock, flags);

        if (likely(mbo->complete))
                mbo->complete(mbo);
        usb_free_urb(urb);
}

/**
 * hdm_read_completion - completion function for submitted Rx URBs
 * @urb: the URB that has been completed
 *
 * This checks the status of the completed URB. In case the URB has been
 * unlinked before it is immediately freed. On any other error the MBO transfer
 * flag is set. On success it frees allocated resources, removes
 * padding bytes -if necessary- and calls the completion function.
 *
 * Context: interrupt!
 *
 * **************************************************************************
 *                   Error codes returned by in urb->status
 *                   or in iso_frame_desc[n].status (for ISO)
 * *************************************************************************
 *
 * USB device drivers may only test urb status values in completion handlers.
 * This is because otherwise there would be a race between HCDs updating
 * these values on one CPU, and device drivers testing them on another CPU.
 *
 * A transfer's actual_length may be positive even when an error has been
 * reported.  That's because transfers often involve several packets, so that
 * one or more packets could finish before an error stops further endpoint I/O.
 *
 * For isochronous URBs, the urb status value is non-zero only if the URB is
 * unlinked, the device is removed, the host controller is disabled or the total
 * transferred length is less than the requested length and the URB_SHORT_NOT_OK
 * flag is set.  Completion handlers for isochronous URBs should only see
 * urb->status set to zero, -ENOENT, -ECONNRESET, -ESHUTDOWN, or -EREMOTEIO.
 * Individual frame descriptor status fields may report more status codes.
 *
 *
 * 0                    Transfer completed successfully
 *
 * -ENOENT              URB was synchronously unlinked by usb_unlink_urb
 *
 * -EINPROGRESS         URB still pending, no results yet
 *                      (That is, if drivers see this it's a bug.)
 *
 * -EPROTO (*, **)      a) bitstuff error
 *                      b) no response packet received within the
 *                         prescribed bus turn-around time
 *                      c) unknown USB error
 *
 * -EILSEQ (*, **)      a) CRC mismatch
 *                      b) no response packet received within the
 *                         prescribed bus turn-around time
 *                      c) unknown USB error
 *
 *                      Note that often the controller hardware does not
 *                      distinguish among cases a), b), and c), so a
 *                      driver cannot tell whether there was a protocol
 *                      error, a failure to respond (often caused by
 *                      device disconnect), or some other fault.
 *
 * -ETIME (**)          No response packet received within the prescribed
 *                      bus turn-around time.  This error may instead be
 *                      reported as -EPROTO or -EILSEQ.
 *
 * -ETIMEDOUT           Synchronous USB message functions use this code
 *                      to indicate timeout expired before the transfer
 *                      completed, and no other error was reported by HC.
 *
 * -EPIPE (**)          Endpoint stalled.  For non-control endpoints,
 *                      reset this status with usb_clear_halt().
 *
 * -ECOMM               During an IN transfer, the host controller
 *                      received data from an endpoint faster than it
 *                      could be written to system memory
 *
 * -ENOSR               During an OUT transfer, the host controller
 *                      could not retrieve data from system memory fast
 *                      enough to keep up with the USB data rate
 *
 * -EOVERFLOW (*)       The amount of data returned by the endpoint was
 *                      greater than either the max packet size of the
 *                      endpoint or the remaining buffer size.  "Babble".
 *
 * -EREMOTEIO           The data read from the endpoint did not fill the
 *                      specified buffer, and URB_SHORT_NOT_OK was set in
 *                      urb->transfer_flags.
 *
 * -ENODEV              Device was removed.  Often preceded by a burst of
 *                      other errors, since the hub driver doesn't detect
 *                      device removal events immediately.
 *
 * -EXDEV               ISO transfer only partially completed
 *                      (only set in iso_frame_desc[n].status, not urb->status)
 *
 * -EINVAL              ISO madness, if this happens: Log off and go home
 *
 * -ECONNRESET          URB was asynchronously unlinked by usb_unlink_urb
 *
 * -ESHUTDOWN           The device or host controller has been disabled due
 *                      to some problem that could not be worked around,
 *                      such as a physical disconnect.
 *
 *
 * (*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
 * hardware problems such as bad devices (including firmware) or cables.
 *
 * (**) This is also one of several codes that different kinds of host
 * controller use to indicate a transfer has failed because of device
 * disconnect.  In the interval before the hub driver starts disconnect
 * processing, devices may receive such fault reports for every request.
 *
 * See <https://www.kernel.org/doc/Documentation/usb/error-codes.txt>
 */
static void hdm_read_completion(struct urb *urb)
{
        struct mbo *mbo = urb->context;
        struct most_dev *mdev = to_mdev(mbo->ifp);
        unsigned int channel = mbo->hdm_channel_id;
        struct device *dev = &mdev->usb_device->dev;
        spinlock_t *lock = mdev->channel_lock + channel;
        unsigned long flags;

        spin_lock_irqsave(lock, flags);

        mbo->processed_length = 0;
        mbo->status = MBO_E_INVAL;
        if (likely(mdev->is_channel_healthy[channel])) {
                switch (urb->status) {
                case 0:
                case -ESHUTDOWN:
                        mbo->processed_length = urb->actual_length;
                        mbo->status = MBO_SUCCESS;
                        if (mdev->padding_active[channel] &&
                            hdm_remove_padding(mdev, channel, mbo)) {
                                mbo->processed_length = 0;
                                mbo->status = MBO_E_INVAL;
                        }
                        break;
                case -EPIPE:
                        dev_warn(dev, "Broken IN pipe detected\n");
                        mdev->is_channel_healthy[channel] = false;
                        mdev->clear_work[channel].pipe = urb->pipe;
                        schedule_work(&mdev->clear_work[channel].ws);
                        break;
                case -ENODEV:
                case -EPROTO:
                        mbo->status = MBO_E_CLOSE;
                        break;
                case -EOVERFLOW:
                        dev_warn(dev, "Babble on IN pipe detected\n");
                        break;
                }
        }

        spin_unlock_irqrestore(lock, flags);

        if (likely(mbo->complete))
                mbo->complete(mbo);
        usb_free_urb(urb);
}

/**
 * hdm_enqueue - receive a buffer to be used for data transfer
 * @iface: interface to enqueue to
 * @channel: ID of the channel
 * @mbo: pointer to the buffer object
 *
 * This allocates a new URB and fills it according to the channel
 * that is being used for transmission of data. Before the URB is
 * submitted it is stored in the private anchor list.
 *
 * Returns 0 on success. On any error the URB is freed and a error code
 * is returned.
 *
 * Context: Could in _some_ cases be interrupt!
 */
static int hdm_enqueue(struct most_interface *iface, int channel,
                       struct mbo *mbo)
{
        struct most_dev *mdev;
        struct most_channel_config *conf;
        struct device *dev;
        int retval = 0;
        struct urb *urb;
        unsigned long length;
        void *virt_address;

        if (unlikely(!iface || !mbo))
                return -EIO;
        if (unlikely(iface->num_channels <= channel || channel < 0))
                return -ECHRNG;

        mdev = to_mdev(iface);
        conf = &mdev->conf[channel];
        dev = &mdev->usb_device->dev;

        if (!mdev->usb_device)
                return -ENODEV;

        urb = usb_alloc_urb(NO_ISOCHRONOUS_URB, GFP_ATOMIC);
        if (!urb)
                return -ENOMEM;

        if ((conf->direction & MOST_CH_TX) && mdev->padding_active[channel] &&
            hdm_add_padding(mdev, channel, mbo)) {
                retval = -EIO;
                goto _error;
        }

        urb->transfer_dma = mbo->bus_address;
        virt_address = mbo->virt_address;
        length = mbo->buffer_length;

        if (conf->direction & MOST_CH_TX) {
                usb_fill_bulk_urb(urb, mdev->usb_device,
                                  usb_sndbulkpipe(mdev->usb_device,
                                                  mdev->ep_address[channel]),
                                  virt_address,
                                  length,
                                  hdm_write_completion,
                                  mbo);
                if (conf->data_type != MOST_CH_ISOC)
                        urb->transfer_flags |= URB_ZERO_PACKET;
        } else {
                usb_fill_bulk_urb(urb, mdev->usb_device,
                                  usb_rcvbulkpipe(mdev->usb_device,
                                                  mdev->ep_address[channel]),
                                  virt_address,
                                  length + conf->extra_len,
                                  hdm_read_completion,
                                  mbo);
        }
        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

        usb_anchor_urb(urb, &mdev->busy_urbs[channel]);

        retval = usb_submit_urb(urb, GFP_KERNEL);
        if (retval) {
                dev_err(dev, "URB submit failed with error %d.\n", retval);
                goto _error_1;
        }
        return 0;

_error_1:
        usb_unanchor_urb(urb);
_error:
        usb_free_urb(urb);
        return retval;
}

/**
 * hdm_configure_channel - receive channel configuration from core
 * @iface: interface
 * @channel: channel ID
 * @conf: structure that holds the configuration information
 *
 * The attached network interface controller (NIC) supports a padding mode
 * to avoid short packets on USB, hence increasing the performance due to a
 * lower interrupt load. This mode is default for synchronous data and can
 * be switched on for isochronous data. In case padding is active the
 * driver needs to know the frame size of the payload in order to calculate
 * the number of bytes it needs to pad when transmitting or to cut off when
 * receiving data.
 *
 */
static int hdm_configure_channel(struct most_interface *iface, int channel,
                                 struct most_channel_config *conf)
{
        unsigned int num_frames;
        unsigned int frame_size;
        unsigned int temp_size;
        unsigned int tail_space;
        struct most_dev *mdev = to_mdev(iface);
        struct device *dev = &mdev->usb_device->dev;

        mdev->is_channel_healthy[channel] = true;
        mdev->clear_work[channel].channel = channel;
        mdev->clear_work[channel].mdev = mdev;
        INIT_WORK(&mdev->clear_work[channel].ws, wq_clear_halt);

        if (unlikely(!iface || !conf)) {
                dev_err(dev, "Bad interface or config pointer.\n");
                return -EINVAL;
        }
        if (unlikely(channel < 0 || channel >= iface->num_channels)) {
                dev_err(dev, "Channel ID out of range.\n");
                return -EINVAL;
        }
        if (!conf->num_buffers || !conf->buffer_size) {
                dev_err(dev, "Misconfig: buffer size or #buffers zero.\n");
                return -EINVAL;
        }

        if (conf->data_type != MOST_CH_SYNC &&
            !(conf->data_type == MOST_CH_ISOC &&
              conf->packets_per_xact != 0xFF)) {
                mdev->padding_active[channel] = false;
                /*
                 * Since the NIC's padding mode is not going to be
                 * used, we can skip the frame size calculations and
                 * move directly on to exit.
                 */
                goto exit;
        }

        mdev->padding_active[channel] = true;
        temp_size = conf->buffer_size;

        frame_size = get_stream_frame_size(conf);
        if (frame_size == 0 || frame_size > USB_MTU) {
                dev_warn(dev, "Misconfig: frame size wrong\n");
                return -EINVAL;
        }

        if (conf->buffer_size % frame_size) {
                u16 tmp_val;

                tmp_val = conf->buffer_size / frame_size;
                conf->buffer_size = tmp_val * frame_size;
                dev_notice(dev,
                           "Channel %d - rounding buffer size to %d bytes, channel config says %d bytes\n",
                           channel,
                           conf->buffer_size,
                           temp_size);
        }

        num_frames = conf->buffer_size / frame_size;
        tail_space = num_frames * (USB_MTU - frame_size);
        temp_size += tail_space;

        /* calculate extra length to comply w/ HW padding */
        conf->extra_len = (DIV_ROUND_UP(temp_size, USB_MTU) * USB_MTU)
                          - conf->buffer_size;
exit:
        mdev->conf[channel] = *conf;
        if (conf->data_type == MOST_CH_ASYNC) {
                u16 ep = mdev->ep_address[channel];

                if (start_sync_ep(mdev->usb_device, ep) < 0)
                        dev_warn(dev, "sync for ep%02x failed", ep);
        }
        return 0;
}

/**
 * hdm_request_netinfo - request network information
 * @iface: pointer to interface
 * @channel: channel ID
 *
 * This is used as trigger to set up the link status timer that
 * polls for the NI state of the INIC every 2 seconds.
 *
 */
static void hdm_request_netinfo(struct most_interface *iface, int channel)
{
        struct most_dev *mdev;

        BUG_ON(!iface);
        mdev = to_mdev(iface);
        mdev->link_stat_timer.expires = jiffies + HZ;
        mod_timer(&mdev->link_stat_timer, mdev->link_stat_timer.expires);
}

/**
 * link_stat_timer_handler - schedule work obtaining mac address and link status
 * @data: pointer to USB device instance
 *
 * The handler runs in interrupt context. That's why we need to defer the
 * tasks to a work queue.
 */
static void link_stat_timer_handler(unsigned long data)
{
        struct most_dev *mdev = (struct most_dev *)data;

        schedule_work(&mdev->poll_work_obj);
        mdev->link_stat_timer.expires = jiffies + (2 * HZ);
        add_timer(&mdev->link_stat_timer);
}

/**
 * wq_netinfo - work queue function to deliver latest networking information
 * @wq_obj: object that holds data for our deferred work to do
 *
 * This retrieves the network interface status of the USB INIC
 */
static void wq_netinfo(struct work_struct *wq_obj)
{
        struct most_dev *mdev = to_mdev_from_work(wq_obj);
        struct usb_device *usb_device = mdev->usb_device;
        struct device *dev = &usb_device->dev;
        u16 hi, mi, lo, link;
        u8 hw_addr[6];

        if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_HI, &hi) < 0) {
                dev_err(dev, "Vendor request 'hw_addr_hi' failed\n");
                return;
        }

        if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_MI, &mi) < 0) {
                dev_err(dev, "Vendor request 'hw_addr_mid' failed\n");
                return;
        }

        if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_LO, &lo) < 0) {
                dev_err(dev, "Vendor request 'hw_addr_low' failed\n");
                return;
        }

        if (drci_rd_reg(usb_device, DRCI_REG_NI_STATE, &link) < 0) {
                dev_err(dev, "Vendor request 'link status' failed\n");
                return;
        }

        hw_addr[0] = hi >> 8;
        hw_addr[1] = hi;
        hw_addr[2] = mi >> 8;
        hw_addr[3] = mi;
        hw_addr[4] = lo >> 8;
        hw_addr[5] = lo;

        most_deliver_netinfo(&mdev->iface, link, hw_addr);
}

/**
 * wq_clear_halt - work queue function
 * @wq_obj: work_struct object to execute
 *
 * This sends a clear_halt to the given USB pipe.
 */
static void wq_clear_halt(struct work_struct *wq_obj)
{
        struct clear_hold_work *clear_work = to_clear_hold_work(wq_obj);
        struct most_dev *mdev = clear_work->mdev;
        unsigned int channel = clear_work->channel;
        int pipe = clear_work->pipe;

        mutex_lock(&mdev->io_mutex);
        most_stop_enqueue(&mdev->iface, channel);
        usb_kill_anchored_urbs(&mdev->busy_urbs[channel]);
        if (usb_clear_halt(mdev->usb_device, pipe))
                dev_warn(&mdev->usb_device->dev, "Failed to reset endpoint.\n");

        mdev->is_channel_healthy[channel] = true;
        most_resume_enqueue(&mdev->iface, channel);
        mutex_unlock(&mdev->io_mutex);
}

/**
 * hdm_usb_fops - file operation table for USB driver
 */
static const struct file_operations hdm_usb_fops = {
        .owner = THIS_MODULE,
};

/**
 * usb_device_id - ID table for HCD device probing
 */
static struct usb_device_id usbid[] = {
        { USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_BRDG), },
        { USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81118), },
        { USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81119), },
        { USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81210), },
        { } /* Terminating entry */
};

#define MOST_DCI_RO_ATTR(_name) \
        struct most_dci_attribute most_dci_attr_##_name = \
                __ATTR(_name, 0444, show_value, NULL)

#define MOST_DCI_ATTR(_name) \
        struct most_dci_attribute most_dci_attr_##_name = \
                __ATTR(_name, 0644, show_value, store_value)

#define MOST_DCI_WO_ATTR(_name) \
        struct most_dci_attribute most_dci_attr_##_name = \
                __ATTR(_name, 0200, NULL, store_value)

/**
 * struct most_dci_attribute - to access the attributes of a dci object
 * @attr: attributes of a dci object
 * @show: pointer to the show function
 * @store: pointer to the store function
 */
struct most_dci_attribute {
        struct attribute attr;
        ssize_t (*show)(struct most_dci_obj *d,
                        struct most_dci_attribute *attr,
                        char *buf);
        ssize_t (*store)(struct most_dci_obj *d,
                         struct most_dci_attribute *attr,
                         const char *buf,
                         size_t count);
};

#define to_dci_attr(a) container_of(a, struct most_dci_attribute, attr)

/**
 * dci_attr_show - show function for dci object
 * @kobj: pointer to kobject
 * @attr: pointer to attribute struct
 * @buf: buffer
 */
static ssize_t dci_attr_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct most_dci_attribute *dci_attr = to_dci_attr(attr);
        struct most_dci_obj *dci_obj = to_dci_obj(kobj);

        if (!dci_attr->show)
                return -EIO;

        return dci_attr->show(dci_obj, dci_attr, buf);
}

/**
 * dci_attr_store - store function for dci object
 * @kobj: pointer to kobject
 * @attr: pointer to attribute struct
 * @buf: buffer
 * @len: length of buffer
 */
static ssize_t dci_attr_store(struct kobject *kobj,
                              struct attribute *attr,
                              const char *buf,
                              size_t len)
{
        struct most_dci_attribute *dci_attr = to_dci_attr(attr);
        struct most_dci_obj *dci_obj = to_dci_obj(kobj);

        if (!dci_attr->store)
                return -EIO;

        return dci_attr->store(dci_obj, dci_attr, buf, len);
}

static const struct sysfs_ops most_dci_sysfs_ops = {
        .show = dci_attr_show,
        .store = dci_attr_store,
};

/**
 * most_dci_release - release function for dci object
 * @kobj: pointer to kobject
 *
 * This frees the memory allocated for the dci object
 */
static void most_dci_release(struct kobject *kobj)
{
        struct most_dci_obj *dci_obj = to_dci_obj(kobj);

        kfree(dci_obj);
}

struct regs {
        const char *name;
        u16 reg;
};

static const struct regs ro_regs[] = {
        { "ni_state", DRCI_REG_NI_STATE },
        { "packet_bandwidth", DRCI_REG_PACKET_BW },
        { "node_address", DRCI_REG_NODE_ADDR },
        { "node_position", DRCI_REG_NODE_POS },
};

static const struct regs rw_regs[] = {
        { "mep_filter", DRCI_REG_MEP_FILTER },
        { "mep_hash0", DRCI_REG_HASH_TBL0 },
        { "mep_hash1", DRCI_REG_HASH_TBL1 },
        { "mep_hash2", DRCI_REG_HASH_TBL2 },
        { "mep_hash3", DRCI_REG_HASH_TBL3 },
        { "mep_eui48_hi", DRCI_REG_HW_ADDR_HI },
        { "mep_eui48_mi", DRCI_REG_HW_ADDR_MI },
        { "mep_eui48_lo", DRCI_REG_HW_ADDR_LO },
};

static int get_stat_reg_addr(const struct regs *regs, int size,
                             const char *name, u16 *reg_addr)
{
        int i;

        for (i = 0; i < size; i++) {
                if (!strcmp(name, regs[i].name)) {
                        *reg_addr = regs[i].reg;
                        return 0;
                }
        }
        return -EFAULT;
}

#define get_static_reg_addr(regs, name, reg_addr) \
        get_stat_reg_addr(regs, ARRAY_SIZE(regs), name, reg_addr)

static ssize_t show_value(struct most_dci_obj *dci_obj,
                          struct most_dci_attribute *attr, char *buf)
{
        const char *name = attr->attr.name;
        u16 val;
        u16 reg_addr;
        int err;

        if (!strcmp(name, "arb_address"))
                return snprintf(buf, PAGE_SIZE, "%04x\n", dci_obj->reg_addr);

        if (!strcmp(name, "arb_value"))
                reg_addr = dci_obj->reg_addr;
        else if (get_static_reg_addr(ro_regs, name, &reg_addr) &&
                 get_static_reg_addr(rw_regs, name, &reg_addr))
                return -EFAULT;

        err = drci_rd_reg(dci_obj->usb_device, reg_addr, &val);
        if (err < 0)
                return err;

        return snprintf(buf, PAGE_SIZE, "%04x\n", val);
}

static ssize_t store_value(struct most_dci_obj *dci_obj,
                           struct most_dci_attribute *attr,

                           const char *buf, size_t count)
{
        u16 val;
        u16 reg_addr;
        const char *name = attr->attr.name;
        struct usb_device *usb_dev = dci_obj->usb_device;
        int err = kstrtou16(buf, 16, &val);

        if (err)
                return err;

        if (!strcmp(name, "arb_address")) {
                dci_obj->reg_addr = val;
                return count;
        }

        if (!strcmp(name, "arb_value"))
                err = drci_wr_reg(usb_dev, dci_obj->reg_addr, val);
        else if (!strcmp(name, "sync_ep"))
                err = start_sync_ep(usb_dev, val);
        else if (!get_static_reg_addr(ro_regs, name, &reg_addr))
                err = drci_wr_reg(usb_dev, reg_addr, val);
        else
                return -EFAULT;

        if (err < 0)
                return err;

        return count;
}

static MOST_DCI_RO_ATTR(ni_state);
static MOST_DCI_RO_ATTR(packet_bandwidth);
static MOST_DCI_RO_ATTR(node_address);
static MOST_DCI_RO_ATTR(node_position);
static MOST_DCI_WO_ATTR(sync_ep);
static MOST_DCI_ATTR(mep_filter);
static MOST_DCI_ATTR(mep_hash0);
static MOST_DCI_ATTR(mep_hash1);
static MOST_DCI_ATTR(mep_hash2);
static MOST_DCI_ATTR(mep_hash3);
static MOST_DCI_ATTR(mep_eui48_hi);
static MOST_DCI_ATTR(mep_eui48_mi);
static MOST_DCI_ATTR(mep_eui48_lo);
static MOST_DCI_ATTR(arb_address);
static MOST_DCI_ATTR(arb_value);

/**
 * most_dci_def_attrs - array of default attribute files of the dci object
 */
static struct attribute *most_dci_def_attrs[] = {
        &most_dci_attr_ni_state.attr,
        &most_dci_attr_packet_bandwidth.attr,
        &most_dci_attr_node_address.attr,
        &most_dci_attr_node_position.attr,
        &most_dci_attr_sync_ep.attr,
        &most_dci_attr_mep_filter.attr,
        &most_dci_attr_mep_hash0.attr,
        &most_dci_attr_mep_hash1.attr,
        &most_dci_attr_mep_hash2.attr,
        &most_dci_attr_mep_hash3.attr,
        &most_dci_attr_mep_eui48_hi.attr,
        &most_dci_attr_mep_eui48_mi.attr,
        &most_dci_attr_mep_eui48_lo.attr,
        &most_dci_attr_arb_address.attr,
        &most_dci_attr_arb_value.attr,
        NULL,
};

/**
 * DCI ktype
 */
static struct kobj_type most_dci_ktype = {
        .sysfs_ops = &most_dci_sysfs_ops,
        .release = most_dci_release,
        .default_attrs = most_dci_def_attrs,
};

/**
 * create_most_dci_obj - allocates a dci object
 * @parent: parent kobject
 *
 * This creates a dci object and registers it with sysfs.
 * Returns a pointer to the object or NULL when something went wrong.
 */
static struct
most_dci_obj *create_most_dci_obj(struct kobject *parent)
{
        struct most_dci_obj *most_dci = kzalloc(sizeof(*most_dci), GFP_KERNEL);
        int retval;

        if (!most_dci)
                return NULL;

        retval = kobject_init_and_add(&most_dci->kobj, &most_dci_ktype, parent,
                                      "dci");
        if (retval) {
                kobject_put(&most_dci->kobj);
                return NULL;
        }
        return most_dci;
}

/**
 * destroy_most_dci_obj - DCI object release function
 * @p: pointer to dci object
 */
static void destroy_most_dci_obj(struct most_dci_obj *p)
{
        kobject_put(&p->kobj);
}

/**
 * hdm_probe - probe function of USB device driver
 * @interface: Interface of the attached USB device
 * @id: Pointer to the USB ID table.
 *
 * This allocates and initializes the device instance, adds the new
 * entry to the internal list, scans the USB descriptors and registers
 * the interface with the core.
 * Additionally, the DCI objects are created and the hardware is sync'd.
 *
 * Return 0 on success. In case of an error a negative number is returned.
 */
static int
hdm_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
        struct usb_host_interface *usb_iface_desc = interface->cur_altsetting;
        struct usb_device *usb_dev = interface_to_usbdev(interface);
        struct device *dev = &usb_dev->dev;
        struct most_dev *mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
        unsigned int i;
        unsigned int num_endpoints;
        struct most_channel_capability *tmp_cap;
        struct usb_endpoint_descriptor *ep_desc;
        int ret = 0;

        if (!mdev)
                goto exit_ENOMEM;

        usb_set_intfdata(interface, mdev);
        num_endpoints = usb_iface_desc->desc.bNumEndpoints;
        mutex_init(&mdev->io_mutex);
        INIT_WORK(&mdev->poll_work_obj, wq_netinfo);
        setup_timer(&mdev->link_stat_timer, link_stat_timer_handler,
                    (unsigned long)mdev);

        mdev->usb_device = usb_dev;
        mdev->link_stat_timer.expires = jiffies + (2 * HZ);

        mdev->iface.mod = hdm_usb_fops.owner;
        mdev->iface.interface = ITYPE_USB;
        mdev->iface.configure = hdm_configure_channel;
        mdev->iface.request_netinfo = hdm_request_netinfo;
        mdev->iface.enqueue = hdm_enqueue;
        mdev->iface.poison_channel = hdm_poison_channel;
        mdev->iface.description = mdev->description;
        mdev->iface.num_channels = num_endpoints;

        snprintf(mdev->description, sizeof(mdev->description),
                 "usb_device %d-%s:%d.%d",
                 usb_dev->bus->busnum,
                 usb_dev->devpath,
                 usb_dev->config->desc.bConfigurationValue,
                 usb_iface_desc->desc.bInterfaceNumber);

        mdev->conf = kcalloc(num_endpoints, sizeof(*mdev->conf), GFP_KERNEL);
        if (!mdev->conf)
                goto exit_free;

        mdev->cap = kcalloc(num_endpoints, sizeof(*mdev->cap), GFP_KERNEL);
        if (!mdev->cap)
                goto exit_free1;

        mdev->iface.channel_vector = mdev->cap;
        mdev->iface.priv = NULL;

        mdev->ep_address =
                kcalloc(num_endpoints, sizeof(*mdev->ep_address), GFP_KERNEL);
        if (!mdev->ep_address)
                goto exit_free2;

        mdev->busy_urbs =
                kcalloc(num_endpoints, sizeof(*mdev->busy_urbs), GFP_KERNEL);
        if (!mdev->busy_urbs)
                goto exit_free3;

        tmp_cap = mdev->cap;
        for (i = 0; i < num_endpoints; i++) {
                ep_desc = &usb_iface_desc->endpoint[i].desc;
                mdev->ep_address[i] = ep_desc->bEndpointAddress;
                mdev->padding_active[i] = false;
                mdev->is_channel_healthy[i] = true;

                snprintf(&mdev->suffix[i][0], MAX_SUFFIX_LEN, "ep%02x",
                         mdev->ep_address[i]);

                tmp_cap->name_suffix = &mdev->suffix[i][0];
                tmp_cap->buffer_size_packet = MAX_BUF_SIZE;
                tmp_cap->buffer_size_streaming = MAX_BUF_SIZE;
                tmp_cap->num_buffers_packet = BUF_CHAIN_SIZE;
                tmp_cap->num_buffers_streaming = BUF_CHAIN_SIZE;
                tmp_cap->data_type = MOST_CH_CONTROL | MOST_CH_ASYNC |
                                     MOST_CH_ISOC | MOST_CH_SYNC;
                if (usb_endpoint_dir_in(ep_desc))
                        tmp_cap->direction = MOST_CH_RX;
                else
                        tmp_cap->direction = MOST_CH_TX;
                tmp_cap++;
                init_usb_anchor(&mdev->busy_urbs[i]);
                spin_lock_init(&mdev->channel_lock[i]);
        }
        dev_notice(dev, "claimed gadget: Vendor=%4.4x ProdID=%4.4x Bus=%02x Device=%02x\n",
                   le16_to_cpu(usb_dev->descriptor.idVendor),
                   le16_to_cpu(usb_dev->descriptor.idProduct),
                   usb_dev->bus->busnum,
                   usb_dev->devnum);

        dev_notice(dev, "device path: /sys/bus/usb/devices/%d-%s:%d.%d\n",
                   usb_dev->bus->busnum,
                   usb_dev->devpath,
                   usb_dev->config->desc.bConfigurationValue,
                   usb_iface_desc->desc.bInterfaceNumber);

        mdev->parent = most_register_interface(&mdev->iface);
        if (IS_ERR(mdev->parent)) {
                ret = PTR_ERR(mdev->parent);
                goto exit_free4;
        }

        mutex_lock(&mdev->io_mutex);
        if (le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81118 ||
            le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81119 ||
            le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81210) {
                /* this increments the reference count of the instance
                 * object of the core
                 */
                mdev->dci = create_most_dci_obj(mdev->parent);
                if (!mdev->dci) {
                        mutex_unlock(&mdev->io_mutex);
                        most_deregister_interface(&mdev->iface);
                        ret = -ENOMEM;
                        goto exit_free4;
                }

                kobject_uevent(&mdev->dci->kobj, KOBJ_ADD);
                mdev->dci->usb_device = mdev->usb_device;
        }
        mutex_unlock(&mdev->io_mutex);
        return 0;

exit_free4:
        kfree(mdev->busy_urbs);
exit_free3:
        kfree(mdev->ep_address);
exit_free2:
        kfree(mdev->cap);
exit_free1:
        kfree(mdev->conf);
exit_free:
        kfree(mdev);
exit_ENOMEM:
        if (ret == 0 || ret == -ENOMEM) {
                ret = -ENOMEM;
                dev_err(dev, "out of memory\n");
        }
        return ret;
}

/**
 * hdm_disconnect - disconnect function of USB device driver
 * @interface: Interface of the attached USB device
 *
 * This deregisters the interface with the core, removes the kernel timer
 * and frees resources.
 *
 * Context: hub kernel thread
 */
static void hdm_disconnect(struct usb_interface *interface)
{
        struct most_dev *mdev = usb_get_intfdata(interface);

        mutex_lock(&mdev->io_mutex);
        usb_set_intfdata(interface, NULL);
        mdev->usb_device = NULL;
        mutex_unlock(&mdev->io_mutex);

        del_timer_sync(&mdev->link_stat_timer);
        cancel_work_sync(&mdev->poll_work_obj);

        destroy_most_dci_obj(mdev->dci);
        most_deregister_interface(&mdev->iface);

        kfree(mdev->busy_urbs);
        kfree(mdev->cap);
        kfree(mdev->conf);
        kfree(mdev->ep_address);
        kfree(mdev);
}

static struct usb_driver hdm_usb = {
        .name = "hdm_usb",
        .id_table = usbid,
        .probe = hdm_probe,
        .disconnect = hdm_disconnect,
};

static int __init hdm_usb_init(void)
{
        pr_info("hdm_usb_init()\n");
        if (usb_register(&hdm_usb)) {
                pr_err("could not register hdm_usb driver\n");
                return -EIO;
        }

        return 0;
}

static void __exit hdm_usb_exit(void)
{
        pr_info("hdm_usb_exit()\n");
        usb_deregister(&hdm_usb);
}

module_init(hdm_usb_init);
module_exit(hdm_usb_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Christian Gromm <christian.gromm@microchip.com>");
MODULE_DESCRIPTION("HDM_4_USB");