// SPDX-License-Identifier: GPL-2.0+
/******************************************************************************
 *  usbatm.c - Generic USB xDSL driver core
 *
 *  Copyright (C) 2001, Alcatel
 *  Copyright (C) 2003, Duncan Sands, SolNegro, Josep Comas
 *  Copyright (C) 2004, David Woodhouse, Roman Kagan
 ******************************************************************************/

/*
 *  Written by Johan Verrept, Duncan Sands (duncan.sands@free.fr) and David Woodhouse
 *
 *  1.7+:       - See the check-in logs
 *
 *  1.6:        - No longer opens a connection if the firmware is not loaded
 *              - Added support for the speedtouch 330
 *              - Removed the limit on the number of devices
 *              - Module now autoloads on device plugin
 *              - Merged relevant parts of sarlib
 *              - Replaced the kernel thread with a tasklet
 *              - New packet transmission code
 *              - Changed proc file contents
 *              - Fixed all known SMP races
 *              - Many fixes and cleanups
 *              - Various fixes by Oliver Neukum (oliver@neukum.name)
 *
 *  1.5A:       - Version for inclusion in 2.5 series kernel
 *              - Modifications by Richard Purdie (rpurdie@rpsys.net)
 *              - made compatible with kernel 2.5.6 onwards by changing
 *              usbatm_usb_send_data_context->urb to a pointer and adding code
 *              to alloc and free it
 *              - remove_wait_queue() added to usbatm_atm_processqueue_thread()
 *
 *  1.5:        - fixed memory leak when atmsar_decode_aal5 returned NULL.
 *              (reported by stephen.robinson@zen.co.uk)
 *
 *  1.4:        - changed the spin_lock() under interrupt to spin_lock_irqsave()
 *              - unlink all active send urbs of a vcc that is being closed.
 *
 *  1.3.1:      - added the version number
 *
 *  1.3:        - Added multiple send urb support
 *              - fixed memory leak and vcc->tx_inuse starvation bug
 *                when not enough memory left in vcc.
 *
 *  1.2:        - Fixed race condition in usbatm_usb_send_data()
 *  1.1:        - Turned off packet debugging
 *
 */

#include "usbatm.h"

#include <linux/uaccess.h>
#include <linux/crc32.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netdevice.h>
#include <linux/proc_fs.h>
#include <linux/sched/signal.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/kthread.h>
#include <linux/ratelimit.h>

#ifdef VERBOSE_DEBUG
static int usbatm_print_packet(struct usbatm_data *instance, const unsigned char *data, int len);
#define PACKETDEBUG(arg...)     usbatm_print_packet(arg)
#define vdbg(arg...)            dev_dbg(arg)
#else
#define PACKETDEBUG(arg...)
#define vdbg(arg...)
#endif

#define DRIVER_AUTHOR   "Johan Verrept, Duncan Sands <duncan.sands@free.fr>"
#define DRIVER_DESC     "Generic USB ATM/DSL I/O"

static const char usbatm_driver_name[] = "usbatm";

#define UDSL_MAX_RCV_URBS               16
#define UDSL_MAX_SND_URBS               16
#define UDSL_MAX_BUF_SIZE               65536
#define UDSL_DEFAULT_RCV_URBS           4
#define UDSL_DEFAULT_SND_URBS           4
#define UDSL_DEFAULT_RCV_BUF_SIZE       3392    /* 64 * ATM_CELL_SIZE */
#define UDSL_DEFAULT_SND_BUF_SIZE       3392    /* 64 * ATM_CELL_SIZE */

#define ATM_CELL_HEADER                 (ATM_CELL_SIZE - ATM_CELL_PAYLOAD)

#define THROTTLE_MSECS                  100     /* delay to recover processing after urb submission fails */

static unsigned int num_rcv_urbs = UDSL_DEFAULT_RCV_URBS;
static unsigned int num_snd_urbs = UDSL_DEFAULT_SND_URBS;
static unsigned int rcv_buf_bytes = UDSL_DEFAULT_RCV_BUF_SIZE;
static unsigned int snd_buf_bytes = UDSL_DEFAULT_SND_BUF_SIZE;

module_param(num_rcv_urbs, uint, S_IRUGO);
MODULE_PARM_DESC(num_rcv_urbs,
                 "Number of urbs used for reception (range: 0-"
                 __MODULE_STRING(UDSL_MAX_RCV_URBS) ", default: "
                 __MODULE_STRING(UDSL_DEFAULT_RCV_URBS) ")");

module_param(num_snd_urbs, uint, S_IRUGO);
MODULE_PARM_DESC(num_snd_urbs,
                 "Number of urbs used for transmission (range: 0-"
                 __MODULE_STRING(UDSL_MAX_SND_URBS) ", default: "
                 __MODULE_STRING(UDSL_DEFAULT_SND_URBS) ")");

module_param(rcv_buf_bytes, uint, S_IRUGO);
MODULE_PARM_DESC(rcv_buf_bytes,
                 "Size of the buffers used for reception, in bytes (range: 1-"
                 __MODULE_STRING(UDSL_MAX_BUF_SIZE) ", default: "
                 __MODULE_STRING(UDSL_DEFAULT_RCV_BUF_SIZE) ")");

module_param(snd_buf_bytes, uint, S_IRUGO);
MODULE_PARM_DESC(snd_buf_bytes,
                 "Size of the buffers used for transmission, in bytes (range: 1-"
                 __MODULE_STRING(UDSL_MAX_BUF_SIZE) ", default: "
                 __MODULE_STRING(UDSL_DEFAULT_SND_BUF_SIZE) ")");


/* receive */

struct usbatm_vcc_data {
        /* vpi/vci lookup */
        struct list_head list;
        short vpi;
        int vci;
        struct atm_vcc *vcc;

        /* raw cell reassembly */
        struct sk_buff *sarb;
};


/* send */

struct usbatm_control {
        struct atm_skb_data atm;
        u32 len;
        u32 crc;
};

#define UDSL_SKB(x)             ((struct usbatm_control *)(x)->cb)


/* ATM */

static void usbatm_atm_dev_close(struct atm_dev *atm_dev);
static int usbatm_atm_open(struct atm_vcc *vcc);
static void usbatm_atm_close(struct atm_vcc *vcc);
static int usbatm_atm_ioctl(struct atm_dev *atm_dev, unsigned int cmd, void __user *arg);
static int usbatm_atm_send(struct atm_vcc *vcc, struct sk_buff *skb);
static int usbatm_atm_proc_read(struct atm_dev *atm_dev, loff_t *pos, char *page);

static const struct atmdev_ops usbatm_atm_devops = {
        .dev_close      = usbatm_atm_dev_close,
        .open           = usbatm_atm_open,
        .close          = usbatm_atm_close,
        .ioctl          = usbatm_atm_ioctl,
        .send           = usbatm_atm_send,
        .proc_read      = usbatm_atm_proc_read,
        .owner          = THIS_MODULE,
};


/***********
**  misc  **
***********/

static inline unsigned int usbatm_pdu_length(unsigned int length)
{
        length += ATM_CELL_PAYLOAD - 1 + ATM_AAL5_TRAILER;
        return length - length % ATM_CELL_PAYLOAD;
}

static inline void usbatm_pop(struct atm_vcc *vcc, struct sk_buff *skb)
{
        if (vcc->pop)
                vcc->pop(vcc, skb);
        else
                dev_kfree_skb_any(skb);
}


/***********
**  urbs  **
************/

static struct urb *usbatm_pop_urb(struct usbatm_channel *channel)
{
        struct urb *urb;

        spin_lock_irq(&channel->lock);
        if (list_empty(&channel->list)) {
                spin_unlock_irq(&channel->lock);
                return NULL;
        }

        urb = list_entry(channel->list.next, struct urb, urb_list);
        list_del(&urb->urb_list);
        spin_unlock_irq(&channel->lock);

        return urb;
}

static int usbatm_submit_urb(struct urb *urb)
{
        struct usbatm_channel *channel = urb->context;
        int ret;

        /* vdbg("%s: submitting urb 0x%p, size %u",
             __func__, urb, urb->transfer_buffer_length); */

        ret = usb_submit_urb(urb, GFP_ATOMIC);
        if (ret) {
                if (printk_ratelimit())
                        atm_warn(channel->usbatm, "%s: urb 0x%p submission failed (%d)!\n",
                                __func__, urb, ret);

                /* consider all errors transient and return the buffer back to the queue */
                urb->status = -EAGAIN;
                spin_lock_irq(&channel->lock);

                /* must add to the front when sending; doesn't matter when receiving */
                list_add(&urb->urb_list, &channel->list);

                spin_unlock_irq(&channel->lock);

                /* make sure the channel doesn't stall */
                mod_timer(&channel->delay, jiffies + msecs_to_jiffies(THROTTLE_MSECS));
        }

        return ret;
}

static void usbatm_complete(struct urb *urb)
{
        struct usbatm_channel *channel = urb->context;
        unsigned long flags;
        int status = urb->status;

        /* vdbg("%s: urb 0x%p, status %d, actual_length %d",
             __func__, urb, status, urb->actual_length); */

        /* Can be invoked from task context, protect against interrupts */
        spin_lock_irqsave(&channel->lock, flags);

        /* must add to the back when receiving; doesn't matter when sending */
        list_add_tail(&urb->urb_list, &channel->list);

        spin_unlock_irqrestore(&channel->lock, flags);

        if (unlikely(status) &&
                        (!(channel->usbatm->flags & UDSL_IGNORE_EILSEQ) ||
                         status != -EILSEQ)) {
                if (status == -ESHUTDOWN)
                        return;

                if (printk_ratelimit())
                        atm_warn(channel->usbatm, "%s: urb 0x%p failed (%d)!\n",
                                __func__, urb, status);
                /* throttle processing in case of an error */
                mod_timer(&channel->delay, jiffies + msecs_to_jiffies(THROTTLE_MSECS));
        } else
                tasklet_schedule(&channel->tasklet);
}


/*************
**  decode  **
*************/

static inline struct usbatm_vcc_data *usbatm_find_vcc(struct usbatm_data *instance,
                                                  short vpi, int vci)
{
        struct usbatm_vcc_data *vcc_data;

        list_for_each_entry(vcc_data, &instance->vcc_list, list)
                if ((vcc_data->vci == vci) && (vcc_data->vpi == vpi))
                        return vcc_data;
        return NULL;
}

static void usbatm_extract_one_cell(struct usbatm_data *instance, unsigned char *source)
{
        struct atm_vcc *vcc;
        struct sk_buff *sarb;
        short vpi = ((source[0] & 0x0f) << 4)  | (source[1] >> 4);
        int vci = ((source[1] & 0x0f) << 12) | (source[2] << 4) | (source[3] >> 4);
        u8 pti = ((source[3] & 0xe) >> 1);

        if ((vci != instance->cached_vci) || (vpi != instance->cached_vpi)) {
                instance->cached_vpi = vpi;
                instance->cached_vci = vci;

                instance->cached_vcc = usbatm_find_vcc(instance, vpi, vci);

                if (!instance->cached_vcc)
                        atm_rldbg(instance, "%s: unknown vpi/vci (%hd/%d)!\n", __func__, vpi, vci);
        }

        if (!instance->cached_vcc)
                return;

        vcc = instance->cached_vcc->vcc;

        /* OAM F5 end-to-end */
        if (pti == ATM_PTI_E2EF5) {
                if (printk_ratelimit())
                        atm_warn(instance, "%s: OAM not supported (vpi %d, vci %d)!\n",
                                __func__, vpi, vci);
                atomic_inc(&vcc->stats->rx_err);
                return;
        }

        sarb = instance->cached_vcc->sarb;

        if (sarb->tail + ATM_CELL_PAYLOAD > sarb->end) {
                atm_rldbg(instance, "%s: buffer overrun (sarb->len %u, vcc: 0x%p)!\n",
                                __func__, sarb->len, vcc);
                /* discard cells already received */
                skb_trim(sarb, 0);
        }

        memcpy(skb_tail_pointer(sarb), source + ATM_CELL_HEADER, ATM_CELL_PAYLOAD);
        __skb_put(sarb, ATM_CELL_PAYLOAD);

        if (pti & 1) {
                struct sk_buff *skb;
                unsigned int length;
                unsigned int pdu_length;

                length = (source[ATM_CELL_SIZE - 6] << 8) + source[ATM_CELL_SIZE - 5];

                /* guard against overflow */
                if (length > ATM_MAX_AAL5_PDU) {
                        atm_rldbg(instance, "%s: bogus length %u (vcc: 0x%p)!\n",
                                  __func__, length, vcc);
                        atomic_inc(&vcc->stats->rx_err);
                        goto out;
                }

                pdu_length = usbatm_pdu_length(length);

                if (sarb->len < pdu_length) {
                        atm_rldbg(instance, "%s: bogus pdu_length %u (sarb->len: %u, vcc: 0x%p)!\n",
                                  __func__, pdu_length, sarb->len, vcc);
                        atomic_inc(&vcc->stats->rx_err);
                        goto out;
                }

                if (crc32_be(~0, skb_tail_pointer(sarb) - pdu_length, pdu_length) != 0xc704dd7b) {
                        atm_rldbg(instance, "%s: packet failed crc check (vcc: 0x%p)!\n",
                                  __func__, vcc);
                        atomic_inc(&vcc->stats->rx_err);
                        goto out;
                }

                vdbg(&instance->usb_intf->dev,
                     "%s: got packet (length: %u, pdu_length: %u, vcc: 0x%p)",
                     __func__, length, pdu_length, vcc);

                skb = dev_alloc_skb(length);
                if (!skb) {
                        if (printk_ratelimit())
                                atm_err(instance, "%s: no memory for skb (length: %u)!\n",
                                        __func__, length);
                        atomic_inc(&vcc->stats->rx_drop);
                        goto out;
                }

                vdbg(&instance->usb_intf->dev,
                     "%s: allocated new sk_buff (skb: 0x%p, skb->truesize: %u)",
                     __func__, skb, skb->truesize);

                if (!atm_charge(vcc, skb->truesize)) {
                        atm_rldbg(instance, "%s: failed atm_charge (skb->truesize: %u)!\n",
                                  __func__, skb->truesize);
                        dev_kfree_skb_any(skb);
                        goto out;       /* atm_charge increments rx_drop */
                }

                skb_copy_to_linear_data(skb,
                                        skb_tail_pointer(sarb) - pdu_length,
                                        length);
                __skb_put(skb, length);

                vdbg(&instance->usb_intf->dev,
                     "%s: sending skb 0x%p, skb->len %u, skb->truesize %u",
                     __func__, skb, skb->len, skb->truesize);

                PACKETDEBUG(instance, skb->data, skb->len);

                vcc->push(vcc, skb);

                atomic_inc(&vcc->stats->rx);
        out:
                skb_trim(sarb, 0);
        }
}

static void usbatm_extract_cells(struct usbatm_data *instance,
                unsigned char *source, unsigned int avail_data)
{
        unsigned int stride = instance->rx_channel.stride;
        unsigned int buf_usage = instance->buf_usage;

        /* extract cells from incoming data, taking into account that
         * the length of avail data may not be a multiple of stride */

        if (buf_usage > 0) {
                /* we have a partially received atm cell */
                unsigned char *cell_buf = instance->cell_buf;
                unsigned int space_left = stride - buf_usage;

                if (avail_data >= space_left) {
                        /* add new data and process cell */
                        memcpy(cell_buf + buf_usage, source, space_left);
                        source += space_left;
                        avail_data -= space_left;
                        usbatm_extract_one_cell(instance, cell_buf);
                        instance->buf_usage = 0;
                } else {
                        /* not enough data to fill the cell */
                        memcpy(cell_buf + buf_usage, source, avail_data);
                        instance->buf_usage = buf_usage + avail_data;
                        return;
                }
        }

        for (; avail_data >= stride; avail_data -= stride, source += stride)
                usbatm_extract_one_cell(instance, source);

        if (avail_data > 0) {
                /* length was not a multiple of stride -
                 * save remaining data for next call */
                memcpy(instance->cell_buf, source, avail_data);
                instance->buf_usage = avail_data;
        }
}


/*************
**  encode  **
*************/

static unsigned int usbatm_write_cells(struct usbatm_data *instance,
                                       struct sk_buff *skb,
                                       u8 *target, unsigned int avail_space)
{
        struct usbatm_control *ctrl = UDSL_SKB(skb);
        struct atm_vcc *vcc = ctrl->atm.vcc;
        unsigned int bytes_written;
        unsigned int stride = instance->tx_channel.stride;

        for (bytes_written = 0; bytes_written < avail_space && ctrl->len;
             bytes_written += stride, target += stride) {
                unsigned int data_len = min_t(unsigned int, skb->len, ATM_CELL_PAYLOAD);
                unsigned int left = ATM_CELL_PAYLOAD - data_len;
                u8 *ptr = target;

                ptr[0] = vcc->vpi >> 4;
                ptr[1] = (vcc->vpi << 4) | (vcc->vci >> 12);
                ptr[2] = vcc->vci >> 4;
                ptr[3] = vcc->vci << 4;
                ptr[4] = 0xec;
                ptr += ATM_CELL_HEADER;

                skb_copy_from_linear_data(skb, ptr, data_len);
                ptr += data_len;
                __skb_pull(skb, data_len);

                if (!left)
                        continue;

                memset(ptr, 0, left);

                if (left >= ATM_AAL5_TRAILER) { /* trailer will go in this cell */
                        u8 *trailer = target + ATM_CELL_SIZE - ATM_AAL5_TRAILER;
                        /* trailer[0] = 0;              UU = 0 */
                        /* trailer[1] = 0;              CPI = 0 */
                        trailer[2] = ctrl->len >> 8;
                        trailer[3] = ctrl->len;

                        ctrl->crc = ~crc32_be(ctrl->crc, ptr, left - 4);

                        trailer[4] = ctrl->crc >> 24;
                        trailer[5] = ctrl->crc >> 16;
                        trailer[6] = ctrl->crc >> 8;
                        trailer[7] = ctrl->crc;

                        target[3] |= 0x2;       /* adjust PTI */

                        ctrl->len = 0;          /* tag this skb finished */
                } else
                        ctrl->crc = crc32_be(ctrl->crc, ptr, left);
        }

        return bytes_written;
}


/**************
**  receive  **
**************/

static void usbatm_rx_process(struct tasklet_struct *t)
{
        struct usbatm_data *instance = from_tasklet(instance, t,
                                                    rx_channel.tasklet);
        struct urb *urb;

        while ((urb = usbatm_pop_urb(&instance->rx_channel))) {
                vdbg(&instance->usb_intf->dev,
                     "%s: processing urb 0x%p", __func__, urb);

                if (usb_pipeisoc(urb->pipe)) {
                        unsigned char *merge_start = NULL;
                        unsigned int merge_length = 0;
                        const unsigned int packet_size = instance->rx_channel.packet_size;
                        int i;

                        for (i = 0; i < urb->number_of_packets; i++) {
                                if (!urb->iso_frame_desc[i].status) {
                                        unsigned int actual_length = urb->iso_frame_desc[i].actual_length;

                                        if (!merge_length)
                                                merge_start = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
                                        merge_length += actual_length;
                                        if (merge_length && (actual_length < packet_size)) {
                                                usbatm_extract_cells(instance, merge_start, merge_length);
                                                merge_length = 0;
                                        }
                                } else {
                                        atm_rldbg(instance, "%s: status %d in frame %d!\n", __func__, urb->status, i);
                                        if (merge_length)
                                                usbatm_extract_cells(instance, merge_start, merge_length);
                                        merge_length = 0;
                                        instance->buf_usage = 0;
                                }
                        }

                        if (merge_length)
                                usbatm_extract_cells(instance, merge_start, merge_length);
                } else
                        if (!urb->status)
                                usbatm_extract_cells(instance, urb->transfer_buffer, urb->actual_length);
                        else
                                instance->buf_usage = 0;

                if (usbatm_submit_urb(urb))
                        return;
        }
}


/***********
**  send  **
***********/

static void usbatm_tx_process(struct tasklet_struct *t)
{
        struct usbatm_data *instance = from_tasklet(instance, t,
                                                    tx_channel.tasklet);
        struct sk_buff *skb = instance->current_skb;
        struct urb *urb = NULL;
        const unsigned int buf_size = instance->tx_channel.buf_size;
        unsigned int bytes_written = 0;
        u8 *buffer = NULL;

        if (!skb)
                skb = skb_dequeue(&instance->sndqueue);

        while (skb) {
                if (!urb) {
                        urb = usbatm_pop_urb(&instance->tx_channel);
                        if (!urb)
                                break;          /* no more senders */
                        buffer = urb->transfer_buffer;
                        bytes_written = (urb->status == -EAGAIN) ?
                                urb->transfer_buffer_length : 0;
                }

                bytes_written += usbatm_write_cells(instance, skb,
                                                  buffer + bytes_written,
                                                  buf_size - bytes_written);

                vdbg(&instance->usb_intf->dev,
                     "%s: wrote %u bytes from skb 0x%p to urb 0x%p",
                     __func__, bytes_written, skb, urb);

                if (!UDSL_SKB(skb)->len) {
                        struct atm_vcc *vcc = UDSL_SKB(skb)->atm.vcc;

                        usbatm_pop(vcc, skb);
                        atomic_inc(&vcc->stats->tx);

                        skb = skb_dequeue(&instance->sndqueue);
                }

                if (bytes_written == buf_size || (!skb && bytes_written)) {
                        urb->transfer_buffer_length = bytes_written;

                        if (usbatm_submit_urb(urb))
                                break;
                        urb = NULL;
                }
        }

        instance->current_skb = skb;
}

static void usbatm_cancel_send(struct usbatm_data *instance,
                               struct atm_vcc *vcc)
{
        struct sk_buff *skb, *n;

        spin_lock_irq(&instance->sndqueue.lock);
        skb_queue_walk_safe(&instance->sndqueue, skb, n) {
                if (UDSL_SKB(skb)->atm.vcc == vcc) {
                        atm_dbg(instance, "%s: popping skb 0x%p\n", __func__, skb);
                        __skb_unlink(skb, &instance->sndqueue);
                        usbatm_pop(vcc, skb);
                }
        }
        spin_unlock_irq(&instance->sndqueue.lock);

        tasklet_disable(&instance->tx_channel.tasklet);
        if ((skb = instance->current_skb) && (UDSL_SKB(skb)->atm.vcc == vcc)) {
                atm_dbg(instance, "%s: popping current skb (0x%p)\n", __func__, skb);
                instance->current_skb = NULL;
                usbatm_pop(vcc, skb);
        }
        tasklet_enable(&instance->tx_channel.tasklet);
}

static int usbatm_atm_send(struct atm_vcc *vcc, struct sk_buff *skb)
{
        struct usbatm_data *instance = vcc->dev->dev_data;
        struct usbatm_control *ctrl = UDSL_SKB(skb);
        int err;

        /* racy disconnection check - fine */
        if (!instance || instance->disconnected) {
#ifdef VERBOSE_DEBUG
                printk_ratelimited(KERN_DEBUG "%s: %s!\n", __func__, instance ? "disconnected" : "NULL instance");
#endif
                err = -ENODEV;
                goto fail;
        }

        if (vcc->qos.aal != ATM_AAL5) {
                atm_rldbg(instance, "%s: unsupported ATM type %d!\n", __func__, vcc->qos.aal);
                err = -EINVAL;
                goto fail;
        }

        if (skb->len > ATM_MAX_AAL5_PDU) {
                atm_rldbg(instance, "%s: packet too long (%d vs %d)!\n",
                                __func__, skb->len, ATM_MAX_AAL5_PDU);
                err = -EINVAL;
                goto fail;
        }

        PACKETDEBUG(instance, skb->data, skb->len);

        /* initialize the control block */
        ctrl->atm.vcc = vcc;
        ctrl->len = skb->len;
        ctrl->crc = crc32_be(~0, skb->data, skb->len);

        skb_queue_tail(&instance->sndqueue, skb);
        tasklet_schedule(&instance->tx_channel.tasklet);

        return 0;

 fail:
        usbatm_pop(vcc, skb);
        return err;
}


/********************
**  bean counting  **
********************/

static void usbatm_destroy_instance(struct kref *kref)
{
        struct usbatm_data *instance = container_of(kref, struct usbatm_data, refcount);

        tasklet_kill(&instance->rx_channel.tasklet);
        tasklet_kill(&instance->tx_channel.tasklet);
        usb_put_dev(instance->usb_dev);
        kfree(instance);
}

static void usbatm_get_instance(struct usbatm_data *instance)
{
        kref_get(&instance->refcount);
}

static void usbatm_put_instance(struct usbatm_data *instance)
{
        kref_put(&instance->refcount, usbatm_destroy_instance);
}


/**********
**  ATM  **
**********/

static void usbatm_atm_dev_close(struct atm_dev *atm_dev)
{
        struct usbatm_data *instance = atm_dev->dev_data;

        if (!instance)
                return;

        atm_dev->dev_data = NULL; /* catch bugs */
        usbatm_put_instance(instance);  /* taken in usbatm_atm_init */
}

static int usbatm_atm_proc_read(struct atm_dev *atm_dev, loff_t *pos, char *page)
{
        struct usbatm_data *instance = atm_dev->dev_data;
        int left = *pos;

        if (!instance)
                return -ENODEV;

        if (!left--)
                return sprintf(page, "%s\n", instance->description);

        if (!left--)
                return sprintf(page, "MAC: %pM\n", atm_dev->esi);

        if (!left--)
                return sprintf(page,
                               "AAL5: tx %d ( %d err ), rx %d ( %d err, %d drop )\n",
                               atomic_read(&atm_dev->stats.aal5.tx),
                               atomic_read(&atm_dev->stats.aal5.tx_err),
                               atomic_read(&atm_dev->stats.aal5.rx),
                               atomic_read(&atm_dev->stats.aal5.rx_err),
                               atomic_read(&atm_dev->stats.aal5.rx_drop));

        if (!left--) {
                if (instance->disconnected)
                        return sprintf(page, "Disconnected\n");
                else
                        switch (atm_dev->signal) {
                        case ATM_PHY_SIG_FOUND:
                                return sprintf(page, "Line up\n");
                        case ATM_PHY_SIG_LOST:
                                return sprintf(page, "Line down\n");
                        default:
                                return sprintf(page, "Line state unknown\n");
                        }
        }

        return 0;
}

static int usbatm_atm_open(struct atm_vcc *vcc)
{
        struct usbatm_data *instance = vcc->dev->dev_data;
        struct usbatm_vcc_data *new = NULL;
        int ret;
        int vci = vcc->vci;
        short vpi = vcc->vpi;

        if (!instance)
                return -ENODEV;

        /* only support AAL5 */
        if ((vcc->qos.aal != ATM_AAL5)) {
                atm_warn(instance, "%s: unsupported ATM type %d!\n", __func__, vcc->qos.aal);
                return -EINVAL;
        }

        /* sanity checks */
        if ((vcc->qos.rxtp.max_sdu < 0) || (vcc->qos.rxtp.max_sdu > ATM_MAX_AAL5_PDU)) {
                atm_dbg(instance, "%s: max_sdu %d out of range!\n", __func__, vcc->qos.rxtp.max_sdu);
                return -EINVAL;
        }

        mutex_lock(&instance->serialize);       /* vs self, usbatm_atm_close, usbatm_usb_disconnect */

        if (instance->disconnected) {
                atm_dbg(instance, "%s: disconnected!\n", __func__);
                ret = -ENODEV;
                goto fail;
        }

        if (usbatm_find_vcc(instance, vpi, vci)) {
                atm_dbg(instance, "%s: %hd/%d already in use!\n", __func__, vpi, vci);
                ret = -EADDRINUSE;
                goto fail;
        }

        new = kzalloc_obj(struct usbatm_vcc_data);
        if (!new) {
                ret = -ENOMEM;
                goto fail;
        }

        new->vcc = vcc;
        new->vpi = vpi;
        new->vci = vci;

        new->sarb = alloc_skb(usbatm_pdu_length(vcc->qos.rxtp.max_sdu), GFP_KERNEL);
        if (!new->sarb) {
                atm_err(instance, "%s: no memory for SAR buffer!\n", __func__);
                ret = -ENOMEM;
                goto fail;
        }

        vcc->dev_data = new;

        tasklet_disable(&instance->rx_channel.tasklet);
        instance->cached_vcc = new;
        instance->cached_vpi = vpi;
        instance->cached_vci = vci;
        list_add(&new->list, &instance->vcc_list);
        tasklet_enable(&instance->rx_channel.tasklet);

        set_bit(ATM_VF_ADDR, &vcc->flags);
        set_bit(ATM_VF_PARTIAL, &vcc->flags);
        set_bit(ATM_VF_READY, &vcc->flags);

        mutex_unlock(&instance->serialize);

        atm_dbg(instance, "%s: allocated vcc data 0x%p\n", __func__, new);

        return 0;

fail:
        kfree(new);
        mutex_unlock(&instance->serialize);
        return ret;
}

static void usbatm_atm_close(struct atm_vcc *vcc)
{
        struct usbatm_data *instance = vcc->dev->dev_data;
        struct usbatm_vcc_data *vcc_data = vcc->dev_data;

        if (!instance || !vcc_data)
                return;

        usbatm_cancel_send(instance, vcc);

        mutex_lock(&instance->serialize);       /* vs self, usbatm_atm_open, usbatm_usb_disconnect */

        tasklet_disable(&instance->rx_channel.tasklet);
        if (instance->cached_vcc == vcc_data) {
                instance->cached_vcc = NULL;
                instance->cached_vpi = ATM_VPI_UNSPEC;
                instance->cached_vci = ATM_VCI_UNSPEC;
        }
        list_del(&vcc_data->list);
        tasklet_enable(&instance->rx_channel.tasklet);

        kfree_skb(vcc_data->sarb);
        vcc_data->sarb = NULL;

        kfree(vcc_data);
        vcc->dev_data = NULL;

        vcc->vpi = ATM_VPI_UNSPEC;
        vcc->vci = ATM_VCI_UNSPEC;
        clear_bit(ATM_VF_READY, &vcc->flags);
        clear_bit(ATM_VF_PARTIAL, &vcc->flags);
        clear_bit(ATM_VF_ADDR, &vcc->flags);

        mutex_unlock(&instance->serialize);
}

static int usbatm_atm_ioctl(struct atm_dev *atm_dev, unsigned int cmd,
                          void __user *arg)
{
        struct usbatm_data *instance = atm_dev->dev_data;

        if (!instance || instance->disconnected)
                return -ENODEV;

        switch (cmd) {
        case ATM_QUERYLOOP:
                return put_user(ATM_LM_NONE, (int __user *)arg) ? -EFAULT : 0;
        default:
                return -ENOIOCTLCMD;
        }
}

static int usbatm_atm_init(struct usbatm_data *instance)
{
        struct atm_dev *atm_dev;
        int ret, i;

        /* ATM init.  The ATM initialization scheme suffers from an intrinsic race
         * condition: callbacks we register can be executed at once, before we have
         * initialized the struct atm_dev.  To protect against this, all callbacks
         * abort if atm_dev->dev_data is NULL. */
        atm_dev = atm_dev_register(instance->driver_name,
                                   &instance->usb_intf->dev, &usbatm_atm_devops,
                                   -1, NULL);
        if (!atm_dev) {
                usb_err(instance, "%s: failed to register ATM device!\n", __func__);
                return -1;
        }

        instance->atm_dev = atm_dev;

        atm_dev->ci_range.vpi_bits = ATM_CI_MAX;
        atm_dev->ci_range.vci_bits = ATM_CI_MAX;
        atm_dev->signal = ATM_PHY_SIG_UNKNOWN;

        /* temp init ATM device, set to 128kbit */
        atm_dev->link_rate = 128 * 1000 / 424;

        if (instance->driver->atm_start && ((ret = instance->driver->atm_start(instance, atm_dev)) < 0)) {
                atm_err(instance, "%s: atm_start failed: %d!\n", __func__, ret);
                goto fail;
        }

        usbatm_get_instance(instance);  /* dropped in usbatm_atm_dev_close */

        /* ready for ATM callbacks */
        mb();
        atm_dev->dev_data = instance;

        /* submit all rx URBs */
        for (i = 0; i < num_rcv_urbs; i++)
                usbatm_submit_urb(instance->urbs[i]);

        return 0;

 fail:
        instance->atm_dev = NULL;
        atm_dev_deregister(atm_dev); /* usbatm_atm_dev_close will eventually be called */
        return ret;
}


/**********
**  USB  **
**********/

static int usbatm_do_heavy_init(void *arg)
{
        struct usbatm_data *instance = arg;
        int ret;

        allow_signal(SIGTERM);
        complete(&instance->thread_started);

        ret = instance->driver->heavy_init(instance, instance->usb_intf);

        if (!ret)
                ret = usbatm_atm_init(instance);

        mutex_lock(&instance->serialize);
        instance->thread = NULL;
        mutex_unlock(&instance->serialize);

        kthread_complete_and_exit(&instance->thread_exited, ret);
}

static int usbatm_heavy_init(struct usbatm_data *instance)
{
        struct task_struct *t;

        t = kthread_create(usbatm_do_heavy_init, instance, "%s",
                        instance->driver->driver_name);
        if (IS_ERR(t)) {
                usb_err(instance, "%s: failed to create kernel_thread (%ld)!\n",
                                __func__, PTR_ERR(t));
                return PTR_ERR(t);
        }

        instance->thread = t;
        wake_up_process(t);
        wait_for_completion(&instance->thread_started);

        return 0;
}

static void usbatm_tasklet_schedule(struct timer_list *t)
{
        struct usbatm_channel *channel = timer_container_of(channel, t, delay);

        tasklet_schedule(&channel->tasklet);
}

static void usbatm_init_channel(struct usbatm_channel *channel)
{
        spin_lock_init(&channel->lock);
        INIT_LIST_HEAD(&channel->list);
        timer_setup(&channel->delay, usbatm_tasklet_schedule, 0);
}

int usbatm_usb_probe(struct usb_interface *intf, const struct usb_device_id *id,
                     struct usbatm_driver *driver)
{
        struct device *dev = &intf->dev;
        struct usb_device *usb_dev = interface_to_usbdev(intf);
        struct usbatm_data *instance;
        char *buf;
        int error = -ENOMEM;
        int i, length;
        unsigned int maxpacket, num_packets;
        size_t size;

        /* instance init */
        size = struct_size(instance, urbs,
                           size_add(num_rcv_urbs, num_snd_urbs));
        instance = kzalloc(size, GFP_KERNEL);
        if (!instance)
                return -ENOMEM;

        /* public fields */

        instance->driver = driver;
        strscpy(instance->driver_name, driver->driver_name,
                sizeof(instance->driver_name));

        instance->usb_dev = usb_dev;
        instance->usb_intf = intf;

        buf = instance->description;
        length = sizeof(instance->description);

        if ((i = usb_string(usb_dev, usb_dev->descriptor.iProduct, buf, length)) < 0)
                goto bind;

        buf += i;
        length -= i;

        i = scnprintf(buf, length, " (");
        buf += i;
        length -= i;

        if (length <= 0 || (i = usb_make_path(usb_dev, buf, length)) < 0)
                goto bind;

        buf += i;
        length -= i;

        snprintf(buf, length, ")");

 bind:
        if (driver->bind && (error = driver->bind(instance, intf, id)) < 0) {
                        dev_err(dev, "%s: bind failed: %d!\n", __func__, error);
                        goto fail_free;
        }

        /* private fields */

        kref_init(&instance->refcount);         /* dropped in usbatm_usb_disconnect */
        mutex_init(&instance->serialize);

        instance->thread = NULL;
        init_completion(&instance->thread_started);
        init_completion(&instance->thread_exited);

        INIT_LIST_HEAD(&instance->vcc_list);
        skb_queue_head_init(&instance->sndqueue);

        usbatm_init_channel(&instance->rx_channel);
        usbatm_init_channel(&instance->tx_channel);
        tasklet_setup(&instance->rx_channel.tasklet, usbatm_rx_process);
        tasklet_setup(&instance->tx_channel.tasklet, usbatm_tx_process);
        instance->rx_channel.stride = ATM_CELL_SIZE + driver->rx_padding;
        instance->tx_channel.stride = ATM_CELL_SIZE + driver->tx_padding;
        instance->rx_channel.usbatm = instance->tx_channel.usbatm = instance;

        if ((instance->flags & UDSL_USE_ISOC) && driver->isoc_in)
                instance->rx_channel.endpoint = usb_rcvisocpipe(usb_dev, driver->isoc_in);
        else
                instance->rx_channel.endpoint = usb_rcvbulkpipe(usb_dev, driver->bulk_in);

        instance->tx_channel.endpoint = usb_sndbulkpipe(usb_dev, driver->bulk_out);

        /* tx buffer size must be a positive multiple of the stride */
        instance->tx_channel.buf_size = max(instance->tx_channel.stride,
                        snd_buf_bytes - (snd_buf_bytes % instance->tx_channel.stride));

        /* rx buffer size must be a positive multiple of the endpoint maxpacket */
        maxpacket = usb_maxpacket(usb_dev, instance->rx_channel.endpoint);

        if ((maxpacket < 1) || (maxpacket > UDSL_MAX_BUF_SIZE)) {
                dev_err(dev, "%s: invalid endpoint %02x!\n", __func__,
                                usb_pipeendpoint(instance->rx_channel.endpoint));
                error = -EINVAL;
                goto fail_unbind;
        }

        num_packets = max(1U, (rcv_buf_bytes + maxpacket / 2) / maxpacket); /* round */

        if (num_packets * maxpacket > UDSL_MAX_BUF_SIZE)
                num_packets--;

        instance->rx_channel.buf_size = num_packets * maxpacket;
        instance->rx_channel.packet_size = maxpacket;

        for (i = 0; i < 2; i++) {
                struct usbatm_channel *channel = i ?
                        &instance->tx_channel : &instance->rx_channel;

                dev_dbg(dev, "%s: using %d byte buffer for %s channel 0x%p\n",
                        __func__, channel->buf_size, i ? "tx" : "rx", channel);
        }

        /* initialize urbs */

        for (i = 0; i < num_rcv_urbs + num_snd_urbs; i++) {
                u8 *buffer;
                struct usbatm_channel *channel = i < num_rcv_urbs ?
                        &instance->rx_channel : &instance->tx_channel;
                struct urb *urb;
                unsigned int iso_packets = usb_pipeisoc(channel->endpoint) ? channel->buf_size / channel->packet_size : 0;

                urb = usb_alloc_urb(iso_packets, GFP_KERNEL);
                if (!urb) {
                        error = -ENOMEM;
                        goto fail_unbind;
                }

                instance->urbs[i] = urb;

                /* zero the tx padding to avoid leaking information */
                buffer = kzalloc(channel->buf_size, GFP_KERNEL);
                if (!buffer) {
                        error = -ENOMEM;
                        goto fail_unbind;
                }

                usb_fill_bulk_urb(urb, instance->usb_dev, channel->endpoint,
                                  buffer, channel->buf_size, usbatm_complete, channel);
                if (iso_packets) {
                        int j;
                        urb->interval = 1;
                        urb->transfer_flags = URB_ISO_ASAP;
                        urb->number_of_packets = iso_packets;
                        for (j = 0; j < iso_packets; j++) {
                                urb->iso_frame_desc[j].offset = channel->packet_size * j;
                                urb->iso_frame_desc[j].length = channel->packet_size;
                        }
                }

                /* put all tx URBs on the list of spares */
                if (i >= num_rcv_urbs)
                        list_add_tail(&urb->urb_list, &channel->list);

                vdbg(&intf->dev, "%s: allocated buffer 0x%p buf size %u urb 0x%p",
                     __func__, urb->transfer_buffer, urb->transfer_buffer_length, urb);
        }

        instance->cached_vpi = ATM_VPI_UNSPEC;
        instance->cached_vci = ATM_VCI_UNSPEC;
        instance->cell_buf = kmalloc(instance->rx_channel.stride, GFP_KERNEL);

        if (!instance->cell_buf) {
                error = -ENOMEM;
                goto fail_unbind;
        }

        if (!(instance->flags & UDSL_SKIP_HEAVY_INIT) && driver->heavy_init) {
                error = usbatm_heavy_init(instance);
        } else {
                complete(&instance->thread_exited);     /* pretend that heavy_init was run */
                error = usbatm_atm_init(instance);
        }

        if (error < 0)
                goto fail_unbind;

        usb_get_dev(usb_dev);
        usb_set_intfdata(intf, instance);

        return 0;

 fail_unbind:
        if (instance->driver->unbind)
                instance->driver->unbind(instance, intf);
 fail_free:
        kfree(instance->cell_buf);

        for (i = 0; i < num_rcv_urbs + num_snd_urbs; i++) {
                if (instance->urbs[i])
                        kfree(instance->urbs[i]->transfer_buffer);
                usb_free_urb(instance->urbs[i]);
        }

        kfree(instance);

        return error;
}
EXPORT_SYMBOL_GPL(usbatm_usb_probe);

void usbatm_usb_disconnect(struct usb_interface *intf)
{
        struct device *dev = &intf->dev;
        struct usbatm_data *instance = usb_get_intfdata(intf);
        struct usbatm_vcc_data *vcc_data;
        int i;

        if (!instance) {
                dev_dbg(dev, "%s: NULL instance!\n", __func__);
                return;
        }

        usb_set_intfdata(intf, NULL);

        mutex_lock(&instance->serialize);
        instance->disconnected = 1;
        if (instance->thread != NULL)
                send_sig(SIGTERM, instance->thread, 1);
        mutex_unlock(&instance->serialize);

        wait_for_completion(&instance->thread_exited);

        mutex_lock(&instance->serialize);
        list_for_each_entry(vcc_data, &instance->vcc_list, list)
                vcc_release_async(vcc_data->vcc, -EPIPE);
        mutex_unlock(&instance->serialize);

        tasklet_disable(&instance->rx_channel.tasklet);
        tasklet_disable(&instance->tx_channel.tasklet);

        for (i = 0; i < num_rcv_urbs + num_snd_urbs; i++)
                usb_kill_urb(instance->urbs[i]);

        timer_delete_sync(&instance->rx_channel.delay);
        timer_delete_sync(&instance->tx_channel.delay);

        /* turn usbatm_[rt]x_process into something close to a no-op */
        /* no need to take the spinlock */
        INIT_LIST_HEAD(&instance->rx_channel.list);
        INIT_LIST_HEAD(&instance->tx_channel.list);

        tasklet_enable(&instance->rx_channel.tasklet);
        tasklet_enable(&instance->tx_channel.tasklet);

        if (instance->atm_dev && instance->driver->atm_stop)
                instance->driver->atm_stop(instance, instance->atm_dev);

        if (instance->driver->unbind)
                instance->driver->unbind(instance, intf);

        instance->driver_data = NULL;

        for (i = 0; i < num_rcv_urbs + num_snd_urbs; i++) {
                kfree(instance->urbs[i]->transfer_buffer);
                usb_free_urb(instance->urbs[i]);
        }

        kfree(instance->cell_buf);

        /* ATM finalize */
        if (instance->atm_dev) {
                atm_dev_deregister(instance->atm_dev);
                instance->atm_dev = NULL;
        }

        usbatm_put_instance(instance);  /* taken in usbatm_usb_probe */
}
EXPORT_SYMBOL_GPL(usbatm_usb_disconnect);


/***********
**  init  **
***********/

static int __init usbatm_usb_init(void)
{
        if (sizeof(struct usbatm_control) > sizeof_field(struct sk_buff, cb)) {
                pr_err("%s unusable with this kernel!\n", usbatm_driver_name);
                return -EIO;
        }

        if ((num_rcv_urbs > UDSL_MAX_RCV_URBS)
            || (num_snd_urbs > UDSL_MAX_SND_URBS)
            || (rcv_buf_bytes < 1)
            || (rcv_buf_bytes > UDSL_MAX_BUF_SIZE)
            || (snd_buf_bytes < 1)
            || (snd_buf_bytes > UDSL_MAX_BUF_SIZE))
                return -EINVAL;

        return 0;
}
module_init(usbatm_usb_init);

static void __exit usbatm_usb_exit(void)
{
}
module_exit(usbatm_usb_exit);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

/************
**  debug  **
************/

#ifdef VERBOSE_DEBUG
static int usbatm_print_packet(struct usbatm_data *instance,
                               const unsigned char *data, int len)
{
        unsigned char buffer[256];
        int i = 0, j = 0;

        for (i = 0; i < len;) {
                buffer[0] = '\0';
                sprintf(buffer, "%.3d :", i);
                for (j = 0; (j < 16) && (i < len); j++, i++)
                        sprintf(buffer, "%s %2.2x", buffer, data[i]);
                dev_dbg(&instance->usb_intf->dev, "%s", buffer);
        }
        return i;
}
#endif