wa-xfer.c

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/*
 * WUSB Wire Adapter
 * Data transfer and URB enqueing
 *
 * Copyright (C) 2005-2006 Intel Corporation
 * Inaky Perez-Gonzalez <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
 * How transfers work: get a buffer, break it up in segments (segment
 * size is a multiple of the maxpacket size). For each segment issue a
 * segment request (struct wa_xfer_*), then send the data buffer if
 * out or nothing if in (all over the DTO endpoint).
 *
 * For each submitted segment request, a notification will come over
 * the NEP endpoint and a transfer result (struct xfer_result) will
 * arrive in the DTI URB. Read it, get the xfer ID, see if there is
 * data coming (inbound transfer), schedule a read and handle it.
 *
 * Sounds simple, it is a pain to implement.
 *
 *
 * ENTRY POINTS
 *
 *   FIXME
 *
 * LIFE CYCLE / STATE DIAGRAM
 *
 *   FIXME
 *
 * THIS CODE IS DISGUSTING
 *
 *   Warned you are; it's my second try and still not happy with it.
 *
 * NOTES:
 *
 *   - No iso
 *
 *   - Supports DMA xfers, control, bulk and maybe interrupt
 *
 *   - Does not recycle unused rpipes
 *
 *     An rpipe is assigned to an endpoint the first time it is used,
 *     and then it's there, assigned, until the endpoint is disabled
 *     (destroyed [{h,d}wahc_op_ep_disable()]. The assignment of the
 *     rpipe to the endpoint is done under the wa->rpipe_sem semaphore
 *     (should be a mutex).
 *
 *     Two methods it could be done:
 *
 *     (a) set up a timer every time an rpipe's use count drops to 1
 *         (which means unused) or when a transfer ends. Reset the
 *         timer when a xfer is queued. If the timer expires, release
 *         the rpipe [see rpipe_ep_disable()].
 *
 *     (b) when looking for free rpipes to attach [rpipe_get_by_ep()],
 *         when none are found go over the list, check their endpoint
 *         and their activity record (if no last-xfer-done-ts in the
 *         last x seconds) take it
 *
 *     However, due to the fact that we have a set of limited
 *     resources (max-segments-at-the-same-time per xfer,
 *     xfers-per-ripe, blocks-per-rpipe, rpipes-per-host), at the end
 *     we are going to have to rebuild all this based on an scheduler,
 *     to where we have a list of transactions to do and based on the
 *     availability of the different required components (blocks,
 *     rpipes, segment slots, etc), we go scheduling them. Painful.
 */
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/ratelimit.h>
#include <linux/export.h>

#include "wa-hc.h"
#include "wusbhc.h"

enum {
    WA_SEGS_MAX = 255,
};

enum wa_seg_status {
    WA_SEG_NOTREADY,
    WA_SEG_READY,
    WA_SEG_DELAYED,
    WA_SEG_SUBMITTED,
    WA_SEG_PENDING,
    WA_SEG_DTI_PENDING,
    WA_SEG_DONE,
    WA_SEG_ERROR,
    WA_SEG_ABORTED,
};

static void wa_xfer_delayed_run(struct wa_rpipe *);

/*
 * Life cycle governed by 'struct urb' (the refcount of the struct is
 * that of the 'struct urb' and usb_free_urb() would free the whole
 * struct).
 */
struct wa_seg {
    struct urb urb;
    struct urb *dto_urb;        /* for data output? */
    struct list_head list_node; /* for rpipe->req_list */
    struct wa_xfer *xfer;       /* out xfer */
    u8 index;           /* which segment we are */
    enum wa_seg_status status;
    ssize_t result;         /* bytes xfered or error */
    struct wa_xfer_hdr xfer_hdr;
    u8 xfer_extra[];        /* xtra space for xfer_hdr_ctl */
};

static void wa_seg_init(struct wa_seg *seg)
{
    /* usb_init_urb() repeats a lot of work, so we do it here */
    kref_init(&seg->urb.kref);
}

/*
 * Protected by xfer->lock
 *
 */
struct wa_xfer {
    struct kref refcnt;
    struct list_head list_node;
    spinlock_t lock;
    u32 id;

    struct wahc *wa;        /* Wire adapter we are plugged to */
    struct usb_host_endpoint *ep;
    struct urb *urb;        /* URB we are transferring for */
    struct wa_seg **seg;        /* transfer segments */
    u8 segs, segs_submitted, segs_done;
    unsigned is_inbound:1;
    unsigned is_dma:1;
    size_t seg_size;
    int result;

    gfp_t gfp;          /* allocation mask */

    struct wusb_dev *wusb_dev;  /* for activity timestamps */
};

static inline void wa_xfer_init(struct wa_xfer *xfer)
{
    kref_init(&xfer->refcnt);
    INIT_LIST_HEAD(&xfer->list_node);
    spin_lock_init(&xfer->lock);
}

/*
 * Destroy a transfer structure
 *
 * Note that the xfer->seg[index] thingies follow the URB life cycle,
 * so we need to put them, not free them.
 */
static void wa_xfer_destroy(struct kref *_xfer)
{
    struct wa_xfer *xfer = container_of(_xfer, struct wa_xfer, refcnt);
    if (xfer->seg) {
        unsigned cnt;
        for (cnt = 0; cnt < xfer->segs; cnt++) {
            if (xfer->is_inbound)
                usb_put_urb(xfer->seg[cnt]->dto_urb);
            usb_put_urb(&xfer->seg[cnt]->urb);
        }
    }
    kfree(xfer);
}

static void wa_xfer_get(struct wa_xfer *xfer)
{
    kref_get(&xfer->refcnt);
}

static void wa_xfer_put(struct wa_xfer *xfer)
{
    kref_put(&xfer->refcnt, wa_xfer_destroy);
}

/*
 * xfer is referenced
 *
 * xfer->lock has to be unlocked
 *
 * We take xfer->lock for setting the result; this is a barrier
 * against drivers/usb/core/hcd.c:unlink1() being called after we call
 * usb_hcd_giveback_urb() and wa_urb_dequeue() trying to get a
 * reference to the transfer.
 */
static void wa_xfer_giveback(struct wa_xfer *xfer)
{
    unsigned long flags;

    spin_lock_irqsave(&xfer->wa->xfer_list_lock, flags);
    list_del_init(&xfer->list_node);
    spin_unlock_irqrestore(&xfer->wa->xfer_list_lock, flags);
    /* FIXME: segmentation broken -- kills DWA */
    wusbhc_giveback_urb(xfer->wa->wusb, xfer->urb, xfer->result);
    wa_put(xfer->wa);
    wa_xfer_put(xfer);
}

/*
 * xfer is referenced
 *
 * xfer->lock has to be unlocked
 */
static void wa_xfer_completion(struct wa_xfer *xfer)
{
    if (xfer->wusb_dev)
        wusb_dev_put(xfer->wusb_dev);
    rpipe_put(xfer->ep->hcpriv);
    wa_xfer_giveback(xfer);
}

/*
 * If transfer is done, wrap it up and return true
 *
 * xfer->lock has to be locked
 */
static unsigned __wa_xfer_is_done(struct wa_xfer *xfer)
{
    struct device *dev = &xfer->wa->usb_iface->dev;
    unsigned result, cnt;
    struct wa_seg *seg;
    struct urb *urb = xfer->urb;
    unsigned found_short = 0;

    result = xfer->segs_done == xfer->segs_submitted;
    if (result == 0)
        goto out;
    urb->actual_length = 0;
    for (cnt = 0; cnt < xfer->segs; cnt++) {
        seg = xfer->seg[cnt];
        switch (seg->status) {
        case WA_SEG_DONE:
            if (found_short && seg->result > 0) {
                dev_dbg(dev, "xfer %p#%u: bad short segments (%zu)\n",
                    xfer, cnt, seg->result);
                urb->status = -EINVAL;
                goto out;
            }
            urb->actual_length += seg->result;
            if (seg->result < xfer->seg_size
                && cnt != xfer->segs-1)
                found_short = 1;
            dev_dbg(dev, "xfer %p#%u: DONE short %d "
                "result %zu urb->actual_length %d\n",
                xfer, seg->index, found_short, seg->result,
                urb->actual_length);
            break;
        case WA_SEG_ERROR:
            xfer->result = seg->result;
            dev_dbg(dev, "xfer %p#%u: ERROR result %zu\n",
                xfer, seg->index, seg->result);
            goto out;
        case WA_SEG_ABORTED:
            dev_dbg(dev, "xfer %p#%u ABORTED: result %d\n",
                xfer, seg->index, urb->status);
            xfer->result = urb->status;
            goto out;
        default:
            dev_warn(dev, "xfer %p#%u: is_done bad state %d\n",
                 xfer, cnt, seg->status);
            xfer->result = -EINVAL;
            goto out;
        }
    }
    xfer->result = 0;
out:
    return result;
}

/*
 * Initialize a transfer's ID
 *
 * We need to use a sequential number; if we use the pointer or the
 * hash of the pointer, it can repeat over sequential transfers and
 * then it will confuse the HWA....wonder why in hell they put a 32
 * bit handle in there then.
 */
static void wa_xfer_id_init(struct wa_xfer *xfer)
{
    xfer->id = atomic_add_return(1, &xfer->wa->xfer_id_count);
}

/*
 * Return the xfer's ID associated with xfer
 *
 * Need to generate a
 */
static u32 wa_xfer_id(struct wa_xfer *xfer)
{
    return xfer->id;
}

/*
 * Search for a transfer list ID on the HCD's URB list
 *
 * For 32 bit architectures, we use the pointer itself; for 64 bits, a
 * 32-bit hash of the pointer.
 *
 * @returns NULL if not found.
 */
static struct wa_xfer *wa_xfer_get_by_id(struct wahc *wa, u32 id)
{
    unsigned long flags;
    struct wa_xfer *xfer_itr;
    spin_lock_irqsave(&wa->xfer_list_lock, flags);
    list_for_each_entry(xfer_itr, &wa->xfer_list, list_node) {
        if (id == xfer_itr->id) {
            wa_xfer_get(xfer_itr);
            goto out;
        }
    }
    xfer_itr = NULL;
out:
    spin_unlock_irqrestore(&wa->xfer_list_lock, flags);
    return xfer_itr;
}

struct wa_xfer_abort_buffer {
    struct urb urb;
    struct wa_xfer_abort cmd;
};

static void __wa_xfer_abort_cb(struct urb *urb)
{
    struct wa_xfer_abort_buffer *b = urb->context;
    usb_put_urb(&b->urb);
}

/*
 * Aborts an ongoing transaction
 *
 * Assumes the transfer is referenced and locked and in a submitted
 * state (mainly that there is an endpoint/rpipe assigned).
 *
 * The callback (see above) does nothing but freeing up the data by
 * putting the URB. Because the URB is allocated at the head of the
 * struct, the whole space we allocated is kfreed.
 *
 * We'll get an 'aborted transaction' xfer result on DTI, that'll
 * politely ignore because at this point the transaction has been
 * marked as aborted already.
 */
static void __wa_xfer_abort(struct wa_xfer *xfer)
{
    int result;
    struct device *dev = &xfer->wa->usb_iface->dev;
    struct wa_xfer_abort_buffer *b;
    struct wa_rpipe *rpipe = xfer->ep->hcpriv;

    b = kmalloc(sizeof(*b), GFP_ATOMIC);
    if (b == NULL)
        goto error_kmalloc;
    b->cmd.bLength =  sizeof(b->cmd);
    b->cmd.bRequestType = WA_XFER_ABORT;
    b->cmd.wRPipe = rpipe->descr.wRPipeIndex;
    b->cmd.dwTransferID = wa_xfer_id(xfer);

    usb_init_urb(&b->urb);
    usb_fill_bulk_urb(&b->urb, xfer->wa->usb_dev,
        usb_sndbulkpipe(xfer->wa->usb_dev,
                xfer->wa->dto_epd->bEndpointAddress),
        &b->cmd, sizeof(b->cmd), __wa_xfer_abort_cb, b);
    result = usb_submit_urb(&b->urb, GFP_ATOMIC);
    if (result < 0)
        goto error_submit;
    return;             /* callback frees! */


error_submit:
    if (printk_ratelimit())
        dev_err(dev, "xfer %p: Can't submit abort request: %d\n",
            xfer, result);
    kfree(b);
error_kmalloc:
    return;

}

/*
 *
 * @returns < 0 on error, transfer segment request size if ok
 */
static ssize_t __wa_xfer_setup_sizes(struct wa_xfer *xfer,
                     enum wa_xfer_type *pxfer_type)
{
    ssize_t result;
    struct device *dev = &xfer->wa->usb_iface->dev;
    size_t maxpktsize;
    struct urb *urb = xfer->urb;
    struct wa_rpipe *rpipe = xfer->ep->hcpriv;

    switch (rpipe->descr.bmAttribute & 0x3) {
    case USB_ENDPOINT_XFER_CONTROL:
        *pxfer_type = WA_XFER_TYPE_CTL;
        result = sizeof(struct wa_xfer_ctl);
        break;
    case USB_ENDPOINT_XFER_INT:
    case USB_ENDPOINT_XFER_BULK:
        *pxfer_type = WA_XFER_TYPE_BI;
        result = sizeof(struct wa_xfer_bi);
        break;
    case USB_ENDPOINT_XFER_ISOC:
        dev_err(dev, "FIXME: ISOC not implemented\n");
        result = -ENOSYS;
        goto error;
    default:
        /* never happens */
        BUG();
        result = -EINVAL;   /* shut gcc up */
    };
    xfer->is_inbound = urb->pipe & USB_DIR_IN ? 1 : 0;
    xfer->is_dma = urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP ? 1 : 0;
    xfer->seg_size = le16_to_cpu(rpipe->descr.wBlocks)
        * 1 << (xfer->wa->wa_descr->bRPipeBlockSize - 1);
    /* Compute the segment size and make sure it is a multiple of
     * the maxpktsize (WUSB1.0[8.3.3.1])...not really too much of
     * a check (FIXME) */
    maxpktsize = le16_to_cpu(rpipe->descr.wMaxPacketSize);
    if (xfer->seg_size < maxpktsize) {
        dev_err(dev, "HW BUG? seg_size %zu smaller than maxpktsize "
            "%zu\n", xfer->seg_size, maxpktsize);
        result = -EINVAL;
        goto error;
    }
    xfer->seg_size = (xfer->seg_size / maxpktsize) * maxpktsize;
    xfer->segs = (urb->transfer_buffer_length + xfer->seg_size - 1)
        / xfer->seg_size;
    if (xfer->segs >= WA_SEGS_MAX) {
        dev_err(dev, "BUG? ops, number of segments %d bigger than %d\n",
            (int)(urb->transfer_buffer_length / xfer->seg_size),
            WA_SEGS_MAX);
        result = -EINVAL;
        goto error;
    }
    if (xfer->segs == 0 && *pxfer_type == WA_XFER_TYPE_CTL)
        xfer->segs = 1;
error:
    return result;
}

/* Fill in the common request header and xfer-type specific data. */
static void __wa_xfer_setup_hdr0(struct wa_xfer *xfer,
                 struct wa_xfer_hdr *xfer_hdr0,
                 enum wa_xfer_type xfer_type,
                 size_t xfer_hdr_size)
{
    struct wa_rpipe *rpipe = xfer->ep->hcpriv;

    xfer_hdr0 = &xfer->seg[0]->xfer_hdr;
    xfer_hdr0->bLength = xfer_hdr_size;
    xfer_hdr0->bRequestType = xfer_type;
    xfer_hdr0->wRPipe = rpipe->descr.wRPipeIndex;
    xfer_hdr0->dwTransferID = wa_xfer_id(xfer);
    xfer_hdr0->bTransferSegment = 0;
    switch (xfer_type) {
    case WA_XFER_TYPE_CTL: {
        struct wa_xfer_ctl *xfer_ctl =
            container_of(xfer_hdr0, struct wa_xfer_ctl, hdr);
        xfer_ctl->bmAttribute = xfer->is_inbound ? 1 : 0;
        memcpy(&xfer_ctl->baSetupData, xfer->urb->setup_packet,
               sizeof(xfer_ctl->baSetupData));
        break;
    }
    case WA_XFER_TYPE_BI:
        break;
    case WA_XFER_TYPE_ISO:
        printk(KERN_ERR "FIXME: ISOC not implemented\n");
    default:
        BUG();
    };
}

/*
 * Callback for the OUT data phase of the segment request
 *
 * Check wa_seg_cb(); most comments also apply here because this
 * function does almost the same thing and they work closely
 * together.
 *
 * If the seg request has failed but this DTO phase has succeeded,
 * wa_seg_cb() has already failed the segment and moved the
 * status to WA_SEG_ERROR, so this will go through 'case 0' and
 * effectively do nothing.
 */
static void wa_seg_dto_cb(struct urb *urb)
{
    struct wa_seg *seg = urb->context;
    struct wa_xfer *xfer = seg->xfer;
    struct wahc *wa;
    struct device *dev;
    struct wa_rpipe *rpipe;
    unsigned long flags;
    unsigned rpipe_ready = 0;
    u8 done = 0;

    switch (urb->status) {
    case 0:
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        dev_dbg(dev, "xfer %p#%u: data out done (%d bytes)\n",
            xfer, seg->index, urb->actual_length);
        if (seg->status < WA_SEG_PENDING)
            seg->status = WA_SEG_PENDING;
        seg->result = urb->actual_length;
        spin_unlock_irqrestore(&xfer->lock, flags);
        break;
    case -ECONNRESET:   /* URB unlinked; no need to do anything */
    case -ENOENT:       /* as it was done by the who unlinked us */
        break;
    default:        /* Other errors ... */
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        rpipe = xfer->ep->hcpriv;
        dev_dbg(dev, "xfer %p#%u: data out error %d\n",
            xfer, seg->index, urb->status);
        if (edc_inc(&wa->nep_edc, EDC_MAX_ERRORS,
                EDC_ERROR_TIMEFRAME)){
            dev_err(dev, "DTO: URB max acceptable errors "
                "exceeded, resetting device\n");
            wa_reset_all(wa);
        }
        if (seg->status != WA_SEG_ERROR) {
            seg->status = WA_SEG_ERROR;
            seg->result = urb->status;
            xfer->segs_done++;
            __wa_xfer_abort(xfer);
            rpipe_ready = rpipe_avail_inc(rpipe);
            done = __wa_xfer_is_done(xfer);
        }
        spin_unlock_irqrestore(&xfer->lock, flags);
        if (done)
            wa_xfer_completion(xfer);
        if (rpipe_ready)
            wa_xfer_delayed_run(rpipe);
    }
}

/*
 * Callback for the segment request
 *
 * If successful transition state (unless already transitioned or
 * outbound transfer); otherwise, take a note of the error, mark this
 * segment done and try completion.
 *
 * Note we don't access until we are sure that the transfer hasn't
 * been cancelled (ECONNRESET, ENOENT), which could mean that
 * seg->xfer could be already gone.
 *
 * We have to check before setting the status to WA_SEG_PENDING
 * because sometimes the xfer result callback arrives before this
 * callback (geeeeeeze), so it might happen that we are already in
 * another state. As well, we don't set it if the transfer is inbound,
 * as in that case, wa_seg_dto_cb will do it when the OUT data phase
 * finishes.
 */
static void wa_seg_cb(struct urb *urb)
{
    struct wa_seg *seg = urb->context;
    struct wa_xfer *xfer = seg->xfer;
    struct wahc *wa;
    struct device *dev;
    struct wa_rpipe *rpipe;
    unsigned long flags;
    unsigned rpipe_ready;
    u8 done = 0;

    switch (urb->status) {
    case 0:
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        dev_dbg(dev, "xfer %p#%u: request done\n", xfer, seg->index);
        if (xfer->is_inbound && seg->status < WA_SEG_PENDING)
            seg->status = WA_SEG_PENDING;
        spin_unlock_irqrestore(&xfer->lock, flags);
        break;
    case -ECONNRESET:   /* URB unlinked; no need to do anything */
    case -ENOENT:       /* as it was done by the who unlinked us */
        break;
    default:        /* Other errors ... */
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        rpipe = xfer->ep->hcpriv;
        if (printk_ratelimit())
            dev_err(dev, "xfer %p#%u: request error %d\n",
                xfer, seg->index, urb->status);
        if (edc_inc(&wa->nep_edc, EDC_MAX_ERRORS,
                EDC_ERROR_TIMEFRAME)){
            dev_err(dev, "DTO: URB max acceptable errors "
                "exceeded, resetting device\n");
            wa_reset_all(wa);
        }
        usb_unlink_urb(seg->dto_urb);
        seg->status = WA_SEG_ERROR;
        seg->result = urb->status;
        xfer->segs_done++;
        __wa_xfer_abort(xfer);
        rpipe_ready = rpipe_avail_inc(rpipe);
        done = __wa_xfer_is_done(xfer);
        spin_unlock_irqrestore(&xfer->lock, flags);
        if (done)
            wa_xfer_completion(xfer);
        if (rpipe_ready)
            wa_xfer_delayed_run(rpipe);
    }
}

/*
 * Allocate the segs array and initialize each of them
 *
 * The segments are freed by wa_xfer_destroy() when the xfer use count
 * drops to zero; however, because each segment is given the same life
 * cycle as the USB URB it contains, it is actually freed by
 * usb_put_urb() on the contained USB URB (twisted, eh?).
 */
static int __wa_xfer_setup_segs(struct wa_xfer *xfer, size_t xfer_hdr_size)
{
    int result, cnt;
    size_t alloc_size = sizeof(*xfer->seg[0])
        - sizeof(xfer->seg[0]->xfer_hdr) + xfer_hdr_size;
    struct usb_device *usb_dev = xfer->wa->usb_dev;
    const struct usb_endpoint_descriptor *dto_epd = xfer->wa->dto_epd;
    struct wa_seg *seg;
    size_t buf_itr, buf_size, buf_itr_size;

    result = -ENOMEM;
    xfer->seg = kcalloc(xfer->segs, sizeof(xfer->seg[0]), GFP_ATOMIC);
    if (xfer->seg == NULL)
        goto error_segs_kzalloc;
    buf_itr = 0;
    buf_size = xfer->urb->transfer_buffer_length;
    for (cnt = 0; cnt < xfer->segs; cnt++) {
        seg = xfer->seg[cnt] = kzalloc(alloc_size, GFP_ATOMIC);
        if (seg == NULL)
            goto error_seg_kzalloc;
        wa_seg_init(seg);
        seg->xfer = xfer;
        seg->index = cnt;
        usb_fill_bulk_urb(&seg->urb, usb_dev,
                  usb_sndbulkpipe(usb_dev,
                          dto_epd->bEndpointAddress),
                  &seg->xfer_hdr, xfer_hdr_size,
                  wa_seg_cb, seg);
        buf_itr_size = buf_size > xfer->seg_size ?
            xfer->seg_size : buf_size;
        if (xfer->is_inbound == 0 && buf_size > 0) {
            seg->dto_urb = usb_alloc_urb(0, GFP_ATOMIC);
            if (seg->dto_urb == NULL)
                goto error_dto_alloc;
            usb_fill_bulk_urb(
                seg->dto_urb, usb_dev,
                usb_sndbulkpipe(usb_dev,
                        dto_epd->bEndpointAddress),
                NULL, 0, wa_seg_dto_cb, seg);
            if (xfer->is_dma) {
                seg->dto_urb->transfer_dma =
                    xfer->urb->transfer_dma + buf_itr;
                seg->dto_urb->transfer_flags |=
                    URB_NO_TRANSFER_DMA_MAP;
            } else
                seg->dto_urb->transfer_buffer =
                    xfer->urb->transfer_buffer + buf_itr;
            seg->dto_urb->transfer_buffer_length = buf_itr_size;
        }
        seg->status = WA_SEG_READY;
        buf_itr += buf_itr_size;
        buf_size -= buf_itr_size;
    }
    return 0;

error_dto_alloc:
    kfree(xfer->seg[cnt]);
    cnt--;
error_seg_kzalloc:
    /* use the fact that cnt is left at were it failed */
    for (; cnt > 0; cnt--) {
        if (xfer->is_inbound == 0)
            kfree(xfer->seg[cnt]->dto_urb);
        kfree(xfer->seg[cnt]);
    }
error_segs_kzalloc:
    return result;
}

/*
 * Allocates all the stuff needed to submit a transfer
 *
 * Breaks the whole data buffer in a list of segments, each one has a
 * structure allocated to it and linked in xfer->seg[index]
 *
 * FIXME: merge setup_segs() and the last part of this function, no
 *        need to do two for loops when we could run everything in a
 *        single one
 */
static int __wa_xfer_setup(struct wa_xfer *xfer, struct urb *urb)
{
    int result;
    struct device *dev = &xfer->wa->usb_iface->dev;
    enum wa_xfer_type xfer_type = 0; /* shut up GCC */
    size_t xfer_hdr_size, cnt, transfer_size;
    struct wa_xfer_hdr *xfer_hdr0, *xfer_hdr;

    result = __wa_xfer_setup_sizes(xfer, &xfer_type);
    if (result < 0)
        goto error_setup_sizes;
    xfer_hdr_size = result;
    result = __wa_xfer_setup_segs(xfer, xfer_hdr_size);
    if (result < 0) {
        dev_err(dev, "xfer %p: Failed to allocate %d segments: %d\n",
            xfer, xfer->segs, result);
        goto error_setup_segs;
    }
    /* Fill the first header */
    xfer_hdr0 = &xfer->seg[0]->xfer_hdr;
    wa_xfer_id_init(xfer);
    __wa_xfer_setup_hdr0(xfer, xfer_hdr0, xfer_type, xfer_hdr_size);

    /* Fill remainig headers */
    xfer_hdr = xfer_hdr0;
    transfer_size = urb->transfer_buffer_length;
    xfer_hdr0->dwTransferLength = transfer_size > xfer->seg_size ?
        xfer->seg_size : transfer_size;
    transfer_size -=  xfer->seg_size;
    for (cnt = 1; cnt < xfer->segs; cnt++) {
        xfer_hdr = &xfer->seg[cnt]->xfer_hdr;
        memcpy(xfer_hdr, xfer_hdr0, xfer_hdr_size);
        xfer_hdr->bTransferSegment = cnt;
        xfer_hdr->dwTransferLength = transfer_size > xfer->seg_size ?
            cpu_to_le32(xfer->seg_size)
            : cpu_to_le32(transfer_size);
        xfer->seg[cnt]->status = WA_SEG_READY;
        transfer_size -=  xfer->seg_size;
    }
    xfer_hdr->bTransferSegment |= 0x80; /* this is the last segment */
    result = 0;
error_setup_segs:
error_setup_sizes:
    return result;
}

/*
 *
 *
 * rpipe->seg_lock is held!
 */
static int __wa_seg_submit(struct wa_rpipe *rpipe, struct wa_xfer *xfer,
               struct wa_seg *seg)
{
    int result;
    result = usb_submit_urb(&seg->urb, GFP_ATOMIC);
    if (result < 0) {
        printk(KERN_ERR "xfer %p#%u: REQ submit failed: %d\n",
               xfer, seg->index, result);
        goto error_seg_submit;
    }
    if (seg->dto_urb) {
        result = usb_submit_urb(seg->dto_urb, GFP_ATOMIC);
        if (result < 0) {
            printk(KERN_ERR "xfer %p#%u: DTO submit failed: %d\n",
                   xfer, seg->index, result);
            goto error_dto_submit;
        }
    }
    seg->status = WA_SEG_SUBMITTED;
    rpipe_avail_dec(rpipe);
    return 0;

error_dto_submit:
    usb_unlink_urb(&seg->urb);
error_seg_submit:
    seg->status = WA_SEG_ERROR;
    seg->result = result;
    return result;
}

/*
 * Execute more queued request segments until the maximum concurrent allowed
 *
 * The ugly unlock/lock sequence on the error path is needed as the
 * xfer->lock normally nests the seg_lock and not viceversa.
 *
 */
static void wa_xfer_delayed_run(struct wa_rpipe *rpipe)
{
    int result;
    struct device *dev = &rpipe->wa->usb_iface->dev;
    struct wa_seg *seg;
    struct wa_xfer *xfer;
    unsigned long flags;

    spin_lock_irqsave(&rpipe->seg_lock, flags);
    while (atomic_read(&rpipe->segs_available) > 0
          && !list_empty(&rpipe->seg_list)) {
        seg = list_entry(rpipe->seg_list.next, struct wa_seg,
                 list_node);
        list_del(&seg->list_node);
        xfer = seg->xfer;
        result = __wa_seg_submit(rpipe, xfer, seg);
        dev_dbg(dev, "xfer %p#%u submitted from delayed [%d segments available] %d\n",
            xfer, seg->index, atomic_read(&rpipe->segs_available), result);
        if (unlikely(result < 0)) {
            spin_unlock_irqrestore(&rpipe->seg_lock, flags);
            spin_lock_irqsave(&xfer->lock, flags);
            __wa_xfer_abort(xfer);
            xfer->segs_done++;
            spin_unlock_irqrestore(&xfer->lock, flags);
            spin_lock_irqsave(&rpipe->seg_lock, flags);
        }
    }
    spin_unlock_irqrestore(&rpipe->seg_lock, flags);
}

/*
 *
 * xfer->lock is taken
 *
 * On failure submitting we just stop submitting and return error;
 * wa_urb_enqueue_b() will execute the completion path
 */
static int __wa_xfer_submit(struct wa_xfer *xfer)
{
    int result;
    struct wahc *wa = xfer->wa;
    struct device *dev = &wa->usb_iface->dev;
    unsigned cnt;
    struct wa_seg *seg;
    unsigned long flags;
    struct wa_rpipe *rpipe = xfer->ep->hcpriv;
    size_t maxrequests = le16_to_cpu(rpipe->descr.wRequests);
    u8 available;
    u8 empty;

    spin_lock_irqsave(&wa->xfer_list_lock, flags);
    list_add_tail(&xfer->list_node, &wa->xfer_list);
    spin_unlock_irqrestore(&wa->xfer_list_lock, flags);

    BUG_ON(atomic_read(&rpipe->segs_available) > maxrequests);
    result = 0;
    spin_lock_irqsave(&rpipe->seg_lock, flags);
    for (cnt = 0; cnt < xfer->segs; cnt++) {
        available = atomic_read(&rpipe->segs_available);
        empty = list_empty(&rpipe->seg_list);
        seg = xfer->seg[cnt];
        dev_dbg(dev, "xfer %p#%u: available %u empty %u (%s)\n",
            xfer, cnt, available, empty,
            available == 0 || !empty ? "delayed" : "submitted");
        if (available == 0 || !empty) {
            dev_dbg(dev, "xfer %p#%u: delayed\n", xfer, cnt);
            seg->status = WA_SEG_DELAYED;
            list_add_tail(&seg->list_node, &rpipe->seg_list);
        } else {
            result = __wa_seg_submit(rpipe, xfer, seg);
            if (result < 0) {
                __wa_xfer_abort(xfer);
                goto error_seg_submit;
            }
        }
        xfer->segs_submitted++;
    }
error_seg_submit:
    spin_unlock_irqrestore(&rpipe->seg_lock, flags);
    return result;
}

/*
 * Second part of a URB/transfer enqueuement
 *
 * Assumes this comes from wa_urb_enqueue() [maybe through
 * wa_urb_enqueue_run()]. At this point:
 *
 * xfer->wa filled and refcounted
 * xfer->ep filled with rpipe refcounted if
 *              delayed == 0
 * xfer->urb    filled and refcounted (this is the case when called
 *              from wa_urb_enqueue() as we come from usb_submit_urb()
 *              and when called by wa_urb_enqueue_run(), as we took an
 *              extra ref dropped by _run() after we return).
 * xfer->gfp    filled
 *
 * If we fail at __wa_xfer_submit(), then we just check if we are done
 * and if so, we run the completion procedure. However, if we are not
 * yet done, we do nothing and wait for the completion handlers from
 * the submitted URBs or from the xfer-result path to kick in. If xfer
 * result never kicks in, the xfer will timeout from the USB code and
 * dequeue() will be called.
 */
static void wa_urb_enqueue_b(struct wa_xfer *xfer)
{
    int result;
    unsigned long flags;
    struct urb *urb = xfer->urb;
    struct wahc *wa = xfer->wa;
    struct wusbhc *wusbhc = wa->wusb;
    struct wusb_dev *wusb_dev;
    unsigned done;

    result = rpipe_get_by_ep(wa, xfer->ep, urb, xfer->gfp);
    if (result < 0)
        goto error_rpipe_get;
    result = -ENODEV;
    /* FIXME: segmentation broken -- kills DWA */
    mutex_lock(&wusbhc->mutex);     /* get a WUSB dev */
    if (urb->dev == NULL) {
        mutex_unlock(&wusbhc->mutex);
        goto error_dev_gone;
    }
    wusb_dev = __wusb_dev_get_by_usb_dev(wusbhc, urb->dev);
    if (wusb_dev == NULL) {
        mutex_unlock(&wusbhc->mutex);
        goto error_dev_gone;
    }
    mutex_unlock(&wusbhc->mutex);

    spin_lock_irqsave(&xfer->lock, flags);
    xfer->wusb_dev = wusb_dev;
    result = urb->status;
    if (urb->status != -EINPROGRESS)
        goto error_dequeued;

    result = __wa_xfer_setup(xfer, urb);
    if (result < 0)
        goto error_xfer_setup;
    result = __wa_xfer_submit(xfer);
    if (result < 0)
        goto error_xfer_submit;
    spin_unlock_irqrestore(&xfer->lock, flags);
    return;

    /* this is basically wa_xfer_completion() broken up wa_xfer_giveback()
     * does a wa_xfer_put() that will call wa_xfer_destroy() and clean
     * upundo setup().
     */
error_xfer_setup:
error_dequeued:
    spin_unlock_irqrestore(&xfer->lock, flags);
    /* FIXME: segmentation broken, kills DWA */
    if (wusb_dev)
        wusb_dev_put(wusb_dev);
error_dev_gone:
    rpipe_put(xfer->ep->hcpriv);
error_rpipe_get:
    xfer->result = result;
    wa_xfer_giveback(xfer);
    return;

error_xfer_submit:
    done = __wa_xfer_is_done(xfer);
    xfer->result = result;
    spin_unlock_irqrestore(&xfer->lock, flags);
    if (done)
        wa_xfer_completion(xfer);
}

/*
 * Execute the delayed transfers in the Wire Adapter @wa
 *
 * We need to be careful here, as dequeue() could be called in the
 * middle.  That's why we do the whole thing under the
 * wa->xfer_list_lock. If dequeue() jumps in, it first locks urb->lock
 * and then checks the list -- so as we would be acquiring in inverse
 * order, we just drop the lock once we have the xfer and reacquire it
 * later.
 */
void wa_urb_enqueue_run(struct work_struct *ws)
{
    struct wahc *wa = container_of(ws, struct wahc, xfer_work);
    struct wa_xfer *xfer, *next;
    struct urb *urb;

    spin_lock_irq(&wa->xfer_list_lock);
    list_for_each_entry_safe(xfer, next, &wa->xfer_delayed_list,
                 list_node) {
        list_del_init(&xfer->list_node);
        spin_unlock_irq(&wa->xfer_list_lock);

        urb = xfer->urb;
        wa_urb_enqueue_b(xfer);
        usb_put_urb(urb);   /* taken when queuing */

        spin_lock_irq(&wa->xfer_list_lock);
    }
    spin_unlock_irq(&wa->xfer_list_lock);
}
EXPORT_SYMBOL_GPL(wa_urb_enqueue_run);

/*
 * Submit a transfer to the Wire Adapter in a delayed way
 *
 * The process of enqueuing involves possible sleeps() [see
 * enqueue_b(), for the rpipe_get() and the mutex_lock()]. If we are
 * in an atomic section, we defer the enqueue_b() call--else we call direct.
 *
 * @urb: We own a reference to it done by the HCI Linux USB stack that
 *       will be given up by calling usb_hcd_giveback_urb() or by
 *       returning error from this function -> ergo we don't have to
 *       refcount it.
 */
int wa_urb_enqueue(struct wahc *wa, struct usb_host_endpoint *ep,
           struct urb *urb, gfp_t gfp)
{
    int result;
    struct device *dev = &wa->usb_iface->dev;
    struct wa_xfer *xfer;
    unsigned long my_flags;
    unsigned cant_sleep = irqs_disabled() | in_atomic();

    if (urb->transfer_buffer == NULL
        && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
        && urb->transfer_buffer_length != 0) {
        dev_err(dev, "BUG? urb %p: NULL xfer buffer & NODMA\n", urb);
        dump_stack();
    }

    result = -ENOMEM;
    xfer = kzalloc(sizeof(*xfer), gfp);
    if (xfer == NULL)
        goto error_kmalloc;

    result = -ENOENT;
    if (urb->status != -EINPROGRESS)    /* cancelled */
        goto error_dequeued;        /* before starting? */
    wa_xfer_init(xfer);
    xfer->wa = wa_get(wa);
    xfer->urb = urb;
    xfer->gfp = gfp;
    xfer->ep = ep;
    urb->hcpriv = xfer;

    dev_dbg(dev, "xfer %p urb %p pipe 0x%02x [%d bytes] %s %s %s\n",
        xfer, urb, urb->pipe, urb->transfer_buffer_length,
        urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP ? "dma" : "nodma",
        urb->pipe & USB_DIR_IN ? "inbound" : "outbound",
        cant_sleep ? "deferred" : "inline");

    if (cant_sleep) {
        usb_get_urb(urb);
        spin_lock_irqsave(&wa->xfer_list_lock, my_flags);
        list_add_tail(&xfer->list_node, &wa->xfer_delayed_list);
        spin_unlock_irqrestore(&wa->xfer_list_lock, my_flags);
        queue_work(wusbd, &wa->xfer_work);
    } else {
        wa_urb_enqueue_b(xfer);
    }
    return 0;

error_dequeued:
    kfree(xfer);
error_kmalloc:
    return result;
}
EXPORT_SYMBOL_GPL(wa_urb_enqueue);

/*
 * Dequeue a URB and make sure uwb_hcd_giveback_urb() [completion
 * handler] is called.
 *
 * Until a transfer goes successfully through wa_urb_enqueue() it
 * needs to be dequeued with completion calling; when stuck in delayed
 * or before wa_xfer_setup() is called, we need to do completion.
 *
 *  not setup  If there is no hcpriv yet, that means that that enqueue
 *             still had no time to set the xfer up. Because
 *             urb->status should be other than -EINPROGRESS,
 *             enqueue() will catch that and bail out.
 *
 * If the transfer has gone through setup, we just need to clean it
 * up. If it has gone through submit(), we have to abort it [with an
 * asynch request] and then make sure we cancel each segment.
 *
 */
int wa_urb_dequeue(struct wahc *wa, struct urb *urb)
{
    unsigned long flags, flags2;
    struct wa_xfer *xfer;
    struct wa_seg *seg;
    struct wa_rpipe *rpipe;
    unsigned cnt;
    unsigned rpipe_ready = 0;

    xfer = urb->hcpriv;
    if (xfer == NULL) {
        /* NOthing setup yet enqueue will see urb->status !=
         * -EINPROGRESS (by hcd layer) and bail out with
         * error, no need to do completion
         */
        BUG_ON(urb->status == -EINPROGRESS);
        goto out;
    }
    spin_lock_irqsave(&xfer->lock, flags);
    rpipe = xfer->ep->hcpriv;
    /* Check the delayed list -> if there, release and complete */
    spin_lock_irqsave(&wa->xfer_list_lock, flags2);
    if (!list_empty(&xfer->list_node) && xfer->seg == NULL)
        goto dequeue_delayed;
    spin_unlock_irqrestore(&wa->xfer_list_lock, flags2);
    if (xfer->seg == NULL)      /* still hasn't reached */
        goto out_unlock;    /* setup(), enqueue_b() completes */
    /* Ok, the xfer is in flight already, it's been setup and submitted.*/
    __wa_xfer_abort(xfer);
    for (cnt = 0; cnt < xfer->segs; cnt++) {
        seg = xfer->seg[cnt];
        switch (seg->status) {
        case WA_SEG_NOTREADY:
        case WA_SEG_READY:
            printk(KERN_ERR "xfer %p#%u: dequeue bad state %u\n",
                   xfer, cnt, seg->status);
            WARN_ON(1);
            break;
        case WA_SEG_DELAYED:
            seg->status = WA_SEG_ABORTED;
            spin_lock_irqsave(&rpipe->seg_lock, flags2);
            list_del(&seg->list_node);
            xfer->segs_done++;
            rpipe_ready = rpipe_avail_inc(rpipe);
            spin_unlock_irqrestore(&rpipe->seg_lock, flags2);
            break;
        case WA_SEG_SUBMITTED:
            seg->status = WA_SEG_ABORTED;
            usb_unlink_urb(&seg->urb);
            if (xfer->is_inbound == 0)
                usb_unlink_urb(seg->dto_urb);
            xfer->segs_done++;
            rpipe_ready = rpipe_avail_inc(rpipe);
            break;
        case WA_SEG_PENDING:
            seg->status = WA_SEG_ABORTED;
            xfer->segs_done++;
            rpipe_ready = rpipe_avail_inc(rpipe);
            break;
        case WA_SEG_DTI_PENDING:
            usb_unlink_urb(wa->dti_urb);
            seg->status = WA_SEG_ABORTED;
            xfer->segs_done++;
            rpipe_ready = rpipe_avail_inc(rpipe);
            break;
        case WA_SEG_DONE:
        case WA_SEG_ERROR:
        case WA_SEG_ABORTED:
            break;
        }
    }
    xfer->result = urb->status; /* -ENOENT or -ECONNRESET */
    __wa_xfer_is_done(xfer);
    spin_unlock_irqrestore(&xfer->lock, flags);
    wa_xfer_completion(xfer);
    if (rpipe_ready)
        wa_xfer_delayed_run(rpipe);
    return 0;

out_unlock:
    spin_unlock_irqrestore(&xfer->lock, flags);
out:
    return 0;

dequeue_delayed:
    list_del_init(&xfer->list_node);
    spin_unlock_irqrestore(&wa->xfer_list_lock, flags2);
    xfer->result = urb->status;
    spin_unlock_irqrestore(&xfer->lock, flags);
    wa_xfer_giveback(xfer);
    usb_put_urb(urb);       /* we got a ref in enqueue() */
    return 0;
}
EXPORT_SYMBOL_GPL(wa_urb_dequeue);

/*
 * Translation from WA status codes (WUSB1.0 Table 8.15) to errno
 * codes
 *
 * Positive errno values are internal inconsistencies and should be
 * flagged louder. Negative are to be passed up to the user in the
 * normal way.
 *
 * @status: USB WA status code -- high two bits are stripped.
 */
static int wa_xfer_status_to_errno(u8 status)
{
    int errno;
    u8 real_status = status;
    static int xlat[] = {
        [WA_XFER_STATUS_SUCCESS] =      0,
        [WA_XFER_STATUS_HALTED] =       -EPIPE,
        [WA_XFER_STATUS_DATA_BUFFER_ERROR] =    -ENOBUFS,
        [WA_XFER_STATUS_BABBLE] =       -EOVERFLOW,
        [WA_XFER_RESERVED] =            EINVAL,
        [WA_XFER_STATUS_NOT_FOUND] =        0,
        [WA_XFER_STATUS_INSUFFICIENT_RESOURCE] = -ENOMEM,
        [WA_XFER_STATUS_TRANSACTION_ERROR] =    -EILSEQ,
        [WA_XFER_STATUS_ABORTED] =      -EINTR,
        [WA_XFER_STATUS_RPIPE_NOT_READY] =  EINVAL,
        [WA_XFER_INVALID_FORMAT] =      EINVAL,
        [WA_XFER_UNEXPECTED_SEGMENT_NUMBER] =   EINVAL,
        [WA_XFER_STATUS_RPIPE_TYPE_MISMATCH] =  EINVAL,
    };
    status &= 0x3f;

    if (status == 0)
        return 0;
    if (status >= ARRAY_SIZE(xlat)) {
        printk_ratelimited(KERN_ERR "%s(): BUG? "
                   "Unknown WA transfer status 0x%02x\n",
                   __func__, real_status);
        return -EINVAL;
    }
    errno = xlat[status];
    if (unlikely(errno > 0)) {
        printk_ratelimited(KERN_ERR "%s(): BUG? "
                   "Inconsistent WA status: 0x%02x\n",
                   __func__, real_status);
        errno = -errno;
    }
    return errno;
}

/*
 * Process a xfer result completion message
 *
 * inbound transfers: need to schedule a DTI read
 *
 * FIXME: this functio needs to be broken up in parts
 */
static void wa_xfer_result_chew(struct wahc *wa, struct wa_xfer *xfer)
{
    int result;
    struct device *dev = &wa->usb_iface->dev;
    unsigned long flags;
    u8 seg_idx;
    struct wa_seg *seg;
    struct wa_rpipe *rpipe;
    struct wa_xfer_result *xfer_result = wa->xfer_result;
    u8 done = 0;
    u8 usb_status;
    unsigned rpipe_ready = 0;

    spin_lock_irqsave(&xfer->lock, flags);
    seg_idx = xfer_result->bTransferSegment & 0x7f;
    if (unlikely(seg_idx >= xfer->segs))
        goto error_bad_seg;
    seg = xfer->seg[seg_idx];
    rpipe = xfer->ep->hcpriv;
    usb_status = xfer_result->bTransferStatus;
    dev_dbg(dev, "xfer %p#%u: bTransferStatus 0x%02x (seg %u)\n",
        xfer, seg_idx, usb_status, seg->status);
    if (seg->status == WA_SEG_ABORTED
        || seg->status == WA_SEG_ERROR) /* already handled */
        goto segment_aborted;
    if (seg->status == WA_SEG_SUBMITTED)    /* ops, got here */
        seg->status = WA_SEG_PENDING;   /* before wa_seg{_dto}_cb() */
    if (seg->status != WA_SEG_PENDING) {
        if (printk_ratelimit())
            dev_err(dev, "xfer %p#%u: Bad segment state %u\n",
                xfer, seg_idx, seg->status);
        seg->status = WA_SEG_PENDING;   /* workaround/"fix" it */
    }
    if (usb_status & 0x80) {
        seg->result = wa_xfer_status_to_errno(usb_status);
        dev_err(dev, "DTI: xfer %p#%u failed (0x%02x)\n",
            xfer, seg->index, usb_status);
        goto error_complete;
    }
    /* FIXME: we ignore warnings, tally them for stats */
    if (usb_status & 0x40)      /* Warning?... */
        usb_status = 0;     /* ... pass */
    if (xfer->is_inbound) { /* IN data phase: read to buffer */
        seg->status = WA_SEG_DTI_PENDING;
        BUG_ON(wa->buf_in_urb->status == -EINPROGRESS);
        if (xfer->is_dma) {
            wa->buf_in_urb->transfer_dma =
                xfer->urb->transfer_dma
                + seg_idx * xfer->seg_size;
            wa->buf_in_urb->transfer_flags
                |= URB_NO_TRANSFER_DMA_MAP;
        } else {
            wa->buf_in_urb->transfer_buffer =
                xfer->urb->transfer_buffer
                + seg_idx * xfer->seg_size;
            wa->buf_in_urb->transfer_flags
                &= ~URB_NO_TRANSFER_DMA_MAP;
        }
        wa->buf_in_urb->transfer_buffer_length =
            le32_to_cpu(xfer_result->dwTransferLength);
        wa->buf_in_urb->context = seg;
        result = usb_submit_urb(wa->buf_in_urb, GFP_ATOMIC);
        if (result < 0)
            goto error_submit_buf_in;
    } else {
        /* OUT data phase, complete it -- */
        seg->status = WA_SEG_DONE;
        seg->result = le32_to_cpu(xfer_result->dwTransferLength);
        xfer->segs_done++;
        rpipe_ready = rpipe_avail_inc(rpipe);
        done = __wa_xfer_is_done(xfer);
    }
    spin_unlock_irqrestore(&xfer->lock, flags);
    if (done)
        wa_xfer_completion(xfer);
    if (rpipe_ready)
        wa_xfer_delayed_run(rpipe);
    return;

error_submit_buf_in:
    if (edc_inc(&wa->dti_edc, EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME)) {
        dev_err(dev, "DTI: URB max acceptable errors "
            "exceeded, resetting device\n");
        wa_reset_all(wa);
    }
    if (printk_ratelimit())
        dev_err(dev, "xfer %p#%u: can't submit DTI data phase: %d\n",
            xfer, seg_idx, result);
    seg->result = result;
error_complete:
    seg->status = WA_SEG_ERROR;
    xfer->segs_done++;
    rpipe_ready = rpipe_avail_inc(rpipe);
    __wa_xfer_abort(xfer);
    done = __wa_xfer_is_done(xfer);
    spin_unlock_irqrestore(&xfer->lock, flags);
    if (done)
        wa_xfer_completion(xfer);
    if (rpipe_ready)
        wa_xfer_delayed_run(rpipe);
    return;

error_bad_seg:
    spin_unlock_irqrestore(&xfer->lock, flags);
    wa_urb_dequeue(wa, xfer->urb);
    if (printk_ratelimit())
        dev_err(dev, "xfer %p#%u: bad segment\n", xfer, seg_idx);
    if (edc_inc(&wa->dti_edc, EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME)) {
        dev_err(dev, "DTI: URB max acceptable errors "
            "exceeded, resetting device\n");
        wa_reset_all(wa);
    }
    return;

segment_aborted:
    /* nothing to do, as the aborter did the completion */
    spin_unlock_irqrestore(&xfer->lock, flags);
}

/*
 * Callback for the IN data phase
 *
 * If successful transition state; otherwise, take a note of the
 * error, mark this segment done and try completion.
 *
 * Note we don't access until we are sure that the transfer hasn't
 * been cancelled (ECONNRESET, ENOENT), which could mean that
 * seg->xfer could be already gone.
 */
static void wa_buf_in_cb(struct urb *urb)
{
    struct wa_seg *seg = urb->context;
    struct wa_xfer *xfer = seg->xfer;
    struct wahc *wa;
    struct device *dev;
    struct wa_rpipe *rpipe;
    unsigned rpipe_ready;
    unsigned long flags;
    u8 done = 0;

    switch (urb->status) {
    case 0:
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        rpipe = xfer->ep->hcpriv;
        dev_dbg(dev, "xfer %p#%u: data in done (%zu bytes)\n",
            xfer, seg->index, (size_t)urb->actual_length);
        seg->status = WA_SEG_DONE;
        seg->result = urb->actual_length;
        xfer->segs_done++;
        rpipe_ready = rpipe_avail_inc(rpipe);
        done = __wa_xfer_is_done(xfer);
        spin_unlock_irqrestore(&xfer->lock, flags);
        if (done)
            wa_xfer_completion(xfer);
        if (rpipe_ready)
            wa_xfer_delayed_run(rpipe);
        break;
    case -ECONNRESET:   /* URB unlinked; no need to do anything */
    case -ENOENT:       /* as it was done by the who unlinked us */
        break;
    default:        /* Other errors ... */
        spin_lock_irqsave(&xfer->lock, flags);
        wa = xfer->wa;
        dev = &wa->usb_iface->dev;
        rpipe = xfer->ep->hcpriv;
        if (printk_ratelimit())
            dev_err(dev, "xfer %p#%u: data in error %d\n",
                xfer, seg->index, urb->status);
        if (edc_inc(&wa->nep_edc, EDC_MAX_ERRORS,
                EDC_ERROR_TIMEFRAME)){
            dev_err(dev, "DTO: URB max acceptable errors "
                "exceeded, resetting device\n");
            wa_reset_all(wa);
        }
        seg->status = WA_SEG_ERROR;
        seg->result = urb->status;
        xfer->segs_done++;
        rpipe_ready = rpipe_avail_inc(rpipe);
        __wa_xfer_abort(xfer);
        done = __wa_xfer_is_done(xfer);
        spin_unlock_irqrestore(&xfer->lock, flags);
        if (done)
            wa_xfer_completion(xfer);
        if (rpipe_ready)
            wa_xfer_delayed_run(rpipe);
    }
}

/*
 * Handle an incoming transfer result buffer
 *
 * Given a transfer result buffer, it completes the transfer (possibly
 * scheduling and buffer in read) and then resubmits the DTI URB for a
 * new transfer result read.
 *
 *
 * The xfer_result DTI URB state machine
 *
 * States: OFF | RXR (Read-Xfer-Result) | RBI (Read-Buffer-In)
 *
 * We start in OFF mode, the first xfer_result notification [through
 * wa_handle_notif_xfer()] moves us to RXR by posting the DTI-URB to
 * read.
 *
 * We receive a buffer -- if it is not a xfer_result, we complain and
 * repost the DTI-URB. If it is a xfer_result then do the xfer seg
 * request accounting. If it is an IN segment, we move to RBI and post
 * a BUF-IN-URB to the right buffer. The BUF-IN-URB callback will
 * repost the DTI-URB and move to RXR state. if there was no IN
 * segment, it will repost the DTI-URB.
 *
 * We go back to OFF when we detect a ENOENT or ESHUTDOWN (or too many
 * errors) in the URBs.
 */
static void wa_xfer_result_cb(struct urb *urb)
{
    int result;
    struct wahc *wa = urb->context;
    struct device *dev = &wa->usb_iface->dev;
    struct wa_xfer_result *xfer_result;
    u32 xfer_id;
    struct wa_xfer *xfer;
    u8 usb_status;

    BUG_ON(wa->dti_urb != urb);
    switch (wa->dti_urb->status) {
    case 0:
        /* We have a xfer result buffer; check it */
        dev_dbg(dev, "DTI: xfer result %d bytes at %p\n",
            urb->actual_length, urb->transfer_buffer);
        if (wa->dti_urb->actual_length != sizeof(*xfer_result)) {
            dev_err(dev, "DTI Error: xfer result--bad size "
                "xfer result (%d bytes vs %zu needed)\n",
                urb->actual_length, sizeof(*xfer_result));
            break;
        }
        xfer_result = wa->xfer_result;
        if (xfer_result->hdr.bLength != sizeof(*xfer_result)) {
            dev_err(dev, "DTI Error: xfer result--"
                "bad header length %u\n",
                xfer_result->hdr.bLength);
            break;
        }
        if (xfer_result->hdr.bNotifyType != WA_XFER_RESULT) {
            dev_err(dev, "DTI Error: xfer result--"
                "bad header type 0x%02x\n",
                xfer_result->hdr.bNotifyType);
            break;
        }
        usb_status = xfer_result->bTransferStatus & 0x3f;
        if (usb_status == WA_XFER_STATUS_ABORTED
            || usb_status == WA_XFER_STATUS_NOT_FOUND)
            /* taken care of already */
            break;
        xfer_id = xfer_result->dwTransferID;
        xfer = wa_xfer_get_by_id(wa, xfer_id);
        if (xfer == NULL) {
            /* FIXME: transaction might have been cancelled */
            dev_err(dev, "DTI Error: xfer result--"
                "unknown xfer 0x%08x (status 0x%02x)\n",
                xfer_id, usb_status);
            break;
        }
        wa_xfer_result_chew(wa, xfer);
        wa_xfer_put(xfer);
        break;
    case -ENOENT:       /* (we killed the URB)...so, no broadcast */
    case -ESHUTDOWN:    /* going away! */
        dev_dbg(dev, "DTI: going down! %d\n", urb->status);
        goto out;
    default:
        /* Unknown error */
        if (edc_inc(&wa->dti_edc, EDC_MAX_ERRORS,
                EDC_ERROR_TIMEFRAME)) {
            dev_err(dev, "DTI: URB max acceptable errors "
                "exceeded, resetting device\n");
            wa_reset_all(wa);
            goto out;
        }
        if (printk_ratelimit())
            dev_err(dev, "DTI: URB error %d\n", urb->status);
        break;
    }
    /* Resubmit the DTI URB */
    result = usb_submit_urb(wa->dti_urb, GFP_ATOMIC);
    if (result < 0) {
        dev_err(dev, "DTI Error: Could not submit DTI URB (%d), "
            "resetting\n", result);
        wa_reset_all(wa);
    }
out:
    return;
}

/*
 * Transfer complete notification
 *
 * Called from the notif.c code. We get a notification on EP2 saying
 * that some endpoint has some transfer result data available. We are
 * about to read it.
 *
 * To speed up things, we always have a URB reading the DTI URB; we
 * don't really set it up and start it until the first xfer complete
 * notification arrives, which is what we do here.
 *
 * Follow up in wa_xfer_result_cb(), as that's where the whole state
 * machine starts.
 *
 * So here we just initialize the DTI URB for reading transfer result
 * notifications and also the buffer-in URB, for reading buffers. Then
 * we just submit the DTI URB.
 *
 * @wa shall be referenced
 */
void wa_handle_notif_xfer(struct wahc *wa, struct wa_notif_hdr *notif_hdr)
{
    int result;
    struct device *dev = &wa->usb_iface->dev;
    struct wa_notif_xfer *notif_xfer;
    const struct usb_endpoint_descriptor *dti_epd = wa->dti_epd;

    notif_xfer = container_of(notif_hdr, struct wa_notif_xfer, hdr);
    BUG_ON(notif_hdr->bNotifyType != WA_NOTIF_TRANSFER);

    if ((0x80 | notif_xfer->bEndpoint) != dti_epd->bEndpointAddress) {
        /* FIXME: hardcoded limitation, adapt */
        dev_err(dev, "BUG: DTI ep is %u, not %u (hack me)\n",
            notif_xfer->bEndpoint, dti_epd->bEndpointAddress);
        goto error;
    }
    if (wa->dti_urb != NULL)    /* DTI URB already started */
        goto out;

    wa->dti_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (wa->dti_urb == NULL) {
        dev_err(dev, "Can't allocate DTI URB\n");
        goto error_dti_urb_alloc;
    }
    usb_fill_bulk_urb(
        wa->dti_urb, wa->usb_dev,
        usb_rcvbulkpipe(wa->usb_dev, 0x80 | notif_xfer->bEndpoint),
        wa->xfer_result, wa->xfer_result_size,
        wa_xfer_result_cb, wa);

    wa->buf_in_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (wa->buf_in_urb == NULL) {
        dev_err(dev, "Can't allocate BUF-IN URB\n");
        goto error_buf_in_urb_alloc;
    }
    usb_fill_bulk_urb(
        wa->buf_in_urb, wa->usb_dev,
        usb_rcvbulkpipe(wa->usb_dev, 0x80 | notif_xfer->bEndpoint),
        NULL, 0, wa_buf_in_cb, wa);
    result = usb_submit_urb(wa->dti_urb, GFP_KERNEL);
    if (result < 0) {
        dev_err(dev, "DTI Error: Could not submit DTI URB (%d), "
            "resetting\n", result);
        goto error_dti_urb_submit;
    }
out:
    return;

error_dti_urb_submit:
    usb_put_urb(wa->buf_in_urb);
error_buf_in_urb_alloc:
    usb_put_urb(wa->dti_urb);
    wa->dti_urb = NULL;
error_dti_urb_alloc:
error:
    wa_reset_all(wa);
}