usb_handle_request.c

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/* $FreeBSD$ */
/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#ifdef USB_GLOBAL_INCLUDE_FILE
#include USB_GLOBAL_INCLUDE_FILE
#else
#include <sys/stdint.h>
#include <sys/stddef.h>
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/bus.h>
#include <sys/module.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/condvar.h>
#include <sys/sysctl.h>
#include <sys/sx.h>
#include <sys/unistd.h>
#include <sys/callout.h>
#include <sys/malloc.h>
#include <sys/priv.h>
 
#include <dev/usb/usb.h>
#include <dev/usb/usbdi.h>
#include <dev/usb/usbdi_util.h>
#include "usb_if.h"
 
#define USB_DEBUG_VAR usb_debug
 
#include <dev/usb/usb_core.h>
#include <dev/usb/usb_process.h>
#include <dev/usb/usb_busdma.h>
#include <dev/usb/usb_transfer.h>
#include <dev/usb/usb_device.h>
#include <dev/usb/usb_debug.h>
#include <dev/usb/usb_dynamic.h>
#include <dev/usb/usb_hub.h>
 
#include <dev/usb/usb_controller.h>
#include <dev/usb/usb_bus.h>
#endif                  /* USB_GLOBAL_INCLUDE_FILE */
 
/* function prototypes */
 
static uint8_t usb_handle_get_stall(struct usb_device *, uint8_t);
static usb_error_t       usb_handle_remote_wakeup(struct usb_xfer *, uint8_t);
static usb_error_t       usb_handle_request(struct usb_xfer *);
static usb_error_t       usb_handle_set_config(struct usb_xfer *, uint8_t);
static usb_error_t       usb_handle_set_stall(struct usb_xfer *, uint8_t,
                            uint8_t);
static usb_error_t       usb_handle_iface_request(struct usb_xfer *, void **,
                            uint16_t *, struct usb_device_request, uint16_t,
                            uint8_t);
 
/*------------------------------------------------------------------------*
 *      usb_handle_request_callback
 *
 * This function is the USB callback for generic USB Device control
 * transfers.
 *------------------------------------------------------------------------*/
void
usb_handle_request_callback(struct usb_xfer *xfer, usb_error_t error)
{
        usb_error_t err;
 
        /* check the current transfer state */
 
        switch (USB_GET_STATE(xfer)) {
        case USB_ST_SETUP:
        case USB_ST_TRANSFERRED:
 
                /* handle the request */
                err = usb_handle_request(xfer);
 
                if (err) {
                        if (err == USB_ERR_BAD_CONTEXT) {
                                /* we need to re-setup the control transfer */
                                usb_needs_explore(xfer->xroot->bus, 0);
                                break;
                        }
                        goto tr_restart;
                }
                usbd_transfer_submit(xfer);
                break;
 
        default:
                /* check if a control transfer is active */
                if (xfer->flags_int.control_rem != 0xFFFF) {
                        /* handle the request */
                        err = usb_handle_request(xfer);
                }
                if (xfer->error != USB_ERR_CANCELLED) {
                        /* should not happen - try stalling */
                        goto tr_restart;
                }
                break;
        }
        return;
 
tr_restart:
        /*
         * If a control transfer is active, stall it, and wait for the
         * next control transfer.
         */
        usbd_xfer_set_frame_len(xfer, 0, sizeof(struct usb_device_request));
        xfer->nframes = 1;
        xfer->flags.manual_status = 1;
        xfer->flags.force_short_xfer = 0;
        usbd_xfer_set_stall(xfer);      /* cancel previous transfer, if any */
        usbd_transfer_submit(xfer);
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_set_config
 *
 * Returns:
 *    0: Success
 * Else: Failure
 *------------------------------------------------------------------------*/
static usb_error_t
usb_handle_set_config(struct usb_xfer *xfer, uint8_t conf_no)
{
        struct usb_device *udev = xfer->xroot->udev;
        usb_error_t err = 0;
        uint8_t do_unlock;
 
        /*
         * We need to protect against other threads doing probe and
         * attach:
         */
        USB_XFER_UNLOCK(xfer);
 
        /* Prevent re-enumeration */
        do_unlock = usbd_enum_lock(udev);
 
        if (conf_no == USB_UNCONFIG_NO) {
                conf_no = USB_UNCONFIG_INDEX;
        } else {
                /*
                 * The relationship between config number and config index
                 * is very simple in our case:
                 */
                conf_no--;
        }
 
        if (usbd_set_config_index(udev, conf_no)) {
                DPRINTF("set config %d failed\n", conf_no);
                err = USB_ERR_STALLED;
                goto done;
        }
        if (usb_probe_and_attach(udev, USB_IFACE_INDEX_ANY)) {
                DPRINTF("probe and attach failed\n");
                err = USB_ERR_STALLED;
                goto done;
        }
done:
        if (do_unlock)
                usbd_enum_unlock(udev);
        USB_XFER_LOCK(xfer);
        return (err);
}
 
static usb_error_t
usb_check_alt_setting(struct usb_device *udev, 
     struct usb_interface *iface, uint8_t alt_index)
{
        uint8_t do_unlock;
        usb_error_t err = 0;
 
        /* Prevent re-enumeration */
        do_unlock = usbd_enum_lock(udev);
 
        if (alt_index >= usbd_get_no_alts(udev->cdesc, iface->idesc))
                err = USB_ERR_INVAL;
 
        if (do_unlock)
                usbd_enum_unlock(udev);
 
        return (err);
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_iface_request
 *
 * Returns:
 *    0: Success
 * Else: Failure
 *------------------------------------------------------------------------*/
static usb_error_t
usb_handle_iface_request(struct usb_xfer *xfer,
    void **ppdata, uint16_t *plen,
    struct usb_device_request req, uint16_t off, uint8_t state)
{
        struct usb_interface *iface;
        struct usb_interface *iface_parent;     /* parent interface */
        struct usb_device *udev = xfer->xroot->udev;
        int error;
        uint8_t iface_index;
        uint8_t temp_state;
        uint8_t do_unlock;
 
        if ((req.bmRequestType & 0x1F) == UT_INTERFACE) {
                iface_index = req.wIndex[0];    /* unicast */
        } else {
                iface_index = 0;        /* broadcast */
        }
 
        /*
         * We need to protect against other threads doing probe and
         * attach:
         */
        USB_XFER_UNLOCK(xfer);
 
        /* Prevent re-enumeration */
        do_unlock = usbd_enum_lock(udev);
 
        error = ENXIO;
 
tr_repeat:
        iface = usbd_get_iface(udev, iface_index);
        if ((iface == NULL) ||
            (iface->idesc == NULL)) {
                /* end of interfaces non-existing interface */
                goto tr_stalled;
        }
        /* set initial state */
 
        temp_state = state;
 
        /* forward request to interface, if any */
 
        if ((error != 0) &&
            (error != ENOTTY) &&
            (iface->subdev != NULL) &&
            device_is_attached(iface->subdev)) {
#if 0
                DEVMETHOD(usb_handle_request, NULL);    /* dummy */
#endif
                error = USB_HANDLE_REQUEST(iface->subdev,
                    &req, ppdata, plen,
                    off, &temp_state);
        }
        iface_parent = usbd_get_iface(udev, iface->parent_iface_index);
 
        if ((iface_parent == NULL) ||
            (iface_parent->idesc == NULL)) {
                /* non-existing interface */
                iface_parent = NULL;
        }
        /* forward request to parent interface, if any */
 
        if ((error != 0) &&
            (error != ENOTTY) &&
            (iface_parent != NULL) &&
            (iface_parent->subdev != NULL) &&
            ((req.bmRequestType & 0x1F) == UT_INTERFACE) &&
            (iface_parent->subdev != iface->subdev) &&
            device_is_attached(iface_parent->subdev)) {
                error = USB_HANDLE_REQUEST(iface_parent->subdev,
                    &req, ppdata, plen, off, &temp_state);
        }
        if (error == 0) {
                /* negativly adjust pointer and length */
                *ppdata = ((uint8_t *)(*ppdata)) - off;
                *plen += off;
 
                if ((state == USB_HR_NOT_COMPLETE) &&
                    (temp_state == USB_HR_COMPLETE_OK))
                        goto tr_short;
                else
                        goto tr_valid;
        } else if (error == ENOTTY) {
                goto tr_stalled;
        }
        if ((req.bmRequestType & 0x1F) != UT_INTERFACE) {
                iface_index++;          /* iterate */
                goto tr_repeat;
        }
        if (state != USB_HR_NOT_COMPLETE) {
                /* we are complete */
                goto tr_valid;
        }
        switch (req.bmRequestType) {
        case UT_WRITE_INTERFACE:
                switch (req.bRequest) {
                case UR_SET_INTERFACE:
                        /*
                         * We assume that the endpoints are the same
                         * across the alternate settings.
                         *
                         * Reset the endpoints, because re-attaching
                         * only a part of the device is not possible.
                         */
                        error = usb_check_alt_setting(udev,
                            iface, req.wValue[0]);
                        if (error) {
                                DPRINTF("alt setting does not exist %s\n",
                                    usbd_errstr(error));
                                goto tr_stalled;
                        }
                        error = usb_reset_iface_endpoints(udev, iface_index);
                        if (error) {
                                DPRINTF("alt setting failed %s\n",
                                    usbd_errstr(error));
                                goto tr_stalled;
                        }
                        /* update the current alternate setting */
                        iface->alt_index = req.wValue[0];
                        break;
 
                default:
                        goto tr_stalled;
                }
                break;
 
        case UT_READ_INTERFACE:
                switch (req.bRequest) {
                case UR_GET_INTERFACE:
                        *ppdata = &iface->alt_index;
                        *plen = 1;
                        break;
 
                default:
                        goto tr_stalled;
                }
                break;
        default:
                goto tr_stalled;
        }
tr_valid:
        if (do_unlock)
                usbd_enum_unlock(udev);
        USB_XFER_LOCK(xfer);
        return (0);
 
tr_short:
        if (do_unlock)
                usbd_enum_unlock(udev);
        USB_XFER_LOCK(xfer);
        return (USB_ERR_SHORT_XFER);
 
tr_stalled:
        if (do_unlock)
                usbd_enum_unlock(udev);
        USB_XFER_LOCK(xfer);
        return (USB_ERR_STALLED);
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_stall
 *
 * Returns:
 *    0: Success
 * Else: Failure
 *------------------------------------------------------------------------*/
static usb_error_t
usb_handle_set_stall(struct usb_xfer *xfer, uint8_t ep, uint8_t do_stall)
{
        struct usb_device *udev = xfer->xroot->udev;
        usb_error_t err;
 
        USB_XFER_UNLOCK(xfer);
        err = usbd_set_endpoint_stall(udev,
            usbd_get_ep_by_addr(udev, ep), do_stall);
        USB_XFER_LOCK(xfer);
        return (err);
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_get_stall
 *
 * Returns:
 *    0: Success
 * Else: Failure
 *------------------------------------------------------------------------*/
static uint8_t
usb_handle_get_stall(struct usb_device *udev, uint8_t ea_val)
{
        struct usb_endpoint *ep;
        uint8_t halted;
 
        ep = usbd_get_ep_by_addr(udev, ea_val);
        if (ep == NULL) {
                /* nothing to do */
                return (0);
        }
        USB_BUS_LOCK(udev->bus);
        halted = ep->is_stalled;
        USB_BUS_UNLOCK(udev->bus);
 
        return (halted);
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_remote_wakeup
 *
 * Returns:
 *    0: Success
 * Else: Failure
 *------------------------------------------------------------------------*/
static usb_error_t
usb_handle_remote_wakeup(struct usb_xfer *xfer, uint8_t is_on)
{
        struct usb_device *udev;
        struct usb_bus *bus;
 
        udev = xfer->xroot->udev;
        bus = udev->bus;
 
        USB_BUS_LOCK(bus);
 
        if (is_on) {
                udev->flags.remote_wakeup = 1;
        } else {
                udev->flags.remote_wakeup = 0;
        }
 
        USB_BUS_UNLOCK(bus);
 
#if USB_HAVE_POWERD
        /* In case we are out of sync, update the power state. */
        usb_bus_power_update(udev->bus);
#endif
        return (0);                     /* success */
}
 
/*------------------------------------------------------------------------*
 *      usb_handle_request
 *
 * Internal state sequence:
 *
 * USB_HR_NOT_COMPLETE -> USB_HR_COMPLETE_OK v USB_HR_COMPLETE_ERR
 *
 * Returns:
 * 0: Ready to start hardware
 * Else: Stall current transfer, if any
 *------------------------------------------------------------------------*/
static usb_error_t
usb_handle_request(struct usb_xfer *xfer)
{
        struct usb_device_request req;
        struct usb_device *udev;
        const void *src_zcopy;          /* zero-copy source pointer */
        const void *src_mcopy;          /* non zero-copy source pointer */
        uint16_t off;                   /* data offset */
        uint16_t rem;                   /* data remainder */
        uint16_t max_len;               /* max fragment length */
        uint16_t wValue;
        uint8_t state;
        uint8_t is_complete = 1;
        usb_error_t err;
        union {
                uWord   wStatus;
                uint8_t buf[2];
        }     temp;
 
        /*
         * Filter the USB transfer state into
         * something which we understand:
         */
 
        switch (USB_GET_STATE(xfer)) {
        case USB_ST_SETUP:
                state = USB_HR_NOT_COMPLETE;
 
                if (!xfer->flags_int.control_act) {
                        /* nothing to do */
                        goto tr_stalled;
                }
                break;
        case USB_ST_TRANSFERRED:
                if (!xfer->flags_int.control_act) {
                        state = USB_HR_COMPLETE_OK;
                } else {
                        state = USB_HR_NOT_COMPLETE;
                }
                break;
        default:
                state = USB_HR_COMPLETE_ERR;
                break;
        }
 
        /* reset frame stuff */
 
        usbd_xfer_set_frame_len(xfer, 0, 0);
 
        usbd_xfer_set_frame_offset(xfer, 0, 0);
        usbd_xfer_set_frame_offset(xfer, sizeof(req), 1);
 
        /* get the current request, if any */
 
        usbd_copy_out(xfer->frbuffers, 0, &req, sizeof(req));
 
        if (xfer->flags_int.control_rem == 0xFFFF) {
                /* first time - not initialised */
                rem = UGETW(req.wLength);
                off = 0;
        } else {
                /* not first time - initialised */
                rem = xfer->flags_int.control_rem;
                off = UGETW(req.wLength) - rem;
        }
 
        /* set some defaults */
 
        max_len = 0;
        src_zcopy = NULL;
        src_mcopy = NULL;
        udev = xfer->xroot->udev;
 
        /* get some request fields decoded */
 
        wValue = UGETW(req.wValue);
 
        DPRINTF("req 0x%02x 0x%02x 0x%04x 0x%04x "
            "off=0x%x rem=0x%x, state=%d\n", req.bmRequestType,
            req.bRequest, wValue, UGETW(req.wIndex), off, rem, state);
 
        /* demultiplex the control request */
 
        switch (req.bmRequestType) {
        case UT_READ_DEVICE:
                if (state != USB_HR_NOT_COMPLETE) {
                        break;
                }
                switch (req.bRequest) {
                case UR_GET_DESCRIPTOR:
                        goto tr_handle_get_descriptor;
                case UR_GET_CONFIG:
                        goto tr_handle_get_config;
                case UR_GET_STATUS:
                        goto tr_handle_get_status;
                default:
                        goto tr_stalled;
                }
                break;
 
        case UT_WRITE_DEVICE:
                switch (req.bRequest) {
                case UR_SET_ADDRESS:
                        goto tr_handle_set_address;
                case UR_SET_CONFIG:
                        goto tr_handle_set_config;
                case UR_CLEAR_FEATURE:
                        switch (wValue) {
                        case UF_DEVICE_REMOTE_WAKEUP:
                                goto tr_handle_clear_wakeup;
                        default:
                                goto tr_stalled;
                        }
                        break;
                case UR_SET_FEATURE:
                        switch (wValue) {
                        case UF_DEVICE_REMOTE_WAKEUP:
                                goto tr_handle_set_wakeup;
                        default:
                                goto tr_stalled;
                        }
                        break;
                default:
                        goto tr_stalled;
                }
                break;
 
        case UT_WRITE_ENDPOINT:
                switch (req.bRequest) {
                case UR_CLEAR_FEATURE:
                        switch (wValue) {
                        case UF_ENDPOINT_HALT:
                                goto tr_handle_clear_halt;
                        default:
                                goto tr_stalled;
                        }
                        break;
                case UR_SET_FEATURE:
                        switch (wValue) {
                        case UF_ENDPOINT_HALT:
                                goto tr_handle_set_halt;
                        default:
                                goto tr_stalled;
                        }
                        break;
                default:
                        goto tr_stalled;
                }
                break;
 
        case UT_READ_ENDPOINT:
                switch (req.bRequest) {
                case UR_GET_STATUS:
                        goto tr_handle_get_ep_status;
                default:
                        goto tr_stalled;
                }
                break;
        default:
                /* we use "USB_ADD_BYTES" to de-const the src_zcopy */
                err = usb_handle_iface_request(xfer,
                    USB_ADD_BYTES(&src_zcopy, 0),
                    &max_len, req, off, state);
                if (err == 0) {
                        is_complete = 0;
                        goto tr_valid;
                } else if (err == USB_ERR_SHORT_XFER) {
                        goto tr_valid;
                }
                /*
                 * Reset zero-copy pointer and max length
                 * variable in case they were unintentionally
                 * set:
                 */
                src_zcopy = NULL;
                max_len = 0;
 
                /*
                 * Check if we have a vendor specific
                 * descriptor:
                 */
                goto tr_handle_get_descriptor;
        }
        goto tr_valid;
 
tr_handle_get_descriptor:
        err = (usb_temp_get_desc_p) (udev, &req, &src_zcopy, &max_len);
        if (err)
                goto tr_stalled;
        if (src_zcopy == NULL)
                goto tr_stalled;
        goto tr_valid;
 
tr_handle_get_config:
        temp.buf[0] = udev->curr_config_no;
        src_mcopy = temp.buf;
        max_len = 1;
        goto tr_valid;
 
tr_handle_get_status:
 
        wValue = 0;
 
        USB_BUS_LOCK(udev->bus);
        if (udev->flags.remote_wakeup) {
                wValue |= UDS_REMOTE_WAKEUP;
        }
        if (udev->flags.self_powered) {
                wValue |= UDS_SELF_POWERED;
        }
        USB_BUS_UNLOCK(udev->bus);
 
        USETW(temp.wStatus, wValue);
        src_mcopy = temp.wStatus;
        max_len = sizeof(temp.wStatus);
        goto tr_valid;
 
tr_handle_set_address:
        if (state == USB_HR_NOT_COMPLETE) {
                if (wValue >= 0x80) {
                        /* invalid value */
                        goto tr_stalled;
                } else if (udev->curr_config_no != 0) {
                        /* we are configured ! */
                        goto tr_stalled;
                }
        } else if (state != USB_HR_NOT_COMPLETE) {
                udev->address = (wValue & 0x7F);
                goto tr_bad_context;
        }
        goto tr_valid;
 
tr_handle_set_config:
        if (state == USB_HR_NOT_COMPLETE) {
                if (usb_handle_set_config(xfer, req.wValue[0])) {
                        goto tr_stalled;
                }
        }
        goto tr_valid;
 
tr_handle_clear_halt:
        if (state == USB_HR_NOT_COMPLETE) {
                if (usb_handle_set_stall(xfer, req.wIndex[0], 0)) {
                        goto tr_stalled;
                }
        }
        goto tr_valid;
 
tr_handle_clear_wakeup:
        if (state == USB_HR_NOT_COMPLETE) {
                if (usb_handle_remote_wakeup(xfer, 0)) {
                        goto tr_stalled;
                }
        }
        goto tr_valid;
 
tr_handle_set_halt:
        if (state == USB_HR_NOT_COMPLETE) {
                if (usb_handle_set_stall(xfer, req.wIndex[0], 1)) {
                        goto tr_stalled;
                }
        }
        goto tr_valid;
 
tr_handle_set_wakeup:
        if (state == USB_HR_NOT_COMPLETE) {
                if (usb_handle_remote_wakeup(xfer, 1)) {
                        goto tr_stalled;
                }
        }
        goto tr_valid;
 
tr_handle_get_ep_status:
        if (state == USB_HR_NOT_COMPLETE) {
                temp.wStatus[0] =
                    usb_handle_get_stall(udev, req.wIndex[0]);
                temp.wStatus[1] = 0;
                src_mcopy = temp.wStatus;
                max_len = sizeof(temp.wStatus);
        }
        goto tr_valid;
 
tr_valid:
        if (state != USB_HR_NOT_COMPLETE) {
                goto tr_stalled;
        }
        /* subtract offset from length */
 
        max_len -= off;
 
        /* Compute the real maximum data length */
 
        if (max_len > xfer->max_data_length) {
                max_len = usbd_xfer_max_len(xfer);
        }
        if (max_len > rem) {
                max_len = rem;
        }
        /*
         * If the remainder is greater than the maximum data length,
         * we need to truncate the value for the sake of the
         * comparison below:
         */
        if (rem > xfer->max_data_length) {
                rem = usbd_xfer_max_len(xfer);
        }
        if ((rem != max_len) && (is_complete != 0)) {
                /*
                 * If we don't transfer the data we can transfer, then
                 * the transfer is short !
                 */
                xfer->flags.force_short_xfer = 1;
                xfer->nframes = 2;
        } else {
                /*
                 * Default case
                 */
                xfer->flags.force_short_xfer = 0;
                xfer->nframes = max_len ? 2 : 1;
        }
        if (max_len > 0) {
                if (src_mcopy) {
                        src_mcopy = USB_ADD_BYTES(src_mcopy, off);
                        usbd_copy_in(xfer->frbuffers + 1, 0,
                            src_mcopy, max_len);
                        usbd_xfer_set_frame_len(xfer, 1, max_len);
                } else {
                        usbd_xfer_set_frame_data(xfer, 1,
                            USB_ADD_BYTES(src_zcopy, off), max_len);
                }
        } else {
                /* the end is reached, send status */
                xfer->flags.manual_status = 0;
                usbd_xfer_set_frame_len(xfer, 1, 0);
        }
        DPRINTF("success\n");
        return (0);                     /* success */
 
tr_stalled:
        DPRINTF("%s\n", (state != USB_HR_NOT_COMPLETE) ?
            "complete" : "stalled");
        return (USB_ERR_STALLED);
 
tr_bad_context:
        DPRINTF("bad context\n");
        return (USB_ERR_BAD_CONTEXT);
}