/*
 * Copyright (c) 2001-2002 by David Brownell
 * 
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/kmod.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/uts.h>                  /* for UTS_SYSNAME */


#ifdef CONFIG_USB_DEBUG
        #define DEBUG
#else
        #undef DEBUG
#endif

#include <linux/usb.h>
#include "hcd.h"

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/system.h>
#include <asm/unaligned.h>


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

/*
 * USB Host Controller Driver framework
 *
 * Plugs into usbcore (usb_bus) and lets HCDs share code, minimizing
 * HCD-specific behaviors/bugs.  Think of it as the "upper level" of
 * some drivers, where the "lower level" is hardware-specific.
 *
 * This does error checks, tracks devices and urbs, and delegates to a
 * "hc_driver" only for code (and data) that really needs to know about
 * hardware differences.  That includes root hub registers, i/o queues,
 * and so on ... but as little else as possible.
 *
 * Shared code includes most of the "root hub" code (these are emulated,
 * though each HC's hardware works differently) and PCI glue, plus request
 * tracking overhead.  The HCD code should only block on spinlocks or on
 * hardware handshaking; blocking on software events (such as other kernel
 * threads releasing resources, or completing actions) is all generic.
 *
 * Happens the USB 2.0 spec says this would be invisible inside the "USBD",
 * and includes mostly a "HCDI" (HCD Interface) along with some APIs used
 * only by the hub driver ... and that neither should be seen or used by
 * usb client device drivers.
 *
 * Contributors of ideas or unattributed patches include: David Brownell,
 * Roman Weissgaerber, Rory Bolt, ...
 *
 * HISTORY:
 * 2002-sept    Merge some 2.5 updates so we can share hardware level HCD
 *      code between the 2.4.20+ and 2.5 trees.
 * 2002-feb     merge to 2.4.19
 * 2001-12-12   Initial patch version for Linux 2.5.1 kernel.
 */

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

/* host controllers we manage */
static LIST_HEAD (hcd_list);

/* used when updating list of hcds */
static DECLARE_MUTEX (hcd_list_lock);

/* used when updating hcd data */
static spinlock_t hcd_data_lock = SPIN_LOCK_UNLOCKED;

static struct usb_operations hcd_operations;

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

/*
 * Sharable chunks of root hub code.
 */

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

#define KERNEL_REL      ((LINUX_VERSION_CODE >> 16) & 0x0ff)
#define KERNEL_VER      ((LINUX_VERSION_CODE >> 8) & 0x0ff)

/* usb 2.0 root hub device descriptor */
static const u8 usb2_rh_dev_descriptor [18] = {
        0x12,       /*  __u8  bLength; */
        0x01,       /*  __u8  bDescriptorType; Device */
        0x00, 0x02, /*  __u16 bcdUSB; v2.0 */

        0x09,       /*  __u8  bDeviceClass; HUB_CLASSCODE */
        0x00,       /*  __u8  bDeviceSubClass; */
        0x01,       /*  __u8  bDeviceProtocol; [ usb 2.0 single TT ]*/
        0x08,       /*  __u8  bMaxPacketSize0; 8 Bytes */

        0x00, 0x00, /*  __u16 idVendor; */
        0x00, 0x00, /*  __u16 idProduct; */
        KERNEL_VER, KERNEL_REL, /*  __u16 bcdDevice */

        0x03,       /*  __u8  iManufacturer; */
        0x02,       /*  __u8  iProduct; */
        0x01,       /*  __u8  iSerialNumber; */
        0x01        /*  __u8  bNumConfigurations; */
};

/* no usb 2.0 root hub "device qualifier" descriptor: one speed only */

/* usb 1.1 root hub device descriptor */
static const u8 usb11_rh_dev_descriptor [18] = {
        0x12,       /*  __u8  bLength; */
        0x01,       /*  __u8  bDescriptorType; Device */
        0x10, 0x01, /*  __u16 bcdUSB; v1.1 */

        0x09,       /*  __u8  bDeviceClass; HUB_CLASSCODE */
        0x00,       /*  __u8  bDeviceSubClass; */
        0x00,       /*  __u8  bDeviceProtocol; [ low/full speeds only ] */
        0x08,       /*  __u8  bMaxPacketSize0; 8 Bytes */

        0x00, 0x00, /*  __u16 idVendor; */
        0x00, 0x00, /*  __u16 idProduct; */
        KERNEL_VER, KERNEL_REL, /*  __u16 bcdDevice */

        0x03,       /*  __u8  iManufacturer; */
        0x02,       /*  __u8  iProduct; */
        0x01,       /*  __u8  iSerialNumber; */
        0x01        /*  __u8  bNumConfigurations; */
};


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

/* Configuration descriptors for our root hubs */

static const u8 fs_rh_config_descriptor [] = {

        /* one configuration */
        0x09,       /*  __u8  bLength; */
        0x02,       /*  __u8  bDescriptorType; Configuration */
        0x19, 0x00, /*  __u16 wTotalLength; */
        0x01,       /*  __u8  bNumInterfaces; (1) */
        0x01,       /*  __u8  bConfigurationValue; */
        0x00,       /*  __u8  iConfiguration; */
        0x40,       /*  __u8  bmAttributes; 
                                 Bit 7: Bus-powered,
                                     6: Self-powered,
                                     5 Remote-wakwup,
                                     4..0: resvd */
        0x00,       /*  __u8  MaxPower; */
      
        /* USB 1.1:
         * USB 2.0, single TT organization (mandatory):
         *      one interface, protocol 0
         *
         * USB 2.0, multiple TT organization (optional):
         *      two interfaces, protocols 1 (like single TT)
         *      and 2 (multiple TT mode) ... config is
         *      sometimes settable
         *      NOT IMPLEMENTED
         */

        /* one interface */
        0x09,       /*  __u8  if_bLength; */
        0x04,       /*  __u8  if_bDescriptorType; Interface */
        0x00,       /*  __u8  if_bInterfaceNumber; */
        0x00,       /*  __u8  if_bAlternateSetting; */
        0x01,       /*  __u8  if_bNumEndpoints; */
        0x09,       /*  __u8  if_bInterfaceClass; HUB_CLASSCODE */
        0x00,       /*  __u8  if_bInterfaceSubClass; */
        0x00,       /*  __u8  if_bInterfaceProtocol; [usb1.1 or single tt] */
        0x00,       /*  __u8  if_iInterface; */
     
        /* one endpoint (status change endpoint) */
        0x07,       /*  __u8  ep_bLength; */
        0x05,       /*  __u8  ep_bDescriptorType; Endpoint */
        0x81,       /*  __u8  ep_bEndpointAddress; IN Endpoint 1 */
        0x03,       /*  __u8  ep_bmAttributes; Interrupt */
        0x02, 0x00, /*  __u16 ep_wMaxPacketSize; 1 + (MAX_ROOT_PORTS / 8) */
        0xff        /*  __u8  ep_bInterval; (255ms -- usb 2.0 spec) */
};

static const u8 hs_rh_config_descriptor [] = {

        /* one configuration */
        0x09,       /*  __u8  bLength; */
        0x02,       /*  __u8  bDescriptorType; Configuration */
        0x19, 0x00, /*  __u16 wTotalLength; */
        0x01,       /*  __u8  bNumInterfaces; (1) */
        0x01,       /*  __u8  bConfigurationValue; */
        0x00,       /*  __u8  iConfiguration; */
        0x40,       /*  __u8  bmAttributes; 
                                 Bit 7: Bus-powered,
                                     6: Self-powered,
                                     5 Remote-wakwup,
                                     4..0: resvd */
        0x00,       /*  __u8  MaxPower; */
      
        /* USB 1.1:
         * USB 2.0, single TT organization (mandatory):
         *      one interface, protocol 0
         *
         * USB 2.0, multiple TT organization (optional):
         *      two interfaces, protocols 1 (like single TT)
         *      and 2 (multiple TT mode) ... config is
         *      sometimes settable
         *      NOT IMPLEMENTED
         */

        /* one interface */
        0x09,       /*  __u8  if_bLength; */
        0x04,       /*  __u8  if_bDescriptorType; Interface */
        0x00,       /*  __u8  if_bInterfaceNumber; */
        0x00,       /*  __u8  if_bAlternateSetting; */
        0x01,       /*  __u8  if_bNumEndpoints; */
        0x09,       /*  __u8  if_bInterfaceClass; HUB_CLASSCODE */
        0x00,       /*  __u8  if_bInterfaceSubClass; */
        0x00,       /*  __u8  if_bInterfaceProtocol; [usb1.1 or single tt] */
        0x00,       /*  __u8  if_iInterface; */
     
        /* one endpoint (status change endpoint) */
        0x07,       /*  __u8  ep_bLength; */
        0x05,       /*  __u8  ep_bDescriptorType; Endpoint */
        0x81,       /*  __u8  ep_bEndpointAddress; IN Endpoint 1 */
        0x03,       /*  __u8  ep_bmAttributes; Interrupt */
        0x02, 0x00, /*  __u16 ep_wMaxPacketSize; 1 + (MAX_ROOT_PORTS / 8) */
        0x0c        /*  __u8  ep_bInterval; (256ms -- usb 2.0 spec) */
};

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

/*
 * helper routine for returning string descriptors in UTF-16LE
 * input can actually be ISO-8859-1; ASCII is its 7-bit subset
 */
static int ascii2utf (char *s, u8 *utf, int utfmax)
{
        int retval;

        for (retval = 0; *s && utfmax > 1; utfmax -= 2, retval += 2) {
                *utf++ = *s++;
                *utf++ = 0;
        }
        return retval;
}

/*
 * rh_string - provides manufacturer, product and serial strings for root hub
 * @id: the string ID number (1: serial number, 2: product, 3: vendor)
 * @pci_desc: PCI device descriptor for the relevant HC
 * @type: string describing our driver 
 * @data: return packet in UTF-16 LE
 * @len: length of the return packet
 *
 * Produces either a manufacturer, product or serial number string for the
 * virtual root hub device.
 */
static int rh_string (
        int             id,
        struct usb_hcd  *hcd,
        u8              *data,
        int             len
) {
        char buf [100];

        // language ids
        if (id == 0) {
                *data++ = 4; *data++ = 3;       /* 4 bytes string data */
                *data++ = 0; *data++ = 0;       /* some language id */
                return 4;

        // serial number
        } else if (id == 1) {
                strcpy (buf, hcd->bus->bus_name);

        // product description
        } else if (id == 2) {
                strcpy (buf, hcd->product_desc);

        // id 3 == vendor description
        } else if (id == 3) {
                sprintf (buf, "%s %s %s", UTS_SYSNAME, UTS_RELEASE,
                        hcd->description);

        // unsupported IDs --> "protocol stall"
        } else
            return 0;

        data [0] = 2 * (strlen (buf) + 1);
        data [1] = 3;   /* type == string */
        return 2 + ascii2utf (buf, data + 2, len - 2);
}


/* Root hub control transfers execute synchronously */
static int rh_call_control (struct usb_hcd *hcd, struct urb *urb)
{
        struct usb_ctrlrequest *cmd = (struct usb_ctrlrequest *) urb->setup_packet;
        u16             typeReq, wValue, wIndex, wLength;
        const u8        *bufp = 0;
        u8              *ubuf = urb->transfer_buffer;
        int             len = 0;

        typeReq  = (cmd->bRequestType << 8) | cmd->bRequest;
        wValue   = le16_to_cpu (cmd->wValue);
        wIndex   = le16_to_cpu (cmd->wIndex);
        wLength  = le16_to_cpu (cmd->wLength);

        if (wLength > urb->transfer_buffer_length)
                goto error;

        /* set up for success */
        urb->status = 0;
        urb->actual_length = wLength;
        switch (typeReq) {

        /* DEVICE REQUESTS */

        case DeviceRequest | USB_REQ_GET_STATUS:
                // DEVICE_REMOTE_WAKEUP
                ubuf [0] = 1; // selfpowered
                ubuf [1] = 0;
                        /* FALLTHROUGH */
        case DeviceOutRequest | USB_REQ_CLEAR_FEATURE:
        case DeviceOutRequest | USB_REQ_SET_FEATURE:
                dbg ("no device features yet yet");
                break;
        case DeviceRequest | USB_REQ_GET_CONFIGURATION:
                ubuf [0] = 1;
                        /* FALLTHROUGH */
        case DeviceOutRequest | USB_REQ_SET_CONFIGURATION:
                break;
        case DeviceRequest | USB_REQ_GET_DESCRIPTOR:
                switch (wValue & 0xff00) {
                case USB_DT_DEVICE << 8:
                        if (hcd->driver->flags & HCD_USB2)
                                bufp = usb2_rh_dev_descriptor;
                        else if (hcd->driver->flags & HCD_USB11)
                                bufp = usb11_rh_dev_descriptor;
                        else
                                goto error;
                        len = 18;
                        break;
                case USB_DT_CONFIG << 8:
                        if (hcd->driver->flags & HCD_USB2) {
                                bufp = hs_rh_config_descriptor;
                                len = sizeof hs_rh_config_descriptor;
                        } else {
                                bufp = fs_rh_config_descriptor;
                                len = sizeof fs_rh_config_descriptor;
                        }
                        break;
                case USB_DT_STRING << 8:
                        urb->actual_length = rh_string (
                                wValue & 0xff, hcd,
                                ubuf, wLength);
                        break;
                default:
                        goto error;
                }
                break;
        case DeviceRequest | USB_REQ_GET_INTERFACE:
                ubuf [0] = 0;
                        /* FALLTHROUGH */
        case DeviceOutRequest | USB_REQ_SET_INTERFACE:
                break;
        case DeviceOutRequest | USB_REQ_SET_ADDRESS:
                // wValue == urb->dev->devaddr
                dbg ("%s root hub device address %d",
                        hcd->bus->bus_name, wValue);
                break;

        /* INTERFACE REQUESTS (no defined feature/status flags) */

        /* ENDPOINT REQUESTS */

        case EndpointRequest | USB_REQ_GET_STATUS:
                // ENDPOINT_HALT flag
                ubuf [0] = 0;
                ubuf [1] = 0;
                        /* FALLTHROUGH */
        case EndpointOutRequest | USB_REQ_CLEAR_FEATURE:
        case EndpointOutRequest | USB_REQ_SET_FEATURE:
                dbg ("no endpoint features yet");
                break;

        /* CLASS REQUESTS (and errors) */

        default:
                /* non-generic request */
                urb->status = hcd->driver->hub_control (hcd,
                        typeReq, wValue, wIndex,
                        ubuf, wLength);
                break;
error:
                /* "protocol stall" on error */
                urb->status = -EPIPE;
                dbg ("unsupported hub control message (maxchild %d)",
                                urb->dev->maxchild);
        }
        if (urb->status) {
                urb->actual_length = 0;
                dbg ("CTRL: TypeReq=0x%x val=0x%x idx=0x%x len=%d ==> %d",
                        typeReq, wValue, wIndex, wLength, urb->status);
        }
        if (bufp) {
                if (urb->transfer_buffer_length < len)
                        len = urb->transfer_buffer_length;
                urb->actual_length = len;
                // always USB_DIR_IN, toward host
                memcpy (ubuf, bufp, len);
        }

        /* any errors get returned through the urb completion */
        usb_hcd_giveback_urb (hcd, urb, 0);
        return 0;
}

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

/*
 * Root Hub interrupt transfers are synthesized with a timer.
 * Completions are called in_interrupt() but not in_irq().
 */

static void rh_report_status (unsigned long ptr);

static int rh_status_urb (struct usb_hcd *hcd, struct urb *urb) 
{
        int     len = 1 + (urb->dev->maxchild / 8);

        /* rh_timer protected by hcd_data_lock */
        if (timer_pending (&hcd->rh_timer)
                        || urb->status != -EINPROGRESS
                        || !HCD_IS_RUNNING (hcd->state)
                        || urb->transfer_buffer_length < len) {
                dbg ("not queuing status urb, stat %d", urb->status);
                return -EINVAL;
        }

        urb->hcpriv = hcd;      /* nonzero to indicate it's queued */
        init_timer (&hcd->rh_timer);
        hcd->rh_timer.function = rh_report_status;
        hcd->rh_timer.data = (unsigned long) urb;
        /* USB 2.0 spec says 256msec; this is close enough */
        hcd->rh_timer.expires = jiffies + HZ/4;
        add_timer (&hcd->rh_timer);
        return 0;
}

/* timer callback */

static void rh_report_status (unsigned long ptr)
{
        struct urb      *urb;
        struct usb_hcd  *hcd;
        int             length;
        unsigned long   flags;

        urb = (struct urb *) ptr;
        spin_lock_irqsave (&urb->lock, flags);
        if (!urb->dev) {
                spin_unlock_irqrestore (&urb->lock, flags);
                return;
        }

        hcd = urb->dev->bus->hcpriv;
        if (urb->status == -EINPROGRESS) {
                if (HCD_IS_RUNNING (hcd->state)) {
                        length = hcd->driver->hub_status_data (hcd,
                                        urb->transfer_buffer);
                        spin_unlock_irqrestore (&urb->lock, flags);
                        if (length > 0) {
                                urb->actual_length = length;
                                urb->status = 0;
                                urb->complete (urb);
                        }
                        spin_lock_irqsave (&hcd_data_lock, flags);
                        urb->status = -EINPROGRESS;
                        if (HCD_IS_RUNNING (hcd->state)
                                        && rh_status_urb (hcd, urb) != 0) {
                                /* another driver snuck in? */
                                dbg ("%s, can't resubmit roothub status urb?",
                                        hcd->bus->bus_name);
                                spin_unlock_irqrestore (&hcd_data_lock, flags);
                                BUG ();
                        }
                        spin_unlock_irqrestore (&hcd_data_lock, flags);
                } else
                        spin_unlock_irqrestore (&urb->lock, flags);
        } else {
                /* this urb's been unlinked */
                urb->hcpriv = 0;
                spin_unlock_irqrestore (&urb->lock, flags);

                usb_hcd_giveback_urb (hcd, urb, 0);
        }
}

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

static int rh_urb_enqueue (struct usb_hcd *hcd, struct urb *urb)
{
        if (usb_pipeint (urb->pipe)) {
                int             retval;
                unsigned long   flags;

                spin_lock_irqsave (&hcd_data_lock, flags);
                retval = rh_status_urb (hcd, urb);
                spin_unlock_irqrestore (&hcd_data_lock, flags);
                return retval;
        }
        if (usb_pipecontrol (urb->pipe))
                return rh_call_control (hcd, urb);
        else
                return -EINVAL;
}

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

static void rh_status_dequeue (struct usb_hcd *hcd, struct urb *urb)
{
        unsigned long   flags;

        spin_lock_irqsave (&hcd_data_lock, flags);
        del_timer_sync (&hcd->rh_timer);
        hcd->rh_timer.data = 0;
        spin_unlock_irqrestore (&hcd_data_lock, flags);

        /* we rely on RH callback code not unlinking its URB! */
        usb_hcd_giveback_urb (hcd, urb, 0);
}

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

#ifdef CONFIG_PCI

/* PCI-based HCs are normal, but custom bus glue should be ok */

static void hcd_irq (int irq, void *__hcd, struct pt_regs *r);
static void hc_died (struct usb_hcd *hcd);

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

/* configure so an HC device and id are always provided */
/* always called with process context; sleeping is OK */

/**
 * usb_hcd_pci_probe - initialize PCI-based HCDs
 * @dev: USB Host Controller being probed
 * @id: pci hotplug id connecting controller to HCD framework
 * Context: !in_interrupt()
 *
 * Allocates basic PCI resources for this USB host controller, and
 * then invokes the start() method for the HCD associated with it
 * through the hotplug entry's driver_data.
 *
 * Store this function in the HCD's struct pci_driver as probe().
 */
int usb_hcd_pci_probe (struct pci_dev *dev, const struct pci_device_id *id)
{
        struct hc_driver        *driver;
        unsigned long           resource, len;
        void                    *base;
        struct usb_bus          *bus;
        struct usb_hcd          *hcd;
        int                     retval, region;
        char                    buf [8], *bufp = buf;

        if (!id || !(driver = (struct hc_driver *) id->driver_data))
                return -EINVAL;

        if (pci_enable_device (dev) < 0)
                return -ENODEV;
        
        if (!dev->irq) {
                err ("Found HC with no IRQ.  Check BIOS/PCI %s setup!",
                        dev->slot_name);
                return -ENODEV;
        }
        
        if (driver->flags & HCD_MEMORY) {       // EHCI, OHCI
                region = 0;
                resource = pci_resource_start (dev, 0);
                len = pci_resource_len (dev, 0);
                if (!request_mem_region (resource, len, driver->description)) {
                        dbg ("controller already in use");
                        return -EBUSY;
                }
                base = ioremap_nocache (resource, len);
                if (base == NULL) {
                        dbg ("error mapping memory");
                        retval = -EFAULT;
clean_1:
                        release_mem_region (resource, len);
                        err ("init %s fail, %d", dev->slot_name, retval);
                        return retval;
                }

        } else {                                // UHCI
                resource = len = 0;
                for (region = 0; region < PCI_ROM_RESOURCE; region++) {
                        if (!(pci_resource_flags (dev, region) & IORESOURCE_IO))
                                continue;

                        resource = pci_resource_start (dev, region);
                        len = pci_resource_len (dev, region);
                        if (request_region (resource, len,
                                        driver->description))
                                break;
                }
                if (region == PCI_ROM_RESOURCE) {
                        dbg ("no i/o regions available");
                        return -EBUSY;
                }
                base = (void *) resource;
        }

        // driver->start(), later on, will transfer device from
        // control by SMM/BIOS to control by Linux (if needed)

        pci_set_master (dev);
        hcd = driver->hcd_alloc ();
        if (hcd == NULL){
                dbg ("hcd alloc fail");
                retval = -ENOMEM;
clean_2:
                if (driver->flags & HCD_MEMORY) {
                        iounmap (base);
                        goto clean_1;
                } else {
                        release_region (resource, len);
                        err ("init %s fail, %d", dev->slot_name, retval);
                        return retval;
                }
        }
        pci_set_drvdata(dev, hcd);
        hcd->driver = driver;
        hcd->description = driver->description;
        hcd->pdev = dev;
        printk (KERN_INFO "%s %s: %s\n",
                        hcd->description,  dev->slot_name, dev->name);

#ifndef __sparc__
        sprintf (buf, "%d", dev->irq);
#else
        bufp = __irq_itoa(dev->irq);
#endif
        if (request_irq (dev->irq, hcd_irq, SA_SHIRQ, hcd->description, hcd)
                        != 0) {
                err ("request interrupt %s failed", bufp);
                retval = -EBUSY;
clean_3:
                driver->hcd_free (hcd);
                goto clean_2;
        }
        hcd->irq = dev->irq;

        hcd->regs = base;
        hcd->region = region;
        printk (KERN_INFO "%s %s: irq %s, %s %p\n",
                hcd->description,  dev->slot_name, bufp,
                (driver->flags & HCD_MEMORY) ? "pci mem" : "io base",
                base);

// FIXME simpler: make "bus" be that data, not pointer to it.
// (fixed in 2.5)
        bus = usb_alloc_bus (&hcd_operations);
        if (bus == NULL) {
                dbg ("usb_alloc_bus fail");
                retval = -ENOMEM;
                free_irq (dev->irq, hcd);
                goto clean_3;
        }
        hcd->bus = bus;
        bus->bus_name = dev->slot_name;
        hcd->product_desc = dev->name;
        bus->hcpriv = (void *) hcd;

        INIT_LIST_HEAD (&hcd->dev_list);
        INIT_LIST_HEAD (&hcd->hcd_list);

        down (&hcd_list_lock);
        list_add (&hcd->hcd_list, &hcd_list);
        up (&hcd_list_lock);

        usb_register_bus (bus);

        if ((retval = driver->start (hcd)) < 0)
                usb_hcd_pci_remove (dev);

        return retval;
} 
EXPORT_SYMBOL (usb_hcd_pci_probe);


/* may be called without controller electrically present */
/* may be called with controller, bus, and devices active */

/**
 * usb_hcd_pci_remove - shutdown processing for PCI-based HCDs
 * @dev: USB Host Controller being removed
 * Context: !in_interrupt()
 *
 * Reverses the effect of usb_hcd_pci_probe(), first invoking
 * the HCD's stop() method.  It is always called from a thread
 * context, normally "rmmod", "apmd", or something similar.
 *
 * Store this function in the HCD's struct pci_driver as remove().
 */
void usb_hcd_pci_remove (struct pci_dev *dev)
{
        struct usb_hcd          *hcd;
        struct usb_device       *hub;

        hcd = pci_get_drvdata(dev);
        if (!hcd)
                return;
        printk (KERN_INFO "%s %s: remove state %x\n",
                hcd->description,  dev->slot_name, hcd->state);

        if (in_interrupt ()) BUG ();

        hub = hcd->bus->root_hub;
        hcd->state = USB_STATE_QUIESCING;

        dbg ("%s: roothub graceful disconnect", hcd->bus->bus_name);
        usb_disconnect (&hub);
        // usb_disconnect (&hcd->bus->root_hub);

        hcd->driver->stop (hcd);
        hcd->state = USB_STATE_HALT;

        free_irq (hcd->irq, hcd);
        if (hcd->driver->flags & HCD_MEMORY) {
                iounmap (hcd->regs);
                release_mem_region (pci_resource_start (dev, 0),
                        pci_resource_len (dev, 0));
        } else {
                release_region (pci_resource_start (dev, hcd->region),
                        pci_resource_len (dev, hcd->region));
        }

        down (&hcd_list_lock);
        list_del (&hcd->hcd_list);
        up (&hcd_list_lock);

        usb_deregister_bus (hcd->bus);
        usb_free_bus (hcd->bus);
        hcd->bus = NULL;

        hcd->driver->hcd_free (hcd);
}
EXPORT_SYMBOL (usb_hcd_pci_remove);


#ifdef  CONFIG_PM

/*
 * Some "sleep" power levels imply updating struct usb_driver
 * to include a callback asking hcds to do their bit by checking
 * if all the drivers can suspend.  Gets involved with remote wakeup.
 *
 * If there are pending urbs, then HCs will need to access memory,
 * causing extra power drain.  New sleep()/wakeup() PM calls might
 * be needed, beyond PCI suspend()/resume().  The root hub timer
 * still be accessing memory though ...
 *
 * FIXME:  USB should have some power budgeting support working with
 * all kinds of hubs.
 *
 * FIXME:  This assumes only D0->D3 suspend and D3->D0 resume.
 * D1 and D2 states should do something, yes?
 *
 * FIXME:  Should provide generic enable_wake(), calling pci_enable_wake()
 * for all supported states, so that USB remote wakeup can work for any
 * devices that support it (and are connected via powered hubs).
 *
 * FIXME:  resume doesn't seem to work right any more...
 */


// 2.4 kernels have issued concurrent resumes (w/APM)
// we defend against that error; PCI doesn't yet.

/**
 * usb_hcd_pci_suspend - power management suspend of a PCI-based HCD
 * @dev: USB Host Controller being suspended
 *
 * Store this function in the HCD's struct pci_driver as suspend().
 */
int usb_hcd_pci_suspend (struct pci_dev *dev, u32 state)
{
        struct usb_hcd          *hcd;
        int                     retval;

        hcd = pci_get_drvdata(dev);
        printk (KERN_INFO "%s %s: suspend to state %d\n",
                hcd->description,  dev->slot_name, state);

        pci_save_state (dev, hcd->pci_state);

        // FIXME for all connected devices, leaf-to-root:
        // driver->suspend()
        // proposed "new 2.5 driver model" will automate that

        /* driver may want to disable DMA etc */
        retval = hcd->driver->suspend (hcd, state);
        hcd->state = USB_STATE_SUSPENDED;

        pci_set_power_state (dev, state);
        return retval;
}
EXPORT_SYMBOL (usb_hcd_pci_suspend);

/**
 * usb_hcd_pci_resume - power management resume of a PCI-based HCD
 * @dev: USB Host Controller being resumed
 *
 * Store this function in the HCD's struct pci_driver as resume().
 */
int usb_hcd_pci_resume (struct pci_dev *dev)
{
        struct usb_hcd          *hcd;
        int                     retval;

        hcd = pci_get_drvdata(dev);
        printk (KERN_INFO "%s %s: resume\n",
                hcd->description,  dev->slot_name);

        /* guard against multiple resumes (APM bug?) */
        atomic_inc (&hcd->resume_count);
        if (atomic_read (&hcd->resume_count) != 1) {
                err ("concurrent PCI resumes for %s", hcd->bus->bus_name);
                retval = 0;
                goto done;
        }

        retval = -EBUSY;
        if (hcd->state != USB_STATE_SUSPENDED) {
                dbg ("can't resume, not suspended!");
                goto done;
        }
        hcd->state = USB_STATE_RESUMING;

        pci_set_power_state (dev, 0);
        pci_restore_state (dev, hcd->pci_state);

        retval = hcd->driver->resume (hcd);
        if (!HCD_IS_RUNNING (hcd->state)) {
                dbg ("resume %s failure, retval %d",
                        hcd->bus->bus_name, retval);
                hc_died (hcd);
// FIXME:  recover, reset etc.
        } else {
                // FIXME for all connected devices, root-to-leaf:
                // driver->resume ();
                // proposed "new 2.5 driver model" will automate that
        }

done:
        atomic_dec (&hcd->resume_count);
        return retval;
}
EXPORT_SYMBOL (usb_hcd_pci_resume);

#endif  /* CONFIG_PM */

#endif

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

/*
 * Generic HC operations.
 */

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

/* called from khubd, or root hub init threads for hcd-private init */
static int hcd_alloc_dev (struct usb_device *udev)
{
        struct hcd_dev          *dev;
        struct usb_hcd          *hcd;
        unsigned long           flags;

        if (!udev || udev->hcpriv)
                return -EINVAL;
        if (!udev->bus || !udev->bus->hcpriv)
                return -ENODEV;
        hcd = udev->bus->hcpriv;
        if (hcd->state == USB_STATE_QUIESCING)
                return -ENOLINK;

        dev = (struct hcd_dev *) kmalloc (sizeof *dev, GFP_KERNEL);
        if (dev == NULL)
                return -ENOMEM;
        memset (dev, 0, sizeof *dev);

        INIT_LIST_HEAD (&dev->dev_list);
        INIT_LIST_HEAD (&dev->urb_list);

        spin_lock_irqsave (&hcd_data_lock, flags);
        list_add (&dev->dev_list, &hcd->dev_list);
        // refcount is implicit
        udev->hcpriv = dev;
        spin_unlock_irqrestore (&hcd_data_lock, flags);

        return 0;
}

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

static void hcd_panic (void *_hcd)
{
        struct usb_hcd *hcd = _hcd;
        hcd->driver->stop (hcd);
}

static void hc_died (struct usb_hcd *hcd)
{
        struct list_head        *devlist, *urblist;
        struct hcd_dev          *dev;
        struct urb              *urb;
        unsigned long           flags;
        
        /* flag every pending urb as done */
        spin_lock_irqsave (&hcd_data_lock, flags);
        list_for_each (devlist, &hcd->dev_list) {
                dev = list_entry (devlist, struct hcd_dev, dev_list);
                list_for_each (urblist, &dev->urb_list) {
                        urb = list_entry (urblist, struct urb, urb_list);
                        dbg ("shutdown %s urb %p pipe %x, current status %d",
                                hcd->bus->bus_name,
                                urb, urb->pipe, urb->status);
                        if (urb->status == -EINPROGRESS)
                                urb->status = -ESHUTDOWN;
                }
        }
        urb = (struct urb *) hcd->rh_timer.data;
        if (urb)
                urb->status = -ESHUTDOWN;
        spin_unlock_irqrestore (&hcd_data_lock, flags);

        if (urb)
                rh_status_dequeue (hcd, urb);

        /* hcd->stop() needs a task context */
        INIT_TQUEUE (&hcd->work, hcd_panic, hcd);
        (void) schedule_task (&hcd->work);
}

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

static void urb_unlink (struct urb *urb)
{
        unsigned long           flags;
        struct usb_device       *dev;

        /* Release any periodic transfer bandwidth */
        if (urb->bandwidth)
                usb_release_bandwidth (urb->dev, urb,
                        usb_pipeisoc (urb->pipe));

        /* clear all state linking urb to this dev (and hcd) */

        spin_lock_irqsave (&hcd_data_lock, flags);
        list_del_init (&urb->urb_list);
        dev = urb->dev;
        urb->dev = NULL;
        usb_dec_dev_use (dev);
        spin_unlock_irqrestore (&hcd_data_lock, flags);
}


/* may be called in any context with a valid urb->dev usecount */

/* caller surrenders "ownership" of urb */

static int hcd_submit_urb (struct urb *urb)
{
        int                     status;
        struct usb_hcd          *hcd;
        struct hcd_dev          *dev;
        unsigned long           flags;
        int                     pipe, temp, max;
        int                     mem_flags;

        if (!urb || urb->hcpriv || !urb->complete)
                return -EINVAL;

        urb->status = -EINPROGRESS;
        urb->actual_length = 0;
        urb->bandwidth = 0;
        INIT_LIST_HEAD (&urb->urb_list);

        if (!urb->dev || !urb->dev->bus || urb->dev->devnum <= 0)
                return -ENODEV;
        hcd = urb->dev->bus->hcpriv;
        dev = urb->dev->hcpriv;
        if (!hcd || !dev)
                return -ENODEV;

        /* can't submit new urbs when quiescing, halted, ... */
        if (hcd->state == USB_STATE_QUIESCING || !HCD_IS_RUNNING (hcd->state))
                return -ESHUTDOWN;
        pipe = urb->pipe;
        temp = usb_pipetype (urb->pipe);
        if (usb_endpoint_halted (urb->dev, usb_pipeendpoint (pipe),
                        usb_pipeout (pipe)))
                return -EPIPE;

        /* NOTE: 2.5 passes this value explicitly in submit() */
        mem_flags = GFP_ATOMIC;

        /* FIXME there should be a sharable lock protecting us against
         * config/altsetting changes and disconnects, kicking in here.
         */

        /* Sanity check, so HCDs can rely on clean data */
        max = usb_maxpacket (urb->dev, pipe, usb_pipeout (pipe));
        if (max <= 0) {
                err ("bogus endpoint (bad maxpacket)");
                return -EINVAL;
        }

        /* "high bandwidth" mode, 1-3 packets/uframe? */
        if (urb->dev->speed == USB_SPEED_HIGH) {
                int     mult;
                switch (temp) {
                case PIPE_ISOCHRONOUS:
                case PIPE_INTERRUPT:
                        mult = 1 + ((max >> 11) & 0x03);
                        max &= 0x03ff;
                        max *= mult;
                }
        }

        /* periodic transfers limit size per frame/uframe */
        switch (temp) {
        case PIPE_ISOCHRONOUS: {
                int     n, len;

                if (urb->number_of_packets <= 0)                    
                        return -EINVAL;
                for (n = 0; n < urb->number_of_packets; n++) {
                        len = urb->iso_frame_desc [n].length;
                        if (len < 0 || len > max) 
                                return -EINVAL;
                }

                }
                break;
        case PIPE_INTERRUPT:
                if (urb->transfer_buffer_length > max)
                        return -EINVAL;
        }

        /* the I/O buffer must usually be mapped/unmapped */
        if (urb->transfer_buffer_length < 0)
                return -EINVAL;

        if (urb->next) {
                warn ("use explicit queuing not urb->next");
                return -EINVAL;
        }

#ifdef DEBUG
        /* stuff that drivers shouldn't do, but which shouldn't
         * cause problems in HCDs if they get it wrong.
         */
        {
        unsigned int    orig_flags = urb->transfer_flags;
        unsigned int    allowed;

        /* enforce simple/standard policy */
        allowed = USB_ASYNC_UNLINK;     // affects later unlinks
        allowed |= USB_NO_FSBR;         // only affects UHCI
        switch (temp) {
        case PIPE_CONTROL:
                allowed |= USB_DISABLE_SPD;
                break;
        case PIPE_BULK:
                allowed |= USB_DISABLE_SPD | USB_QUEUE_BULK
                                | USB_ZERO_PACKET | URB_NO_INTERRUPT;
                break;
        case PIPE_INTERRUPT:
                allowed |= USB_DISABLE_SPD;
                break;
        case PIPE_ISOCHRONOUS:
                allowed |= USB_ISO_ASAP;
                break;
        }
        urb->transfer_flags &= allowed;

        /* fail if submitter gave bogus flags */
        if (urb->transfer_flags != orig_flags) {
                err ("BOGUS urb flags, %x --> %x",
                        orig_flags, urb->transfer_flags);
                return -EINVAL;
        }
        }
#endif
        /*
         * Force periodic transfer intervals to be legal values that are
         * a power of two (so HCDs don't need to).
         *
         * FIXME want bus->{intr,iso}_sched_horizon values here.  Each HC
         * supports different values... this uses EHCI/UHCI defaults (and
         * EHCI can use smaller non-default values).
         */
        switch (temp) {
        case PIPE_ISOCHRONOUS:
        case PIPE_INTERRUPT:
                /* too small? */
                if (urb->interval <= 0)
                        return -EINVAL;
                /* too big? */
                switch (urb->dev->speed) {
                case USB_SPEED_HIGH:    /* units are microframes */
                        // NOTE usb handles 2^15
                        if (urb->interval > (1024 * 8))
                                urb->interval = 1024 * 8;
                        temp = 1024 * 8;
                        break;
                case USB_SPEED_FULL:    /* units are frames/msec */
                case USB_SPEED_LOW:
                        if (temp == PIPE_INTERRUPT) {
                                if (urb->interval > 255)
                                        return -EINVAL;
                                // NOTE ohci only handles up to 32
                                temp = 128;
                        } else {
                                if (urb->interval > 1024)
                                        urb->interval = 1024;
                                // NOTE usb and ohci handle up to 2^15
                                temp = 1024;
                        }
                        break;
                default:
                        return -EINVAL;
                }
                /* power of two? */
                while (temp > urb->interval)
                        temp >>= 1;
                urb->interval = temp;
        }


        /*
         * FIXME:  make urb timeouts be generic, keeping the HCD cores
         * as simple as possible.
         */

        // NOTE:  a generic device/urb monitoring hook would go here.
        // hcd_monitor_hook(MONITOR_URB_SUBMIT, urb)
        // It would catch submission paths for all urbs.

        /*
         * Atomically queue the urb,  first to our records, then to the HCD.
         * Access to urb->status is controlled by urb->lock ... changes on
         * i/o completion (normal or fault) or unlinking.
         */

        // FIXME:  verify that quiescing hc works right (RH cleans up)

        spin_lock_irqsave (&hcd_data_lock, flags);
        if (HCD_IS_RUNNING (hcd->state) && hcd->state != USB_STATE_QUIESCING) {
                usb_inc_dev_use (urb->dev);
                list_add (&urb->urb_list, &dev->urb_list);
                status = 0;
        } else {
                INIT_LIST_HEAD (&urb->urb_list);
                status = -ESHUTDOWN;
        }
        spin_unlock_irqrestore (&hcd_data_lock, flags);
        if (status)
                return status;

        // NOTE:  2.5 does this if !URB_NO_DMA_MAP transfer flag
        
        /* For 2.4, don't map bounce buffer if it's a root hub operation. */
        if (urb->dev == hcd->bus->root_hub) {
                status = rh_urb_enqueue (hcd, urb);
        } else {
                if (usb_pipecontrol (urb->pipe))
                        urb->setup_dma = pci_map_single (
                                        hcd->pdev,
                                        urb->setup_packet,
                                        sizeof (struct usb_ctrlrequest),
                                        PCI_DMA_TODEVICE);
                if (urb->transfer_buffer_length != 0)
                        urb->transfer_dma = pci_map_single (
                                        hcd->pdev,
                                        urb->transfer_buffer,
                                        urb->transfer_buffer_length,
                                        usb_pipein (urb->pipe)
                                            ? PCI_DMA_FROMDEVICE
                                            : PCI_DMA_TODEVICE);
                status = hcd->driver->urb_enqueue (hcd, urb, mem_flags);
        }
        return status;
}

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

/* called in any context */
static int hcd_get_frame_number (struct usb_device *udev)
{
        struct usb_hcd  *hcd = (struct usb_hcd *)udev->bus->hcpriv;
        return hcd->driver->get_frame_number (hcd);
}

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

struct completion_splice {              // modified urb context:
        /* did we complete? */
        struct completion       done;

        /* original urb data */
        void                    (*complete)(struct urb *);
        void                    *context;
};

static void unlink_complete (struct urb *urb)
{
        struct completion_splice        *splice;

        splice = (struct completion_splice *) urb->context;

        /* issue original completion call */
        urb->complete = splice->complete;
        urb->context = splice->context;
        urb->complete (urb);

        /* then let the synchronous unlink call complete */
        complete (&splice->done);
}

/*
 * called in any context; note ASYNC_UNLINK restrictions
 *
 * caller guarantees urb won't be recycled till both unlink()
 * and the urb's completion function return
 */
static int hcd_unlink_urb (struct urb *urb)
{
        struct hcd_dev                  *dev;
        struct usb_hcd                  *hcd = 0;
        unsigned long                   flags;
        struct completion_splice        splice;
        int                             retval;

        if (!urb)
                return -EINVAL;

        /*
         * we contend for urb->status with the hcd core,
         * which changes it while returning the urb.
         *
         * Caller guaranteed that the urb pointer hasn't been freed, and
         * that it was submitted.  But as a rule it can't know whether or
         * not it's already been unlinked ... so we respect the reversed
         * lock sequence needed for the usb_hcd_giveback_urb() code paths
         * (urb lock, then hcd_data_lock) in case some other CPU is now
         * unlinking it.
         */
        spin_lock_irqsave (&urb->lock, flags);
        spin_lock (&hcd_data_lock);
        if (!urb->hcpriv || urb->transfer_flags & USB_TIMEOUT_KILLED) {
                retval = -EINVAL;
                goto done;
        }

        if (!urb->dev || !urb->dev->bus) {
                retval = -ENODEV;
                goto done;
        }

        /* giveback clears dev; non-null means it's linked at this level */
        dev = urb->dev->hcpriv;
        hcd = urb->dev->bus->hcpriv;
        if (!dev || !hcd) {
                retval = -ENODEV;
                goto done;
        }

        /* Any status except -EINPROGRESS means the HCD has already started
         * to return this URB to the driver.  In that case, there's no
         * more work for us to do.
         *
         * There's much magic because of "automagic resubmit" of interrupt
         * transfers, stopped only by explicit unlinking.  We won't issue
         * an "it's unlinked" callback more than once, but device drivers
         * can need to retry (SMP, -EAGAIN) an unlink request as well as
         * fake out the "not yet completed" state (set -EINPROGRESS) if
         * unlinking from complete().  Automagic eventually vanishes.
         *
         * FIXME use an URB_UNLINKED flag to match URB_TIMEOUT_KILLED
         */
        if (urb->status != -EINPROGRESS) {
                if (usb_pipetype (urb->pipe) == PIPE_INTERRUPT)
                        retval = -EAGAIN;
                else
                        retval = -EBUSY;
                goto done;
        }

        /* maybe set up to block on completion notification */
        if ((urb->transfer_flags & USB_TIMEOUT_KILLED))
                urb->status = -ETIMEDOUT;
        else if (!(urb->transfer_flags & USB_ASYNC_UNLINK)) {
                if (in_interrupt ()) {
                        dbg ("non-async unlink in_interrupt");
                        retval = -EWOULDBLOCK;
                        goto done;
                }
                /* synchronous unlink: block till we see the completion */
                init_completion (&splice.done);
                splice.complete = urb->complete;
                splice.context = urb->context;
                urb->complete = unlink_complete;
                urb->context = &splice;
                urb->status = -ENOENT;
        } else {
                /* asynchronous unlink */
                urb->status = -ECONNRESET;
        }
        spin_unlock (&hcd_data_lock);
        spin_unlock_irqrestore (&urb->lock, flags);

        if (urb == (struct urb *) hcd->rh_timer.data) {
                rh_status_dequeue (hcd, urb);
                retval = 0;
        } else {
                retval = hcd->driver->urb_dequeue (hcd, urb);
// FIXME:  if retval and we tried to splice, whoa!!
if (retval && urb->status == -ENOENT) err ("whoa! retval %d", retval);
        }

        /* block till giveback, if needed */
        if (!(urb->transfer_flags & (USB_ASYNC_UNLINK|USB_TIMEOUT_KILLED))
                        && HCD_IS_RUNNING (hcd->state)
                        && !retval) {
                wait_for_completion (&splice.done);
        } else if ((urb->transfer_flags & USB_ASYNC_UNLINK) && retval == 0) {
                return -EINPROGRESS;
        }
        goto bye;
done:
        spin_unlock (&hcd_data_lock);
        spin_unlock_irqrestore (&urb->lock, flags);
bye:
        if (retval)
                dbg ("%s: hcd_unlink_urb fail %d",
                    hcd ? hcd->bus->bus_name : "(no bus?)",
                    retval);
        return retval;
}

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

/* called by khubd, rmmod, apmd, or other thread for hcd-private cleanup */

// FIXME:  likely best to have explicit per-setting (config+alt)
// setup primitives in the usbcore-to-hcd driver API, so nothing
// is implicit.  kernel 2.5 needs a bunch of config cleanup...

static int hcd_free_dev (struct usb_device *udev)
{
        struct hcd_dev          *dev;
        struct usb_hcd          *hcd;
        unsigned long           flags;

        if (!udev || !udev->hcpriv)
                return -EINVAL;

        if (!udev->bus || !udev->bus->hcpriv)
                return -ENODEV;

        // should udev->devnum == -1 ??

        dev = udev->hcpriv;
        hcd = udev->bus->hcpriv;

        /* device driver problem with refcounts? */
        if (!list_empty (&dev->urb_list)) {
                dbg ("free busy dev, %s devnum %d (bug!)",
                        hcd->bus->bus_name, udev->devnum);
                return -EINVAL;
        }

        hcd->driver->free_config (hcd, udev);

        spin_lock_irqsave (&hcd_data_lock, flags);
        list_del (&dev->dev_list);
        udev->hcpriv = NULL;
        spin_unlock_irqrestore (&hcd_data_lock, flags);

        kfree (dev);
        return 0;
}

static struct usb_operations hcd_operations = {
        allocate:               hcd_alloc_dev,
        get_frame_number:       hcd_get_frame_number,
        submit_urb:             hcd_submit_urb,
        unlink_urb:             hcd_unlink_urb,
        deallocate:             hcd_free_dev,
};

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

static void hcd_irq (int irq, void *__hcd, struct pt_regs * r)
{
        struct usb_hcd          *hcd = __hcd;
        int                     start = hcd->state;

        if (unlikely (hcd->state == USB_STATE_HALT))    /* irq sharing? */
                return;

        hcd->driver->irq (hcd, r);
        if (hcd->state != start && hcd->state == USB_STATE_HALT)
                hc_died (hcd);
}

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

/**
 * usb_hcd_giveback_urb - return URB from HCD to device driver
 * @hcd: host controller returning the URB
 * @urb: urb being returned to the USB device driver.
 * @regs: saved hardware registers (ignored on 2.4 kernels)
 * Context: in_interrupt()
 *
 * This hands the URB from HCD to its USB device driver, using its
 * completion function.  The HCD has freed all per-urb resources
 * (and is done using urb->hcpriv).  It also released all HCD locks;
 * the device driver won't cause deadlocks if it resubmits this URB,
 * and won't confuse things by modifying and resubmitting this one.
 * Bandwidth and other resources will be deallocated.
 *
 * HCDs must not use this for periodic URBs that are still scheduled
 * and will be reissued.  They should just call their completion handlers
 * until the urb is returned to the device driver by unlinking.
 *
 * NOTE that no urb->next processing is done, even for isochronous URBs.
 * ISO streaming functionality can be achieved by having completion handlers
 * re-queue URBs.  Such explicit queuing doesn't discard error reports.
 */
void usb_hcd_giveback_urb (struct usb_hcd *hcd, struct urb *urb, struct pt_regs *regs)
{
        int is_root_hub_operation;

        /* Work this out here as urb_unlink clears urb->dev */
        is_root_hub_operation = (urb->dev == hcd->bus->root_hub);

        urb_unlink (urb);

        // NOTE:  a generic device/urb monitoring hook would go here.
        // hcd_monitor_hook(MONITOR_URB_FINISH, urb, dev)
        // It would catch exit/unlink paths for all urbs, but non-exit
        // completions for periodic urbs need hooks inside the HCD.
        // hcd_monitor_hook(MONITOR_URB_UPDATE, urb, dev)

        // NOTE:  2.5 does this if !URB_NO_DMA_MAP transfer flag
        
        /* For 2.4, don't unmap bounce buffer if it's a root hub operation. */
        if (usb_pipecontrol (urb->pipe) && !is_root_hub_operation)
                pci_unmap_single (hcd->pdev, urb->setup_dma,
                                sizeof (struct usb_ctrlrequest),
                                PCI_DMA_TODEVICE);

        if ((urb->transfer_buffer_length != 0) && !is_root_hub_operation)
                pci_unmap_single (hcd->pdev, urb->transfer_dma,
                                urb->transfer_buffer_length,
                                usb_pipein (urb->pipe)
                                    ? PCI_DMA_FROMDEVICE
                                    : PCI_DMA_TODEVICE);

        /* pass ownership to the completion handler */
        urb->complete (urb);
}
EXPORT_SYMBOL (usb_hcd_giveback_urb);