/* ZD1211 USB-WLAN driver for Linux
 *
 * Copyright (C) 2005-2007 Ulrich Kunitz <kune@deine-taler.de>
 * Copyright (C) 2006-2007 Daniel Drake <dsd@gentoo.org>
 * Copyright (C) 2006-2007 Michael Wu <flamingice@sourmilk.net>
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/firmware.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/usb.h>
#include <linux/workqueue.h>
#include <linux/module.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>

#include "zd_def.h"
#include "zd_mac.h"
#include "zd_usb.h"

static struct usb_device_id usb_ids[] = {
        /* ZD1211 */
        { USB_DEVICE(0x0105, 0x145f), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0586, 0x3401), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0586, 0x3402), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0586, 0x3407), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0586, 0x3409), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x079b, 0x004a), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x07b8, 0x6001), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0ace, 0x1211), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0ace, 0xa211), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0b05, 0x170c), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0b3b, 0x1630), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0b3b, 0x5630), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0df6, 0x9071), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x0df6, 0x9075), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x126f, 0xa006), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x129b, 0x1666), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x13b1, 0x001e), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x1435, 0x0711), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x14ea, 0xab10), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x14ea, 0xab13), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x157e, 0x300a), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x157e, 0x300b), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x157e, 0x3204), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x157e, 0x3207), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x1740, 0x2000), .driver_info = DEVICE_ZD1211 },
        { USB_DEVICE(0x6891, 0xa727), .driver_info = DEVICE_ZD1211 },
        /* ZD1211B */
        { USB_DEVICE(0x0053, 0x5301), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0409, 0x0248), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0411, 0x00da), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0471, 0x1236), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0471, 0x1237), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x050d, 0x705c), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x054c, 0x0257), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0586, 0x340a), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0586, 0x340f), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0586, 0x3410), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0586, 0x3412), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0586, 0x3413), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x079b, 0x0062), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x07b8, 0x6001), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x07fa, 0x1196), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x083a, 0x4505), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x083a, 0xe501), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x083a, 0xe503), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x083a, 0xe506), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0ace, 0x1215), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0ace, 0xb215), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0b05, 0x171b), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0baf, 0x0121), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0cde, 0x001a), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x0df6, 0x0036), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x129b, 0x1667), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x13b1, 0x0024), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x157e, 0x300d), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x1582, 0x6003), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x2019, 0x5303), .driver_info = DEVICE_ZD1211B },
        { USB_DEVICE(0x2019, 0xed01), .driver_info = DEVICE_ZD1211B },
        /* "Driverless" devices that need ejecting */
        { USB_DEVICE(0x0ace, 0x2011), .driver_info = DEVICE_INSTALLER },
        { USB_DEVICE(0x0ace, 0x20ff), .driver_info = DEVICE_INSTALLER },
        {}
};

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("USB driver for devices with the ZD1211 chip.");
MODULE_AUTHOR("Ulrich Kunitz");
MODULE_AUTHOR("Daniel Drake");
MODULE_VERSION("1.0");
MODULE_DEVICE_TABLE(usb, usb_ids);

#define FW_ZD1211_PREFIX        "zd1211/zd1211_"
#define FW_ZD1211B_PREFIX       "zd1211/zd1211b_"

static bool check_read_regs(struct zd_usb *usb, struct usb_req_read_regs *req,
                            unsigned int count);

/* USB device initialization */
static void int_urb_complete(struct urb *urb);

static int request_fw_file(
        const struct firmware **fw, const char *name, struct device *device)
{
        int r;

        dev_dbg_f(device, "fw name %s\n", name);

        r = request_firmware(fw, name, device);
        if (r)
                dev_err(device,
                       "Could not load firmware file %s. Error number %d\n",
                       name, r);
        return r;
}

static inline u16 get_bcdDevice(const struct usb_device *udev)
{
        return le16_to_cpu(udev->descriptor.bcdDevice);
}

enum upload_code_flags {
        REBOOT = 1,
};

/* Ensures that MAX_TRANSFER_SIZE is even. */
#define MAX_TRANSFER_SIZE (USB_MAX_TRANSFER_SIZE & ~1)

static int upload_code(struct usb_device *udev,
        const u8 *data, size_t size, u16 code_offset, int flags)
{
        u8 *p;
        int r;

        /* USB request blocks need "kmalloced" buffers.
         */
        p = kmalloc(MAX_TRANSFER_SIZE, GFP_KERNEL);
        if (!p) {
                dev_err(&udev->dev, "out of memory\n");
                r = -ENOMEM;
                goto error;
        }

        size &= ~1;
        while (size > 0) {
                size_t transfer_size = size <= MAX_TRANSFER_SIZE ?
                        size : MAX_TRANSFER_SIZE;

                dev_dbg_f(&udev->dev, "transfer size %zu\n", transfer_size);

                memcpy(p, data, transfer_size);
                r = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
                        USB_REQ_FIRMWARE_DOWNLOAD,
                        USB_DIR_OUT | USB_TYPE_VENDOR,
                        code_offset, 0, p, transfer_size, 1000 /* ms */);
                if (r < 0) {
                        dev_err(&udev->dev,
                               "USB control request for firmware upload"
                               " failed. Error number %d\n", r);
                        goto error;
                }
                transfer_size = r & ~1;

                size -= transfer_size;
                data += transfer_size;
                code_offset += transfer_size/sizeof(u16);
        }

        if (flags & REBOOT) {
                u8 ret;

                /* Use "DMA-aware" buffer. */
                r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
                        USB_REQ_FIRMWARE_CONFIRM,
                        USB_DIR_IN | USB_TYPE_VENDOR,
                        0, 0, p, sizeof(ret), 5000 /* ms */);
                if (r != sizeof(ret)) {
                        dev_err(&udev->dev,
                                "control request firmeware confirmation failed."
                                " Return value %d\n", r);
                        if (r >= 0)
                                r = -ENODEV;
                        goto error;
                }
                ret = p[0];
                if (ret & 0x80) {
                        dev_err(&udev->dev,
                                "Internal error while downloading."
                                " Firmware confirm return value %#04x\n",
                                (unsigned int)ret);
                        r = -ENODEV;
                        goto error;
                }
                dev_dbg_f(&udev->dev, "firmware confirm return value %#04x\n",
                        (unsigned int)ret);
        }

        r = 0;
error:
        kfree(p);
        return r;
}

static u16 get_word(const void *data, u16 offset)
{
        const __le16 *p = data;
        return le16_to_cpu(p[offset]);
}

static char *get_fw_name(struct zd_usb *usb, char *buffer, size_t size,
                       const char* postfix)
{
        scnprintf(buffer, size, "%s%s",
                usb->is_zd1211b ?
                        FW_ZD1211B_PREFIX : FW_ZD1211_PREFIX,
                postfix);
        return buffer;
}

static int handle_version_mismatch(struct zd_usb *usb,
        const struct firmware *ub_fw)
{
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        const struct firmware *ur_fw = NULL;
        int offset;
        int r = 0;
        char fw_name[128];

        r = request_fw_file(&ur_fw,
                get_fw_name(usb, fw_name, sizeof(fw_name), "ur"),
                &udev->dev);
        if (r)
                goto error;

        r = upload_code(udev, ur_fw->data, ur_fw->size, FW_START, REBOOT);
        if (r)
                goto error;

        offset = (E2P_BOOT_CODE_OFFSET * sizeof(u16));
        r = upload_code(udev, ub_fw->data + offset, ub_fw->size - offset,
                E2P_START + E2P_BOOT_CODE_OFFSET, REBOOT);

        /* At this point, the vendor driver downloads the whole firmware
         * image, hacks around with version IDs, and uploads it again,
         * completely overwriting the boot code. We do not do this here as
         * it is not required on any tested devices, and it is suspected to
         * cause problems. */
error:
        release_firmware(ur_fw);
        return r;
}

static int upload_firmware(struct zd_usb *usb)
{
        int r;
        u16 fw_bcdDevice;
        u16 bcdDevice;
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        const struct firmware *ub_fw = NULL;
        const struct firmware *uph_fw = NULL;
        char fw_name[128];

        bcdDevice = get_bcdDevice(udev);

        r = request_fw_file(&ub_fw,
                get_fw_name(usb, fw_name, sizeof(fw_name), "ub"),
                &udev->dev);
        if (r)
                goto error;

        fw_bcdDevice = get_word(ub_fw->data, E2P_DATA_OFFSET);

        if (fw_bcdDevice != bcdDevice) {
                dev_info(&udev->dev,
                        "firmware version %#06x and device bootcode version "
                        "%#06x differ\n", fw_bcdDevice, bcdDevice);
                if (bcdDevice <= 0x4313)
                        dev_warn(&udev->dev, "device has old bootcode, please "
                                "report success or failure\n");

                r = handle_version_mismatch(usb, ub_fw);
                if (r)
                        goto error;
        } else {
                dev_dbg_f(&udev->dev,
                        "firmware device id %#06x is equal to the "
                        "actual device id\n", fw_bcdDevice);
        }


        r = request_fw_file(&uph_fw,
                get_fw_name(usb, fw_name, sizeof(fw_name), "uphr"),
                &udev->dev);
        if (r)
                goto error;

        r = upload_code(udev, uph_fw->data, uph_fw->size, FW_START, REBOOT);
        if (r) {
                dev_err(&udev->dev,
                        "Could not upload firmware code uph. Error number %d\n",
                        r);
        }

        /* FALL-THROUGH */
error:
        release_firmware(ub_fw);
        release_firmware(uph_fw);
        return r;
}

MODULE_FIRMWARE(FW_ZD1211B_PREFIX "ur");
MODULE_FIRMWARE(FW_ZD1211_PREFIX "ur");
MODULE_FIRMWARE(FW_ZD1211B_PREFIX "ub");
MODULE_FIRMWARE(FW_ZD1211_PREFIX "ub");
MODULE_FIRMWARE(FW_ZD1211B_PREFIX "uphr");
MODULE_FIRMWARE(FW_ZD1211_PREFIX "uphr");

/* Read data from device address space using "firmware interface" which does
 * not require firmware to be loaded. */
int zd_usb_read_fw(struct zd_usb *usb, zd_addr_t addr, u8 *data, u16 len)
{
        int r;
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        u8 *buf;

        /* Use "DMA-aware" buffer. */
        buf = kmalloc(len, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
                USB_REQ_FIRMWARE_READ_DATA, USB_DIR_IN | 0x40, addr, 0,
                buf, len, 5000);
        if (r < 0) {
                dev_err(&udev->dev,
                        "read over firmware interface failed: %d\n", r);
                goto exit;
        } else if (r != len) {
                dev_err(&udev->dev,
                        "incomplete read over firmware interface: %d/%d\n",
                        r, len);
                r = -EIO;
                goto exit;
        }
        r = 0;
        memcpy(data, buf, len);
exit:
        kfree(buf);
        return r;
}

#define urb_dev(urb) (&(urb)->dev->dev)

static inline void handle_regs_int_override(struct urb *urb)
{
        struct zd_usb *usb = urb->context;
        struct zd_usb_interrupt *intr = &usb->intr;

        spin_lock(&intr->lock);
        if (atomic_read(&intr->read_regs_enabled)) {
                atomic_set(&intr->read_regs_enabled, 0);
                intr->read_regs_int_overridden = 1;
                complete(&intr->read_regs.completion);
        }
        spin_unlock(&intr->lock);
}

static inline void handle_regs_int(struct urb *urb)
{
        struct zd_usb *usb = urb->context;
        struct zd_usb_interrupt *intr = &usb->intr;
        int len;
        u16 int_num;

        ZD_ASSERT(in_interrupt());
        spin_lock(&intr->lock);

        int_num = le16_to_cpu(*(__le16 *)(urb->transfer_buffer+2));
        if (int_num == CR_INTERRUPT) {
                struct zd_mac *mac = zd_hw_mac(zd_usb_to_hw(urb->context));
                spin_lock(&mac->lock);
                memcpy(&mac->intr_buffer, urb->transfer_buffer,
                                USB_MAX_EP_INT_BUFFER);
                spin_unlock(&mac->lock);
                schedule_work(&mac->process_intr);
        } else if (atomic_read(&intr->read_regs_enabled)) {
                len = urb->actual_length;
                intr->read_regs.length = urb->actual_length;
                if (len > sizeof(intr->read_regs.buffer))
                        len = sizeof(intr->read_regs.buffer);

                memcpy(intr->read_regs.buffer, urb->transfer_buffer, len);

                /* Sometimes USB_INT_ID_REGS is not overridden, but comes after
                 * USB_INT_ID_RETRY_FAILED. Read-reg retry then gets this
                 * delayed USB_INT_ID_REGS, but leaves USB_INT_ID_REGS of
                 * retry unhandled. Next read-reg command then might catch
                 * this wrong USB_INT_ID_REGS. Fix by ignoring wrong reads.
                 */
                if (!check_read_regs(usb, intr->read_regs.req,
                                                intr->read_regs.req_count))
                        goto out;

                atomic_set(&intr->read_regs_enabled, 0);
                intr->read_regs_int_overridden = 0;
                complete(&intr->read_regs.completion);

                goto out;
        }

out:
        spin_unlock(&intr->lock);

        /* CR_INTERRUPT might override read_reg too. */
        if (int_num == CR_INTERRUPT && atomic_read(&intr->read_regs_enabled))
                handle_regs_int_override(urb);
}

static void int_urb_complete(struct urb *urb)
{
        int r;
        struct usb_int_header *hdr;
        struct zd_usb *usb;
        struct zd_usb_interrupt *intr;

        switch (urb->status) {
        case 0:
                break;
        case -ESHUTDOWN:
        case -EINVAL:
        case -ENODEV:
        case -ENOENT:
        case -ECONNRESET:
        case -EPIPE:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                return;
        default:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                goto resubmit;
        }

        if (urb->actual_length < sizeof(hdr)) {
                dev_dbg_f(urb_dev(urb), "error: urb %p to small\n", urb);
                goto resubmit;
        }

        hdr = urb->transfer_buffer;
        if (hdr->type != USB_INT_TYPE) {
                dev_dbg_f(urb_dev(urb), "error: urb %p wrong type\n", urb);
                goto resubmit;
        }

        /* USB_INT_ID_RETRY_FAILED triggered by tx-urb submit can override
         * pending USB_INT_ID_REGS causing read command timeout.
         */
        usb = urb->context;
        intr = &usb->intr;
        if (hdr->id != USB_INT_ID_REGS && atomic_read(&intr->read_regs_enabled))
                handle_regs_int_override(urb);

        switch (hdr->id) {
        case USB_INT_ID_REGS:
                handle_regs_int(urb);
                break;
        case USB_INT_ID_RETRY_FAILED:
                zd_mac_tx_failed(urb);
                break;
        default:
                dev_dbg_f(urb_dev(urb), "error: urb %p unknown id %x\n", urb,
                        (unsigned int)hdr->id);
                goto resubmit;
        }

resubmit:
        r = usb_submit_urb(urb, GFP_ATOMIC);
        if (r) {
                dev_dbg_f(urb_dev(urb), "error: resubmit urb %p err code %d\n",
                          urb, r);
                /* TODO: add worker to reset intr->urb */
        }
        return;
}

static inline int int_urb_interval(struct usb_device *udev)
{
        switch (udev->speed) {
        case USB_SPEED_HIGH:
                return 4;
        case USB_SPEED_LOW:
                return 10;
        case USB_SPEED_FULL:
        default:
                return 1;
        }
}

static inline int usb_int_enabled(struct zd_usb *usb)
{
        unsigned long flags;
        struct zd_usb_interrupt *intr = &usb->intr;
        struct urb *urb;

        spin_lock_irqsave(&intr->lock, flags);
        urb = intr->urb;
        spin_unlock_irqrestore(&intr->lock, flags);
        return urb != NULL;
}

int zd_usb_enable_int(struct zd_usb *usb)
{
        int r;
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        struct zd_usb_interrupt *intr = &usb->intr;
        struct urb *urb;

        dev_dbg_f(zd_usb_dev(usb), "\n");

        urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!urb) {
                r = -ENOMEM;
                goto out;
        }

        ZD_ASSERT(!irqs_disabled());
        spin_lock_irq(&intr->lock);
        if (intr->urb) {
                spin_unlock_irq(&intr->lock);
                r = 0;
                goto error_free_urb;
        }
        intr->urb = urb;
        spin_unlock_irq(&intr->lock);

        r = -ENOMEM;
        intr->buffer = usb_alloc_coherent(udev, USB_MAX_EP_INT_BUFFER,
                                          GFP_KERNEL, &intr->buffer_dma);
        if (!intr->buffer) {
                dev_dbg_f(zd_usb_dev(usb),
                        "couldn't allocate transfer_buffer\n");
                goto error_set_urb_null;
        }

        usb_fill_int_urb(urb, udev, usb_rcvintpipe(udev, EP_INT_IN),
                         intr->buffer, USB_MAX_EP_INT_BUFFER,
                         int_urb_complete, usb,
                         intr->interval);
        urb->transfer_dma = intr->buffer_dma;
        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

        dev_dbg_f(zd_usb_dev(usb), "submit urb %p\n", intr->urb);
        r = usb_submit_urb(urb, GFP_KERNEL);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                         "Couldn't submit urb. Error number %d\n", r);
                goto error;
        }

        return 0;
error:
        usb_free_coherent(udev, USB_MAX_EP_INT_BUFFER,
                          intr->buffer, intr->buffer_dma);
error_set_urb_null:
        spin_lock_irq(&intr->lock);
        intr->urb = NULL;
        spin_unlock_irq(&intr->lock);
error_free_urb:
        usb_free_urb(urb);
out:
        return r;
}

void zd_usb_disable_int(struct zd_usb *usb)
{
        unsigned long flags;
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        struct zd_usb_interrupt *intr = &usb->intr;
        struct urb *urb;
        void *buffer;
        dma_addr_t buffer_dma;

        spin_lock_irqsave(&intr->lock, flags);
        urb = intr->urb;
        if (!urb) {
                spin_unlock_irqrestore(&intr->lock, flags);
                return;
        }
        intr->urb = NULL;
        buffer = intr->buffer;
        buffer_dma = intr->buffer_dma;
        intr->buffer = NULL;
        spin_unlock_irqrestore(&intr->lock, flags);

        usb_kill_urb(urb);
        dev_dbg_f(zd_usb_dev(usb), "urb %p killed\n", urb);
        usb_free_urb(urb);

        if (buffer)
                usb_free_coherent(udev, USB_MAX_EP_INT_BUFFER,
                                  buffer, buffer_dma);
}

static void handle_rx_packet(struct zd_usb *usb, const u8 *buffer,
                             unsigned int length)
{
        int i;
        const struct rx_length_info *length_info;

        if (length < sizeof(struct rx_length_info)) {
                /* It's not a complete packet anyhow. */
                dev_dbg_f(zd_usb_dev(usb), "invalid, small RX packet : %d\n",
                                           length);
                return;
        }
        length_info = (struct rx_length_info *)
                (buffer + length - sizeof(struct rx_length_info));

        /* It might be that three frames are merged into a single URB
         * transaction. We have to check for the length info tag.
         *
         * While testing we discovered that length_info might be unaligned,
         * because if USB transactions are merged, the last packet will not
         * be padded. Unaligned access might also happen if the length_info
         * structure is not present.
         */
        if (get_unaligned_le16(&length_info->tag) == RX_LENGTH_INFO_TAG)
        {
                unsigned int l, k, n;
                for (i = 0, l = 0;; i++) {
                        k = get_unaligned_le16(&length_info->length[i]);
                        if (k == 0)
                                return;
                        n = l+k;
                        if (n > length)
                                return;
                        zd_mac_rx(zd_usb_to_hw(usb), buffer+l, k);
                        if (i >= 2)
                                return;
                        l = (n+3) & ~3;
                }
        } else {
                zd_mac_rx(zd_usb_to_hw(usb), buffer, length);
        }
}

static void rx_urb_complete(struct urb *urb)
{
        int r;
        struct zd_usb *usb;
        struct zd_usb_rx *rx;
        const u8 *buffer;
        unsigned int length;

        switch (urb->status) {
        case 0:
                break;
        case -ESHUTDOWN:
        case -EINVAL:
        case -ENODEV:
        case -ENOENT:
        case -ECONNRESET:
        case -EPIPE:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                return;
        default:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                goto resubmit;
        }

        buffer = urb->transfer_buffer;
        length = urb->actual_length;
        usb = urb->context;
        rx = &usb->rx;

        tasklet_schedule(&rx->reset_timer_tasklet);

        if (length%rx->usb_packet_size > rx->usb_packet_size-4) {
                /* If there is an old first fragment, we don't care. */
                dev_dbg_f(urb_dev(urb), "*** first fragment ***\n");
                ZD_ASSERT(length <= ARRAY_SIZE(rx->fragment));
                spin_lock(&rx->lock);
                memcpy(rx->fragment, buffer, length);
                rx->fragment_length = length;
                spin_unlock(&rx->lock);
                goto resubmit;
        }

        spin_lock(&rx->lock);
        if (rx->fragment_length > 0) {
                /* We are on a second fragment, we believe */
                ZD_ASSERT(length + rx->fragment_length <=
                          ARRAY_SIZE(rx->fragment));
                dev_dbg_f(urb_dev(urb), "*** second fragment ***\n");
                memcpy(rx->fragment+rx->fragment_length, buffer, length);
                handle_rx_packet(usb, rx->fragment,
                                 rx->fragment_length + length);
                rx->fragment_length = 0;
                spin_unlock(&rx->lock);
        } else {
                spin_unlock(&rx->lock);
                handle_rx_packet(usb, buffer, length);
        }

resubmit:
        r = usb_submit_urb(urb, GFP_ATOMIC);
        if (r)
                dev_dbg_f(urb_dev(urb), "urb %p resubmit error %d\n", urb, r);
}

static struct urb *alloc_rx_urb(struct zd_usb *usb)
{
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        struct urb *urb;
        void *buffer;

        urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!urb)
                return NULL;
        buffer = usb_alloc_coherent(udev, USB_MAX_RX_SIZE, GFP_KERNEL,
                                    &urb->transfer_dma);
        if (!buffer) {
                usb_free_urb(urb);
                return NULL;
        }

        usb_fill_bulk_urb(urb, udev, usb_rcvbulkpipe(udev, EP_DATA_IN),
                          buffer, USB_MAX_RX_SIZE,
                          rx_urb_complete, usb);
        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

        return urb;
}

static void free_rx_urb(struct urb *urb)
{
        if (!urb)
                return;
        usb_free_coherent(urb->dev, urb->transfer_buffer_length,
                          urb->transfer_buffer, urb->transfer_dma);
        usb_free_urb(urb);
}

static int __zd_usb_enable_rx(struct zd_usb *usb)
{
        int i, r;
        struct zd_usb_rx *rx = &usb->rx;
        struct urb **urbs;

        dev_dbg_f(zd_usb_dev(usb), "\n");

        r = -ENOMEM;
        urbs = kcalloc(RX_URBS_COUNT, sizeof(struct urb *), GFP_KERNEL);
        if (!urbs)
                goto error;
        for (i = 0; i < RX_URBS_COUNT; i++) {
                urbs[i] = alloc_rx_urb(usb);
                if (!urbs[i])
                        goto error;
        }

        ZD_ASSERT(!irqs_disabled());
        spin_lock_irq(&rx->lock);
        if (rx->urbs) {
                spin_unlock_irq(&rx->lock);
                r = 0;
                goto error;
        }
        rx->urbs = urbs;
        rx->urbs_count = RX_URBS_COUNT;
        spin_unlock_irq(&rx->lock);

        for (i = 0; i < RX_URBS_COUNT; i++) {
                r = usb_submit_urb(urbs[i], GFP_KERNEL);
                if (r)
                        goto error_submit;
        }

        return 0;
error_submit:
        for (i = 0; i < RX_URBS_COUNT; i++) {
                usb_kill_urb(urbs[i]);
        }
        spin_lock_irq(&rx->lock);
        rx->urbs = NULL;
        rx->urbs_count = 0;
        spin_unlock_irq(&rx->lock);
error:
        if (urbs) {
                for (i = 0; i < RX_URBS_COUNT; i++)
                        free_rx_urb(urbs[i]);
        }
        return r;
}

int zd_usb_enable_rx(struct zd_usb *usb)
{
        int r;
        struct zd_usb_rx *rx = &usb->rx;

        mutex_lock(&rx->setup_mutex);
        r = __zd_usb_enable_rx(usb);
        mutex_unlock(&rx->setup_mutex);

        zd_usb_reset_rx_idle_timer(usb);

        return r;
}

static void __zd_usb_disable_rx(struct zd_usb *usb)
{
        int i;
        unsigned long flags;
        struct urb **urbs;
        unsigned int count;
        struct zd_usb_rx *rx = &usb->rx;

        spin_lock_irqsave(&rx->lock, flags);
        urbs = rx->urbs;
        count = rx->urbs_count;
        spin_unlock_irqrestore(&rx->lock, flags);
        if (!urbs)
                return;

        for (i = 0; i < count; i++) {
                usb_kill_urb(urbs[i]);
                free_rx_urb(urbs[i]);
        }
        kfree(urbs);

        spin_lock_irqsave(&rx->lock, flags);
        rx->urbs = NULL;
        rx->urbs_count = 0;
        spin_unlock_irqrestore(&rx->lock, flags);
}

void zd_usb_disable_rx(struct zd_usb *usb)
{
        struct zd_usb_rx *rx = &usb->rx;

        mutex_lock(&rx->setup_mutex);
        __zd_usb_disable_rx(usb);
        mutex_unlock(&rx->setup_mutex);

        tasklet_kill(&rx->reset_timer_tasklet);
        cancel_delayed_work_sync(&rx->idle_work);
}

static void zd_usb_reset_rx(struct zd_usb *usb)
{
        bool do_reset;
        struct zd_usb_rx *rx = &usb->rx;
        unsigned long flags;

        mutex_lock(&rx->setup_mutex);

        spin_lock_irqsave(&rx->lock, flags);
        do_reset = rx->urbs != NULL;
        spin_unlock_irqrestore(&rx->lock, flags);

        if (do_reset) {
                __zd_usb_disable_rx(usb);
                __zd_usb_enable_rx(usb);
        }

        mutex_unlock(&rx->setup_mutex);

        if (do_reset)
                zd_usb_reset_rx_idle_timer(usb);
}

/**
 * zd_usb_disable_tx - disable transmission
 * @usb: the zd1211rw-private USB structure
 *
 * Frees all URBs in the free list and marks the transmission as disabled.
 */
void zd_usb_disable_tx(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;
        unsigned long flags;

        atomic_set(&tx->enabled, 0);

        /* kill all submitted tx-urbs */
        usb_kill_anchored_urbs(&tx->submitted);

        spin_lock_irqsave(&tx->lock, flags);
        WARN_ON(!skb_queue_empty(&tx->submitted_skbs));
        WARN_ON(tx->submitted_urbs != 0);
        tx->submitted_urbs = 0;
        spin_unlock_irqrestore(&tx->lock, flags);

        /* The stopped state is ignored, relying on ieee80211_wake_queues()
         * in a potentionally following zd_usb_enable_tx().
         */
}

/**
 * zd_usb_enable_tx - enables transmission
 * @usb: a &struct zd_usb pointer
 *
 * This function enables transmission and prepares the &zd_usb_tx data
 * structure.
 */
void zd_usb_enable_tx(struct zd_usb *usb)
{
        unsigned long flags;
        struct zd_usb_tx *tx = &usb->tx;

        spin_lock_irqsave(&tx->lock, flags);
        atomic_set(&tx->enabled, 1);
        tx->submitted_urbs = 0;
        ieee80211_wake_queues(zd_usb_to_hw(usb));
        tx->stopped = 0;
        spin_unlock_irqrestore(&tx->lock, flags);
}

static void tx_dec_submitted_urbs(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;
        unsigned long flags;

        spin_lock_irqsave(&tx->lock, flags);
        --tx->submitted_urbs;
        if (tx->stopped && tx->submitted_urbs <= ZD_USB_TX_LOW) {
                ieee80211_wake_queues(zd_usb_to_hw(usb));
                tx->stopped = 0;
        }
        spin_unlock_irqrestore(&tx->lock, flags);
}

static void tx_inc_submitted_urbs(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;
        unsigned long flags;

        spin_lock_irqsave(&tx->lock, flags);
        ++tx->submitted_urbs;
        if (!tx->stopped && tx->submitted_urbs > ZD_USB_TX_HIGH) {
                ieee80211_stop_queues(zd_usb_to_hw(usb));
                tx->stopped = 1;
        }
        spin_unlock_irqrestore(&tx->lock, flags);
}

/**
 * tx_urb_complete - completes the execution of an URB
 * @urb: a URB
 *
 * This function is called if the URB has been transferred to a device or an
 * error has happened.
 */
static void tx_urb_complete(struct urb *urb)
{
        int r;
        struct sk_buff *skb;
        struct ieee80211_tx_info *info;
        struct zd_usb *usb;
        struct zd_usb_tx *tx;

        skb = (struct sk_buff *)urb->context;
        info = IEEE80211_SKB_CB(skb);
        /*
         * grab 'usb' pointer before handing off the skb (since
         * it might be freed by zd_mac_tx_to_dev or mac80211)
         */
        usb = &zd_hw_mac(info->rate_driver_data[0])->chip.usb;
        tx = &usb->tx;

        switch (urb->status) {
        case 0:
                break;
        case -ESHUTDOWN:
        case -EINVAL:
        case -ENODEV:
        case -ENOENT:
        case -ECONNRESET:
        case -EPIPE:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                break;
        default:
                dev_dbg_f(urb_dev(urb), "urb %p error %d\n", urb, urb->status);
                goto resubmit;

        }
free_urb:
        skb_unlink(skb, &usb->tx.submitted_skbs);
        zd_mac_tx_to_dev(skb, urb->status);
        usb_free_urb(urb);
        tx_dec_submitted_urbs(usb);
        return;
resubmit:
        usb_anchor_urb(urb, &tx->submitted);
        r = usb_submit_urb(urb, GFP_ATOMIC);
        if (r) {
                usb_unanchor_urb(urb);
                dev_dbg_f(urb_dev(urb), "error resubmit urb %p %d\n", urb, r);
                goto free_urb;
        }
}

/**
 * zd_usb_tx: initiates transfer of a frame of the device
 *
 * @usb: the zd1211rw-private USB structure
 * @skb: a &struct sk_buff pointer
 *
 * This function tranmits a frame to the device. It doesn't wait for
 * completion. The frame must contain the control set and have all the
 * control set information available.
 *
 * The function returns 0 if the transfer has been successfully initiated.
 */
int zd_usb_tx(struct zd_usb *usb, struct sk_buff *skb)
{
        int r;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        struct usb_device *udev = zd_usb_to_usbdev(usb);
        struct urb *urb;
        struct zd_usb_tx *tx = &usb->tx;

        if (!atomic_read(&tx->enabled)) {
                r = -ENOENT;
                goto out;
        }

        urb = usb_alloc_urb(0, GFP_ATOMIC);
        if (!urb) {
                r = -ENOMEM;
                goto out;
        }

        usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, EP_DATA_OUT),
                          skb->data, skb->len, tx_urb_complete, skb);

        info->rate_driver_data[1] = (void *)jiffies;
        skb_queue_tail(&tx->submitted_skbs, skb);
        usb_anchor_urb(urb, &tx->submitted);

        r = usb_submit_urb(urb, GFP_ATOMIC);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb), "error submit urb %p %d\n", urb, r);
                usb_unanchor_urb(urb);
                skb_unlink(skb, &tx->submitted_skbs);
                goto error;
        }
        tx_inc_submitted_urbs(usb);
        return 0;
error:
        usb_free_urb(urb);
out:
        return r;
}

static bool zd_tx_timeout(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;
        struct sk_buff_head *q = &tx->submitted_skbs;
        struct sk_buff *skb, *skbnext;
        struct ieee80211_tx_info *info;
        unsigned long flags, trans_start;
        bool have_timedout = false;

        spin_lock_irqsave(&q->lock, flags);
        skb_queue_walk_safe(q, skb, skbnext) {
                info = IEEE80211_SKB_CB(skb);
                trans_start = (unsigned long)info->rate_driver_data[1];

                if (time_is_before_jiffies(trans_start + ZD_TX_TIMEOUT)) {
                        have_timedout = true;
                        break;
                }
        }
        spin_unlock_irqrestore(&q->lock, flags);

        return have_timedout;
}

static void zd_tx_watchdog_handler(struct work_struct *work)
{
        struct zd_usb *usb =
                container_of(work, struct zd_usb, tx.watchdog_work.work);
        struct zd_usb_tx *tx = &usb->tx;

        if (!atomic_read(&tx->enabled) || !tx->watchdog_enabled)
                goto out;
        if (!zd_tx_timeout(usb))
                goto out;

        /* TX halted, try reset */
        dev_warn(zd_usb_dev(usb), "TX-stall detected, reseting device...");

        usb_queue_reset_device(usb->intf);

        /* reset will stop this worker, don't rearm */
        return;
out:
        queue_delayed_work(zd_workqueue, &tx->watchdog_work,
                           ZD_TX_WATCHDOG_INTERVAL);
}

void zd_tx_watchdog_enable(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;

        if (!tx->watchdog_enabled) {
                dev_dbg_f(zd_usb_dev(usb), "\n");
                queue_delayed_work(zd_workqueue, &tx->watchdog_work,
                                   ZD_TX_WATCHDOG_INTERVAL);
                tx->watchdog_enabled = 1;
        }
}

void zd_tx_watchdog_disable(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;

        if (tx->watchdog_enabled) {
                dev_dbg_f(zd_usb_dev(usb), "\n");
                tx->watchdog_enabled = 0;
                cancel_delayed_work_sync(&tx->watchdog_work);
        }
}

static void zd_rx_idle_timer_handler(struct work_struct *work)
{
        struct zd_usb *usb =
                container_of(work, struct zd_usb, rx.idle_work.work);
        struct zd_mac *mac = zd_usb_to_mac(usb);

        if (!test_bit(ZD_DEVICE_RUNNING, &mac->flags))
                return;

        dev_dbg_f(zd_usb_dev(usb), "\n");

        /* 30 seconds since last rx, reset rx */
        zd_usb_reset_rx(usb);
}

static void zd_usb_reset_rx_idle_timer_tasklet(unsigned long param)
{
        struct zd_usb *usb = (struct zd_usb *)param;

        zd_usb_reset_rx_idle_timer(usb);
}

void zd_usb_reset_rx_idle_timer(struct zd_usb *usb)
{
        struct zd_usb_rx *rx = &usb->rx;

        cancel_delayed_work(&rx->idle_work);
        queue_delayed_work(zd_workqueue, &rx->idle_work, ZD_RX_IDLE_INTERVAL);
}

static inline void init_usb_interrupt(struct zd_usb *usb)
{
        struct zd_usb_interrupt *intr = &usb->intr;

        spin_lock_init(&intr->lock);
        intr->interval = int_urb_interval(zd_usb_to_usbdev(usb));
        init_completion(&intr->read_regs.completion);
        atomic_set(&intr->read_regs_enabled, 0);
        intr->read_regs.cr_int_addr = cpu_to_le16((u16)CR_INTERRUPT);
}

static inline void init_usb_rx(struct zd_usb *usb)
{
        struct zd_usb_rx *rx = &usb->rx;

        spin_lock_init(&rx->lock);
        mutex_init(&rx->setup_mutex);
        if (interface_to_usbdev(usb->intf)->speed == USB_SPEED_HIGH) {
                rx->usb_packet_size = 512;
        } else {
                rx->usb_packet_size = 64;
        }
        ZD_ASSERT(rx->fragment_length == 0);
        INIT_DELAYED_WORK(&rx->idle_work, zd_rx_idle_timer_handler);
        rx->reset_timer_tasklet.func = zd_usb_reset_rx_idle_timer_tasklet;
        rx->reset_timer_tasklet.data = (unsigned long)usb;
}

static inline void init_usb_tx(struct zd_usb *usb)
{
        struct zd_usb_tx *tx = &usb->tx;

        spin_lock_init(&tx->lock);
        atomic_set(&tx->enabled, 0);
        tx->stopped = 0;
        skb_queue_head_init(&tx->submitted_skbs);
        init_usb_anchor(&tx->submitted);
        tx->submitted_urbs = 0;
        tx->watchdog_enabled = 0;
        INIT_DELAYED_WORK(&tx->watchdog_work, zd_tx_watchdog_handler);
}

void zd_usb_init(struct zd_usb *usb, struct ieee80211_hw *hw,
                 struct usb_interface *intf)
{
        memset(usb, 0, sizeof(*usb));
        usb->intf = usb_get_intf(intf);
        usb_set_intfdata(usb->intf, hw);
        init_usb_anchor(&usb->submitted_cmds);
        init_usb_interrupt(usb);
        init_usb_tx(usb);
        init_usb_rx(usb);
}

void zd_usb_clear(struct zd_usb *usb)
{
        usb_set_intfdata(usb->intf, NULL);
        usb_put_intf(usb->intf);
        ZD_MEMCLEAR(usb, sizeof(*usb));
        /* FIXME: usb_interrupt, usb_tx, usb_rx? */
}

static const char *speed(enum usb_device_speed speed)
{
        switch (speed) {
        case USB_SPEED_LOW:
                return "low";
        case USB_SPEED_FULL:
                return "full";
        case USB_SPEED_HIGH:
                return "high";
        default:
                return "unknown speed";
        }
}

static int scnprint_id(struct usb_device *udev, char *buffer, size_t size)
{
        return scnprintf(buffer, size, "%04hx:%04hx v%04hx %s",
                le16_to_cpu(udev->descriptor.idVendor),
                le16_to_cpu(udev->descriptor.idProduct),
                get_bcdDevice(udev),
                speed(udev->speed));
}

int zd_usb_scnprint_id(struct zd_usb *usb, char *buffer, size_t size)
{
        struct usb_device *udev = interface_to_usbdev(usb->intf);
        return scnprint_id(udev, buffer, size);
}

#ifdef DEBUG
static void print_id(struct usb_device *udev)
{
        char buffer[40];

        scnprint_id(udev, buffer, sizeof(buffer));
        buffer[sizeof(buffer)-1] = 0;
        dev_dbg_f(&udev->dev, "%s\n", buffer);
}
#else
#define print_id(udev) do { } while (0)
#endif

static int eject_installer(struct usb_interface *intf)
{
        struct usb_device *udev = interface_to_usbdev(intf);
        struct usb_host_interface *iface_desc = &intf->altsetting[0];
        struct usb_endpoint_descriptor *endpoint;
        unsigned char *cmd;
        u8 bulk_out_ep;
        int r;

        /* Find bulk out endpoint */
        for (r = 1; r >= 0; r--) {
                endpoint = &iface_desc->endpoint[r].desc;
                if (usb_endpoint_dir_out(endpoint) &&
                    usb_endpoint_xfer_bulk(endpoint)) {
                        bulk_out_ep = endpoint->bEndpointAddress;
                        break;
                }
        }
        if (r == -1) {
                dev_err(&udev->dev,
                        "zd1211rw: Could not find bulk out endpoint\n");
                return -ENODEV;
        }

        cmd = kzalloc(31, GFP_KERNEL);
        if (cmd == NULL)
                return -ENODEV;

        /* USB bulk command block */
        cmd[0] = 0x55;  /* bulk command signature */
        cmd[1] = 0x53;  /* bulk command signature */
        cmd[2] = 0x42;  /* bulk command signature */
        cmd[3] = 0x43;  /* bulk command signature */
        cmd[14] = 6;    /* command length */

        cmd[15] = 0x1b; /* SCSI command: START STOP UNIT */
        cmd[19] = 0x2;  /* eject disc */

        dev_info(&udev->dev, "Ejecting virtual installer media...\n");
        r = usb_bulk_msg(udev, usb_sndbulkpipe(udev, bulk_out_ep),
                cmd, 31, NULL, 2000);
        kfree(cmd);
        if (r)
                return r;

        /* At this point, the device disconnects and reconnects with the real
         * ID numbers. */

        usb_set_intfdata(intf, NULL);
        return 0;
}

int zd_usb_init_hw(struct zd_usb *usb)
{
        int r;
        struct zd_mac *mac = zd_usb_to_mac(usb);

        dev_dbg_f(zd_usb_dev(usb), "\n");

        r = upload_firmware(usb);
        if (r) {
                dev_err(zd_usb_dev(usb),
                       "couldn't load firmware. Error number %d\n", r);
                return r;
        }

        r = usb_reset_configuration(zd_usb_to_usbdev(usb));
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "couldn't reset configuration. Error number %d\n", r);
                return r;
        }

        r = zd_mac_init_hw(mac->hw);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                         "couldn't initialize mac. Error number %d\n", r);
                return r;
        }

        usb->initialized = 1;
        return 0;
}

static int probe(struct usb_interface *intf, const struct usb_device_id *id)
{
        int r;
        struct usb_device *udev = interface_to_usbdev(intf);
        struct zd_usb *usb;
        struct ieee80211_hw *hw = NULL;

        print_id(udev);

        if (id->driver_info & DEVICE_INSTALLER)
                return eject_installer(intf);

        switch (udev->speed) {
        case USB_SPEED_LOW:
        case USB_SPEED_FULL:
        case USB_SPEED_HIGH:
                break;
        default:
                dev_dbg_f(&intf->dev, "Unknown USB speed\n");
                r = -ENODEV;
                goto error;
        }

        r = usb_reset_device(udev);
        if (r) {
                dev_err(&intf->dev,
                        "couldn't reset usb device. Error number %d\n", r);
                goto error;
        }

        hw = zd_mac_alloc_hw(intf);
        if (hw == NULL) {
                r = -ENOMEM;
                goto error;
        }

        usb = &zd_hw_mac(hw)->chip.usb;
        usb->is_zd1211b = (id->driver_info == DEVICE_ZD1211B) != 0;

        r = zd_mac_preinit_hw(hw);
        if (r) {
                dev_dbg_f(&intf->dev,
                         "couldn't initialize mac. Error number %d\n", r);
                goto error;
        }

        r = ieee80211_register_hw(hw);
        if (r) {
                dev_dbg_f(&intf->dev,
                         "couldn't register device. Error number %d\n", r);
                goto error;
        }

        dev_dbg_f(&intf->dev, "successful\n");
        dev_info(&intf->dev, "%s\n", wiphy_name(hw->wiphy));
        return 0;
error:
        usb_reset_device(interface_to_usbdev(intf));
        if (hw) {
                zd_mac_clear(zd_hw_mac(hw));
                ieee80211_free_hw(hw);
        }
        return r;
}

static void disconnect(struct usb_interface *intf)
{
        struct ieee80211_hw *hw = zd_intf_to_hw(intf);
        struct zd_mac *mac;
        struct zd_usb *usb;

        /* Either something really bad happened, or we're just dealing with
         * a DEVICE_INSTALLER. */
        if (hw == NULL)
                return;

        mac = zd_hw_mac(hw);
        usb = &mac->chip.usb;

        dev_dbg_f(zd_usb_dev(usb), "\n");

        ieee80211_unregister_hw(hw);

        /* Just in case something has gone wrong! */
        zd_usb_disable_tx(usb);
        zd_usb_disable_rx(usb);
        zd_usb_disable_int(usb);

        /* If the disconnect has been caused by a removal of the
         * driver module, the reset allows reloading of the driver. If the
         * reset will not be executed here, the upload of the firmware in the
         * probe function caused by the reloading of the driver will fail.
         */
        usb_reset_device(interface_to_usbdev(intf));

        zd_mac_clear(mac);
        ieee80211_free_hw(hw);
        dev_dbg(&intf->dev, "disconnected\n");
}

static void zd_usb_resume(struct zd_usb *usb)
{
        struct zd_mac *mac = zd_usb_to_mac(usb);
        int r;

        dev_dbg_f(zd_usb_dev(usb), "\n");

        r = zd_op_start(zd_usb_to_hw(usb));
        if (r < 0) {
                dev_warn(zd_usb_dev(usb), "Device resume failed "
                         "with error code %d. Retrying...\n", r);
                if (usb->was_running)
                        set_bit(ZD_DEVICE_RUNNING, &mac->flags);
                usb_queue_reset_device(usb->intf);
                return;
        }

        if (mac->type != NL80211_IFTYPE_UNSPECIFIED) {
                r = zd_restore_settings(mac);
                if (r < 0) {
                        dev_dbg(zd_usb_dev(usb),
                                "failed to restore settings, %d\n", r);
                        return;
                }
        }
}

static void zd_usb_stop(struct zd_usb *usb)
{
        dev_dbg_f(zd_usb_dev(usb), "\n");

        zd_op_stop(zd_usb_to_hw(usb));

        zd_usb_disable_tx(usb);
        zd_usb_disable_rx(usb);
        zd_usb_disable_int(usb);

        usb->initialized = 0;
}

static int pre_reset(struct usb_interface *intf)
{
        struct ieee80211_hw *hw = usb_get_intfdata(intf);
        struct zd_mac *mac;
        struct zd_usb *usb;

        if (!hw || intf->condition != USB_INTERFACE_BOUND)
                return 0;

        mac = zd_hw_mac(hw);
        usb = &mac->chip.usb;

        usb->was_running = test_bit(ZD_DEVICE_RUNNING, &mac->flags);

        zd_usb_stop(usb);

        mutex_lock(&mac->chip.mutex);
        return 0;
}

static int post_reset(struct usb_interface *intf)
{
        struct ieee80211_hw *hw = usb_get_intfdata(intf);
        struct zd_mac *mac;
        struct zd_usb *usb;

        if (!hw || intf->condition != USB_INTERFACE_BOUND)
                return 0;

        mac = zd_hw_mac(hw);
        usb = &mac->chip.usb;

        mutex_unlock(&mac->chip.mutex);

        if (usb->was_running)
                zd_usb_resume(usb);
        return 0;
}

static struct usb_driver driver = {
        .name           = KBUILD_MODNAME,
        .id_table       = usb_ids,
        .probe          = probe,
        .disconnect     = disconnect,
        .pre_reset      = pre_reset,
        .post_reset     = post_reset,
};

struct workqueue_struct *zd_workqueue;

static int __init usb_init(void)
{
        int r;

        pr_debug("%s usb_init()\n", driver.name);

        zd_workqueue = create_singlethread_workqueue(driver.name);
        if (zd_workqueue == NULL) {
                printk(KERN_ERR "%s couldn't create workqueue\n", driver.name);
                return -ENOMEM;
        }

        r = usb_register(&driver);
        if (r) {
                destroy_workqueue(zd_workqueue);
                printk(KERN_ERR "%s usb_register() failed. Error number %d\n",
                       driver.name, r);
                return r;
        }

        pr_debug("%s initialized\n", driver.name);
        return 0;
}

static void __exit usb_exit(void)
{
        pr_debug("%s usb_exit()\n", driver.name);
        usb_deregister(&driver);
        destroy_workqueue(zd_workqueue);
}

module_init(usb_init);
module_exit(usb_exit);

static int zd_ep_regs_out_msg(struct usb_device *udev, void *data, int len,
                              int *actual_length, int timeout)
{
        /* In USB 2.0 mode EP_REGS_OUT endpoint is interrupt type. However in
         * USB 1.1 mode endpoint is bulk. Select correct type URB by endpoint
         * descriptor.
         */
        struct usb_host_endpoint *ep;
        unsigned int pipe;

        pipe = usb_sndintpipe(udev, EP_REGS_OUT);
        ep = usb_pipe_endpoint(udev, pipe);
        if (!ep)
                return -EINVAL;

        if (usb_endpoint_xfer_int(&ep->desc)) {
                return usb_interrupt_msg(udev, pipe, data, len,
                                         actual_length, timeout);
        } else {
                pipe = usb_sndbulkpipe(udev, EP_REGS_OUT);
                return usb_bulk_msg(udev, pipe, data, len, actual_length,
                                    timeout);
        }
}

static int usb_int_regs_length(unsigned int count)
{
        return sizeof(struct usb_int_regs) + count * sizeof(struct reg_data);
}

static void prepare_read_regs_int(struct zd_usb *usb,
                                  struct usb_req_read_regs *req,
                                  unsigned int count)
{
        struct zd_usb_interrupt *intr = &usb->intr;

        spin_lock_irq(&intr->lock);
        atomic_set(&intr->read_regs_enabled, 1);
        intr->read_regs.req = req;
        intr->read_regs.req_count = count;
        INIT_COMPLETION(intr->read_regs.completion);
        spin_unlock_irq(&intr->lock);
}

static void disable_read_regs_int(struct zd_usb *usb)
{
        struct zd_usb_interrupt *intr = &usb->intr;

        spin_lock_irq(&intr->lock);
        atomic_set(&intr->read_regs_enabled, 0);
        spin_unlock_irq(&intr->lock);
}

static bool check_read_regs(struct zd_usb *usb, struct usb_req_read_regs *req,
                            unsigned int count)
{
        int i;
        struct zd_usb_interrupt *intr = &usb->intr;
        struct read_regs_int *rr = &intr->read_regs;
        struct usb_int_regs *regs = (struct usb_int_regs *)rr->buffer;

        /* The created block size seems to be larger than expected.
         * However results appear to be correct.
         */
        if (rr->length < usb_int_regs_length(count)) {
                dev_dbg_f(zd_usb_dev(usb),
                         "error: actual length %d less than expected %d\n",
                         rr->length, usb_int_regs_length(count));
                return false;
        }

        if (rr->length > sizeof(rr->buffer)) {
                dev_dbg_f(zd_usb_dev(usb),
                         "error: actual length %d exceeds buffer size %zu\n",
                         rr->length, sizeof(rr->buffer));
                return false;
        }

        for (i = 0; i < count; i++) {
                struct reg_data *rd = &regs->regs[i];
                if (rd->addr != req->addr[i]) {
                        dev_dbg_f(zd_usb_dev(usb),
                                 "rd[%d] addr %#06hx expected %#06hx\n", i,
                                 le16_to_cpu(rd->addr),
                                 le16_to_cpu(req->addr[i]));
                        return false;
                }
        }

        return true;
}

static int get_results(struct zd_usb *usb, u16 *values,
                       struct usb_req_read_regs *req, unsigned int count,
                       bool *retry)
{
        int r;
        int i;
        struct zd_usb_interrupt *intr = &usb->intr;
        struct read_regs_int *rr = &intr->read_regs;
        struct usb_int_regs *regs = (struct usb_int_regs *)rr->buffer;

        spin_lock_irq(&intr->lock);

        r = -EIO;

        /* Read failed because firmware bug? */
        *retry = !!intr->read_regs_int_overridden;
        if (*retry)
                goto error_unlock;

        if (!check_read_regs(usb, req, count)) {
                dev_dbg_f(zd_usb_dev(usb), "error: invalid read regs\n");
                goto error_unlock;
        }

        for (i = 0; i < count; i++) {
                struct reg_data *rd = &regs->regs[i];
                values[i] = le16_to_cpu(rd->value);
        }

        r = 0;
error_unlock:
        spin_unlock_irq(&intr->lock);
        return r;
}

int zd_usb_ioread16v(struct zd_usb *usb, u16 *values,
                     const zd_addr_t *addresses, unsigned int count)
{
        int r, i, req_len, actual_req_len, try_count = 0;
        struct usb_device *udev;
        struct usb_req_read_regs *req = NULL;
        unsigned long timeout;
        bool retry = false;

        if (count < 1) {
                dev_dbg_f(zd_usb_dev(usb), "error: count is zero\n");
                return -EINVAL;
        }
        if (count > USB_MAX_IOREAD16_COUNT) {
                dev_dbg_f(zd_usb_dev(usb),
                         "error: count %u exceeds possible max %u\n",
                         count, USB_MAX_IOREAD16_COUNT);
                return -EINVAL;
        }
        if (in_atomic()) {
                dev_dbg_f(zd_usb_dev(usb),
                         "error: io in atomic context not supported\n");
                return -EWOULDBLOCK;
        }
        if (!usb_int_enabled(usb)) {
                dev_dbg_f(zd_usb_dev(usb),
                          "error: usb interrupt not enabled\n");
                return -EWOULDBLOCK;
        }

        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
        BUILD_BUG_ON(sizeof(struct usb_req_read_regs) + USB_MAX_IOREAD16_COUNT *
                     sizeof(__le16) > sizeof(usb->req_buf));
        BUG_ON(sizeof(struct usb_req_read_regs) + count * sizeof(__le16) >
               sizeof(usb->req_buf));

        req_len = sizeof(struct usb_req_read_regs) + count * sizeof(__le16);
        req = (void *)usb->req_buf;

        req->id = cpu_to_le16(USB_REQ_READ_REGS);
        for (i = 0; i < count; i++)
                req->addr[i] = cpu_to_le16((u16)addresses[i]);

retry_read:
        try_count++;
        udev = zd_usb_to_usbdev(usb);
        prepare_read_regs_int(usb, req, count);
        r = zd_ep_regs_out_msg(udev, req, req_len, &actual_req_len, 50 /*ms*/);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error in zd_ep_regs_out_msg(). Error number %d\n", r);
                goto error;
        }
        if (req_len != actual_req_len) {
                dev_dbg_f(zd_usb_dev(usb), "error in zd_ep_regs_out_msg()\n"
                        " req_len %d != actual_req_len %d\n",
                        req_len, actual_req_len);
                r = -EIO;
                goto error;
        }

        timeout = wait_for_completion_timeout(&usb->intr.read_regs.completion,
                                              msecs_to_jiffies(50));
        if (!timeout) {
                disable_read_regs_int(usb);
                dev_dbg_f(zd_usb_dev(usb), "read timed out\n");
                r = -ETIMEDOUT;
                goto error;
        }

        r = get_results(usb, values, req, count, &retry);
        if (retry && try_count < 20) {
                dev_dbg_f(zd_usb_dev(usb), "read retry, tries so far: %d\n",
                                try_count);
                goto retry_read;
        }
error:
        return r;
}

static void iowrite16v_urb_complete(struct urb *urb)
{
        struct zd_usb *usb = urb->context;

        if (urb->status && !usb->cmd_error)
                usb->cmd_error = urb->status;

        if (!usb->cmd_error &&
                        urb->actual_length != urb->transfer_buffer_length)
                usb->cmd_error = -EIO;
}

static int zd_submit_waiting_urb(struct zd_usb *usb, bool last)
{
        int r = 0;
        struct urb *urb = usb->urb_async_waiting;

        if (!urb)
                return 0;

        usb->urb_async_waiting = NULL;

        if (!last)
                urb->transfer_flags |= URB_NO_INTERRUPT;

        usb_anchor_urb(urb, &usb->submitted_cmds);
        r = usb_submit_urb(urb, GFP_KERNEL);
        if (r) {
                usb_unanchor_urb(urb);
                dev_dbg_f(zd_usb_dev(usb),
                        "error in usb_submit_urb(). Error number %d\n", r);
                goto error;
        }

        /* fall-through with r == 0 */
error:
        usb_free_urb(urb);
        return r;
}

void zd_usb_iowrite16v_async_start(struct zd_usb *usb)
{
        ZD_ASSERT(usb_anchor_empty(&usb->submitted_cmds));
        ZD_ASSERT(usb->urb_async_waiting == NULL);
        ZD_ASSERT(!usb->in_async);

        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));

        usb->in_async = 1;
        usb->cmd_error = 0;
        usb->urb_async_waiting = NULL;
}

int zd_usb_iowrite16v_async_end(struct zd_usb *usb, unsigned int timeout)
{
        int r;

        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
        ZD_ASSERT(usb->in_async);

        /* Submit last iowrite16v URB */
        r = zd_submit_waiting_urb(usb, true);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error in zd_submit_waiting_usb(). "
                        "Error number %d\n", r);

                usb_kill_anchored_urbs(&usb->submitted_cmds);
                goto error;
        }

        if (timeout)
                timeout = usb_wait_anchor_empty_timeout(&usb->submitted_cmds,
                                                        timeout);
        if (!timeout) {
                usb_kill_anchored_urbs(&usb->submitted_cmds);
                if (usb->cmd_error == -ENOENT) {
                        dev_dbg_f(zd_usb_dev(usb), "timed out");
                        r = -ETIMEDOUT;
                        goto error;
                }
        }

        r = usb->cmd_error;
error:
        usb->in_async = 0;
        return r;
}

int zd_usb_iowrite16v_async(struct zd_usb *usb, const struct zd_ioreq16 *ioreqs,
                            unsigned int count)
{
        int r;
        struct usb_device *udev;
        struct usb_req_write_regs *req = NULL;
        int i, req_len;
        struct urb *urb;
        struct usb_host_endpoint *ep;

        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
        ZD_ASSERT(usb->in_async);

        if (count == 0)
                return 0;
        if (count > USB_MAX_IOWRITE16_COUNT) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: count %u exceeds possible max %u\n",
                        count, USB_MAX_IOWRITE16_COUNT);
                return -EINVAL;
        }
        if (in_atomic()) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: io in atomic context not supported\n");
                return -EWOULDBLOCK;
        }

        udev = zd_usb_to_usbdev(usb);

        ep = usb_pipe_endpoint(udev, usb_sndintpipe(udev, EP_REGS_OUT));
        if (!ep)
                return -ENOENT;

        urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!urb)
                return -ENOMEM;

        req_len = sizeof(struct usb_req_write_regs) +
                  count * sizeof(struct reg_data);
        req = kmalloc(req_len, GFP_KERNEL);
        if (!req) {
                r = -ENOMEM;
                goto error;
        }

        req->id = cpu_to_le16(USB_REQ_WRITE_REGS);
        for (i = 0; i < count; i++) {
                struct reg_data *rw  = &req->reg_writes[i];
                rw->addr = cpu_to_le16((u16)ioreqs[i].addr);
                rw->value = cpu_to_le16(ioreqs[i].value);
        }

        /* In USB 2.0 mode endpoint is interrupt type. However in USB 1.1 mode
         * endpoint is bulk. Select correct type URB by endpoint descriptor.
         */
        if (usb_endpoint_xfer_int(&ep->desc))
                usb_fill_int_urb(urb, udev, usb_sndintpipe(udev, EP_REGS_OUT),
                                 req, req_len, iowrite16v_urb_complete, usb,
                                 ep->desc.bInterval);
        else
                usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, EP_REGS_OUT),
                                  req, req_len, iowrite16v_urb_complete, usb);

        urb->transfer_flags |= URB_FREE_BUFFER;

        /* Submit previous URB */
        r = zd_submit_waiting_urb(usb, false);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error in zd_submit_waiting_usb(). "
                        "Error number %d\n", r);
                goto error;
        }

        /* Delay submit so that URB_NO_INTERRUPT flag can be set for all URBs
         * of currect batch except for very last.
         */
        usb->urb_async_waiting = urb;
        return 0;
error:
        usb_free_urb(urb);
        return r;
}

int zd_usb_iowrite16v(struct zd_usb *usb, const struct zd_ioreq16 *ioreqs,
                        unsigned int count)
{
        int r;

        zd_usb_iowrite16v_async_start(usb);
        r = zd_usb_iowrite16v_async(usb, ioreqs, count);
        if (r) {
                zd_usb_iowrite16v_async_end(usb, 0);
                return r;
        }
        return zd_usb_iowrite16v_async_end(usb, 50 /* ms */);
}

int zd_usb_rfwrite(struct zd_usb *usb, u32 value, u8 bits)
{
        int r;
        struct usb_device *udev;
        struct usb_req_rfwrite *req = NULL;
        int i, req_len, actual_req_len;
        u16 bit_value_template;

        if (in_atomic()) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: io in atomic context not supported\n");
                return -EWOULDBLOCK;
        }
        if (bits < USB_MIN_RFWRITE_BIT_COUNT) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: bits %d are smaller than"
                        " USB_MIN_RFWRITE_BIT_COUNT %d\n",
                        bits, USB_MIN_RFWRITE_BIT_COUNT);
                return -EINVAL;
        }
        if (bits > USB_MAX_RFWRITE_BIT_COUNT) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: bits %d exceed USB_MAX_RFWRITE_BIT_COUNT %d\n",
                        bits, USB_MAX_RFWRITE_BIT_COUNT);

                return -EINVAL;
        }
#ifdef DEBUG
        if (value & (~0UL << bits)) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error: value %#09x has bits >= %d set\n",
                        value, bits);
                return -EINVAL;
        }
#endif /* DEBUG */

        dev_dbg_f(zd_usb_dev(usb), "value %#09x bits %d\n", value, bits);

        r = zd_usb_ioread16(usb, &bit_value_template, ZD_CR203);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error %d: Couldn't read ZD_CR203\n", r);
                return r;
        }
        bit_value_template &= ~(RF_IF_LE|RF_CLK|RF_DATA);

        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
        BUILD_BUG_ON(sizeof(struct usb_req_rfwrite) +
                     USB_MAX_RFWRITE_BIT_COUNT * sizeof(__le16) >
                     sizeof(usb->req_buf));
        BUG_ON(sizeof(struct usb_req_rfwrite) + bits * sizeof(__le16) >
               sizeof(usb->req_buf));

        req_len = sizeof(struct usb_req_rfwrite) + bits * sizeof(__le16);
        req = (void *)usb->req_buf;

        req->id = cpu_to_le16(USB_REQ_WRITE_RF);
        /* 1: 3683a, but not used in ZYDAS driver */
        req->value = cpu_to_le16(2);
        req->bits = cpu_to_le16(bits);

        for (i = 0; i < bits; i++) {
                u16 bv = bit_value_template;
                if (value & (1 << (bits-1-i)))
                        bv |= RF_DATA;
                req->bit_values[i] = cpu_to_le16(bv);
        }

        udev = zd_usb_to_usbdev(usb);
        r = zd_ep_regs_out_msg(udev, req, req_len, &actual_req_len, 50 /*ms*/);
        if (r) {
                dev_dbg_f(zd_usb_dev(usb),
                        "error in zd_ep_regs_out_msg(). Error number %d\n", r);
                goto out;
        }
        if (req_len != actual_req_len) {
                dev_dbg_f(zd_usb_dev(usb), "error in zd_ep_regs_out_msg()"
                        " req_len %d != actual_req_len %d\n",
                        req_len, actual_req_len);
                r = -EIO;
                goto out;
        }

        /* FALL-THROUGH with r == 0 */
out:
        return r;
}