[mirror_ubuntu-focal-kernel.git] / drivers / usb / gadget / zero.c

/*
 * zero.c -- Gadget Zero, for USB development
 *
 * Copyright (C) 2003-2004 David Brownell
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the above-listed copyright holders may not be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * ALTERNATIVELY, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") as published by the Free Software
 * Foundation, either version 2 of that License or (at your option) any
 * later version.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


/*
 * Gadget Zero only needs two bulk endpoints, and is an example of how you
 * can write a hardware-agnostic gadget driver running inside a USB device.
 *
 * Hardware details are visible (see CONFIG_USB_ZERO_* below) but don't
 * affect most of the driver.
 *
 * Use it with the Linux host/master side "usbtest" driver to get a basic
 * functional test of your device-side usb stack, or with "usb-skeleton".
 *
 * It supports two similar configurations.  One sinks whatever the usb host
 * writes, and in return sources zeroes.  The other loops whatever the host
 * writes back, so the host can read it.  Module options include:
 *
 *   buflen=N           default N=4096, buffer size used
 *   qlen=N             default N=32, how many buffers in the loopback queue
 *   loopdefault        default false, list loopback config first
 *
 * Many drivers will only have one configuration, letting them be much
 * simpler if they also don't support high speed operation (like this
 * driver does).
 */

#define DEBUG 1
// #define VERBOSE

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/utsname.h>
#include <linux/device.h>
#include <linux/moduleparam.h>

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

#include <linux/usb/ch9.h>
#include <linux/usb_gadget.h>

#include "gadget_chips.h"


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

#define DRIVER_VERSION          "St Patrick's Day 2004"

static const char shortname [] = "zero";
static const char longname [] = "Gadget Zero";

static const char source_sink [] = "source and sink data";
static const char loopback [] = "loop input to output";

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

/*
 * driver assumes self-powered hardware, and
 * has no way for users to trigger remote wakeup.
 *
 * this version autoconfigures as much as possible,
 * which is reasonable for most "bulk-only" drivers.
 */
static const char *EP_IN_NAME;          /* source */
static const char *EP_OUT_NAME;         /* sink */

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

/* big enough to hold our biggest descriptor */
#define USB_BUFSIZ      256

struct zero_dev {
        spinlock_t              lock;
        struct usb_gadget       *gadget;
        struct usb_request      *req;           /* for control responses */

        /* when configured, we have one of two configs:
         * - source data (in to host) and sink it (out from host)
         * - or loop it back (out from host back in to host)
         */
        u8                      config;
        struct usb_ep           *in_ep, *out_ep;

        /* autoresume timer */
        struct timer_list       resume;
};

#define xprintk(d,level,fmt,args...) \
        dev_printk(level , &(d)->gadget->dev , fmt , ## args)

#ifdef DEBUG
#define DBG(dev,fmt,args...) \
        xprintk(dev , KERN_DEBUG , fmt , ## args)
#else
#define DBG(dev,fmt,args...) \
        do { } while (0)
#endif /* DEBUG */

#ifdef VERBOSE
#define VDBG    DBG
#else
#define VDBG(dev,fmt,args...) \
        do { } while (0)
#endif /* VERBOSE */

#define ERROR(dev,fmt,args...) \
        xprintk(dev , KERN_ERR , fmt , ## args)
#define WARN(dev,fmt,args...) \
        xprintk(dev , KERN_WARNING , fmt , ## args)
#define INFO(dev,fmt,args...) \
        xprintk(dev , KERN_INFO , fmt , ## args)

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

static unsigned buflen = 4096;
static unsigned qlen = 32;
static unsigned pattern = 0;

module_param (buflen, uint, S_IRUGO);
module_param (qlen, uint, S_IRUGO);
module_param (pattern, uint, S_IRUGO|S_IWUSR);

/*
 * if it's nonzero, autoresume says how many seconds to wait
 * before trying to wake up the host after suspend.
 */
static unsigned autoresume = 0;
module_param (autoresume, uint, 0);

/*
 * Normally the "loopback" configuration is second (index 1) so
 * it's not the default.  Here's where to change that order, to
 * work better with hosts where config changes are problematic.
 * Or controllers (like superh) that only support one config.
 */
static int loopdefault = 0;

module_param (loopdefault, bool, S_IRUGO|S_IWUSR);

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

/* Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with a protocol-incompatible driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures.
 */
#ifndef CONFIG_USB_ZERO_HNPTEST
#define DRIVER_VENDOR_NUM       0x0525          /* NetChip */
#define DRIVER_PRODUCT_NUM      0xa4a0          /* Linux-USB "Gadget Zero" */
#else
#define DRIVER_VENDOR_NUM       0x1a0a          /* OTG test device IDs */
#define DRIVER_PRODUCT_NUM      0xbadd
#endif

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

/*
 * DESCRIPTORS ... most are static, but strings and (full)
 * configuration descriptors are built on demand.
 */

#define STRING_MANUFACTURER             25
#define STRING_PRODUCT                  42
#define STRING_SERIAL                   101
#define STRING_SOURCE_SINK              250
#define STRING_LOOPBACK                 251

/*
 * This device advertises two configurations; these numbers work
 * on a pxa250 as well as more flexible hardware.
 */
#define CONFIG_SOURCE_SINK      3
#define CONFIG_LOOPBACK         2

static struct usb_device_descriptor
device_desc = {
        .bLength =              sizeof device_desc,
        .bDescriptorType =      USB_DT_DEVICE,

        .bcdUSB =               __constant_cpu_to_le16 (0x0200),
        .bDeviceClass =         USB_CLASS_VENDOR_SPEC,

        .idVendor =             __constant_cpu_to_le16 (DRIVER_VENDOR_NUM),
        .idProduct =            __constant_cpu_to_le16 (DRIVER_PRODUCT_NUM),
        .iManufacturer =        STRING_MANUFACTURER,
        .iProduct =             STRING_PRODUCT,
        .iSerialNumber =        STRING_SERIAL,
        .bNumConfigurations =   2,
};

static struct usb_config_descriptor
source_sink_config = {
        .bLength =              sizeof source_sink_config,
        .bDescriptorType =      USB_DT_CONFIG,

        /* compute wTotalLength on the fly */
        .bNumInterfaces =       1,
        .bConfigurationValue =  CONFIG_SOURCE_SINK,
        .iConfiguration =       STRING_SOURCE_SINK,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            1,      /* self-powered */
};

static struct usb_config_descriptor
loopback_config = {
        .bLength =              sizeof loopback_config,
        .bDescriptorType =      USB_DT_CONFIG,

        /* compute wTotalLength on the fly */
        .bNumInterfaces =       1,
        .bConfigurationValue =  CONFIG_LOOPBACK,
        .iConfiguration =       STRING_LOOPBACK,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            1,      /* self-powered */
};

static struct usb_otg_descriptor
otg_descriptor = {
        .bLength =              sizeof otg_descriptor,
        .bDescriptorType =      USB_DT_OTG,

        .bmAttributes =         USB_OTG_SRP,
};

/* one interface in each configuration */

static const struct usb_interface_descriptor
source_sink_intf = {
        .bLength =              sizeof source_sink_intf,
        .bDescriptorType =      USB_DT_INTERFACE,

        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_VENDOR_SPEC,
        .iInterface =           STRING_SOURCE_SINK,
};

static const struct usb_interface_descriptor
loopback_intf = {
        .bLength =              sizeof loopback_intf,
        .bDescriptorType =      USB_DT_INTERFACE,

        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_VENDOR_SPEC,
        .iInterface =           STRING_LOOPBACK,
};

/* two full speed bulk endpoints; their use is config-dependent */

static struct usb_endpoint_descriptor
fs_source_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor
fs_sink_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static const struct usb_descriptor_header *fs_source_sink_function [] = {
        (struct usb_descriptor_header *) &otg_descriptor,
        (struct usb_descriptor_header *) &source_sink_intf,
        (struct usb_descriptor_header *) &fs_sink_desc,
        (struct usb_descriptor_header *) &fs_source_desc,
        NULL,
};

static const struct usb_descriptor_header *fs_loopback_function [] = {
        (struct usb_descriptor_header *) &otg_descriptor,
        (struct usb_descriptor_header *) &loopback_intf,
        (struct usb_descriptor_header *) &fs_sink_desc,
        (struct usb_descriptor_header *) &fs_source_desc,
        NULL,
};

#ifdef  CONFIG_USB_GADGET_DUALSPEED

/*
 * usb 2.0 devices need to expose both high speed and full speed
 * descriptors, unless they only run at full speed.
 *
 * that means alternate endpoint descriptors (bigger packets)
 * and a "device qualifier" ... plus more construction options
 * for the config descriptor.
 */

static struct usb_endpoint_descriptor
hs_source_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16 (512),
};

static struct usb_endpoint_descriptor
hs_sink_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16 (512),
};

static struct usb_qualifier_descriptor
dev_qualifier = {
        .bLength =              sizeof dev_qualifier,
        .bDescriptorType =      USB_DT_DEVICE_QUALIFIER,

        .bcdUSB =               __constant_cpu_to_le16 (0x0200),
        .bDeviceClass =         USB_CLASS_VENDOR_SPEC,

        .bNumConfigurations =   2,
};

static const struct usb_descriptor_header *hs_source_sink_function [] = {
        (struct usb_descriptor_header *) &otg_descriptor,
        (struct usb_descriptor_header *) &source_sink_intf,
        (struct usb_descriptor_header *) &hs_source_desc,
        (struct usb_descriptor_header *) &hs_sink_desc,
        NULL,
};

static const struct usb_descriptor_header *hs_loopback_function [] = {
        (struct usb_descriptor_header *) &otg_descriptor,
        (struct usb_descriptor_header *) &loopback_intf,
        (struct usb_descriptor_header *) &hs_source_desc,
        (struct usb_descriptor_header *) &hs_sink_desc,
        NULL,
};

/* maxpacket and other transfer characteristics vary by speed. */
#define ep_desc(g,hs,fs) (((g)->speed==USB_SPEED_HIGH)?(hs):(fs))

#else

/* if there's no high speed support, maxpacket doesn't change. */
#define ep_desc(g,hs,fs) fs

#endif  /* !CONFIG_USB_GADGET_DUALSPEED */

static char                             manufacturer [50];
static char                             serial [40];

/* static strings, in UTF-8 */
static struct usb_string                strings [] = {
        { STRING_MANUFACTURER, manufacturer, },
        { STRING_PRODUCT, longname, },
        { STRING_SERIAL, serial, },
        { STRING_LOOPBACK, loopback, },
        { STRING_SOURCE_SINK, source_sink, },
        {  }                    /* end of list */
};

static struct usb_gadget_strings        stringtab = {
        .language       = 0x0409,       /* en-us */
        .strings        = strings,
};

/*
 * config descriptors are also handcrafted.  these must agree with code
 * that sets configurations, and with code managing interfaces and their
 * altsettings.  other complexity may come from:
 *
 *  - high speed support, including "other speed config" rules
 *  - multiple configurations
 *  - interfaces with alternate settings
 *  - embedded class or vendor-specific descriptors
 *
 * this handles high speed, and has a second config that could as easily
 * have been an alternate interface setting (on most hardware).
 *
 * NOTE:  to demonstrate (and test) more USB capabilities, this driver
 * should include an altsetting to test interrupt transfers, including
 * high bandwidth modes at high speed.  (Maybe work like Intel's test
 * device?)
 */
static int
config_buf (struct usb_gadget *gadget,
                u8 *buf, u8 type, unsigned index)
{
        int                             is_source_sink;
        int                             len;
        const struct usb_descriptor_header **function;
#ifdef CONFIG_USB_GADGET_DUALSPEED
        int                             hs = (gadget->speed == USB_SPEED_HIGH);
#endif

        /* two configurations will always be index 0 and index 1 */
        if (index > 1)
                return -EINVAL;
        is_source_sink = loopdefault ? (index == 1) : (index == 0);

#ifdef CONFIG_USB_GADGET_DUALSPEED
        if (type == USB_DT_OTHER_SPEED_CONFIG)
                hs = !hs;
        if (hs)
                function = is_source_sink
                        ? hs_source_sink_function
                        : hs_loopback_function;
        else
#endif
                function = is_source_sink
                        ? fs_source_sink_function
                        : fs_loopback_function;

        /* for now, don't advertise srp-only devices */
        if (!gadget->is_otg)
                function++;

        len = usb_gadget_config_buf (is_source_sink
                                        ? &source_sink_config
                                        : &loopback_config,
                        buf, USB_BUFSIZ, function);
        if (len < 0)
                return len;
        ((struct usb_config_descriptor *) buf)->bDescriptorType = type;
        return len;
}

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

static struct usb_request *
alloc_ep_req (struct usb_ep *ep, unsigned length)
{
        struct usb_request      *req;

        req = usb_ep_alloc_request (ep, GFP_ATOMIC);
        if (req) {
                req->length = length;
                req->buf = usb_ep_alloc_buffer (ep, length,
                                &req->dma, GFP_ATOMIC);
                if (!req->buf) {
                        usb_ep_free_request (ep, req);
                        req = NULL;
                }
        }
        return req;
}

static void free_ep_req (struct usb_ep *ep, struct usb_request *req)
{
        if (req->buf)
                usb_ep_free_buffer (ep, req->buf, req->dma, req->length);
        usb_ep_free_request (ep, req);
}

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

/* optionally require specific source/sink data patterns  */

static int
check_read_data (
        struct zero_dev         *dev,
        struct usb_ep           *ep,
        struct usb_request      *req
)
{
        unsigned        i;
        u8              *buf = req->buf;

        for (i = 0; i < req->actual; i++, buf++) {
                switch (pattern) {
                /* all-zeroes has no synchronization issues */
                case 0:
                        if (*buf == 0)
                                continue;
                        break;
                /* mod63 stays in sync with short-terminated transfers,
                 * or otherwise when host and gadget agree on how large
                 * each usb transfer request should be.  resync is done
                 * with set_interface or set_config.
                 */
                case 1:
                        if (*buf == (u8)(i % 63))
                                continue;
                        break;
                }
                ERROR (dev, "bad OUT byte, buf [%d] = %d\n", i, *buf);
                usb_ep_set_halt (ep);
                return -EINVAL;
        }
        return 0;
}

static void
reinit_write_data (
        struct zero_dev         *dev,
        struct usb_ep           *ep,
        struct usb_request      *req
)
{
        unsigned        i;
        u8              *buf = req->buf;

        switch (pattern) {
        case 0:
                memset (req->buf, 0, req->length);
                break;
        case 1:
                for  (i = 0; i < req->length; i++)
                        *buf++ = (u8) (i % 63);
                break;
        }
}

/* if there is only one request in the queue, there'll always be an
 * irq delay between end of one request and start of the next.
 * that prevents using hardware dma queues.
 */
static void source_sink_complete (struct usb_ep *ep, struct usb_request *req)
{
        struct zero_dev *dev = ep->driver_data;
        int             status = req->status;

        switch (status) {

        case 0:                         /* normal completion? */
                if (ep == dev->out_ep) {
                        check_read_data (dev, ep, req);
                        memset (req->buf, 0x55, req->length);
                } else
                        reinit_write_data (dev, ep, req);
                break;

        /* this endpoint is normally active while we're configured */
        case -ECONNABORTED:             /* hardware forced ep reset */
        case -ECONNRESET:               /* request dequeued */
        case -ESHUTDOWN:                /* disconnect from host */
                VDBG (dev, "%s gone (%d), %d/%d\n", ep->name, status,
                                req->actual, req->length);
                if (ep == dev->out_ep)
                        check_read_data (dev, ep, req);
                free_ep_req (ep, req);
                return;

        case -EOVERFLOW:                /* buffer overrun on read means that
                                         * we didn't provide a big enough
                                         * buffer.
                                         */
        default:
#if 1
                DBG (dev, "%s complete --> %d, %d/%d\n", ep->name,
                                status, req->actual, req->length);
#endif
        case -EREMOTEIO:                /* short read */
                break;
        }

        status = usb_ep_queue (ep, req, GFP_ATOMIC);
        if (status) {
                ERROR (dev, "kill %s:  resubmit %d bytes --> %d\n",
                                ep->name, req->length, status);
                usb_ep_set_halt (ep);
                /* FIXME recover later ... somehow */
        }
}

static struct usb_request *
source_sink_start_ep (struct usb_ep *ep, gfp_t gfp_flags)
{
        struct usb_request      *req;
        int                     status;

        req = alloc_ep_req (ep, buflen);
        if (!req)
                return NULL;

        memset (req->buf, 0, req->length);
        req->complete = source_sink_complete;

        if (strcmp (ep->name, EP_IN_NAME) == 0)
                reinit_write_data (ep->driver_data, ep, req);
        else
                memset (req->buf, 0x55, req->length);

        status = usb_ep_queue (ep, req, gfp_flags);
        if (status) {
                struct zero_dev *dev = ep->driver_data;

                ERROR (dev, "start %s --> %d\n", ep->name, status);
                free_ep_req (ep, req);
                req = NULL;
        }

        return req;
}

static int
set_source_sink_config (struct zero_dev *dev, gfp_t gfp_flags)
{
        int                     result = 0;
        struct usb_ep           *ep;
        struct usb_gadget       *gadget = dev->gadget;

        gadget_for_each_ep (ep, gadget) {
                const struct usb_endpoint_descriptor    *d;

                /* one endpoint writes (sources) zeroes in (to the host) */
                if (strcmp (ep->name, EP_IN_NAME) == 0) {
                        d = ep_desc (gadget, &hs_source_desc, &fs_source_desc);
                        result = usb_ep_enable (ep, d);
                        if (result == 0) {
                                ep->driver_data = dev;
                                if (source_sink_start_ep (ep, gfp_flags) != 0) {
                                        dev->in_ep = ep;
                                        continue;
                                }
                                usb_ep_disable (ep);
                                result = -EIO;
                        }

                /* one endpoint reads (sinks) anything out (from the host) */
                } else if (strcmp (ep->name, EP_OUT_NAME) == 0) {
                        d = ep_desc (gadget, &hs_sink_desc, &fs_sink_desc);
                        result = usb_ep_enable (ep, d);
                        if (result == 0) {
                                ep->driver_data = dev;
                                if (source_sink_start_ep (ep, gfp_flags) != 0) {
                                        dev->out_ep = ep;
                                        continue;
                                }
                                usb_ep_disable (ep);
                                result = -EIO;
                        }

                /* ignore any other endpoints */
                } else
                        continue;

                /* stop on error */
                ERROR (dev, "can't start %s, result %d\n", ep->name, result);
                break;
        }
        if (result == 0)
                DBG (dev, "buflen %d\n", buflen);

        /* caller is responsible for cleanup on error */
        return result;
}

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

static void loopback_complete (struct usb_ep *ep, struct usb_request *req)
{
        struct zero_dev *dev = ep->driver_data;
        int             status = req->status;

        switch (status) {

        case 0:                         /* normal completion? */
                if (ep == dev->out_ep) {
                        /* loop this OUT packet back IN to the host */
                        req->zero = (req->actual < req->length);
                        req->length = req->actual;
                        status = usb_ep_queue (dev->in_ep, req, GFP_ATOMIC);
                        if (status == 0)
                                return;

                        /* "should never get here" */
                        ERROR (dev, "can't loop %s to %s: %d\n",
                                ep->name, dev->in_ep->name,
                                status);
                }

                /* queue the buffer for some later OUT packet */
                req->length = buflen;
                status = usb_ep_queue (dev->out_ep, req, GFP_ATOMIC);
                if (status == 0)
                        return;

                /* "should never get here" */
                /* FALLTHROUGH */

        default:
                ERROR (dev, "%s loop complete --> %d, %d/%d\n", ep->name,
                                status, req->actual, req->length);
                /* FALLTHROUGH */

        /* NOTE:  since this driver doesn't maintain an explicit record
         * of requests it submitted (just maintains qlen count), we
         * rely on the hardware driver to clean up on disconnect or
         * endpoint disable.
         */
        case -ECONNABORTED:             /* hardware forced ep reset */
        case -ECONNRESET:               /* request dequeued */
        case -ESHUTDOWN:                /* disconnect from host */
                free_ep_req (ep, req);
                return;
        }
}

static int
set_loopback_config (struct zero_dev *dev, gfp_t gfp_flags)
{
        int                     result = 0;
        struct usb_ep           *ep;
        struct usb_gadget       *gadget = dev->gadget;

        gadget_for_each_ep (ep, gadget) {
                const struct usb_endpoint_descriptor    *d;

                /* one endpoint writes data back IN to the host */
                if (strcmp (ep->name, EP_IN_NAME) == 0) {
                        d = ep_desc (gadget, &hs_source_desc, &fs_source_desc);
                        result = usb_ep_enable (ep, d);
                        if (result == 0) {
                                ep->driver_data = dev;
                                dev->in_ep = ep;
                                continue;
                        }

                /* one endpoint just reads OUT packets */
                } else if (strcmp (ep->name, EP_OUT_NAME) == 0) {
                        d = ep_desc (gadget, &hs_sink_desc, &fs_sink_desc);
                        result = usb_ep_enable (ep, d);
                        if (result == 0) {
                                ep->driver_data = dev;
                                dev->out_ep = ep;
                                continue;
                        }

                /* ignore any other endpoints */
                } else
                        continue;

                /* stop on error */
                ERROR (dev, "can't enable %s, result %d\n", ep->name, result);
                break;
        }

        /* allocate a bunch of read buffers and queue them all at once.
         * we buffer at most 'qlen' transfers; fewer if any need more
         * than 'buflen' bytes each.
         */
        if (result == 0) {
                struct usb_request      *req;
                unsigned                i;

                ep = dev->out_ep;
                for (i = 0; i < qlen && result == 0; i++) {
                        req = alloc_ep_req (ep, buflen);
                        if (req) {
                                req->complete = loopback_complete;
                                result = usb_ep_queue (ep, req, GFP_ATOMIC);
                                if (result)
                                        DBG (dev, "%s queue req --> %d\n",
                                                        ep->name, result);
                        } else
                                result = -ENOMEM;
                }
        }
        if (result == 0)
                DBG (dev, "qlen %d, buflen %d\n", qlen, buflen);

        /* caller is responsible for cleanup on error */
        return result;
}

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

static void zero_reset_config (struct zero_dev *dev)
{
        if (dev->config == 0)
                return;

        DBG (dev, "reset config\n");

        /* just disable endpoints, forcing completion of pending i/o.
         * all our completion handlers free their requests in this case.
         */
        if (dev->in_ep) {
                usb_ep_disable (dev->in_ep);
                dev->in_ep = NULL;
        }
        if (dev->out_ep) {
                usb_ep_disable (dev->out_ep);
                dev->out_ep = NULL;
        }
        dev->config = 0;
        del_timer (&dev->resume);
}

/* change our operational config.  this code must agree with the code
 * that returns config descriptors, and altsetting code.
 *
 * it's also responsible for power management interactions. some
 * configurations might not work with our current power sources.
 *
 * note that some device controller hardware will constrain what this
 * code can do, perhaps by disallowing more than one configuration or
 * by limiting configuration choices (like the pxa2xx).
 */
static int
zero_set_config (struct zero_dev *dev, unsigned number, gfp_t gfp_flags)
{
        int                     result = 0;
        struct usb_gadget       *gadget = dev->gadget;

        if (number == dev->config)
                return 0;

        if (gadget_is_sa1100 (gadget) && dev->config) {
                /* tx fifo is full, but we can't clear it...*/
                INFO (dev, "can't change configurations\n");
                return -ESPIPE;
        }
        zero_reset_config (dev);

        switch (number) {
        case CONFIG_SOURCE_SINK:
                result = set_source_sink_config (dev, gfp_flags);
                break;
        case CONFIG_LOOPBACK:
                result = set_loopback_config (dev, gfp_flags);
                break;
        default:
                result = -EINVAL;
                /* FALL THROUGH */
        case 0:
                return result;
        }

        if (!result && (!dev->in_ep || !dev->out_ep))
                result = -ENODEV;
        if (result)
                zero_reset_config (dev);
        else {
                char *speed;

                switch (gadget->speed) {
                case USB_SPEED_LOW:     speed = "low"; break;
                case USB_SPEED_FULL:    speed = "full"; break;
                case USB_SPEED_HIGH:    speed = "high"; break;
                default:                speed = "?"; break;
                }

                dev->config = number;
                INFO (dev, "%s speed config #%d: %s\n", speed, number,
                                (number == CONFIG_SOURCE_SINK)
                                        ? source_sink : loopback);
        }
        return result;
}

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

static void zero_setup_complete (struct usb_ep *ep, struct usb_request *req)
{
        if (req->status || req->actual != req->length)
                DBG ((struct zero_dev *) ep->driver_data,
                                "setup complete --> %d, %d/%d\n",
                                req->status, req->actual, req->length);
}

/*
 * The setup() callback implements all the ep0 functionality that's
 * not handled lower down, in hardware or the hardware driver (like
 * device and endpoint feature flags, and their status).  It's all
 * housekeeping for the gadget function we're implementing.  Most of
 * the work is in config-specific setup.
 */
static int
zero_setup (struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
{
        struct zero_dev         *dev = get_gadget_data (gadget);
        struct usb_request      *req = dev->req;
        int                     value = -EOPNOTSUPP;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        /* usually this stores reply data in the pre-allocated ep0 buffer,
         * but config change events will reconfigure hardware.
         */
        req->zero = 0;
        switch (ctrl->bRequest) {

        case USB_REQ_GET_DESCRIPTOR:
                if (ctrl->bRequestType != USB_DIR_IN)
                        goto unknown;
                switch (w_value >> 8) {

                case USB_DT_DEVICE:
                        value = min (w_length, (u16) sizeof device_desc);
                        memcpy (req->buf, &device_desc, value);
                        break;
#ifdef CONFIG_USB_GADGET_DUALSPEED
                case USB_DT_DEVICE_QUALIFIER:
                        if (!gadget->is_dualspeed)
                                break;
                        value = min (w_length, (u16) sizeof dev_qualifier);
                        memcpy (req->buf, &dev_qualifier, value);
                        break;

                case USB_DT_OTHER_SPEED_CONFIG:
                        if (!gadget->is_dualspeed)
                                break;
                        // FALLTHROUGH
#endif /* CONFIG_USB_GADGET_DUALSPEED */
                case USB_DT_CONFIG:
                        value = config_buf (gadget, req->buf,
                                        w_value >> 8,
                                        w_value & 0xff);
                        if (value >= 0)
                                value = min (w_length, (u16) value);
                        break;

                case USB_DT_STRING:
                        /* wIndex == language code.
                         * this driver only handles one language, you can
                         * add string tables for other languages, using
                         * any UTF-8 characters
                         */
                        value = usb_gadget_get_string (&stringtab,
                                        w_value & 0xff, req->buf);
                        if (value >= 0)
                                value = min (w_length, (u16) value);
                        break;
                }
                break;

        /* currently two configs, two speeds */
        case USB_REQ_SET_CONFIGURATION:
                if (ctrl->bRequestType != 0)
                        goto unknown;
                if (gadget->a_hnp_support)
                        DBG (dev, "HNP available\n");
                else if (gadget->a_alt_hnp_support)
                        DBG (dev, "HNP needs a different root port\n");
                else
                        VDBG (dev, "HNP inactive\n");
                spin_lock (&dev->lock);
                value = zero_set_config (dev, w_value, GFP_ATOMIC);
                spin_unlock (&dev->lock);
                break;
        case USB_REQ_GET_CONFIGURATION:
                if (ctrl->bRequestType != USB_DIR_IN)
                        goto unknown;
                *(u8 *)req->buf = dev->config;
                value = min (w_length, (u16) 1);
                break;

        /* until we add altsetting support, or other interfaces,
         * only 0/0 are possible.  pxa2xx only supports 0/0 (poorly)
         * and already killed pending endpoint I/O.
         */
        case USB_REQ_SET_INTERFACE:
                if (ctrl->bRequestType != USB_RECIP_INTERFACE)
                        goto unknown;
                spin_lock (&dev->lock);
                if (dev->config && w_index == 0 && w_value == 0) {
                        u8              config = dev->config;

                        /* resets interface configuration, forgets about
                         * previous transaction state (queued bufs, etc)
                         * and re-inits endpoint state (toggle etc)
                         * no response queued, just zero status == success.
                         * if we had more than one interface we couldn't
                         * use this "reset the config" shortcut.
                         */
                        zero_reset_config (dev);
                        zero_set_config (dev, config, GFP_ATOMIC);
                        value = 0;
                }
                spin_unlock (&dev->lock);
                break;
        case USB_REQ_GET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE))
                        goto unknown;
                if (!dev->config)
                        break;
                if (w_index != 0) {
                        value = -EDOM;
                        break;
                }
                *(u8 *)req->buf = 0;
                value = min (w_length, (u16) 1);
                break;

        /*
         * These are the same vendor-specific requests supported by
         * Intel's USB 2.0 compliance test devices.  We exceed that
         * device spec by allowing multiple-packet requests.
         */
        case 0x5b:      /* control WRITE test -- fill the buffer */
                if (ctrl->bRequestType != (USB_DIR_OUT|USB_TYPE_VENDOR))
                        goto unknown;
                if (w_value || w_index)
                        break;
                /* just read that many bytes into the buffer */
                if (w_length > USB_BUFSIZ)
                        break;
                value = w_length;
                break;
        case 0x5c:      /* control READ test -- return the buffer */
                if (ctrl->bRequestType != (USB_DIR_IN|USB_TYPE_VENDOR))
                        goto unknown;
                if (w_value || w_index)
                        break;
                /* expect those bytes are still in the buffer; send back */
                if (w_length > USB_BUFSIZ
                                || w_length != req->length)
                        break;
                value = w_length;
                break;

        default:
unknown:
                VDBG (dev,
                        "unknown control req%02x.%02x v%04x i%04x l%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        w_value, w_index, w_length);
        }

        /* respond with data transfer before status phase? */
        if (value >= 0) {
                req->length = value;
                req->zero = value < w_length;
                value = usb_ep_queue (gadget->ep0, req, GFP_ATOMIC);
                if (value < 0) {
                        DBG (dev, "ep_queue --> %d\n", value);
                        req->status = 0;
                        zero_setup_complete (gadget->ep0, req);
                }
        }

        /* device either stalls (value < 0) or reports success */
        return value;
}

static void
zero_disconnect (struct usb_gadget *gadget)
{
        struct zero_dev         *dev = get_gadget_data (gadget);
        unsigned long           flags;

        spin_lock_irqsave (&dev->lock, flags);
        zero_reset_config (dev);

        /* a more significant application might have some non-usb
         * activities to quiesce here, saving resources like power
         * or pushing the notification up a network stack.
         */
        spin_unlock_irqrestore (&dev->lock, flags);

        /* next we may get setup() calls to enumerate new connections;
         * or an unbind() during shutdown (including removing module).
         */
}

static void
zero_autoresume (unsigned long _dev)
{
        struct zero_dev *dev = (struct zero_dev *) _dev;
        int             status;

        /* normally the host would be woken up for something
         * more significant than just a timer firing...
         */
        if (dev->gadget->speed != USB_SPEED_UNKNOWN) {
                status = usb_gadget_wakeup (dev->gadget);
                DBG (dev, "wakeup --> %d\n", status);
        }
}

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

static void /* __init_or_exit */
zero_unbind (struct usb_gadget *gadget)
{
        struct zero_dev         *dev = get_gadget_data (gadget);

        DBG (dev, "unbind\n");

        /* we've already been disconnected ... no i/o is active */
        if (dev->req) {
                dev->req->length = USB_BUFSIZ;
                free_ep_req (gadget->ep0, dev->req);
        }
        del_timer_sync (&dev->resume);
        kfree (dev);
        set_gadget_data (gadget, NULL);
}

static int __init
zero_bind (struct usb_gadget *gadget)
{
        struct zero_dev         *dev;
        struct usb_ep           *ep;
        int                     gcnum;

        /* FIXME this can't yet work right with SH ... it has only
         * one configuration, numbered one.
         */
        if (gadget_is_sh(gadget))
                return -ENODEV;

        /* Bulk-only drivers like this one SHOULD be able to
         * autoconfigure on any sane usb controller driver,
         * but there may also be important quirks to address.
         */
        usb_ep_autoconfig_reset (gadget);
        ep = usb_ep_autoconfig (gadget, &fs_source_desc);
        if (!ep) {
autoconf_fail:
                printk (KERN_ERR "%s: can't autoconfigure on %s\n",
                        shortname, gadget->name);
                return -ENODEV;
        }
        EP_IN_NAME = ep->name;
        ep->driver_data = ep;   /* claim */
        
        ep = usb_ep_autoconfig (gadget, &fs_sink_desc);
        if (!ep)
                goto autoconf_fail;
        EP_OUT_NAME = ep->name;
        ep->driver_data = ep;   /* claim */

        gcnum = usb_gadget_controller_number (gadget);
        if (gcnum >= 0)
                device_desc.bcdDevice = cpu_to_le16 (0x0200 + gcnum);
        else {
                /* gadget zero is so simple (for now, no altsettings) that
                 * it SHOULD NOT have problems with bulk-capable hardware.
                 * so warn about unrcognized controllers, don't panic.
                 *
                 * things like configuration and altsetting numbering
                 * can need hardware-specific attention though.
                 */
                printk (KERN_WARNING "%s: controller '%s' not recognized\n",
                        shortname, gadget->name);
                device_desc.bcdDevice = __constant_cpu_to_le16 (0x9999);
        }


        /* ok, we made sense of the hardware ... */
        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                return -ENOMEM;
        spin_lock_init (&dev->lock);
        dev->gadget = gadget;
        set_gadget_data (gadget, dev);

        /* preallocate control response and buffer */
        dev->req = usb_ep_alloc_request (gadget->ep0, GFP_KERNEL);
        if (!dev->req)
                goto enomem;
        dev->req->buf = usb_ep_alloc_buffer (gadget->ep0, USB_BUFSIZ,
                                &dev->req->dma, GFP_KERNEL);
        if (!dev->req->buf)
                goto enomem;

        dev->req->complete = zero_setup_complete;

        device_desc.bMaxPacketSize0 = gadget->ep0->maxpacket;

#ifdef CONFIG_USB_GADGET_DUALSPEED
        /* assume ep0 uses the same value for both speeds ... */
        dev_qualifier.bMaxPacketSize0 = device_desc.bMaxPacketSize0;

        /* and that all endpoints are dual-speed */
        hs_source_desc.bEndpointAddress = fs_source_desc.bEndpointAddress;
        hs_sink_desc.bEndpointAddress = fs_sink_desc.bEndpointAddress;
#endif

        if (gadget->is_otg) {
                otg_descriptor.bmAttributes |= USB_OTG_HNP,
                source_sink_config.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
                loopback_config.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
        }

        usb_gadget_set_selfpowered (gadget);

        init_timer (&dev->resume);
        dev->resume.function = zero_autoresume;
        dev->resume.data = (unsigned long) dev;
        if (autoresume) {
                source_sink_config.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
                loopback_config.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
        }

        gadget->ep0->driver_data = dev;

        INFO (dev, "%s, version: " DRIVER_VERSION "\n", longname);
        INFO (dev, "using %s, OUT %s IN %s\n", gadget->name,
                EP_OUT_NAME, EP_IN_NAME);

        snprintf (manufacturer, sizeof manufacturer, "%s %s with %s",
                init_utsname()->sysname, init_utsname()->release,
                gadget->name);

        return 0;

enomem:
        zero_unbind (gadget);
        return -ENOMEM;
}

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

static void
zero_suspend (struct usb_gadget *gadget)
{
        struct zero_dev         *dev = get_gadget_data (gadget);

        if (gadget->speed == USB_SPEED_UNKNOWN)
                return;

        if (autoresume) {
                mod_timer (&dev->resume, jiffies + (HZ * autoresume));
                DBG (dev, "suspend, wakeup in %d seconds\n", autoresume);
        } else
                DBG (dev, "suspend\n");
}

static void
zero_resume (struct usb_gadget *gadget)
{
        struct zero_dev         *dev = get_gadget_data (gadget);

        DBG (dev, "resume\n");
        del_timer (&dev->resume);
}


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

static struct usb_gadget_driver zero_driver = {
#ifdef CONFIG_USB_GADGET_DUALSPEED
        .speed          = USB_SPEED_HIGH,
#else
        .speed          = USB_SPEED_FULL,
#endif
        .function       = (char *) longname,
        .bind           = zero_bind,
        .unbind         = __exit_p(zero_unbind),

        .setup          = zero_setup,
        .disconnect     = zero_disconnect,

        .suspend        = zero_suspend,
        .resume         = zero_resume,

        .driver         = {
                .name           = (char *) shortname,
                .owner          = THIS_MODULE,
        },
};

MODULE_AUTHOR ("David Brownell");
MODULE_LICENSE ("Dual BSD/GPL");


static int __init init (void)
{
        /* a real value would likely come through some id prom
         * or module option.  this one takes at least two packets.
         */
        strlcpy (serial, "0123456789.0123456789.0123456789", sizeof serial);

        return usb_gadget_register_driver (&zero_driver);
}
module_init (init);

static void __exit cleanup (void)
{
        usb_gadget_unregister_driver (&zero_driver);
}
module_exit (cleanup);