Merge tag 'tty-3.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / usb / gadget / composite.c

/*
 * composite.c - infrastructure for Composite USB Gadgets
 *
 * Copyright (C) 2006-2008 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

/* #define VERBOSE_DEBUG */

#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/utsname.h>

#include <linux/usb/composite.h>
#include <asm/unaligned.h>

/*
 * The code in this file is utility code, used to build a gadget driver
 * from one or more "function" drivers, one or more "configuration"
 * objects, and a "usb_composite_driver" by gluing them together along
 * with the relevant device-wide data.
 */

/* big enough to hold our biggest descriptor */
#define USB_BUFSIZ      1024

static struct usb_composite_driver *composite;
static int (*composite_gadget_bind)(struct usb_composite_dev *cdev);

/* Some systems will need runtime overrides for the  product identifiers
 * published in the device descriptor, either numbers or strings or both.
 * String parameters are in UTF-8 (superset of ASCII's 7 bit characters).
 */

static ushort idVendor;
module_param(idVendor, ushort, 0);
MODULE_PARM_DESC(idVendor, "USB Vendor ID");

static ushort idProduct;
module_param(idProduct, ushort, 0);
MODULE_PARM_DESC(idProduct, "USB Product ID");

static ushort bcdDevice;
module_param(bcdDevice, ushort, 0);
MODULE_PARM_DESC(bcdDevice, "USB Device version (BCD)");

static char *iManufacturer;
module_param(iManufacturer, charp, 0);
MODULE_PARM_DESC(iManufacturer, "USB Manufacturer string");

static char *iProduct;
module_param(iProduct, charp, 0);
MODULE_PARM_DESC(iProduct, "USB Product string");

static char *iSerialNumber;
module_param(iSerialNumber, charp, 0);
MODULE_PARM_DESC(iSerialNumber, "SerialNumber string");

static char composite_manufacturer[50];

/*-------------------------------------------------------------------------*/
/**
 * next_ep_desc() - advance to the next EP descriptor
 * @t: currect pointer within descriptor array
 *
 * Return: next EP descriptor or NULL
 *
 * Iterate over @t until either EP descriptor found or
 * NULL (that indicates end of list) encountered
 */
static struct usb_descriptor_header**
next_ep_desc(struct usb_descriptor_header **t)
{
        for (; *t; t++) {
                if ((*t)->bDescriptorType == USB_DT_ENDPOINT)
                        return t;
        }
        return NULL;
}

/*
 * for_each_ep_desc()- iterate over endpoint descriptors in the
 *              descriptors list
 * @start:      pointer within descriptor array.
 * @ep_desc:    endpoint descriptor to use as the loop cursor
 */
#define for_each_ep_desc(start, ep_desc) \
        for (ep_desc = next_ep_desc(start); \
              ep_desc; ep_desc = next_ep_desc(ep_desc+1))

/**
 * config_ep_by_speed() - configures the given endpoint
 * according to gadget speed.
 * @g: pointer to the gadget
 * @f: usb function
 * @_ep: the endpoint to configure
 *
 * Return: error code, 0 on success
 *
 * This function chooses the right descriptors for a given
 * endpoint according to gadget speed and saves it in the
 * endpoint desc field. If the endpoint already has a descriptor
 * assigned to it - overwrites it with currently corresponding
 * descriptor. The endpoint maxpacket field is updated according
 * to the chosen descriptor.
 * Note: the supplied function should hold all the descriptors
 * for supported speeds
 */
int config_ep_by_speed(struct usb_gadget *g,
                        struct usb_function *f,
                        struct usb_ep *_ep)
{
        struct usb_endpoint_descriptor *chosen_desc = NULL;
        struct usb_descriptor_header **speed_desc = NULL;

        struct usb_ss_ep_comp_descriptor *comp_desc = NULL;
        int want_comp_desc = 0;

        struct usb_descriptor_header **d_spd; /* cursor for speed desc */

        if (!g || !f || !_ep)
                return -EIO;

        /* select desired speed */
        switch (g->speed) {
        case USB_SPEED_SUPER:
                if (gadget_is_superspeed(g)) {
                        speed_desc = f->ss_descriptors;
                        want_comp_desc = 1;
                        break;
                }
                /* else: Fall trough */
        case USB_SPEED_HIGH:
                if (gadget_is_dualspeed(g)) {
                        speed_desc = f->hs_descriptors;
                        break;
                }
                /* else: fall through */
        default:
                speed_desc = f->descriptors;
        }
        /* find descriptors */
        for_each_ep_desc(speed_desc, d_spd) {
                chosen_desc = (struct usb_endpoint_descriptor *)*d_spd;
                if (chosen_desc->bEndpointAddress == _ep->address)
                        goto ep_found;
        }
        return -EIO;

ep_found:
        /* commit results */
        _ep->maxpacket = usb_endpoint_maxp(chosen_desc);
        _ep->desc = chosen_desc;
        _ep->comp_desc = NULL;
        _ep->maxburst = 0;
        _ep->mult = 0;
        if (!want_comp_desc)
                return 0;

        /*
         * Companion descriptor should follow EP descriptor
         * USB 3.0 spec, #9.6.7
         */
        comp_desc = (struct usb_ss_ep_comp_descriptor *)*(++d_spd);
        if (!comp_desc ||
            (comp_desc->bDescriptorType != USB_DT_SS_ENDPOINT_COMP))
                return -EIO;
        _ep->comp_desc = comp_desc;
        if (g->speed == USB_SPEED_SUPER) {
                switch (usb_endpoint_type(_ep->desc)) {
                case USB_ENDPOINT_XFER_ISOC:
                        /* mult: bits 1:0 of bmAttributes */
                        _ep->mult = comp_desc->bmAttributes & 0x3;
                case USB_ENDPOINT_XFER_BULK:
                case USB_ENDPOINT_XFER_INT:
                        _ep->maxburst = comp_desc->bMaxBurst;
                        break;
                default:
                        /* Do nothing for control endpoints */
                        break;
                }
        }
        return 0;
}

/**
 * usb_add_function() - add a function to a configuration
 * @config: the configuration
 * @function: the function being added
 * Context: single threaded during gadget setup
 *
 * After initialization, each configuration must have one or more
 * functions added to it.  Adding a function involves calling its @bind()
 * method to allocate resources such as interface and string identifiers
 * and endpoints.
 *
 * This function returns the value of the function's bind(), which is
 * zero for success else a negative errno value.
 */
int usb_add_function(struct usb_configuration *config,
                struct usb_function *function)
{
        int     value = -EINVAL;

        DBG(config->cdev, "adding '%s'/%p to config '%s'/%p\n",
                        function->name, function,
                        config->label, config);

        if (!function->set_alt || !function->disable)
                goto done;

        function->config = config;
        list_add_tail(&function->list, &config->functions);

        /* REVISIT *require* function->bind? */
        if (function->bind) {
                value = function->bind(config, function);
                if (value < 0) {
                        list_del(&function->list);
                        function->config = NULL;
                }
        } else
                value = 0;

        /* We allow configurations that don't work at both speeds.
         * If we run into a lowspeed Linux system, treat it the same
         * as full speed ... it's the function drivers that will need
         * to avoid bulk and ISO transfers.
         */
        if (!config->fullspeed && function->descriptors)
                config->fullspeed = true;
        if (!config->highspeed && function->hs_descriptors)
                config->highspeed = true;
        if (!config->superspeed && function->ss_descriptors)
                config->superspeed = true;

done:
        if (value)
                DBG(config->cdev, "adding '%s'/%p --> %d\n",
                                function->name, function, value);
        return value;
}

/**
 * usb_function_deactivate - prevent function and gadget enumeration
 * @function: the function that isn't yet ready to respond
 *
 * Blocks response of the gadget driver to host enumeration by
 * preventing the data line pullup from being activated.  This is
 * normally called during @bind() processing to change from the
 * initial "ready to respond" state, or when a required resource
 * becomes available.
 *
 * For example, drivers that serve as a passthrough to a userspace
 * daemon can block enumeration unless that daemon (such as an OBEX,
 * MTP, or print server) is ready to handle host requests.
 *
 * Not all systems support software control of their USB peripheral
 * data pullups.
 *
 * Returns zero on success, else negative errno.
 */
int usb_function_deactivate(struct usb_function *function)
{
        struct usb_composite_dev        *cdev = function->config->cdev;
        unsigned long                   flags;
        int                             status = 0;

        spin_lock_irqsave(&cdev->lock, flags);

        if (cdev->deactivations == 0)
                status = usb_gadget_disconnect(cdev->gadget);
        if (status == 0)
                cdev->deactivations++;

        spin_unlock_irqrestore(&cdev->lock, flags);
        return status;
}

/**
 * usb_function_activate - allow function and gadget enumeration
 * @function: function on which usb_function_activate() was called
 *
 * Reverses effect of usb_function_deactivate().  If no more functions
 * are delaying their activation, the gadget driver will respond to
 * host enumeration procedures.
 *
 * Returns zero on success, else negative errno.
 */
int usb_function_activate(struct usb_function *function)
{
        struct usb_composite_dev        *cdev = function->config->cdev;
        int                             status = 0;

        spin_lock(&cdev->lock);

        if (WARN_ON(cdev->deactivations == 0))
                status = -EINVAL;
        else {
                cdev->deactivations--;
                if (cdev->deactivations == 0)
                        status = usb_gadget_connect(cdev->gadget);
        }

        spin_unlock(&cdev->lock);
        return status;
}

/**
 * usb_interface_id() - allocate an unused interface ID
 * @config: configuration associated with the interface
 * @function: function handling the interface
 * Context: single threaded during gadget setup
 *
 * usb_interface_id() is called from usb_function.bind() callbacks to
 * allocate new interface IDs.  The function driver will then store that
 * ID in interface, association, CDC union, and other descriptors.  It
 * will also handle any control requests targeted at that interface,
 * particularly changing its altsetting via set_alt().  There may
 * also be class-specific or vendor-specific requests to handle.
 *
 * All interface identifier should be allocated using this routine, to
 * ensure that for example different functions don't wrongly assign
 * different meanings to the same identifier.  Note that since interface
 * identifiers are configuration-specific, functions used in more than
 * one configuration (or more than once in a given configuration) need
 * multiple versions of the relevant descriptors.
 *
 * Returns the interface ID which was allocated; or -ENODEV if no
 * more interface IDs can be allocated.
 */
int usb_interface_id(struct usb_configuration *config,
                struct usb_function *function)
{
        unsigned id = config->next_interface_id;

        if (id < MAX_CONFIG_INTERFACES) {
                config->interface[id] = function;
                config->next_interface_id = id + 1;
                return id;
        }
        return -ENODEV;
}

static int config_buf(struct usb_configuration *config,
                enum usb_device_speed speed, void *buf, u8 type)
{
        struct usb_config_descriptor    *c = buf;
        void                            *next = buf + USB_DT_CONFIG_SIZE;
        int                             len = USB_BUFSIZ - USB_DT_CONFIG_SIZE;
        struct usb_function             *f;
        int                             status;

        /* write the config descriptor */
        c = buf;
        c->bLength = USB_DT_CONFIG_SIZE;
        c->bDescriptorType = type;
        /* wTotalLength is written later */
        c->bNumInterfaces = config->next_interface_id;
        c->bConfigurationValue = config->bConfigurationValue;
        c->iConfiguration = config->iConfiguration;
        c->bmAttributes = USB_CONFIG_ATT_ONE | config->bmAttributes;
        c->bMaxPower = config->bMaxPower ? : (CONFIG_USB_GADGET_VBUS_DRAW / 2);

        /* There may be e.g. OTG descriptors */
        if (config->descriptors) {
                status = usb_descriptor_fillbuf(next, len,
                                config->descriptors);
                if (status < 0)
                        return status;
                len -= status;
                next += status;
        }

        /* add each function's descriptors */
        list_for_each_entry(f, &config->functions, list) {
                struct usb_descriptor_header **descriptors;

                switch (speed) {
                case USB_SPEED_SUPER:
                        descriptors = f->ss_descriptors;
                        break;
                case USB_SPEED_HIGH:
                        descriptors = f->hs_descriptors;
                        break;
                default:
                        descriptors = f->descriptors;
                }

                if (!descriptors)
                        continue;
                status = usb_descriptor_fillbuf(next, len,
                        (const struct usb_descriptor_header **) descriptors);
                if (status < 0)
                        return status;
                len -= status;
                next += status;
        }

        len = next - buf;
        c->wTotalLength = cpu_to_le16(len);
        return len;
}

static int config_desc(struct usb_composite_dev *cdev, unsigned w_value)
{
        struct usb_gadget               *gadget = cdev->gadget;
        struct usb_configuration        *c;
        u8                              type = w_value >> 8;
        enum usb_device_speed           speed = USB_SPEED_UNKNOWN;

        if (gadget->speed == USB_SPEED_SUPER)
                speed = gadget->speed;
        else if (gadget_is_dualspeed(gadget)) {
                int     hs = 0;
                if (gadget->speed == USB_SPEED_HIGH)
                        hs = 1;
                if (type == USB_DT_OTHER_SPEED_CONFIG)
                        hs = !hs;
                if (hs)
                        speed = USB_SPEED_HIGH;

        }

        /* This is a lookup by config *INDEX* */
        w_value &= 0xff;
        list_for_each_entry(c, &cdev->configs, list) {
                /* ignore configs that won't work at this speed */
                switch (speed) {
                case USB_SPEED_SUPER:
                        if (!c->superspeed)
                                continue;
                        break;
                case USB_SPEED_HIGH:
                        if (!c->highspeed)
                                continue;
                        break;
                default:
                        if (!c->fullspeed)
                                continue;
                }

                if (w_value == 0)
                        return config_buf(c, speed, cdev->req->buf, type);
                w_value--;
        }
        return -EINVAL;
}

static int count_configs(struct usb_composite_dev *cdev, unsigned type)
{
        struct usb_gadget               *gadget = cdev->gadget;
        struct usb_configuration        *c;
        unsigned                        count = 0;
        int                             hs = 0;
        int                             ss = 0;

        if (gadget_is_dualspeed(gadget)) {
                if (gadget->speed == USB_SPEED_HIGH)
                        hs = 1;
                if (gadget->speed == USB_SPEED_SUPER)
                        ss = 1;
                if (type == USB_DT_DEVICE_QUALIFIER)
                        hs = !hs;
        }
        list_for_each_entry(c, &cdev->configs, list) {
                /* ignore configs that won't work at this speed */
                if (ss) {
                        if (!c->superspeed)
                                continue;
                } else if (hs) {
                        if (!c->highspeed)
                                continue;
                } else {
                        if (!c->fullspeed)
                                continue;
                }
                count++;
        }
        return count;
}

/**
 * bos_desc() - prepares the BOS descriptor.
 * @cdev: pointer to usb_composite device to generate the bos
 *      descriptor for
 *
 * This function generates the BOS (Binary Device Object)
 * descriptor and its device capabilities descriptors. The BOS
 * descriptor should be supported by a SuperSpeed device.
 */
static int bos_desc(struct usb_composite_dev *cdev)
{
        struct usb_ext_cap_descriptor   *usb_ext;
        struct usb_ss_cap_descriptor    *ss_cap;
        struct usb_dcd_config_params    dcd_config_params;
        struct usb_bos_descriptor       *bos = cdev->req->buf;

        bos->bLength = USB_DT_BOS_SIZE;
        bos->bDescriptorType = USB_DT_BOS;

        bos->wTotalLength = cpu_to_le16(USB_DT_BOS_SIZE);
        bos->bNumDeviceCaps = 0;

        /*
         * A SuperSpeed device shall include the USB2.0 extension descriptor
         * and shall support LPM when operating in USB2.0 HS mode.
         */
        usb_ext = cdev->req->buf + le16_to_cpu(bos->wTotalLength);
        bos->bNumDeviceCaps++;
        le16_add_cpu(&bos->wTotalLength, USB_DT_USB_EXT_CAP_SIZE);
        usb_ext->bLength = USB_DT_USB_EXT_CAP_SIZE;
        usb_ext->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
        usb_ext->bDevCapabilityType = USB_CAP_TYPE_EXT;
        usb_ext->bmAttributes = cpu_to_le32(USB_LPM_SUPPORT);

        /*
         * The Superspeed USB Capability descriptor shall be implemented by all
         * SuperSpeed devices.
         */
        ss_cap = cdev->req->buf + le16_to_cpu(bos->wTotalLength);
        bos->bNumDeviceCaps++;
        le16_add_cpu(&bos->wTotalLength, USB_DT_USB_SS_CAP_SIZE);
        ss_cap->bLength = USB_DT_USB_SS_CAP_SIZE;
        ss_cap->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
        ss_cap->bDevCapabilityType = USB_SS_CAP_TYPE;
        ss_cap->bmAttributes = 0; /* LTM is not supported yet */
        ss_cap->wSpeedSupported = cpu_to_le16(USB_LOW_SPEED_OPERATION |
                                USB_FULL_SPEED_OPERATION |
                                USB_HIGH_SPEED_OPERATION |
                                USB_5GBPS_OPERATION);
        ss_cap->bFunctionalitySupport = USB_LOW_SPEED_OPERATION;

        /* Get Controller configuration */
        if (cdev->gadget->ops->get_config_params)
                cdev->gadget->ops->get_config_params(&dcd_config_params);
        else {
                dcd_config_params.bU1devExitLat = USB_DEFAULT_U1_DEV_EXIT_LAT;
                dcd_config_params.bU2DevExitLat =
                        cpu_to_le16(USB_DEFAULT_U2_DEV_EXIT_LAT);
        }
        ss_cap->bU1devExitLat = dcd_config_params.bU1devExitLat;
        ss_cap->bU2DevExitLat = dcd_config_params.bU2DevExitLat;

        return le16_to_cpu(bos->wTotalLength);
}

static void device_qual(struct usb_composite_dev *cdev)
{
        struct usb_qualifier_descriptor *qual = cdev->req->buf;

        qual->bLength = sizeof(*qual);
        qual->bDescriptorType = USB_DT_DEVICE_QUALIFIER;
        /* POLICY: same bcdUSB and device type info at both speeds */
        qual->bcdUSB = cdev->desc.bcdUSB;
        qual->bDeviceClass = cdev->desc.bDeviceClass;
        qual->bDeviceSubClass = cdev->desc.bDeviceSubClass;
        qual->bDeviceProtocol = cdev->desc.bDeviceProtocol;
        /* ASSUME same EP0 fifo size at both speeds */
        qual->bMaxPacketSize0 = cdev->gadget->ep0->maxpacket;
        qual->bNumConfigurations = count_configs(cdev, USB_DT_DEVICE_QUALIFIER);
        qual->bRESERVED = 0;
}

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

static void reset_config(struct usb_composite_dev *cdev)
{
        struct usb_function             *f;

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

        list_for_each_entry(f, &cdev->config->functions, list) {
                if (f->disable)
                        f->disable(f);

                bitmap_zero(f->endpoints, 32);
        }
        cdev->config = NULL;
}

static int set_config(struct usb_composite_dev *cdev,
                const struct usb_ctrlrequest *ctrl, unsigned number)
{
        struct usb_gadget       *gadget = cdev->gadget;
        struct usb_configuration *c = NULL;
        int                     result = -EINVAL;
        unsigned                power = gadget_is_otg(gadget) ? 8 : 100;
        int                     tmp;

        if (number) {
                list_for_each_entry(c, &cdev->configs, list) {
                        if (c->bConfigurationValue == number) {
                                /*
                                 * We disable the FDs of the previous
                                 * configuration only if the new configuration
                                 * is a valid one
                                 */
                                if (cdev->config)
                                        reset_config(cdev);
                                result = 0;
                                break;
                        }
                }
                if (result < 0)
                        goto done;
        } else { /* Zero configuration value - need to reset the config */
                if (cdev->config)
                        reset_config(cdev);
                result = 0;
        }

        INFO(cdev, "%s config #%d: %s\n",
             usb_speed_string(gadget->speed),
             number, c ? c->label : "unconfigured");

        if (!c)
                goto done;

        cdev->config = c;

        /* Initialize all interfaces by setting them to altsetting zero. */
        for (tmp = 0; tmp < MAX_CONFIG_INTERFACES; tmp++) {
                struct usb_function     *f = c->interface[tmp];
                struct usb_descriptor_header **descriptors;

                if (!f)
                        break;

                /*
                 * Record which endpoints are used by the function. This is used
                 * to dispatch control requests targeted at that endpoint to the
                 * function's setup callback instead of the current
                 * configuration's setup callback.
                 */
                switch (gadget->speed) {
                case USB_SPEED_SUPER:
                        descriptors = f->ss_descriptors;
                        break;
                case USB_SPEED_HIGH:
                        descriptors = f->hs_descriptors;
                        break;
                default:
                        descriptors = f->descriptors;
                }

                for (; *descriptors; ++descriptors) {
                        struct usb_endpoint_descriptor *ep;
                        int addr;

                        if ((*descriptors)->bDescriptorType != USB_DT_ENDPOINT)
                                continue;

                        ep = (struct usb_endpoint_descriptor *)*descriptors;
                        addr = ((ep->bEndpointAddress & 0x80) >> 3)
                             |  (ep->bEndpointAddress & 0x0f);
                        set_bit(addr, f->endpoints);
                }

                result = f->set_alt(f, tmp, 0);
                if (result < 0) {
                        DBG(cdev, "interface %d (%s/%p) alt 0 --> %d\n",
                                        tmp, f->name, f, result);

                        reset_config(cdev);
                        goto done;
                }

                if (result == USB_GADGET_DELAYED_STATUS) {
                        DBG(cdev,
                         "%s: interface %d (%s) requested delayed status\n",
                                        __func__, tmp, f->name);
                        cdev->delayed_status++;
                        DBG(cdev, "delayed_status count %d\n",
                                        cdev->delayed_status);
                }
        }

        /* when we return, be sure our power usage is valid */
        power = c->bMaxPower ? (2 * c->bMaxPower) : CONFIG_USB_GADGET_VBUS_DRAW;
done:
        usb_gadget_vbus_draw(gadget, power);
        if (result >= 0 && cdev->delayed_status)
                result = USB_GADGET_DELAYED_STATUS;
        return result;
}

/**
 * usb_add_config() - add a configuration to a device.
 * @cdev: wraps the USB gadget
 * @config: the configuration, with bConfigurationValue assigned
 * @bind: the configuration's bind function
 * Context: single threaded during gadget setup
 *
 * One of the main tasks of a composite @bind() routine is to
 * add each of the configurations it supports, using this routine.
 *
 * This function returns the value of the configuration's @bind(), which
 * is zero for success else a negative errno value.  Binding configurations
 * assigns global resources including string IDs, and per-configuration
 * resources such as interface IDs and endpoints.
 */
int usb_add_config(struct usb_composite_dev *cdev,
                struct usb_configuration *config,
                int (*bind)(struct usb_configuration *))
{
        int                             status = -EINVAL;
        struct usb_configuration        *c;

        DBG(cdev, "adding config #%u '%s'/%p\n",
                        config->bConfigurationValue,
                        config->label, config);

        if (!config->bConfigurationValue || !bind)
                goto done;

        /* Prevent duplicate configuration identifiers */
        list_for_each_entry(c, &cdev->configs, list) {
                if (c->bConfigurationValue == config->bConfigurationValue) {
                        status = -EBUSY;
                        goto done;
                }
        }

        config->cdev = cdev;
        list_add_tail(&config->list, &cdev->configs);

        INIT_LIST_HEAD(&config->functions);
        config->next_interface_id = 0;

        status = bind(config);
        if (status < 0) {
                list_del(&config->list);
                config->cdev = NULL;
        } else {
                unsigned        i;

                DBG(cdev, "cfg %d/%p speeds:%s%s%s\n",
                        config->bConfigurationValue, config,
                        config->superspeed ? " super" : "",
                        config->highspeed ? " high" : "",
                        config->fullspeed
                                ? (gadget_is_dualspeed(cdev->gadget)
                                        ? " full"
                                        : " full/low")
                                : "");

                for (i = 0; i < MAX_CONFIG_INTERFACES; i++) {
                        struct usb_function     *f = config->interface[i];

                        if (!f)
                                continue;
                        DBG(cdev, "  interface %d = %s/%p\n",
                                i, f->name, f);
                }
        }

        /* set_alt(), or next bind(), sets up
         * ep->driver_data as needed.
         */
        usb_ep_autoconfig_reset(cdev->gadget);

done:
        if (status)
                DBG(cdev, "added config '%s'/%u --> %d\n", config->label,
                                config->bConfigurationValue, status);
        return status;
}

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

/* We support strings in multiple languages ... string descriptor zero
 * says which languages are supported.  The typical case will be that
 * only one language (probably English) is used, with I18N handled on
 * the host side.
 */

static void collect_langs(struct usb_gadget_strings **sp, __le16 *buf)
{
        const struct usb_gadget_strings *s;
        u16                             language;
        __le16                          *tmp;

        while (*sp) {
                s = *sp;
                language = cpu_to_le16(s->language);
                for (tmp = buf; *tmp && tmp < &buf[126]; tmp++) {
                        if (*tmp == language)
                                goto repeat;
                }
                *tmp++ = language;
repeat:
                sp++;
        }
}

static int lookup_string(
        struct usb_gadget_strings       **sp,
        void                            *buf,
        u16                             language,
        int                             id
)
{
        struct usb_gadget_strings       *s;
        int                             value;

        while (*sp) {
                s = *sp++;
                if (s->language != language)
                        continue;
                value = usb_gadget_get_string(s, id, buf);
                if (value > 0)
                        return value;
        }
        return -EINVAL;
}

static int get_string(struct usb_composite_dev *cdev,
                void *buf, u16 language, int id)
{
        struct usb_configuration        *c;
        struct usb_function             *f;
        int                             len;
        const char                      *str;

        /* Yes, not only is USB's I18N support probably more than most
         * folk will ever care about ... also, it's all supported here.
         * (Except for UTF8 support for Unicode's "Astral Planes".)
         */

        /* 0 == report all available language codes */
        if (id == 0) {
                struct usb_string_descriptor    *s = buf;
                struct usb_gadget_strings       **sp;

                memset(s, 0, 256);
                s->bDescriptorType = USB_DT_STRING;

                sp = composite->strings;
                if (sp)
                        collect_langs(sp, s->wData);

                list_for_each_entry(c, &cdev->configs, list) {
                        sp = c->strings;
                        if (sp)
                                collect_langs(sp, s->wData);

                        list_for_each_entry(f, &c->functions, list) {
                                sp = f->strings;
                                if (sp)
                                        collect_langs(sp, s->wData);
                        }
                }

                for (len = 0; len <= 126 && s->wData[len]; len++)
                        continue;
                if (!len)
                        return -EINVAL;

                s->bLength = 2 * (len + 1);
                return s->bLength;
        }

        /* Otherwise, look up and return a specified string.  First
         * check if the string has not been overridden.
         */
        if (cdev->manufacturer_override == id)
                str = iManufacturer ?: composite->iManufacturer ?:
                        composite_manufacturer;
        else if (cdev->product_override == id)
                str = iProduct ?: composite->iProduct;
        else if (cdev->serial_override == id)
                str = iSerialNumber;
        else
                str = NULL;
        if (str) {
                struct usb_gadget_strings strings = {
                        .language = language,
                        .strings  = &(struct usb_string) { 0xff, str }
                };
                return usb_gadget_get_string(&strings, 0xff, buf);
        }

        /* String IDs are device-scoped, so we look up each string
         * table we're told about.  These lookups are infrequent;
         * simpler-is-better here.
         */
        if (composite->strings) {
                len = lookup_string(composite->strings, buf, language, id);
                if (len > 0)
                        return len;
        }
        list_for_each_entry(c, &cdev->configs, list) {
                if (c->strings) {
                        len = lookup_string(c->strings, buf, language, id);
                        if (len > 0)
                                return len;
                }
                list_for_each_entry(f, &c->functions, list) {
                        if (!f->strings)
                                continue;
                        len = lookup_string(f->strings, buf, language, id);
                        if (len > 0)
                                return len;
                }
        }
        return -EINVAL;
}

/**
 * usb_string_id() - allocate an unused string ID
 * @cdev: the device whose string descriptor IDs are being allocated
 * Context: single threaded during gadget setup
 *
 * @usb_string_id() is called from bind() callbacks to allocate
 * string IDs.  Drivers for functions, configurations, or gadgets will
 * then store that ID in the appropriate descriptors and string table.
 *
 * All string identifier should be allocated using this,
 * @usb_string_ids_tab() or @usb_string_ids_n() routine, to ensure
 * that for example different functions don't wrongly assign different
 * meanings to the same identifier.
 */
int usb_string_id(struct usb_composite_dev *cdev)
{
        if (cdev->next_string_id < 254) {
                /* string id 0 is reserved by USB spec for list of
                 * supported languages */
                /* 255 reserved as well? -- mina86 */
                cdev->next_string_id++;
                return cdev->next_string_id;
        }
        return -ENODEV;
}

/**
 * usb_string_ids() - allocate unused string IDs in batch
 * @cdev: the device whose string descriptor IDs are being allocated
 * @str: an array of usb_string objects to assign numbers to
 * Context: single threaded during gadget setup
 *
 * @usb_string_ids() is called from bind() callbacks to allocate
 * string IDs.  Drivers for functions, configurations, or gadgets will
 * then copy IDs from the string table to the appropriate descriptors
 * and string table for other languages.
 *
 * All string identifier should be allocated using this,
 * @usb_string_id() or @usb_string_ids_n() routine, to ensure that for
 * example different functions don't wrongly assign different meanings
 * to the same identifier.
 */
int usb_string_ids_tab(struct usb_composite_dev *cdev, struct usb_string *str)
{
        int next = cdev->next_string_id;

        for (; str->s; ++str) {
                if (unlikely(next >= 254))
                        return -ENODEV;
                str->id = ++next;
        }

        cdev->next_string_id = next;

        return 0;
}

/**
 * usb_string_ids_n() - allocate unused string IDs in batch
 * @c: the device whose string descriptor IDs are being allocated
 * @n: number of string IDs to allocate
 * Context: single threaded during gadget setup
 *
 * Returns the first requested ID.  This ID and next @n-1 IDs are now
 * valid IDs.  At least provided that @n is non-zero because if it
 * is, returns last requested ID which is now very useful information.
 *
 * @usb_string_ids_n() is called from bind() callbacks to allocate
 * string IDs.  Drivers for functions, configurations, or gadgets will
 * then store that ID in the appropriate descriptors and string table.
 *
 * All string identifier should be allocated using this,
 * @usb_string_id() or @usb_string_ids_n() routine, to ensure that for
 * example different functions don't wrongly assign different meanings
 * to the same identifier.
 */
int usb_string_ids_n(struct usb_composite_dev *c, unsigned n)
{
        unsigned next = c->next_string_id;
        if (unlikely(n > 254 || (unsigned)next + n > 254))
                return -ENODEV;
        c->next_string_id += n;
        return next + 1;
}


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

static void composite_setup_complete(struct usb_ep *ep, struct usb_request *req)
{
        if (req->status || req->actual != req->length)
                DBG((struct usb_composite_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 and function specific setup.
 */
static int
composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
{
        struct usb_composite_dev        *cdev = get_gadget_data(gadget);
        struct usb_request              *req = cdev->req;
        int                             value = -EOPNOTSUPP;
        int                             status = 0;
        u16                             w_index = le16_to_cpu(ctrl->wIndex);
        u8                              intf = w_index & 0xFF;
        u16                             w_value = le16_to_cpu(ctrl->wValue);
        u16                             w_length = le16_to_cpu(ctrl->wLength);
        struct usb_function             *f = NULL;
        u8                              endp;

        /* partial re-init of the response message; the function or the
         * gadget might need to intercept e.g. a control-OUT completion
         * when we delegate to it.
         */
        req->zero = 0;
        req->complete = composite_setup_complete;
        req->length = 0;
        gadget->ep0->driver_data = cdev;

        switch (ctrl->bRequest) {

        /* we handle all standard USB descriptors */
        case USB_REQ_GET_DESCRIPTOR:
                if (ctrl->bRequestType != USB_DIR_IN)
                        goto unknown;
                switch (w_value >> 8) {

                case USB_DT_DEVICE:
                        cdev->desc.bNumConfigurations =
                                count_configs(cdev, USB_DT_DEVICE);
                        cdev->desc.bMaxPacketSize0 =
                                cdev->gadget->ep0->maxpacket;
                        if (gadget_is_superspeed(gadget)) {
                                if (gadget->speed >= USB_SPEED_SUPER) {
                                        cdev->desc.bcdUSB = cpu_to_le16(0x0300);
                                        cdev->desc.bMaxPacketSize0 = 9;
                                } else {
                                        cdev->desc.bcdUSB = cpu_to_le16(0x0210);
                                }
                        }

                        value = min(w_length, (u16) sizeof cdev->desc);
                        memcpy(req->buf, &cdev->desc, value);
                        break;
                case USB_DT_DEVICE_QUALIFIER:
                        if (!gadget_is_dualspeed(gadget) ||
                            gadget->speed >= USB_SPEED_SUPER)
                                break;
                        device_qual(cdev);
                        value = min_t(int, w_length,
                                sizeof(struct usb_qualifier_descriptor));
                        break;
                case USB_DT_OTHER_SPEED_CONFIG:
                        if (!gadget_is_dualspeed(gadget) ||
                            gadget->speed >= USB_SPEED_SUPER)
                                break;
                        /* FALLTHROUGH */
                case USB_DT_CONFIG:
                        value = config_desc(cdev, w_value);
                        if (value >= 0)
                                value = min(w_length, (u16) value);
                        break;
                case USB_DT_STRING:
                        value = get_string(cdev, req->buf,
                                        w_index, w_value & 0xff);
                        if (value >= 0)
                                value = min(w_length, (u16) value);
                        break;
                case USB_DT_BOS:
                        if (gadget_is_superspeed(gadget)) {
                                value = bos_desc(cdev);
                                value = min(w_length, (u16) value);
                        }
                        break;
                }
                break;

        /* any number of configs can work */
        case USB_REQ_SET_CONFIGURATION:
                if (ctrl->bRequestType != 0)
                        goto unknown;
                if (gadget_is_otg(gadget)) {
                        if (gadget->a_hnp_support)
                                DBG(cdev, "HNP available\n");
                        else if (gadget->a_alt_hnp_support)
                                DBG(cdev, "HNP on another port\n");
                        else
                                VDBG(cdev, "HNP inactive\n");
                }
                spin_lock(&cdev->lock);
                value = set_config(cdev, ctrl, w_value);
                spin_unlock(&cdev->lock);
                break;
        case USB_REQ_GET_CONFIGURATION:
                if (ctrl->bRequestType != USB_DIR_IN)
                        goto unknown;
                if (cdev->config)
                        *(u8 *)req->buf = cdev->config->bConfigurationValue;
                else
                        *(u8 *)req->buf = 0;
                value = min(w_length, (u16) 1);
                break;

        /* function drivers must handle get/set altsetting; if there's
         * no get() method, we know only altsetting zero works.
         */
        case USB_REQ_SET_INTERFACE:
                if (ctrl->bRequestType != USB_RECIP_INTERFACE)
                        goto unknown;
                if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
                        break;
                f = cdev->config->interface[intf];
                if (!f)
                        break;
                if (w_value && !f->set_alt)
                        break;
                value = f->set_alt(f, w_index, w_value);
                if (value == USB_GADGET_DELAYED_STATUS) {
                        DBG(cdev,
                         "%s: interface %d (%s) requested delayed status\n",
                                        __func__, intf, f->name);
                        cdev->delayed_status++;
                        DBG(cdev, "delayed_status count %d\n",
                                        cdev->delayed_status);
                }
                break;
        case USB_REQ_GET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE))
                        goto unknown;
                if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
                        break;
                f = cdev->config->interface[intf];
                if (!f)
                        break;
                /* lots of interfaces only need altsetting zero... */
                value = f->get_alt ? f->get_alt(f, w_index) : 0;
                if (value < 0)
                        break;
                *((u8 *)req->buf) = value;
                value = min(w_length, (u16) 1);
                break;

        /*
         * USB 3.0 additions:
         * Function driver should handle get_status request. If such cb
         * wasn't supplied we respond with default value = 0
         * Note: function driver should supply such cb only for the first
         * interface of the function
         */
        case USB_REQ_GET_STATUS:
                if (!gadget_is_superspeed(gadget))
                        goto unknown;
                if (ctrl->bRequestType != (USB_DIR_IN | USB_RECIP_INTERFACE))
                        goto unknown;
                value = 2;      /* This is the length of the get_status reply */
                put_unaligned_le16(0, req->buf);
                if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
                        break;
                f = cdev->config->interface[intf];
                if (!f)
                        break;
                status = f->get_status ? f->get_status(f) : 0;
                if (status < 0)
                        break;
                put_unaligned_le16(status & 0x0000ffff, req->buf);
                break;
        /*
         * Function drivers should handle SetFeature/ClearFeature
         * (FUNCTION_SUSPEND) request. function_suspend cb should be supplied
         * only for the first interface of the function
         */
        case USB_REQ_CLEAR_FEATURE:
        case USB_REQ_SET_FEATURE:
                if (!gadget_is_superspeed(gadget))
                        goto unknown;
                if (ctrl->bRequestType != (USB_DIR_OUT | USB_RECIP_INTERFACE))
                        goto unknown;
                switch (w_value) {
                case USB_INTRF_FUNC_SUSPEND:
                        if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
                                break;
                        f = cdev->config->interface[intf];
                        if (!f)
                                break;
                        value = 0;
                        if (f->func_suspend)
                                value = f->func_suspend(f, w_index >> 8);
                        if (value < 0) {
                                ERROR(cdev,
                                      "func_suspend() returned error %d\n",
                                      value);
                                value = 0;
                        }
                        break;
                }
                break;
        default:
unknown:
                VDBG(cdev,
                        "non-core control req%02x.%02x v%04x i%04x l%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        w_value, w_index, w_length);

                /* functions always handle their interfaces and endpoints...
                 * punt other recipients (other, WUSB, ...) to the current
                 * configuration code.
                 *
                 * REVISIT it could make sense to let the composite device
                 * take such requests too, if that's ever needed:  to work
                 * in config 0, etc.
                 */
                switch (ctrl->bRequestType & USB_RECIP_MASK) {
                case USB_RECIP_INTERFACE:
                        if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
                                break;
                        f = cdev->config->interface[intf];
                        break;

                case USB_RECIP_ENDPOINT:
                        endp = ((w_index & 0x80) >> 3) | (w_index & 0x0f);
                        list_for_each_entry(f, &cdev->config->functions, list) {
                                if (test_bit(endp, f->endpoints))
                                        break;
                        }
                        if (&f->list == &cdev->config->functions)
                                f = NULL;
                        break;
                }

                if (f && f->setup)
                        value = f->setup(f, ctrl);
                else {
                        struct usb_configuration        *c;

                        c = cdev->config;
                        if (c && c->setup)
                                value = c->setup(c, ctrl);
                }

                goto done;
        }

        /* respond with data transfer before status phase? */
        if (value >= 0 && value != USB_GADGET_DELAYED_STATUS) {
                req->length = value;
                req->zero = value < w_length;
                value = usb_ep_queue(gadget->ep0, req, GFP_ATOMIC);
                if (value < 0) {
                        DBG(cdev, "ep_queue --> %d\n", value);
                        req->status = 0;
                        composite_setup_complete(gadget->ep0, req);
                }
        } else if (value == USB_GADGET_DELAYED_STATUS && w_length != 0) {
                WARN(cdev,
                        "%s: Delayed status not supported for w_length != 0",
                        __func__);
        }

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

static void composite_disconnect(struct usb_gadget *gadget)
{
        struct usb_composite_dev        *cdev = get_gadget_data(gadget);
        unsigned long                   flags;

        /* REVISIT:  should we have config and device level
         * disconnect callbacks?
         */
        spin_lock_irqsave(&cdev->lock, flags);
        if (cdev->config)
                reset_config(cdev);
        if (composite->disconnect)
                composite->disconnect(cdev);
        spin_unlock_irqrestore(&cdev->lock, flags);
}

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

static ssize_t composite_show_suspended(struct device *dev,
                                        struct device_attribute *attr,
                                        char *buf)
{
        struct usb_gadget *gadget = dev_to_usb_gadget(dev);
        struct usb_composite_dev *cdev = get_gadget_data(gadget);

        return sprintf(buf, "%d\n", cdev->suspended);
}

static DEVICE_ATTR(suspended, 0444, composite_show_suspended, NULL);

static void
composite_unbind(struct usb_gadget *gadget)
{
        struct usb_composite_dev        *cdev = get_gadget_data(gadget);

        /* composite_disconnect() must already have been called
         * by the underlying peripheral controller driver!
         * so there's no i/o concurrency that could affect the
         * state protected by cdev->lock.
         */
        WARN_ON(cdev->config);

        while (!list_empty(&cdev->configs)) {
                struct usb_configuration        *c;

                c = list_first_entry(&cdev->configs,
                                struct usb_configuration, list);
                while (!list_empty(&c->functions)) {
                        struct usb_function             *f;

                        f = list_first_entry(&c->functions,
                                        struct usb_function, list);
                        list_del(&f->list);
                        if (f->unbind) {
                                DBG(cdev, "unbind function '%s'/%p\n",
                                                f->name, f);
                                f->unbind(c, f);
                                /* may free memory for "f" */
                        }
                }
                list_del(&c->list);
                if (c->unbind) {
                        DBG(cdev, "unbind config '%s'/%p\n", c->label, c);
                        c->unbind(c);
                        /* may free memory for "c" */
                }
        }
        if (composite->unbind)
                composite->unbind(cdev);

        if (cdev->req) {
                kfree(cdev->req->buf);
                usb_ep_free_request(gadget->ep0, cdev->req);
        }
        device_remove_file(&gadget->dev, &dev_attr_suspended);
        kfree(cdev);
        set_gadget_data(gadget, NULL);
        composite = NULL;
}

static u8 override_id(struct usb_composite_dev *cdev, u8 *desc)
{
        if (!*desc) {
                int ret = usb_string_id(cdev);
                if (unlikely(ret < 0))
                        WARNING(cdev, "failed to override string ID\n");
                else
                        *desc = ret;
        }

        return *desc;
}

static int composite_bind(struct usb_gadget *gadget)
{
        struct usb_composite_dev        *cdev;
        int                             status = -ENOMEM;

        cdev = kzalloc(sizeof *cdev, GFP_KERNEL);
        if (!cdev)
                return status;

        spin_lock_init(&cdev->lock);
        cdev->gadget = gadget;
        set_gadget_data(gadget, cdev);
        INIT_LIST_HEAD(&cdev->configs);

        /* preallocate control response and buffer */
        cdev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
        if (!cdev->req)
                goto fail;
        cdev->req->buf = kmalloc(USB_BUFSIZ, GFP_KERNEL);
        if (!cdev->req->buf)
                goto fail;
        cdev->req->complete = composite_setup_complete;
        gadget->ep0->driver_data = cdev;

        cdev->bufsiz = USB_BUFSIZ;
        cdev->driver = composite;

        /*
         * As per USB compliance update, a device that is actively drawing
         * more than 100mA from USB must report itself as bus-powered in
         * the GetStatus(DEVICE) call.
         */
        if (CONFIG_USB_GADGET_VBUS_DRAW <= USB_SELF_POWER_VBUS_MAX_DRAW)
                usb_gadget_set_selfpowered(gadget);

        /* interface and string IDs start at zero via kzalloc.
         * we force endpoints to start unassigned; few controller
         * drivers will zero ep->driver_data.
         */
        usb_ep_autoconfig_reset(cdev->gadget);

        /* composite gadget needs to assign strings for whole device (like
         * serial number), register function drivers, potentially update
         * power state and consumption, etc
         */
        status = composite_gadget_bind(cdev);
        if (status < 0)
                goto fail;

        cdev->desc = *composite->dev;

        /* standardized runtime overrides for device ID data */
        if (idVendor)
                cdev->desc.idVendor = cpu_to_le16(idVendor);
        if (idProduct)
                cdev->desc.idProduct = cpu_to_le16(idProduct);
        if (bcdDevice)
                cdev->desc.bcdDevice = cpu_to_le16(bcdDevice);

        /* string overrides */
        if (iManufacturer || !cdev->desc.iManufacturer) {
                if (!iManufacturer && !composite->iManufacturer &&
                    !*composite_manufacturer)
                        snprintf(composite_manufacturer,
                                 sizeof composite_manufacturer,
                                 "%s %s with %s",
                                 init_utsname()->sysname,
                                 init_utsname()->release,
                                 gadget->name);

                cdev->manufacturer_override =
                        override_id(cdev, &cdev->desc.iManufacturer);
        }

        if (iProduct || (!cdev->desc.iProduct && composite->iProduct))
                cdev->product_override =
                        override_id(cdev, &cdev->desc.iProduct);

        if (iSerialNumber)
                cdev->serial_override =
                        override_id(cdev, &cdev->desc.iSerialNumber);

        /* has userspace failed to provide a serial number? */
        if (composite->needs_serial && !cdev->desc.iSerialNumber)
                WARNING(cdev, "userspace failed to provide iSerialNumber\n");

        /* finish up */
        status = device_create_file(&gadget->dev, &dev_attr_suspended);
        if (status)
                goto fail;

        INFO(cdev, "%s ready\n", composite->name);
        return 0;

fail:
        composite_unbind(gadget);
        return status;
}

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

static void
composite_suspend(struct usb_gadget *gadget)
{
        struct usb_composite_dev        *cdev = get_gadget_data(gadget);
        struct usb_function             *f;

        /* REVISIT:  should we have config level
         * suspend/resume callbacks?
         */
        DBG(cdev, "suspend\n");
        if (cdev->config) {
                list_for_each_entry(f, &cdev->config->functions, list) {
                        if (f->suspend)
                                f->suspend(f);
                }
        }
        if (composite->suspend)
                composite->suspend(cdev);

        cdev->suspended = 1;

        usb_gadget_vbus_draw(gadget, 2);
}

static void
composite_resume(struct usb_gadget *gadget)
{
        struct usb_composite_dev        *cdev = get_gadget_data(gadget);
        struct usb_function             *f;
        u8                              maxpower;

        /* REVISIT:  should we have config level
         * suspend/resume callbacks?
         */
        DBG(cdev, "resume\n");
        if (composite->resume)
                composite->resume(cdev);
        if (cdev->config) {
                list_for_each_entry(f, &cdev->config->functions, list) {
                        if (f->resume)
                                f->resume(f);
                }

                maxpower = cdev->config->bMaxPower;

                usb_gadget_vbus_draw(gadget, maxpower ?
                        (2 * maxpower) : CONFIG_USB_GADGET_VBUS_DRAW);
        }

        cdev->suspended = 0;
}

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

static struct usb_gadget_driver composite_driver = {
#ifdef CONFIG_USB_GADGET_SUPERSPEED
        .max_speed      = USB_SPEED_SUPER,
#else
        .max_speed      = USB_SPEED_HIGH,
#endif

        .unbind         = composite_unbind,

        .setup          = composite_setup,
        .disconnect     = composite_disconnect,

        .suspend        = composite_suspend,
        .resume         = composite_resume,

        .driver = {
                .owner          = THIS_MODULE,
        },
};

/**
 * usb_composite_probe() - register a composite driver
 * @driver: the driver to register
 * @bind: the callback used to allocate resources that are shared across the
 *      whole device, such as string IDs, and add its configurations using
 *      @usb_add_config().  This may fail by returning a negative errno
 *      value; it should return zero on successful initialization.
 * Context: single threaded during gadget setup
 *
 * This function is used to register drivers using the composite driver
 * framework.  The return value is zero, or a negative errno value.
 * Those values normally come from the driver's @bind method, which does
 * all the work of setting up the driver to match the hardware.
 *
 * On successful return, the gadget is ready to respond to requests from
 * the host, unless one of its components invokes usb_gadget_disconnect()
 * while it was binding.  That would usually be done in order to wait for
 * some userspace participation.
 */
int usb_composite_probe(struct usb_composite_driver *driver,
                               int (*bind)(struct usb_composite_dev *cdev))
{
        if (!driver || !driver->dev || !bind || composite)
                return -EINVAL;

        if (!driver->name)
                driver->name = "composite";
        if (!driver->iProduct)
                driver->iProduct = driver->name;
        composite_driver.function =  (char *) driver->name;
        composite_driver.driver.name = driver->name;
        composite_driver.max_speed =
                min_t(u8, composite_driver.max_speed, driver->max_speed);
        composite = driver;
        composite_gadget_bind = bind;

        return usb_gadget_probe_driver(&composite_driver, composite_bind);
}

/**
 * usb_composite_unregister() - unregister a composite driver
 * @driver: the driver to unregister
 *
 * This function is used to unregister drivers using the composite
 * driver framework.
 */
void usb_composite_unregister(struct usb_composite_driver *driver)
{
        if (composite != driver)
                return;
        usb_gadget_unregister_driver(&composite_driver);
}

/**
 * usb_composite_setup_continue() - Continue with the control transfer
 * @cdev: the composite device who's control transfer was kept waiting
 *
 * This function must be called by the USB function driver to continue
 * with the control transfer's data/status stage in case it had requested to
 * delay the data/status stages. A USB function's setup handler (e.g. set_alt())
 * can request the composite framework to delay the setup request's data/status
 * stages by returning USB_GADGET_DELAYED_STATUS.
 */
void usb_composite_setup_continue(struct usb_composite_dev *cdev)
{
        int                     value;
        struct usb_request      *req = cdev->req;
        unsigned long           flags;

        DBG(cdev, "%s\n", __func__);
        spin_lock_irqsave(&cdev->lock, flags);

        if (cdev->delayed_status == 0) {
                WARN(cdev, "%s: Unexpected call\n", __func__);

        } else if (--cdev->delayed_status == 0) {
                DBG(cdev, "%s: Completing delayed status\n", __func__);
                req->length = 0;
                value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
                if (value < 0) {
                        DBG(cdev, "ep_queue --> %d\n", value);
                        req->status = 0;
                        composite_setup_complete(cdev->gadget->ep0, req);
                }
        }

        spin_unlock_irqrestore(&cdev->lock, flags);
}