xref: /linux-6.6.21/drivers/usb/gadget/udc/core.c

// SPDX-License-Identifier: GPL-2.0
/*
 * udc.c - Core UDC Framework
 *
 * Copyright (C) 2010 Texas Instruments
 * Author: Felipe Balbi <balbi@ti.com>
 */

#define pr_fmt(fmt)	"UDC core: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/idr.h>
#include <linux/err.h>
#include <linux/dma-mapping.h>
#include <linux/sched/task_stack.h>
#include <linux/workqueue.h>

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

#include "trace.h"

static DEFINE_IDA(gadget_id_numbers);

static const struct bus_type gadget_bus_type;

/**
 * struct usb_udc - describes one usb device controller
 * @driver: the gadget driver pointer. For use by the class code
 * @dev: the child device to the actual controller
 * @gadget: the gadget. For use by the class code
 * @list: for use by the udc class driver
 * @vbus: for udcs who care about vbus status, this value is real vbus status;
 * for udcs who do not care about vbus status, this value is always true
 * @started: the UDC's started state. True if the UDC had started.
 * @allow_connect: Indicates whether UDC is allowed to be pulled up.
 * Set/cleared by gadget_(un)bind_driver() after gadget driver is bound or
 * unbound.
 * @vbus_work: work routine to handle VBUS status change notifications.
 * @connect_lock: protects udc->started, gadget->connect,
 * gadget->allow_connect and gadget->deactivate. The routines
 * usb_gadget_connect_locked(), usb_gadget_disconnect_locked(),
 * usb_udc_connect_control_locked(), usb_gadget_udc_start_locked() and
 * usb_gadget_udc_stop_locked() are called with this lock held.
 *
 * This represents the internal data structure which is used by the UDC-class
 * to hold information about udc driver and gadget together.
 */
struct usb_udc {
	struct usb_gadget_driver	*driver;
	struct usb_gadget		*gadget;
	struct device			dev;
	struct list_head		list;
	bool				vbus;
	bool				started;
	bool				allow_connect;
	struct work_struct		vbus_work;
	struct mutex			connect_lock;
};

static const struct class udc_class;
static LIST_HEAD(udc_list);

/* Protects udc_list, udc->driver, driver->is_bound, and related calls */
static DEFINE_MUTEX(udc_lock);

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

/**
 * usb_ep_set_maxpacket_limit - set maximum packet size limit for endpoint
 * @ep:the endpoint being configured
 * @maxpacket_limit:value of maximum packet size limit
 *
 * This function should be used only in UDC drivers to initialize endpoint
 * (usually in probe function).
 */
void usb_ep_set_maxpacket_limit(struct usb_ep *ep,
					      unsigned maxpacket_limit)
{
	ep->maxpacket_limit = maxpacket_limit;
	ep->maxpacket = maxpacket_limit;

	trace_usb_ep_set_maxpacket_limit(ep, 0);
}
EXPORT_SYMBOL_GPL(usb_ep_set_maxpacket_limit);

/**
 * usb_ep_enable - configure endpoint, making it usable
 * @ep:the endpoint being configured.  may not be the endpoint named "ep0".
 *	drivers discover endpoints through the ep_list of a usb_gadget.
 *
 * When configurations are set, or when interface settings change, the driver
 * will enable or disable the relevant endpoints.  while it is enabled, an
 * endpoint may be used for i/o until the driver receives a disconnect() from
 * the host or until the endpoint is disabled.
 *
 * the ep0 implementation (which calls this routine) must ensure that the
 * hardware capabilities of each endpoint match the descriptor provided
 * for it.  for example, an endpoint named "ep2in-bulk" would be usable
 * for interrupt transfers as well as bulk, but it likely couldn't be used
 * for iso transfers or for endpoint 14.  some endpoints are fully
 * configurable, with more generic names like "ep-a".  (remember that for
 * USB, "in" means "towards the USB host".)
 *
 * This routine may be called in an atomic (interrupt) context.
 *
 * returns zero, or a negative error code.
 */
int usb_ep_enable(struct usb_ep *ep)
{
	int ret = 0;

	if (ep->enabled)
		goto out;

	/* UDC drivers can't handle endpoints with maxpacket size 0 */
	if (usb_endpoint_maxp(ep->desc) == 0) {
		/*
		 * We should log an error message here, but we can't call
		 * dev_err() because there's no way to find the gadget
		 * given only ep.
		 */
		ret = -EINVAL;
		goto out;
	}

	ret = ep->ops->enable(ep, ep->desc);
	if (ret)
		goto out;

	ep->enabled = true;

out:
	trace_usb_ep_enable(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_enable);

/**
 * usb_ep_disable - endpoint is no longer usable
 * @ep:the endpoint being unconfigured.  may not be the endpoint named "ep0".
 *
 * no other task may be using this endpoint when this is called.
 * any pending and uncompleted requests will complete with status
 * indicating disconnect (-ESHUTDOWN) before this call returns.
 * gadget drivers must call usb_ep_enable() again before queueing
 * requests to the endpoint.
 *
 * This routine may be called in an atomic (interrupt) context.
 *
 * returns zero, or a negative error code.
 */
int usb_ep_disable(struct usb_ep *ep)
{
	int ret = 0;

	if (!ep->enabled)
		goto out;

	ret = ep->ops->disable(ep);
	if (ret)
		goto out;

	ep->enabled = false;

out:
	trace_usb_ep_disable(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_disable);

/**
 * usb_ep_alloc_request - allocate a request object to use with this endpoint
 * @ep:the endpoint to be used with with the request
 * @gfp_flags:GFP_* flags to use
 *
 * Request objects must be allocated with this call, since they normally
 * need controller-specific setup and may even need endpoint-specific
 * resources such as allocation of DMA descriptors.
 * Requests may be submitted with usb_ep_queue(), and receive a single
 * completion callback.  Free requests with usb_ep_free_request(), when
 * they are no longer needed.
 *
 * Returns the request, or null if one could not be allocated.
 */
struct usb_request *usb_ep_alloc_request(struct usb_ep *ep,
						       gfp_t gfp_flags)
{
	struct usb_request *req = NULL;

	req = ep->ops->alloc_request(ep, gfp_flags);

	trace_usb_ep_alloc_request(ep, req, req ? 0 : -ENOMEM);

	return req;
}
EXPORT_SYMBOL_GPL(usb_ep_alloc_request);

/**
 * usb_ep_free_request - frees a request object
 * @ep:the endpoint associated with the request
 * @req:the request being freed
 *
 * Reverses the effect of usb_ep_alloc_request().
 * Caller guarantees the request is not queued, and that it will
 * no longer be requeued (or otherwise used).
 */
void usb_ep_free_request(struct usb_ep *ep,
				       struct usb_request *req)
{
	trace_usb_ep_free_request(ep, req, 0);
	ep->ops->free_request(ep, req);
}
EXPORT_SYMBOL_GPL(usb_ep_free_request);

/**
 * usb_ep_queue - queues (submits) an I/O request to an endpoint.
 * @ep:the endpoint associated with the request
 * @req:the request being submitted
 * @gfp_flags: GFP_* flags to use in case the lower level driver couldn't
 *	pre-allocate all necessary memory with the request.
 *
 * This tells the device controller to perform the specified request through
 * that endpoint (reading or writing a buffer).  When the request completes,
 * including being canceled by usb_ep_dequeue(), the request's completion
 * routine is called to return the request to the driver.  Any endpoint
 * (except control endpoints like ep0) may have more than one transfer
 * request queued; they complete in FIFO order.  Once a gadget driver
 * submits a request, that request may not be examined or modified until it
 * is given back to that driver through the completion callback.
 *
 * Each request is turned into one or more packets.  The controller driver
 * never merges adjacent requests into the same packet.  OUT transfers
 * will sometimes use data that's already buffered in the hardware.
 * Drivers can rely on the fact that the first byte of the request's buffer
 * always corresponds to the first byte of some USB packet, for both
 * IN and OUT transfers.
 *
 * Bulk endpoints can queue any amount of data; the transfer is packetized
 * automatically.  The last packet will be short if the request doesn't fill it
 * out completely.  Zero length packets (ZLPs) should be avoided in portable
 * protocols since not all usb hardware can successfully handle zero length
 * packets.  (ZLPs may be explicitly written, and may be implicitly written if
 * the request 'zero' flag is set.)  Bulk endpoints may also be used
 * for interrupt transfers; but the reverse is not true, and some endpoints
 * won't support every interrupt transfer.  (Such as 768 byte packets.)
 *
 * Interrupt-only endpoints are less functional than bulk endpoints, for
 * example by not supporting queueing or not handling buffers that are
 * larger than the endpoint's maxpacket size.  They may also treat data
 * toggle differently.
 *
 * Control endpoints ... after getting a setup() callback, the driver queues
 * one response (even if it would be zero length).  That enables the
 * status ack, after transferring data as specified in the response.  Setup
 * functions may return negative error codes to generate protocol stalls.
 * (Note that some USB device controllers disallow protocol stall responses
 * in some cases.)  When control responses are deferred (the response is
 * written after the setup callback returns), then usb_ep_set_halt() may be
 * used on ep0 to trigger protocol stalls.  Depending on the controller,
 * it may not be possible to trigger a status-stage protocol stall when the
 * data stage is over, that is, from within the response's completion
 * routine.
 *
 * For periodic endpoints, like interrupt or isochronous ones, the usb host
 * arranges to poll once per interval, and the gadget driver usually will
 * have queued some data to transfer at that time.
 *
 * Note that @req's ->complete() callback must never be called from
 * within usb_ep_queue() as that can create deadlock situations.
 *
 * This routine may be called in interrupt context.
 *
 * Returns zero, or a negative error code.  Endpoints that are not enabled
 * report errors; errors will also be
 * reported when the usb peripheral is disconnected.
 *
 * If and only if @req is successfully queued (the return value is zero),
 * @req->complete() will be called exactly once, when the Gadget core and
 * UDC are finished with the request.  When the completion function is called,
 * control of the request is returned to the device driver which submitted it.
 * The completion handler may then immediately free or reuse @req.
 */
int usb_ep_queue(struct usb_ep *ep,
			       struct usb_request *req, gfp_t gfp_flags)
{
	int ret = 0;

	if (WARN_ON_ONCE(!ep->enabled && ep->address)) {
		ret = -ESHUTDOWN;
		goto out;
	}

	ret = ep->ops->queue(ep, req, gfp_flags);

out:
	trace_usb_ep_queue(ep, req, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_queue);

/**
 * usb_ep_dequeue - dequeues (cancels, unlinks) an I/O request from an endpoint
 * @ep:the endpoint associated with the request
 * @req:the request being canceled
 *
 * If the request is still active on the endpoint, it is dequeued and
 * eventually its completion routine is called (with status -ECONNRESET);
 * else a negative error code is returned.  This routine is asynchronous,
 * that is, it may return before the completion routine runs.
 *
 * Note that some hardware can't clear out write fifos (to unlink the request
 * at the head of the queue) except as part of disconnecting from usb. Such
 * restrictions prevent drivers from supporting configuration changes,
 * even to configuration zero (a "chapter 9" requirement).
 *
 * This routine may be called in interrupt context.
 */
int usb_ep_dequeue(struct usb_ep *ep, struct usb_request *req)
{
	int ret;

	ret = ep->ops->dequeue(ep, req);
	trace_usb_ep_dequeue(ep, req, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_dequeue);

/**
 * usb_ep_set_halt - sets the endpoint halt feature.
 * @ep: the non-isochronous endpoint being stalled
 *
 * Use this to stall an endpoint, perhaps as an error report.
 * Except for control endpoints,
 * the endpoint stays halted (will not stream any data) until the host
 * clears this feature; drivers may need to empty the endpoint's request
 * queue first, to make sure no inappropriate transfers happen.
 *
 * Note that while an endpoint CLEAR_FEATURE will be invisible to the
 * gadget driver, a SET_INTERFACE will not be.  To reset endpoints for the
 * current altsetting, see usb_ep_clear_halt().  When switching altsettings,
 * it's simplest to use usb_ep_enable() or usb_ep_disable() for the endpoints.
 *
 * This routine may be called in interrupt context.
 *
 * Returns zero, or a negative error code.  On success, this call sets
 * underlying hardware state that blocks data transfers.
 * Attempts to halt IN endpoints will fail (returning -EAGAIN) if any
 * transfer requests are still queued, or if the controller hardware
 * (usually a FIFO) still holds bytes that the host hasn't collected.
 */
int usb_ep_set_halt(struct usb_ep *ep)
{
	int ret;

	ret = ep->ops->set_halt(ep, 1);
	trace_usb_ep_set_halt(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_set_halt);

/**
 * usb_ep_clear_halt - clears endpoint halt, and resets toggle
 * @ep:the bulk or interrupt endpoint being reset
 *
 * Use this when responding to the standard usb "set interface" request,
 * for endpoints that aren't reconfigured, after clearing any other state
 * in the endpoint's i/o queue.
 *
 * This routine may be called in interrupt context.
 *
 * Returns zero, or a negative error code.  On success, this call clears
 * the underlying hardware state reflecting endpoint halt and data toggle.
 * Note that some hardware can't support this request (like pxa2xx_udc),
 * and accordingly can't correctly implement interface altsettings.
 */
int usb_ep_clear_halt(struct usb_ep *ep)
{
	int ret;

	ret = ep->ops->set_halt(ep, 0);
	trace_usb_ep_clear_halt(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_clear_halt);

/**
 * usb_ep_set_wedge - sets the halt feature and ignores clear requests
 * @ep: the endpoint being wedged
 *
 * Use this to stall an endpoint and ignore CLEAR_FEATURE(HALT_ENDPOINT)
 * requests. If the gadget driver clears the halt status, it will
 * automatically unwedge the endpoint.
 *
 * This routine may be called in interrupt context.
 *
 * Returns zero on success, else negative errno.
 */
int usb_ep_set_wedge(struct usb_ep *ep)
{
	int ret;

	if (ep->ops->set_wedge)
		ret = ep->ops->set_wedge(ep);
	else
		ret = ep->ops->set_halt(ep, 1);

	trace_usb_ep_set_wedge(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_set_wedge);

/**
 * usb_ep_fifo_status - returns number of bytes in fifo, or error
 * @ep: the endpoint whose fifo status is being checked.
 *
 * FIFO endpoints may have "unclaimed data" in them in certain cases,
 * such as after aborted transfers.  Hosts may not have collected all
 * the IN data written by the gadget driver (and reported by a request
 * completion).  The gadget driver may not have collected all the data
 * written OUT to it by the host.  Drivers that need precise handling for
 * fault reporting or recovery may need to use this call.
 *
 * This routine may be called in interrupt context.
 *
 * This returns the number of such bytes in the fifo, or a negative
 * errno if the endpoint doesn't use a FIFO or doesn't support such
 * precise handling.
 */
int usb_ep_fifo_status(struct usb_ep *ep)
{
	int ret;

	if (ep->ops->fifo_status)
		ret = ep->ops->fifo_status(ep);
	else
		ret = -EOPNOTSUPP;

	trace_usb_ep_fifo_status(ep, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_ep_fifo_status);

/**
 * usb_ep_fifo_flush - flushes contents of a fifo
 * @ep: the endpoint whose fifo is being flushed.
 *
 * This call may be used to flush the "unclaimed data" that may exist in
 * an endpoint fifo after abnormal transaction terminations.  The call
 * must never be used except when endpoint is not being used for any
 * protocol translation.
 *
 * This routine may be called in interrupt context.
 */
void usb_ep_fifo_flush(struct usb_ep *ep)
{
	if (ep->ops->fifo_flush)
		ep->ops->fifo_flush(ep);

	trace_usb_ep_fifo_flush(ep, 0);
}
EXPORT_SYMBOL_GPL(usb_ep_fifo_flush);

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

/**
 * usb_gadget_frame_number - returns the current frame number
 * @gadget: controller that reports the frame number
 *
 * Returns the usb frame number, normally eleven bits from a SOF packet,
 * or negative errno if this device doesn't support this capability.
 */
int usb_gadget_frame_number(struct usb_gadget *gadget)
{
	int ret;

	ret = gadget->ops->get_frame(gadget);

	trace_usb_gadget_frame_number(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_frame_number);

/**
 * usb_gadget_wakeup - tries to wake up the host connected to this gadget
 * @gadget: controller used to wake up the host
 *
 * Returns zero on success, else negative error code if the hardware
 * doesn't support such attempts, or its support has not been enabled
 * by the usb host.  Drivers must return device descriptors that report
 * their ability to support this, or hosts won't enable it.
 *
 * This may also try to use SRP to wake the host and start enumeration,
 * even if OTG isn't otherwise in use.  OTG devices may also start
 * remote wakeup even when hosts don't explicitly enable it.
 */
int usb_gadget_wakeup(struct usb_gadget *gadget)
{
	int ret = 0;

	if (!gadget->ops->wakeup) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->wakeup(gadget);

out:
	trace_usb_gadget_wakeup(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_wakeup);

/**
 * usb_gadget_set_remote_wakeup - configures the device remote wakeup feature.
 * @gadget:the device being configured for remote wakeup
 * @set:value to be configured.
 *
 * set to one to enable remote wakeup feature and zero to disable it.
 *
 * returns zero on success, else negative errno.
 */
int usb_gadget_set_remote_wakeup(struct usb_gadget *gadget, int set)
{
	int ret = 0;

	if (!gadget->ops->set_remote_wakeup) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->set_remote_wakeup(gadget, set);

out:
	trace_usb_gadget_set_remote_wakeup(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_set_remote_wakeup);

/**
 * usb_gadget_set_selfpowered - sets the device selfpowered feature.
 * @gadget:the device being declared as self-powered
 *
 * this affects the device status reported by the hardware driver
 * to reflect that it now has a local power supply.
 *
 * returns zero on success, else negative errno.
 */
int usb_gadget_set_selfpowered(struct usb_gadget *gadget)
{
	int ret = 0;

	if (!gadget->ops->set_selfpowered) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->set_selfpowered(gadget, 1);

out:
	trace_usb_gadget_set_selfpowered(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_set_selfpowered);

/**
 * usb_gadget_clear_selfpowered - clear the device selfpowered feature.
 * @gadget:the device being declared as bus-powered
 *
 * this affects the device status reported by the hardware driver.
 * some hardware may not support bus-powered operation, in which
 * case this feature's value can never change.
 *
 * returns zero on success, else negative errno.
 */
int usb_gadget_clear_selfpowered(struct usb_gadget *gadget)
{
	int ret = 0;

	if (!gadget->ops->set_selfpowered) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->set_selfpowered(gadget, 0);

out:
	trace_usb_gadget_clear_selfpowered(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_clear_selfpowered);

/**
 * usb_gadget_vbus_connect - Notify controller that VBUS is powered
 * @gadget:The device which now has VBUS power.
 * Context: can sleep
 *
 * This call is used by a driver for an external transceiver (or GPIO)
 * that detects a VBUS power session starting.  Common responses include
 * resuming the controller, activating the D+ (or D-) pullup to let the
 * host detect that a USB device is attached, and starting to draw power
 * (8mA or possibly more, especially after SET_CONFIGURATION).
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_vbus_connect(struct usb_gadget *gadget)
{
	int ret = 0;

	if (!gadget->ops->vbus_session) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->vbus_session(gadget, 1);

out:
	trace_usb_gadget_vbus_connect(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_vbus_connect);

/**
 * usb_gadget_vbus_draw - constrain controller's VBUS power usage
 * @gadget:The device whose VBUS usage is being described
 * @mA:How much current to draw, in milliAmperes.  This should be twice
 *	the value listed in the configuration descriptor bMaxPower field.
 *
 * This call is used by gadget drivers during SET_CONFIGURATION calls,
 * reporting how much power the device may consume.  For example, this
 * could affect how quickly batteries are recharged.
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_vbus_draw(struct usb_gadget *gadget, unsigned mA)
{
	int ret = 0;

	if (!gadget->ops->vbus_draw) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->vbus_draw(gadget, mA);
	if (!ret)
		gadget->mA = mA;

out:
	trace_usb_gadget_vbus_draw(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_vbus_draw);

/**
 * usb_gadget_vbus_disconnect - notify controller about VBUS session end
 * @gadget:the device whose VBUS supply is being described
 * Context: can sleep
 *
 * This call is used by a driver for an external transceiver (or GPIO)
 * that detects a VBUS power session ending.  Common responses include
 * reversing everything done in usb_gadget_vbus_connect().
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
{
	int ret = 0;

	if (!gadget->ops->vbus_session) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	ret = gadget->ops->vbus_session(gadget, 0);

out:
	trace_usb_gadget_vbus_disconnect(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_vbus_disconnect);

static int usb_gadget_connect_locked(struct usb_gadget *gadget)
	__must_hold(&gadget->udc->connect_lock)
{
	int ret = 0;

	if (!gadget->ops->pullup) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	if (gadget->deactivated || !gadget->udc->allow_connect || !gadget->udc->started) {
		/*
		 * If the gadget isn't usable (because it is deactivated,
		 * unbound, or not yet started), we only save the new state.
		 * The gadget will be connected automatically when it is
		 * activated/bound/started.
		 */
		gadget->connected = true;
		goto out;
	}

	ret = gadget->ops->pullup(gadget, 1);
	if (!ret)
		gadget->connected = 1;

out:
	trace_usb_gadget_connect(gadget, ret);

	return ret;
}

/**
 * usb_gadget_connect - software-controlled connect to USB host
 * @gadget:the peripheral being connected
 *
 * Enables the D+ (or potentially D-) pullup.  The host will start
 * enumerating this gadget when the pullup is active and a VBUS session
 * is active (the link is powered).
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_connect(struct usb_gadget *gadget)
{
	int ret;

	mutex_lock(&gadget->udc->connect_lock);
	ret = usb_gadget_connect_locked(gadget);
	mutex_unlock(&gadget->udc->connect_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_connect);

static int usb_gadget_disconnect_locked(struct usb_gadget *gadget)
	__must_hold(&gadget->udc->connect_lock)
{
	int ret = 0;

	if (!gadget->ops->pullup) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	if (!gadget->connected)
		goto out;

	if (gadget->deactivated || !gadget->udc->started) {
		/*
		 * If gadget is deactivated we only save new state.
		 * Gadget will stay disconnected after activation.
		 */
		gadget->connected = false;
		goto out;
	}

	ret = gadget->ops->pullup(gadget, 0);
	if (!ret)
		gadget->connected = 0;

	mutex_lock(&udc_lock);
	if (gadget->udc->driver)
		gadget->udc->driver->disconnect(gadget);
	mutex_unlock(&udc_lock);

out:
	trace_usb_gadget_disconnect(gadget, ret);

	return ret;
}

/**
 * usb_gadget_disconnect - software-controlled disconnect from USB host
 * @gadget:the peripheral being disconnected
 *
 * Disables the D+ (or potentially D-) pullup, which the host may see
 * as a disconnect (when a VBUS session is active).  Not all systems
 * support software pullup controls.
 *
 * Following a successful disconnect, invoke the ->disconnect() callback
 * for the current gadget driver so that UDC drivers don't need to.
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_disconnect(struct usb_gadget *gadget)
{
	int ret;

	mutex_lock(&gadget->udc->connect_lock);
	ret = usb_gadget_disconnect_locked(gadget);
	mutex_unlock(&gadget->udc->connect_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_disconnect);

/**
 * usb_gadget_deactivate - deactivate function which is not ready to work
 * @gadget: the peripheral being deactivated
 *
 * This routine may be used during the gadget driver bind() call to prevent
 * the peripheral from ever being visible to the USB host, unless later
 * usb_gadget_activate() is called.  For example, user mode components may
 * need to be activated before the system can talk to hosts.
 *
 * This routine may sleep; it must not be called in interrupt context
 * (such as from within a gadget driver's disconnect() callback).
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_deactivate(struct usb_gadget *gadget)
{
	int ret = 0;

	mutex_lock(&gadget->udc->connect_lock);
	if (gadget->deactivated)
		goto unlock;

	if (gadget->connected) {
		ret = usb_gadget_disconnect_locked(gadget);
		if (ret)
			goto unlock;

		/*
		 * If gadget was being connected before deactivation, we want
		 * to reconnect it in usb_gadget_activate().
		 */
		gadget->connected = true;
	}
	gadget->deactivated = true;

unlock:
	mutex_unlock(&gadget->udc->connect_lock);
	trace_usb_gadget_deactivate(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_deactivate);

/**
 * usb_gadget_activate - activate function which is not ready to work
 * @gadget: the peripheral being activated
 *
 * This routine activates gadget which was previously deactivated with
 * usb_gadget_deactivate() call. It calls usb_gadget_connect() if needed.
 *
 * This routine may sleep; it must not be called in interrupt context.
 *
 * Returns zero on success, else negative errno.
 */
int usb_gadget_activate(struct usb_gadget *gadget)
{
	int ret = 0;

	mutex_lock(&gadget->udc->connect_lock);
	if (!gadget->deactivated)
		goto unlock;

	gadget->deactivated = false;

	/*
	 * If gadget has been connected before deactivation, or became connected
	 * while it was being deactivated, we call usb_gadget_connect().
	 */
	if (gadget->connected)
		ret = usb_gadget_connect_locked(gadget);

unlock:
	mutex_unlock(&gadget->udc->connect_lock);
	trace_usb_gadget_activate(gadget, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_activate);

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

#ifdef	CONFIG_HAS_DMA

int usb_gadget_map_request_by_dev(struct device *dev,
		struct usb_request *req, int is_in)
{
	if (req->length == 0)
		return 0;

	if (req->num_sgs) {
		int     mapped;

		mapped = dma_map_sg(dev, req->sg, req->num_sgs,
				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
		if (mapped == 0) {
			dev_err(dev, "failed to map SGs\n");
			return -EFAULT;
		}

		req->num_mapped_sgs = mapped;
	} else {
		if (is_vmalloc_addr(req->buf)) {
			dev_err(dev, "buffer is not dma capable\n");
			return -EFAULT;
		} else if (object_is_on_stack(req->buf)) {
			dev_err(dev, "buffer is on stack\n");
			return -EFAULT;
		}

		req->dma = dma_map_single(dev, req->buf, req->length,
				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);

		if (dma_mapping_error(dev, req->dma)) {
			dev_err(dev, "failed to map buffer\n");
			return -EFAULT;
		}

		req->dma_mapped = 1;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(usb_gadget_map_request_by_dev);

int usb_gadget_map_request(struct usb_gadget *gadget,
		struct usb_request *req, int is_in)
{
	return usb_gadget_map_request_by_dev(gadget->dev.parent, req, is_in);
}
EXPORT_SYMBOL_GPL(usb_gadget_map_request);

void usb_gadget_unmap_request_by_dev(struct device *dev,
		struct usb_request *req, int is_in)
{
	if (req->length == 0)
		return;

	if (req->num_mapped_sgs) {
		dma_unmap_sg(dev, req->sg, req->num_sgs,
				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);

		req->num_mapped_sgs = 0;
	} else if (req->dma_mapped) {
		dma_unmap_single(dev, req->dma, req->length,
				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
		req->dma_mapped = 0;
	}
}
EXPORT_SYMBOL_GPL(usb_gadget_unmap_request_by_dev);

void usb_gadget_unmap_request(struct usb_gadget *gadget,
		struct usb_request *req, int is_in)
{
	usb_gadget_unmap_request_by_dev(gadget->dev.parent, req, is_in);
}
EXPORT_SYMBOL_GPL(usb_gadget_unmap_request);

#endif	/* CONFIG_HAS_DMA */

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

/**
 * usb_gadget_giveback_request - give the request back to the gadget layer
 * @ep: the endpoint to be used with with the request
 * @req: the request being given back
 *
 * This is called by device controller drivers in order to return the
 * completed request back to the gadget layer.
 */
void usb_gadget_giveback_request(struct usb_ep *ep,
		struct usb_request *req)
{
	if (likely(req->status == 0))
		usb_led_activity(USB_LED_EVENT_GADGET);

	trace_usb_gadget_giveback_request(ep, req, 0);

	req->complete(ep, req);
}
EXPORT_SYMBOL_GPL(usb_gadget_giveback_request);

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

/**
 * gadget_find_ep_by_name - returns ep whose name is the same as sting passed
 *	in second parameter or NULL if searched endpoint not found
 * @g: controller to check for quirk
 * @name: name of searched endpoint
 */
struct usb_ep *gadget_find_ep_by_name(struct usb_gadget *g, const char *name)
{
	struct usb_ep *ep;

	gadget_for_each_ep(ep, g) {
		if (!strcmp(ep->name, name))
			return ep;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL(gadget_find_ep_by_name);

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

int usb_gadget_ep_match_desc(struct usb_gadget *gadget,
		struct usb_ep *ep, struct usb_endpoint_descriptor *desc,
		struct usb_ss_ep_comp_descriptor *ep_comp)
{
	u8		type;
	u16		max;
	int		num_req_streams = 0;

	/* endpoint already claimed? */
	if (ep->claimed)
		return 0;

	type = usb_endpoint_type(desc);
	max = usb_endpoint_maxp(desc);

	if (usb_endpoint_dir_in(desc) && !ep->caps.dir_in)
		return 0;
	if (usb_endpoint_dir_out(desc) && !ep->caps.dir_out)
		return 0;

	if (max > ep->maxpacket_limit)
		return 0;

	/* "high bandwidth" works only at high speed */
	if (!gadget_is_dualspeed(gadget) && usb_endpoint_maxp_mult(desc) > 1)
		return 0;

	switch (type) {
	case USB_ENDPOINT_XFER_CONTROL:
		/* only support ep0 for portable CONTROL traffic */
		return 0;
	case USB_ENDPOINT_XFER_ISOC:
		if (!ep->caps.type_iso)
			return 0;
		/* ISO:  limit 1023 bytes full speed, 1024 high/super speed */
		if (!gadget_is_dualspeed(gadget) && max > 1023)
			return 0;
		break;
	case USB_ENDPOINT_XFER_BULK:
		if (!ep->caps.type_bulk)
			return 0;
		if (ep_comp && gadget_is_superspeed(gadget)) {
			/* Get the number of required streams from the
			 * EP companion descriptor and see if the EP
			 * matches it
			 */
			num_req_streams = ep_comp->bmAttributes & 0x1f;
			if (num_req_streams > ep->max_streams)
				return 0;
		}
		break;
	case USB_ENDPOINT_XFER_INT:
		/* Bulk endpoints handle interrupt transfers,
		 * except the toggle-quirky iso-synch kind
		 */
		if (!ep->caps.type_int && !ep->caps.type_bulk)
			return 0;
		/* INT:  limit 64 bytes full speed, 1024 high/super speed */
		if (!gadget_is_dualspeed(gadget) && max > 64)
			return 0;
		break;
	}

	return 1;
}
EXPORT_SYMBOL_GPL(usb_gadget_ep_match_desc);

/**
 * usb_gadget_check_config - checks if the UDC can support the binded
 *	configuration
 * @gadget: controller to check the USB configuration
 *
 * Ensure that a UDC is able to support the requested resources by a
 * configuration, and that there are no resource limitations, such as
 * internal memory allocated to all requested endpoints.
 *
 * Returns zero on success, else a negative errno.
 */
int usb_gadget_check_config(struct usb_gadget *gadget)
{
	if (gadget->ops->check_config)
		return gadget->ops->check_config(gadget);
	return 0;
}
EXPORT_SYMBOL_GPL(usb_gadget_check_config);

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

static void usb_gadget_state_work(struct work_struct *work)
{
	struct usb_gadget *gadget = work_to_gadget(work);
	struct usb_udc *udc = gadget->udc;

	if (udc)
		sysfs_notify(&udc->dev.kobj, NULL, "state");
}

void usb_gadget_set_state(struct usb_gadget *gadget,
		enum usb_device_state state)
{
	gadget->state = state;
	schedule_work(&gadget->work);
}
EXPORT_SYMBOL_GPL(usb_gadget_set_state);

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

/* Acquire connect_lock before calling this function. */
static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
{
	if (udc->vbus)
		usb_gadget_connect_locked(udc->gadget);
	else
		usb_gadget_disconnect_locked(udc->gadget);
}

static void vbus_event_work(struct work_struct *work)
{
	struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);

	mutex_lock(&udc->connect_lock);
	usb_udc_connect_control_locked(udc);
	mutex_unlock(&udc->connect_lock);
}

/**
 * usb_udc_vbus_handler - updates the udc core vbus status, and try to
 * connect or disconnect gadget
 * @gadget: The gadget which vbus change occurs
 * @status: The vbus status
 *
 * The udc driver calls it when it wants to connect or disconnect gadget
 * according to vbus status.
 *
 * This function can be invoked from interrupt context by irq handlers of
 * the gadget drivers, however, usb_udc_connect_control() has to run in
 * non-atomic context due to the following:
 * a. Some of the gadget driver implementations expect the ->pullup
 * callback to be invoked in non-atomic context.
 * b. usb_gadget_disconnect() acquires udc_lock which is a mutex.
 * Hence offload invocation of usb_udc_connect_control() to workqueue.
 */
void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
{
	struct usb_udc *udc = gadget->udc;

	if (udc) {
		udc->vbus = status;
		schedule_work(&udc->vbus_work);
	}
}
EXPORT_SYMBOL_GPL(usb_udc_vbus_handler);

/**
 * usb_gadget_udc_reset - notifies the udc core that bus reset occurs
 * @gadget: The gadget which bus reset occurs
 * @driver: The gadget driver we want to notify
 *
 * If the udc driver has bus reset handler, it needs to call this when the bus
 * reset occurs, it notifies the gadget driver that the bus reset occurs as
 * well as updates gadget state.
 */
void usb_gadget_udc_reset(struct usb_gadget *gadget,
		struct usb_gadget_driver *driver)
{
	driver->reset(gadget);
	usb_gadget_set_state(gadget, USB_STATE_DEFAULT);
}
EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);

/**
 * usb_gadget_udc_start_locked - tells usb device controller to start up
 * @udc: The UDC to be started
 *
 * This call is issued by the UDC Class driver when it's about
 * to register a gadget driver to the device controller, before
 * calling gadget driver's bind() method.
 *
 * It allows the controller to be powered off until strictly
 * necessary to have it powered on.
 *
 * Returns zero on success, else negative errno.
 *
 * Caller should acquire connect_lock before invoking this function.
 */
static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
	__must_hold(&udc->connect_lock)
{
	int ret;

	if (udc->started) {
		dev_err(&udc->dev, "UDC had already started\n");
		return -EBUSY;
	}

	ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
	if (!ret)
		udc->started = true;

	return ret;
}

/**
 * usb_gadget_udc_stop_locked - tells usb device controller we don't need it anymore
 * @udc: The UDC to be stopped
 *
 * This call is issued by the UDC Class driver after calling
 * gadget driver's unbind() method.
 *
 * The details are implementation specific, but it can go as
 * far as powering off UDC completely and disable its data
 * line pullups.
 *
 * Caller should acquire connect lock before invoking this function.
 */
static inline void usb_gadget_udc_stop_locked(struct usb_udc *udc)
	__must_hold(&udc->connect_lock)
{
	if (!udc->started) {
		dev_err(&udc->dev, "UDC had already stopped\n");
		return;
	}

	udc->gadget->ops->udc_stop(udc->gadget);
	udc->started = false;
}

/**
 * usb_gadget_udc_set_speed - tells usb device controller speed supported by
 *    current driver
 * @udc: The device we want to set maximum speed
 * @speed: The maximum speed to allowed to run
 *
 * This call is issued by the UDC Class driver before calling
 * usb_gadget_udc_start() in order to make sure that we don't try to
 * connect on speeds the gadget driver doesn't support.
 */
static inline void usb_gadget_udc_set_speed(struct usb_udc *udc,
					    enum usb_device_speed speed)
{
	struct usb_gadget *gadget = udc->gadget;
	enum usb_device_speed s;

	if (speed == USB_SPEED_UNKNOWN)
		s = gadget->max_speed;
	else
		s = min(speed, gadget->max_speed);

	if (s == USB_SPEED_SUPER_PLUS && gadget->ops->udc_set_ssp_rate)
		gadget->ops->udc_set_ssp_rate(gadget, gadget->max_ssp_rate);
	else if (gadget->ops->udc_set_speed)
		gadget->ops->udc_set_speed(gadget, s);
}

/**
 * usb_gadget_enable_async_callbacks - tell usb device controller to enable asynchronous callbacks
 * @udc: The UDC which should enable async callbacks
 *
 * This routine is used when binding gadget drivers.  It undoes the effect
 * of usb_gadget_disable_async_callbacks(); the UDC driver should enable IRQs
 * (if necessary) and resume issuing callbacks.
 *
 * This routine will always be called in process context.
 */
static inline void usb_gadget_enable_async_callbacks(struct usb_udc *udc)
{
	struct usb_gadget *gadget = udc->gadget;

	if (gadget->ops->udc_async_callbacks)
		gadget->ops->udc_async_callbacks(gadget, true);
}

/**
 * usb_gadget_disable_async_callbacks - tell usb device controller to disable asynchronous callbacks
 * @udc: The UDC which should disable async callbacks
 *
 * This routine is used when unbinding gadget drivers.  It prevents a race:
 * The UDC driver doesn't know when the gadget driver's ->unbind callback
 * runs, so unless it is told to disable asynchronous callbacks, it might
 * issue a callback (such as ->disconnect) after the unbind has completed.
 *
 * After this function runs, the UDC driver must suppress all ->suspend,
 * ->resume, ->disconnect, ->reset, and ->setup callbacks to the gadget driver
 * until async callbacks are again enabled.  A simple-minded but effective
 * way to accomplish this is to tell the UDC hardware not to generate any
 * more IRQs.
 *
 * Request completion callbacks must still be issued.  However, it's okay
 * to defer them until the request is cancelled, since the pull-up will be
 * turned off during the time period when async callbacks are disabled.
 *
 * This routine will always be called in process context.
 */
static inline void usb_gadget_disable_async_callbacks(struct usb_udc *udc)
{
	struct usb_gadget *gadget = udc->gadget;

	if (gadget->ops->udc_async_callbacks)
		gadget->ops->udc_async_callbacks(gadget, false);
}

/**
 * usb_udc_release - release the usb_udc struct
 * @dev: the dev member within usb_udc
 *
 * This is called by driver's core in order to free memory once the last
 * reference is released.
 */
static void usb_udc_release(struct device *dev)
{
	struct usb_udc *udc;

	udc = container_of(dev, struct usb_udc, dev);
	dev_dbg(dev, "releasing '%s'\n", dev_name(dev));
	kfree(udc);
}

static const struct attribute_group *usb_udc_attr_groups[];

static void usb_udc_nop_release(struct device *dev)
{
	dev_vdbg(dev, "%s\n", __func__);
}

/**
 * usb_initialize_gadget - initialize a gadget and its embedded struct device
 * @parent: the parent device to this udc. Usually the controller driver's
 * device.
 * @gadget: the gadget to be initialized.
 * @release: a gadget release function.
 */
void usb_initialize_gadget(struct device *parent, struct usb_gadget *gadget,
		void (*release)(struct device *dev))
{
	INIT_WORK(&gadget->work, usb_gadget_state_work);
	gadget->dev.parent = parent;

	if (release)
		gadget->dev.release = release;
	else
		gadget->dev.release = usb_udc_nop_release;

	device_initialize(&gadget->dev);
	gadget->dev.bus = &gadget_bus_type;
}
EXPORT_SYMBOL_GPL(usb_initialize_gadget);

/**
 * usb_add_gadget - adds a new gadget to the udc class driver list
 * @gadget: the gadget to be added to the list.
 *
 * Returns zero on success, negative errno otherwise.
 * Does not do a final usb_put_gadget() if an error occurs.
 */
int usb_add_gadget(struct usb_gadget *gadget)
{
	struct usb_udc		*udc;
	int			ret = -ENOMEM;

	udc = kzalloc(sizeof(*udc), GFP_KERNEL);
	if (!udc)
		goto error;

	device_initialize(&udc->dev);
	udc->dev.release = usb_udc_release;
	udc->dev.class = &udc_class;
	udc->dev.groups = usb_udc_attr_groups;
	udc->dev.parent = gadget->dev.parent;
	ret = dev_set_name(&udc->dev, "%s",
			kobject_name(&gadget->dev.parent->kobj));
	if (ret)
		goto err_put_udc;

	udc->gadget = gadget;
	gadget->udc = udc;
	mutex_init(&udc->connect_lock);

	udc->started = false;

	mutex_lock(&udc_lock);
	list_add_tail(&udc->list, &udc_list);
	mutex_unlock(&udc_lock);
	INIT_WORK(&udc->vbus_work, vbus_event_work);

	ret = device_add(&udc->dev);
	if (ret)
		goto err_unlist_udc;

	usb_gadget_set_state(gadget, USB_STATE_NOTATTACHED);
	udc->vbus = true;

	ret = ida_alloc(&gadget_id_numbers, GFP_KERNEL);
	if (ret < 0)
		goto err_del_udc;
	gadget->id_number = ret;
	dev_set_name(&gadget->dev, "gadget.%d", ret);

	ret = device_add(&gadget->dev);
	if (ret)
		goto err_free_id;

	return 0;

 err_free_id:
	ida_free(&gadget_id_numbers, gadget->id_number);

 err_del_udc:
	flush_work(&gadget->work);
	device_del(&udc->dev);

 err_unlist_udc:
	mutex_lock(&udc_lock);
	list_del(&udc->list);
	mutex_unlock(&udc_lock);

 err_put_udc:
	put_device(&udc->dev);

 error:
	return ret;
}
EXPORT_SYMBOL_GPL(usb_add_gadget);

/**
 * usb_add_gadget_udc_release - adds a new gadget to the udc class driver list
 * @parent: the parent device to this udc. Usually the controller driver's
 * device.
 * @gadget: the gadget to be added to the list.
 * @release: a gadget release function.
 *
 * Returns zero on success, negative errno otherwise.
 * Calls the gadget release function in the latter case.
 */
int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
		void (*release)(struct device *dev))
{
	int	ret;

	usb_initialize_gadget(parent, gadget, release);
	ret = usb_add_gadget(gadget);
	if (ret)
		usb_put_gadget(gadget);
	return ret;
}
EXPORT_SYMBOL_GPL(usb_add_gadget_udc_release);

/**
 * usb_get_gadget_udc_name - get the name of the first UDC controller
 * This functions returns the name of the first UDC controller in the system.
 * Please note that this interface is usefull only for legacy drivers which
 * assume that there is only one UDC controller in the system and they need to
 * get its name before initialization. There is no guarantee that the UDC
 * of the returned name will be still available, when gadget driver registers
 * itself.
 *
 * Returns pointer to string with UDC controller name on success, NULL
 * otherwise. Caller should kfree() returned string.
 */
char *usb_get_gadget_udc_name(void)
{
	struct usb_udc *udc;
	char *name = NULL;

	/* For now we take the first available UDC */
	mutex_lock(&udc_lock);
	list_for_each_entry(udc, &udc_list, list) {
		if (!udc->driver) {
			name = kstrdup(udc->gadget->name, GFP_KERNEL);
			break;
		}
	}
	mutex_unlock(&udc_lock);
	return name;
}
EXPORT_SYMBOL_GPL(usb_get_gadget_udc_name);

/**
 * usb_add_gadget_udc - adds a new gadget to the udc class driver list
 * @parent: the parent device to this udc. Usually the controller
 * driver's device.
 * @gadget: the gadget to be added to the list
 *
 * Returns zero on success, negative errno otherwise.
 */
int usb_add_gadget_udc(struct device *parent, struct usb_gadget *gadget)
{
	return usb_add_gadget_udc_release(parent, gadget, NULL);
}
EXPORT_SYMBOL_GPL(usb_add_gadget_udc);

/**
 * usb_del_gadget - deletes a gadget and unregisters its udc
 * @gadget: the gadget to be deleted.
 *
 * This will unbind @gadget, if it is bound.
 * It will not do a final usb_put_gadget().
 */
void usb_del_gadget(struct usb_gadget *gadget)
{
	struct usb_udc *udc = gadget->udc;

	if (!udc)
		return;

	dev_vdbg(gadget->dev.parent, "unregistering gadget\n");

	mutex_lock(&udc_lock);
	list_del(&udc->list);
	mutex_unlock(&udc_lock);

	kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
	flush_work(&gadget->work);
	device_del(&gadget->dev);
	ida_free(&gadget_id_numbers, gadget->id_number);
	cancel_work_sync(&udc->vbus_work);
	device_unregister(&udc->dev);
}
EXPORT_SYMBOL_GPL(usb_del_gadget);

/**
 * usb_del_gadget_udc - unregisters a gadget
 * @gadget: the gadget to be unregistered.
 *
 * Calls usb_del_gadget() and does a final usb_put_gadget().
 */
void usb_del_gadget_udc(struct usb_gadget *gadget)
{
	usb_del_gadget(gadget);
	usb_put_gadget(gadget);
}
EXPORT_SYMBOL_GPL(usb_del_gadget_udc);

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

static int gadget_match_driver(struct device *dev, struct device_driver *drv)
{
	struct usb_gadget *gadget = dev_to_usb_gadget(dev);
	struct usb_udc *udc = gadget->udc;
	struct usb_gadget_driver *driver = container_of(drv,
			struct usb_gadget_driver, driver);

	/* If the driver specifies a udc_name, it must match the UDC's name */
	if (driver->udc_name &&
			strcmp(driver->udc_name, dev_name(&udc->dev)) != 0)
		return 0;

	/* If the driver is already bound to a gadget, it doesn't match */
	if (driver->is_bound)
		return 0;

	/* Otherwise any gadget driver matches any UDC */
	return 1;
}

static int gadget_bind_driver(struct device *dev)
{
	struct usb_gadget *gadget = dev_to_usb_gadget(dev);
	struct usb_udc *udc = gadget->udc;
	struct usb_gadget_driver *driver = container_of(dev->driver,
			struct usb_gadget_driver, driver);
	int ret = 0;

	mutex_lock(&udc_lock);
	if (driver->is_bound) {
		mutex_unlock(&udc_lock);
		return -ENXIO;		/* Driver binds to only one gadget */
	}
	driver->is_bound = true;
	udc->driver = driver;
	mutex_unlock(&udc_lock);

	dev_dbg(&udc->dev, "binding gadget driver [%s]\n", driver->function);

	usb_gadget_udc_set_speed(udc, driver->max_speed);

	ret = driver->bind(udc->gadget, driver);
	if (ret)
		goto err_bind;

	mutex_lock(&udc->connect_lock);
	ret = usb_gadget_udc_start_locked(udc);
	if (ret) {
		mutex_unlock(&udc->connect_lock);
		goto err_start;
	}
	usb_gadget_enable_async_callbacks(udc);
	udc->allow_connect = true;
	usb_udc_connect_control_locked(udc);
	mutex_unlock(&udc->connect_lock);

	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
	return 0;

 err_start:
	driver->unbind(udc->gadget);

 err_bind:
	if (ret != -EISNAM)
		dev_err(&udc->dev, "failed to start %s: %d\n",
			driver->function, ret);

	mutex_lock(&udc_lock);
	udc->driver = NULL;
	driver->is_bound = false;
	mutex_unlock(&udc_lock);

	return ret;
}

static void gadget_unbind_driver(struct device *dev)
{
	struct usb_gadget *gadget = dev_to_usb_gadget(dev);
	struct usb_udc *udc = gadget->udc;
	struct usb_gadget_driver *driver = udc->driver;

	dev_dbg(&udc->dev, "unbinding gadget driver [%s]\n", driver->function);

	udc->allow_connect = false;
	cancel_work_sync(&udc->vbus_work);
	mutex_lock(&udc->connect_lock);
	usb_gadget_disconnect_locked(gadget);
	usb_gadget_disable_async_callbacks(udc);
	if (gadget->irq)
		synchronize_irq(gadget->irq);
	mutex_unlock(&udc->connect_lock);

	udc->driver->unbind(gadget);

	mutex_lock(&udc->connect_lock);
	usb_gadget_udc_stop_locked(udc);
	mutex_unlock(&udc->connect_lock);

	mutex_lock(&udc_lock);
	driver->is_bound = false;
	udc->driver = NULL;
	mutex_unlock(&udc_lock);

	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
}

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

int usb_gadget_register_driver_owner(struct usb_gadget_driver *driver,
		struct module *owner, const char *mod_name)
{
	int ret;

	if (!driver || !driver->bind || !driver->setup)
		return -EINVAL;

	driver->driver.bus = &gadget_bus_type;
	driver->driver.owner = owner;
	driver->driver.mod_name = mod_name;
	ret = driver_register(&driver->driver);
	if (ret) {
		pr_warn("%s: driver registration failed: %d\n",
				driver->function, ret);
		return ret;
	}

	mutex_lock(&udc_lock);
	if (!driver->is_bound) {
		if (driver->match_existing_only) {
			pr_warn("%s: couldn't find an available UDC or it's busy\n",
					driver->function);
			ret = -EBUSY;
		} else {
			pr_info("%s: couldn't find an available UDC\n",
					driver->function);
			ret = 0;
		}
	}
	mutex_unlock(&udc_lock);

	if (ret)
		driver_unregister(&driver->driver);
	return ret;
}
EXPORT_SYMBOL_GPL(usb_gadget_register_driver_owner);

int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
{
	if (!driver || !driver->unbind)
		return -EINVAL;

	driver_unregister(&driver->driver);
	return 0;
}
EXPORT_SYMBOL_GPL(usb_gadget_unregister_driver);

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

static ssize_t srp_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t n)
{
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);

	if (sysfs_streq(buf, "1"))
		usb_gadget_wakeup(udc->gadget);

	return n;
}
static DEVICE_ATTR_WO(srp);

static ssize_t soft_connect_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t n)
{
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);
	ssize_t			ret;

	device_lock(&udc->gadget->dev);
	if (!udc->driver) {
		dev_err(dev, "soft-connect without a gadget driver\n");
		ret = -EOPNOTSUPP;
		goto out;
	}

	if (sysfs_streq(buf, "connect")) {
		mutex_lock(&udc->connect_lock);
		usb_gadget_udc_start_locked(udc);
		usb_gadget_connect_locked(udc->gadget);
		mutex_unlock(&udc->connect_lock);
	} else if (sysfs_streq(buf, "disconnect")) {
		mutex_lock(&udc->connect_lock);
		usb_gadget_disconnect_locked(udc->gadget);
		usb_gadget_udc_stop_locked(udc);
		mutex_unlock(&udc->connect_lock);
	} else {
		dev_err(dev, "unsupported command '%s'\n", buf);
		ret = -EINVAL;
		goto out;
	}

	ret = n;
out:
	device_unlock(&udc->gadget->dev);
	return ret;
}
static DEVICE_ATTR_WO(soft_connect);

static ssize_t state_show(struct device *dev, struct device_attribute *attr,
			  char *buf)
{
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);
	struct usb_gadget	*gadget = udc->gadget;

	return sprintf(buf, "%s\n", usb_state_string(gadget->state));
}
static DEVICE_ATTR_RO(state);

static ssize_t function_show(struct device *dev, struct device_attribute *attr,
			     char *buf)
{
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);
	struct usb_gadget_driver *drv;
	int			rc = 0;

	mutex_lock(&udc_lock);
	drv = udc->driver;
	if (drv && drv->function)
		rc = scnprintf(buf, PAGE_SIZE, "%s\n", drv->function);
	mutex_unlock(&udc_lock);
	return rc;
}
static DEVICE_ATTR_RO(function);

#define USB_UDC_SPEED_ATTR(name, param)					\
ssize_t name##_show(struct device *dev,					\
		struct device_attribute *attr, char *buf)		\
{									\
	struct usb_udc *udc = container_of(dev, struct usb_udc, dev);	\
	return scnprintf(buf, PAGE_SIZE, "%s\n",			\
			usb_speed_string(udc->gadget->param));		\
}									\
static DEVICE_ATTR_RO(name)

static USB_UDC_SPEED_ATTR(current_speed, speed);
static USB_UDC_SPEED_ATTR(maximum_speed, max_speed);

#define USB_UDC_ATTR(name)					\
ssize_t name##_show(struct device *dev,				\
		struct device_attribute *attr, char *buf)	\
{								\
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev); \
	struct usb_gadget	*gadget = udc->gadget;		\
								\
	return scnprintf(buf, PAGE_SIZE, "%d\n", gadget->name);	\
}								\
static DEVICE_ATTR_RO(name)

static USB_UDC_ATTR(is_otg);
static USB_UDC_ATTR(is_a_peripheral);
static USB_UDC_ATTR(b_hnp_enable);
static USB_UDC_ATTR(a_hnp_support);
static USB_UDC_ATTR(a_alt_hnp_support);
static USB_UDC_ATTR(is_selfpowered);

static struct attribute *usb_udc_attrs[] = {
	&dev_attr_srp.attr,
	&dev_attr_soft_connect.attr,
	&dev_attr_state.attr,
	&dev_attr_function.attr,
	&dev_attr_current_speed.attr,
	&dev_attr_maximum_speed.attr,

	&dev_attr_is_otg.attr,
	&dev_attr_is_a_peripheral.attr,
	&dev_attr_b_hnp_enable.attr,
	&dev_attr_a_hnp_support.attr,
	&dev_attr_a_alt_hnp_support.attr,
	&dev_attr_is_selfpowered.attr,
	NULL,
};

static const struct attribute_group usb_udc_attr_group = {
	.attrs = usb_udc_attrs,
};

static const struct attribute_group *usb_udc_attr_groups[] = {
	&usb_udc_attr_group,
	NULL,
};

static int usb_udc_uevent(const struct device *dev, struct kobj_uevent_env *env)
{
	const struct usb_udc	*udc = container_of(dev, struct usb_udc, dev);
	int			ret;

	ret = add_uevent_var(env, "USB_UDC_NAME=%s", udc->gadget->name);
	if (ret) {
		dev_err(dev, "failed to add uevent USB_UDC_NAME\n");
		return ret;
	}

	mutex_lock(&udc_lock);
	if (udc->driver)
		ret = add_uevent_var(env, "USB_UDC_DRIVER=%s",
				udc->driver->function);
	mutex_unlock(&udc_lock);
	if (ret) {
		dev_err(dev, "failed to add uevent USB_UDC_DRIVER\n");
		return ret;
	}

	return 0;
}

static const struct class udc_class = {
	.name		= "udc",
	.dev_uevent	= usb_udc_uevent,
};

static const struct bus_type gadget_bus_type = {
	.name = "gadget",
	.probe = gadget_bind_driver,
	.remove = gadget_unbind_driver,
	.match = gadget_match_driver,
};

static int __init usb_udc_init(void)
{
	int rc;

	rc = class_register(&udc_class);
	if (rc)
		return rc;

	rc = bus_register(&gadget_bus_type);
	if (rc)
		class_unregister(&udc_class);
	return rc;
}
subsys_initcall(usb_udc_init);

static void __exit usb_udc_exit(void)
{
	bus_unregister(&gadget_bus_type);
	class_unregister(&udc_class);
}
module_exit(usb_udc_exit);

MODULE_DESCRIPTION("UDC Framework");
MODULE_AUTHOR("Felipe Balbi <balbi@ti.com>");
MODULE_LICENSE("GPL v2");