USB: move <linux/usb_gadget.h> to <linux/usb/gadget.h>

Move <linux/usb_gadget.h> to <linux/usb/gadget.h>, reducing
some of the clutter in the main include directory.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 866 insertions, 0 deletions

diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
new file mode 100644
index 000000000000..46705e91573d
--- /dev/null
+++ b/include/linux/usb/gadget.h
@@ -0,0 +1,866 @@
+/*
+ * <linux/usb/gadget.h>
+ *
+ * We call the USB code inside a Linux-based peripheral device a "gadget"
+ * driver, except for the hardware-specific bus glue.  One USB host can
+ * master many USB gadgets, but the gadgets are only slaved to one host.
+ *
+ *
+ * (C) Copyright 2002-2004 by David Brownell
+ * All Rights Reserved.
+ *
+ * This software is licensed under the GNU GPL version 2.
+ */
+
+#ifndef __LINUX_USB_GADGET_H
+#define __LINUX_USB_GADGET_H
+
+#ifdef __KERNEL__
+
+struct usb_ep;
+
+/**
+ * struct usb_request - describes one i/o request
+ * @buf: Buffer used for data.  Always provide this; some controllers
+ *      only use PIO, or don't use DMA for some endpoints.
+ * @dma: DMA address corresponding to 'buf'.  If you don't set this
+ *      field, and the usb controller needs one, it is responsible
+ *      for mapping and unmapping the buffer.
+ * @length: Length of that data
+ * @no_interrupt: If true, hints that no completion irq is needed.
+ *      Helpful sometimes with deep request queues that are handled
+ *      directly by DMA controllers.
+ * @zero: If true, when writing data, makes the last packet be "short"
+ *     by adding a zero length packet as needed;
+ * @short_not_ok: When reading data, makes short packets be
+ *     treated as errors (queue stops advancing till cleanup).
+ * @complete: Function called when request completes, so this request and
+ *      its buffer may be re-used.
+ *      Reads terminate with a short packet, or when the buffer fills,
+ *      whichever comes first.  When writes terminate, some data bytes
+ *      will usually still be in flight (often in a hardware fifo).
+ *      Errors (for reads or writes) stop the queue from advancing
+ *      until the completion function returns, so that any transfers
+ *      invalidated by the error may first be dequeued.
+ * @context: For use by the completion callback
+ * @list: For use by the gadget driver.
+ * @status: Reports completion code, zero or a negative errno.
+ *      Normally, faults block the transfer queue from advancing until
+ *      the completion callback returns.
+ *      Code "-ESHUTDOWN" indicates completion caused by device disconnect,
+ *      or when the driver disabled the endpoint.
+ * @actual: Reports bytes transferred to/from the buffer.  For reads (OUT
+ *      transfers) this may be less than the requested length.  If the
+ *      short_not_ok flag is set, short reads are treated as errors
+ *      even when status otherwise indicates successful completion.
+ *      Note that for writes (IN transfers) some data bytes may still
+ *      reside in a device-side FIFO when the request is reported as
+ *      complete.
+ *
+ * These are allocated/freed through the endpoint they're used with.  The
+ * hardware's driver can add extra per-request data to the memory it returns,
+ * which often avoids separate memory allocations (potential failures),
+ * later when the request is queued.
+ *
+ * Request flags affect request handling, such as whether a zero length
+ * packet is written (the "zero" flag), whether a short read should be
+ * treated as an error (blocking request queue advance, the "short_not_ok"
+ * flag), or hinting that an interrupt is not required (the "no_interrupt"
+ * flag, for use with deep request queues).
+ *
+ * Bulk endpoints can use any size buffers, and can also be used for interrupt
+ * transfers. interrupt-only endpoints can be much less functional.
+ */
+        // NOTE this is analagous to 'struct urb' on the host side,
+        // except that it's thinner and promotes more pre-allocation.
+
+struct usb_request {
+        void                    *buf;
+        unsigned                length;
+        dma_addr_t              dma;
+
+        unsigned                no_interrupt:1;
+        unsigned                zero:1;
+        unsigned                short_not_ok:1;
+
+        void                    (*complete)(struct usb_ep *ep,
+                                        struct usb_request *req);
+        void                    *context;
+        struct list_head        list;
+
+        int                     status;
+        unsigned                actual;
+};
+
+/*-------------------------------------------------------------------------*/
+
+/* endpoint-specific parts of the api to the usb controller hardware.
+ * unlike the urb model, (de)multiplexing layers are not required.
+ * (so this api could slash overhead if used on the host side...)
+ *
+ * note that device side usb controllers commonly differ in how many
+ * endpoints they support, as well as their capabilities.
+ */
+struct usb_ep_ops {
+        int (*enable) (struct usb_ep *ep,
+                const struct usb_endpoint_descriptor *desc);
+        int (*disable) (struct usb_ep *ep);
+
+        struct usb_request *(*alloc_request) (struct usb_ep *ep,
+                gfp_t gfp_flags);
+        void (*free_request) (struct usb_ep *ep, struct usb_request *req);
+
+        int (*queue) (struct usb_ep *ep, struct usb_request *req,
+                gfp_t gfp_flags);
+        int (*dequeue) (struct usb_ep *ep, struct usb_request *req);
+
+        int (*set_halt) (struct usb_ep *ep, int value);
+        int (*fifo_status) (struct usb_ep *ep);
+        void (*fifo_flush) (struct usb_ep *ep);
+};
+
+/**
+ * struct usb_ep - device side representation of USB endpoint
+ * @name:identifier for the endpoint, such as "ep-a" or "ep9in-bulk"
+ * @ops: Function pointers used to access hardware-specific operations.
+ * @ep_list:the gadget's ep_list holds all of its endpoints
+ * @maxpacket:The maximum packet size used on this endpoint.  The initial
+ *      value can sometimes be reduced (hardware allowing), according to
+ *      the endpoint descriptor used to configure the endpoint.
+ * @driver_data:for use by the gadget driver.  all other fields are
+ *      read-only to gadget drivers.
+ *
+ * the bus controller driver lists all the general purpose endpoints in
+ * gadget->ep_list.  the control endpoint (gadget->ep0) is not in that list,
+ * and is accessed only in response to a driver setup() callback.
+ */
+struct usb_ep {
+        void                    *driver_data;
+
+        const char              *name;
+        const struct usb_ep_ops *ops;
+        struct list_head        ep_list;
+        unsigned                maxpacket:16;
+};
+
+/*-------------------------------------------------------------------------*/
+
+/**
+ * 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.
+ * @desc:descriptor for desired behavior.  caller guarantees this pointer
+ *      remains valid until the endpoint is disabled; the data byte order
+ *      is little-endian (usb-standard).
+ *
+ * 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 master".)
+ *
+ * returns zero, or a negative error code.
+ */
+static inline int
+usb_ep_enable (struct usb_ep *ep, const struct usb_endpoint_descriptor *desc)
+{
+        return ep->ops->enable (ep, desc);
+}
+
+/**
+ * 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.
+ *
+ * returns zero, or a negative error code.
+ */
+static inline int
+usb_ep_disable (struct usb_ep *ep)
+{
+        return ep->ops->disable (ep);
+}
+
+/**
+ * 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.
+ */
+static inline struct usb_request *
+usb_ep_alloc_request (struct usb_ep *ep, gfp_t gfp_flags)
+{
+        return ep->ops->alloc_request (ep, gfp_flags);
+}
+
+/**
+ * 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).
+ */
+static inline void
+usb_ep_free_request (struct usb_ep *ep, struct usb_request *req)
+{
+        ep->ops->free_request (ep, req);
+}
+
+/**
+ * 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 transfering 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.
+ *
+ * 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.
+ *
+ * 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.
+ */
+static inline int
+usb_ep_queue (struct usb_ep *ep, struct usb_request *req, gfp_t gfp_flags)
+{
+        return ep->ops->queue (ep, req, gfp_flags);
+}
+
+/**
+ * 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 its
+ * completion routine is called (with status -ECONNRESET); else a negative
+ * error code is returned.
+ *
+ * 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).
+ */
+static inline int usb_ep_dequeue (struct usb_ep *ep, struct usb_request *req)
+{
+        return ep->ops->dequeue (ep, req);
+}
+
+/**
+ * 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.
+ *
+ * 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.
+ */
+static inline int
+usb_ep_set_halt (struct usb_ep *ep)
+{
+        return ep->ops->set_halt (ep, 1);
+}
+
+/**
+ * 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.
+ *
+ * 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.
+ */
+static inline int
+usb_ep_clear_halt (struct usb_ep *ep)
+{
+        return ep->ops->set_halt (ep, 0);
+}
+
+/**
+ * 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 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.
+ */
+static inline int
+usb_ep_fifo_status (struct usb_ep *ep)
+{
+        if (ep->ops->fifo_status)
+                return ep->ops->fifo_status (ep);
+        else
+                return -EOPNOTSUPP;
+}
+
+/**
+ * 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.
+ */
+static inline void
+usb_ep_fifo_flush (struct usb_ep *ep)
+{
+        if (ep->ops->fifo_flush)
+                ep->ops->fifo_flush (ep);
+}
+
+
+/*-------------------------------------------------------------------------*/
+
+struct usb_gadget;
+
+/* the rest of the api to the controller hardware: device operations,
+ * which don't involve endpoints (or i/o).
+ */
+struct usb_gadget_ops {
+        int     (*get_frame)(struct usb_gadget *);
+        int     (*wakeup)(struct usb_gadget *);
+        int     (*set_selfpowered) (struct usb_gadget *, int is_selfpowered);
+        int     (*vbus_session) (struct usb_gadget *, int is_active);
+        int     (*vbus_draw) (struct usb_gadget *, unsigned mA);
+        int     (*pullup) (struct usb_gadget *, int is_on);
+        int     (*ioctl)(struct usb_gadget *,
+                                unsigned code, unsigned long param);
+};
+
+/**
+ * struct usb_gadget - represents a usb slave device
+ * @ops: Function pointers used to access hardware-specific operations.
+ * @ep0: Endpoint zero, used when reading or writing responses to
+ *      driver setup() requests
+ * @ep_list: List of other endpoints supported by the device.
+ * @speed: Speed of current connection to USB host.
+ * @is_dualspeed: True if the controller supports both high and full speed
+ *      operation.  If it does, the gadget driver must also support both.
+ * @is_otg: True if the USB device port uses a Mini-AB jack, so that the
+ *      gadget driver must provide a USB OTG descriptor.
+ * @is_a_peripheral: False unless is_otg, the "A" end of a USB cable
+ *      is in the Mini-AB jack, and HNP has been used to switch roles
+ *      so that the "A" device currently acts as A-Peripheral, not A-Host.
+ * @a_hnp_support: OTG device feature flag, indicating that the A-Host
+ *      supports HNP at this port.
+ * @a_alt_hnp_support: OTG device feature flag, indicating that the A-Host
+ *      only supports HNP on a different root port.
+ * @b_hnp_enable: OTG device feature flag, indicating that the A-Host
+ *      enabled HNP support.
+ * @name: Identifies the controller hardware type.  Used in diagnostics
+ *      and sometimes configuration.
+ * @dev: Driver model state for this abstract device.
+ *
+ * Gadgets have a mostly-portable "gadget driver" implementing device
+ * functions, handling all usb configurations and interfaces.  Gadget
+ * drivers talk to hardware-specific code indirectly, through ops vectors.
+ * That insulates the gadget driver from hardware details, and packages
+ * the hardware endpoints through generic i/o queues.  The "usb_gadget"
+ * and "usb_ep" interfaces provide that insulation from the hardware.
+ *
+ * Except for the driver data, all fields in this structure are
+ * read-only to the gadget driver.  That driver data is part of the
+ * "driver model" infrastructure in 2.6 (and later) kernels, and for
+ * earlier systems is grouped in a similar structure that's not known
+ * to the rest of the kernel.
+ *
+ * Values of the three OTG device feature flags are updated before the
+ * setup() call corresponding to USB_REQ_SET_CONFIGURATION, and before
+ * driver suspend() calls.  They are valid only when is_otg, and when the
+ * device is acting as a B-Peripheral (so is_a_peripheral is false).
+ */
+struct usb_gadget {
+        /* readonly to gadget driver */
+        const struct usb_gadget_ops     *ops;
+        struct usb_ep                   *ep0;
+        struct list_head                ep_list;        /* of usb_ep */
+        enum usb_device_speed           speed;
+        unsigned                        is_dualspeed:1;
+        unsigned                        is_otg:1;
+        unsigned                        is_a_peripheral:1;
+        unsigned                        b_hnp_enable:1;
+        unsigned                        a_hnp_support:1;
+        unsigned                        a_alt_hnp_support:1;
+        const char                      *name;
+        struct device                   dev;
+};
+
+static inline void set_gadget_data (struct usb_gadget *gadget, void *data)
+        { dev_set_drvdata (&gadget->dev, data); }
+static inline void *get_gadget_data (struct usb_gadget *gadget)
+        { return dev_get_drvdata (&gadget->dev); }
+
+/* iterates the non-control endpoints; 'tmp' is a struct usb_ep pointer */
+#define gadget_for_each_ep(tmp,gadget) \
+        list_for_each_entry(tmp, &(gadget)->ep_list, ep_list)
+
+
+/**
+ * gadget_is_dualspeed - return true iff the hardware handles high speed
+ * @gadget: controller that might support both high and full speeds
+ */
+static inline int gadget_is_dualspeed(struct usb_gadget *g)
+{
+#ifdef CONFIG_USB_GADGET_DUALSPEED
+        /* runtime test would check "g->is_dualspeed" ... that might be
+         * useful to work around hardware bugs, but is mostly pointless
+         */
+        return 1;
+#else
+        return 0;
+#endif
+}
+
+/**
+ * gadget_is_otg - return true iff the hardware is OTG-ready
+ * @gadget: controller that might have a Mini-AB connector
+ *
+ * This is a runtime test, since kernels with a USB-OTG stack sometimes
+ * run on boards which only have a Mini-B (or Mini-A) connector.
+ */
+static inline int gadget_is_otg(struct usb_gadget *g)
+{
+#ifdef CONFIG_USB_OTG
+        return g->is_otg;
+#else
+        return 0;
+#endif
+}
+
+
+/**
+ * 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.
+ */
+static inline int usb_gadget_frame_number (struct usb_gadget *gadget)
+{
+        return gadget->ops->get_frame (gadget);
+}
+
+/**
+ * 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.
+ */
+static inline int usb_gadget_wakeup (struct usb_gadget *gadget)
+{
+        if (!gadget->ops->wakeup)
+                return -EOPNOTSUPP;
+        return gadget->ops->wakeup (gadget);
+}
+
+/**
+ * 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.
+ */
+static inline int
+usb_gadget_set_selfpowered (struct usb_gadget *gadget)
+{
+        if (!gadget->ops->set_selfpowered)
+                return -EOPNOTSUPP;
+        return gadget->ops->set_selfpowered (gadget, 1);
+}
+
+/**
+ * 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.
+ */
+static inline int
+usb_gadget_clear_selfpowered (struct usb_gadget *gadget)
+{
+        if (!gadget->ops->set_selfpowered)
+                return -EOPNOTSUPP;
+        return gadget->ops->set_selfpowered (gadget, 0);
+}
+
+/**
+ * usb_gadget_vbus_connect - Notify controller that VBUS is powered
+ * @gadget:The device which now has VBUS power.
+ *
+ * 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.
+ */
+static inline int
+usb_gadget_vbus_connect(struct usb_gadget *gadget)
+{
+        if (!gadget->ops->vbus_session)
+                return -EOPNOTSUPP;
+        return gadget->ops->vbus_session (gadget, 1);
+}
+
+/**
+ * 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.
+ */
+static inline int
+usb_gadget_vbus_draw(struct usb_gadget *gadget, unsigned mA)
+{
+        if (!gadget->ops->vbus_draw)
+                return -EOPNOTSUPP;
+        return gadget->ops->vbus_draw (gadget, mA);
+}
+
+/**
+ * usb_gadget_vbus_disconnect - notify controller about VBUS session end
+ * @gadget:the device whose VBUS supply is being described
+ *
+ * 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.
+ */
+static inline int
+usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
+{
+        if (!gadget->ops->vbus_session)
+                return -EOPNOTSUPP;
+        return gadget->ops->vbus_session (gadget, 0);
+}
+
+/**
+ * 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).  This pullup is always enabled unless
+ * usb_gadget_disconnect() has been used to disable it.
+ *
+ * Returns zero on success, else negative errno.
+ */
+static inline int
+usb_gadget_connect (struct usb_gadget *gadget)
+{
+        if (!gadget->ops->pullup)
+                return -EOPNOTSUPP;
+        return gadget->ops->pullup (gadget, 1);
+}
+
+/**
+ * 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.
+ *
+ * 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_connect() is called.  For example, user mode components may
+ * need to be activated before the system can talk to hosts.
+ *
+ * Returns zero on success, else negative errno.
+ */
+static inline int
+usb_gadget_disconnect (struct usb_gadget *gadget)
+{
+        if (!gadget->ops->pullup)
+                return -EOPNOTSUPP;
+        return gadget->ops->pullup (gadget, 0);
+}
+
+
+
+/*-------------------------------------------------------------------------*/
+
+/**
+ * struct usb_gadget_driver - driver for usb 'slave' devices
+ * @function: String describing the gadget's function
+ * @speed: Highest speed the driver handles.
+ * @bind: Invoked when the driver is bound to a gadget, usually
+ *      after registering the driver.
+ *      At that point, ep0 is fully initialized, and ep_list holds
+ *      the currently-available endpoints.
+ *      Called in a context that permits sleeping.
+ * @setup: Invoked for ep0 control requests that aren't handled by
+ *      the hardware level driver. Most calls must be handled by
+ *      the gadget driver, including descriptor and configuration
+ *      management.  The 16 bit members of the setup data are in
+ *      USB byte order. Called in_interrupt; this may not sleep.  Driver
+ *      queues a response to ep0, or returns negative to stall.
+ * @disconnect: Invoked after all transfers have been stopped,
+ *      when the host is disconnected.  May be called in_interrupt; this
+ *      may not sleep.  Some devices can't detect disconnect, so this might
+ *      not be called except as part of controller shutdown.
+ * @unbind: Invoked when the driver is unbound from a gadget,
+ *      usually from rmmod (after a disconnect is reported).
+ *      Called in a context that permits sleeping.
+ * @suspend: Invoked on USB suspend.  May be called in_interrupt.
+ * @resume: Invoked on USB resume.  May be called in_interrupt.
+ * @driver: Driver model state for this driver.
+ *
+ * Devices are disabled till a gadget driver successfully bind()s, which
+ * means the driver will handle setup() requests needed to enumerate (and
+ * meet "chapter 9" requirements) then do some useful work.
+ *
+ * If gadget->is_otg is true, the gadget driver must provide an OTG
+ * descriptor during enumeration, or else fail the bind() call.  In such
+ * cases, no USB traffic may flow until both bind() returns without
+ * having called usb_gadget_disconnect(), and the USB host stack has
+ * initialized.
+ *
+ * Drivers use hardware-specific knowledge to configure the usb hardware.
+ * endpoint addressing is only one of several hardware characteristics that
+ * are in descriptors the ep0 implementation returns from setup() calls.
+ *
+ * Except for ep0 implementation, most driver code shouldn't need change to
+ * run on top of different usb controllers.  It'll use endpoints set up by
+ * that ep0 implementation.
+ *
+ * The usb controller driver handles a few standard usb requests.  Those
+ * include set_address, and feature flags for devices, interfaces, and
+ * endpoints (the get_status, set_feature, and clear_feature requests).
+ *
+ * Accordingly, the driver's setup() callback must always implement all
+ * get_descriptor requests, returning at least a device descriptor and
+ * a configuration descriptor.  Drivers must make sure the endpoint
+ * descriptors match any hardware constraints. Some hardware also constrains
+ * other descriptors. (The pxa250 allows only configurations 1, 2, or 3).
+ *
+ * The driver's setup() callback must also implement set_configuration,
+ * and should also implement set_interface, get_configuration, and
+ * get_interface.  Setting a configuration (or interface) is where
+ * endpoints should be activated or (config 0) shut down.
+ *
+ * (Note that only the default control endpoint is supported.  Neither
+ * hosts nor devices generally support control traffic except to ep0.)
+ *
+ * Most devices will ignore USB suspend/resume operations, and so will
+ * not provide those callbacks.  However, some may need to change modes
+ * when the host is not longer directing those activities.  For example,
+ * local controls (buttons, dials, etc) may need to be re-enabled since
+ * the (remote) host can't do that any longer; or an error state might
+ * be cleared, to make the device behave identically whether or not
+ * power is maintained.
+ */
+struct usb_gadget_driver {
+        char                    *function;
+        enum usb_device_speed   speed;
+        int                     (*bind)(struct usb_gadget *);
+        void                    (*unbind)(struct usb_gadget *);
+        int                     (*setup)(struct usb_gadget *,
+                                        const struct usb_ctrlrequest *);
+        void                    (*disconnect)(struct usb_gadget *);
+        void                    (*suspend)(struct usb_gadget *);
+        void                    (*resume)(struct usb_gadget *);
+
+        // FIXME support safe rmmod
+        struct device_driver    driver;
+};
+
+
+
+/*-------------------------------------------------------------------------*/
+
+/* driver modules register and unregister, as usual.
+ * these calls must be made in a context that can sleep.
+ *
+ * these will usually be implemented directly by the hardware-dependent
+ * usb bus interface driver, which will only support a single driver.
+ */
+
+/**
+ * usb_gadget_register_driver - register a gadget driver
+ * @driver:the driver being registered
+ *
+ * Call this in your gadget driver's module initialization function,
+ * to tell the underlying usb controller driver about your driver.
+ * The driver's bind() function will be called to bind it to a
+ * gadget before this registration call returns.  It's expected that
+ * the bind() functions will be in init sections.
+ * This function must be called in a context that can sleep.
+ */
+int usb_gadget_register_driver (struct usb_gadget_driver *driver);
+
+/**
+ * usb_gadget_unregister_driver - unregister a gadget driver
+ * @driver:the driver being unregistered
+ *
+ * Call this in your gadget driver's module cleanup function,
+ * to tell the underlying usb controller that your driver is
+ * going away.  If the controller is connected to a USB host,
+ * it will first disconnect().  The driver is also requested
+ * to unbind() and clean up any device state, before this procedure
+ * finally returns.  It's expected that the unbind() functions
+ * will in in exit sections, so may not be linked in some kernels.
+ * This function must be called in a context that can sleep.
+ */
+int usb_gadget_unregister_driver (struct usb_gadget_driver *driver);
+
+/*-------------------------------------------------------------------------*/
+
+/* utility to simplify dealing with string descriptors */
+
+/**
+ * struct usb_string - wraps a C string and its USB id
+ * @id:the (nonzero) ID for this string
+ * @s:the string, in UTF-8 encoding
+ *
+ * If you're using usb_gadget_get_string(), use this to wrap a string
+ * together with its ID.
+ */
+struct usb_string {
+        u8                      id;
+        const char              *s;
+};
+
+/**
+ * struct usb_gadget_strings - a set of USB strings in a given language
+ * @language:identifies the strings' language (0x0409 for en-us)
+ * @strings:array of strings with their ids
+ *
+ * If you're using usb_gadget_get_string(), use this to wrap all the
+ * strings for a given language.
+ */
+struct usb_gadget_strings {
+        u16                     language;       /* 0x0409 for en-us */
+        struct usb_string       *strings;
+};
+
+/* put descriptor for string with that id into buf (buflen >= 256) */
+int usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf);
+
+/*-------------------------------------------------------------------------*/
+
+/* utility to simplify managing config descriptors */
+
+/* write vector of descriptors into buffer */
+int usb_descriptor_fillbuf(void *, unsigned,
+                const struct usb_descriptor_header **);
+
+/* build config descriptor from single descriptor vector */
+int usb_gadget_config_buf(const struct usb_config_descriptor *config,
+        void *buf, unsigned buflen, const struct usb_descriptor_header **desc);
+
+/*-------------------------------------------------------------------------*/
+
+/* utility wrapping a simple endpoint selection policy */
+
+extern struct usb_ep *usb_ep_autoconfig (struct usb_gadget *,
+                        struct usb_endpoint_descriptor *) __devinit;
+
+extern void usb_ep_autoconfig_reset (struct usb_gadget *) __devinit;
+
+#endif  /* __KERNEL__ */
+
+#endif  /* __LINUX_USB_GADGET_H */