usb_gadget.h

linux得一些常用命令,以及linux环境下的c编程

/*
 * <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,
		int gfp_flags);
	void (*free_request) (struct usb_ep *ep, struct usb_request *req);

	void *(*alloc_buffer) (struct usb_ep *ep, unsigned bytes,
		dma_addr_t *dma, int gfp_flags);
	void (*free_buffer) (struct usb_ep *ep, void *buf, dma_addr_t dma,
		unsigned bytes);
	// NOTE:  on 2.6, drivers may also use dma_map() and
	// dma_sync_single_*() to directly manage dma overhead. 

	int (*queue) (struct usb_ep *ep, struct usb_request *req,
		int 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, int 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_alloc_buffer - allocate an I/O buffer
 * @ep:the endpoint associated with the buffer
 * @len:length of the desired buffer
 * @dma:pointer to the buffer's DMA address; must be valid
 * @gfp_flags:GFP_* flags to use
 *
 * Returns a new buffer, or null if one could not be allocated.
 * The buffer is suitably aligned for dma, if that endpoint uses DMA,
 * and the caller won't have to care about dma-inconsistency
 * or any hidden "bounce buffer" mechanism.  No additional per-request
 * DMA mapping will be required for such buffers.
 * Free it later with usb_ep_free_buffer().
 *
 * You don't need to use this call to allocate I/O buffers unless you
 * want to make sure drivers don't incur costs for such "bounce buffer"
 * copies or per-request DMA mappings.
 */
static inline void *
usb_ep_alloc_buffer (struct usb_ep *ep, unsigned len, dma_addr_t *dma,
	int gfp_flags)
{
	return ep->ops->alloc_buffer (ep, len, dma, gfp_flags);
}

/**
 * usb_ep_free_buffer - frees an i/o buffer
 * @ep:the endpoint associated with the buffer
 * @buf:CPU view address of the buffer
 * @dma:the buffer's DMA address
 * @len:length of the buffer
 *
 * reverses the effect of usb_ep_alloc_buffer().
 * caller guarantees the buffer will no longer be accessed
 */
static inline void
usb_ep_free_buffer (struct usb_ep *ep, void *buf, dma_addr_t dma, unsigned len)
{
	ep->ops->free_buffer (ep, buf, dma, len);
}

/**
 * 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