drivers/usb/gadget/epautoconf.c

Source file repositories/reference/linux-study-clean/drivers/usb/gadget/epautoconf.c

File Facts

System
Linux kernel
Corpus path
drivers/usb/gadget/epautoconf.c
Extension
.c
Size
7303 bytes
Lines
215
Domain
Driver Families
Bucket
drivers/usb
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0+
/*
 * epautoconf.c -- endpoint autoconfiguration for usb gadget drivers
 *
 * Copyright (C) 2004 David Brownell
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/device.h>

#include <linux/ctype.h>
#include <linux/string.h>

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

/**
 * usb_ep_autoconfig_ss() - choose an endpoint matching the ep
 * descriptor and ep companion descriptor
 * @gadget: The device to which the endpoint must belong.
 * @desc: Endpoint descriptor, with endpoint direction and transfer mode
 *    initialized.  For periodic transfers, the maximum packet
 *    size must also be initialized.  This is modified on
 *    success.
 * @ep_comp: Endpoint companion descriptor, with the required
 *    number of streams. Will be modified when the chosen EP
 *    supports a different number of streams.
 *
 * This routine replaces the usb_ep_autoconfig when needed
 * superspeed enhancments. If such enhancemnets are required,
 * the FD should call usb_ep_autoconfig_ss directly and provide
 * the additional ep_comp parameter.
 *
 * By choosing an endpoint to use with the specified descriptor,
 * this routine simplifies writing gadget drivers that work with
 * multiple USB device controllers.  The endpoint would be
 * passed later to usb_ep_enable(), along with some descriptor.
 *
 * That second descriptor won't always be the same as the first one.
 * For example, isochronous endpoints can be autoconfigured for high
 * bandwidth, and then used in several lower bandwidth altsettings.
 * Also, high and full speed descriptors will be different.
 *
 * Be sure to examine and test the results of autoconfiguration
 * on your hardware.  This code may not make the best choices
 * about how to use the USB controller, and it can't know all
 * the restrictions that may apply. Some combinations of driver
 * and hardware won't be able to autoconfigure.
 *
 * On success, this returns an claimed usb_ep, and modifies the endpoint
 * descriptor bEndpointAddress.  For bulk endpoints, the wMaxPacket value
 * is initialized as if the endpoint were used at full speed and
 * the bmAttribute field in the ep companion descriptor is
 * updated with the assigned number of streams if it is
 * different from the original value. To prevent the endpoint
 * from being returned by a later autoconfig call, claims it by
 * assigning ep->claimed to true.
 *
 * On failure, this returns a null endpoint descriptor.
 */
struct usb_ep *usb_ep_autoconfig_ss(
	struct usb_gadget		*gadget,
	struct usb_endpoint_descriptor	*desc,
	struct usb_ss_ep_comp_descriptor *ep_comp
)
{
	struct usb_ep	*ep;

	if (gadget->ops->match_ep) {
		ep = gadget->ops->match_ep(gadget, desc, ep_comp);
		if (ep)
			goto found_ep;
	}

	/* Second, look at endpoints until an unclaimed one looks usable */
	list_for_each_entry (ep, &gadget->ep_list, ep_list) {
		if (usb_gadget_ep_match_desc(gadget, ep, desc, ep_comp))
			goto found_ep;
	}

	/* Fail */
	return NULL;
found_ep:

	/*
	 * If the protocol driver hasn't yet decided on wMaxPacketSize
	 * and wants to know the maximum possible, provide the info.
	 */

Annotation

Implementation Notes