kernel/drivers/usb/gadget/epautoconf.c

// 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.
	 */
	if (desc->wMaxPacketSize == 0)
		desc->wMaxPacketSize = cpu_to_le16(ep->maxpacket_limit);

	/* report address */
	desc->bEndpointAddress &= USB_DIR_IN;
	if (isdigit(ep->name[2])) {
		u8 num = simple_strtoul(&ep->name[2], NULL, 10);
		desc->bEndpointAddress |= num;
	} else if (desc->bEndpointAddress & USB_DIR_IN) {
		if (++gadget->in_epnum > 15)
			return NULL;
		desc->bEndpointAddress = USB_DIR_IN | gadget->in_epnum;
	} else {
		if (++gadget->out_epnum > 15)
			return NULL;
		desc->bEndpointAddress |= gadget->out_epnum;
	}

	ep->address = desc->bEndpointAddress;
	ep->desc = NULL;
	ep->comp_desc = NULL;
	ep->claimed = true;
	return ep;
}
EXPORT_SYMBOL_GPL(usb_ep_autoconfig_ss);

/**
 * usb_ep_autoconfig() - choose an endpoint matching the
 * 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.
 *
 * 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. Because of
 * that the users must consider adjusting the autoconfigured descriptor.
 * 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(
	struct usb_gadget		*gadget,
	struct usb_endpoint_descriptor	*desc
)
{
	struct usb_ep	*ep;
	u8		type;

	ep = usb_ep_autoconfig_ss(gadget, desc, NULL);
	if (!ep)
		return NULL;

	type = desc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;

	/* report (variable) full speed bulk maxpacket */
	if (type == USB_ENDPOINT_XFER_BULK) {
		int size = ep->maxpacket_limit;

		/* min() doesn't work on bitfields with gcc-3.5 */
		if (size > 64)
			size = 64;
		desc->wMaxPacketSize = cpu_to_le16(size);
	}

	return ep;
}
EXPORT_SYMBOL_GPL(usb_ep_autoconfig);

/**
 * usb_ep_autoconfig_release - releases endpoint and set it to initial state
 * @ep: endpoint which should be released
 *
 * This function can be used during function bind for endpoints obtained
 * from usb_ep_autoconfig(). It unclaims endpoint claimed by
 * usb_ep_autoconfig() to make it available for other functions. Endpoint
 * which was released is no longer valid and shouldn't be used in
 * context of function which released it.
 */
void usb_ep_autoconfig_release(struct usb_ep *ep)
{
	ep->claimed = false;
	ep->driver_data = NULL;
}
EXPORT_SYMBOL_GPL(usb_ep_autoconfig_release);

/**
 * usb_ep_autoconfig_reset - reset endpoint autoconfig state
 * @gadget: device for which autoconfig state will be reset
 *
 * Use this for devices where one configuration may need to assign
 * endpoint resources very differently from the next one.  It clears
 * state such as ep->claimed and the record of assigned endpoints
 * used by usb_ep_autoconfig().
 */
void usb_ep_autoconfig_reset (struct usb_gadget *gadget)
{
	struct usb_ep	*ep;

	list_for_each_entry (ep, &gadget->ep_list, ep_list) {
		ep->claimed = false;
		ep->driver_data = NULL;
	}
	gadget->in_epnum = 0;
	gadget->out_epnum = 0;
}
EXPORT_SYMBOL_GPL(usb_ep_autoconfig_reset);