drivers/usb/gadget/epautoconf.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * epautoconf.c -- endpoint autoconfiguration for usb gadget drivers
 *
 * Copyright (C) 2004 David Brownell
 *
 * Ported to U-Boot by: Thomas Smits <ts.smits@gmail.com> and
 *                      Remy Bohmer <linux@bohmer.net>
 */

#include <linux/usb/ch9.h>
#include <linux/errno.h>
#include <linux/usb/gadget.h>
#include <asm/unaligned.h>

#define isdigit(c)      ('0' <= (c) && (c) <= '9')

/* we must assign addresses for configurable endpoints (like net2280) */
static unsigned epnum;

/* #define MANY_ENDPOINTS */
#ifdef MANY_ENDPOINTS
/* more than 15 configurable endpoints */
static unsigned in_epnum;
#endif

/*
 * This should work with endpoints from controller drivers sharing the
 * same endpoint naming convention.  By example:
 *
 *	- ep1, ep2, ... address is fixed, not direction or type
 *	- ep1in, ep2out, ... address and direction are fixed, not type
 *	- ep1-bulk, ep2-bulk, ... address and type are fixed, not direction
 *	- ep1in-bulk, ep2out-iso, ... all three are fixed
 *	- ep-* ... no functionality restrictions
 *
 * Type suffixes are "-bulk", "-iso", or "-int".  Numbers are decimal.
 * Less common restrictions are implied by gadget_is_*().
 *
 * NOTE:  each endpoint is unidirectional, as specified by its USB
 * descriptor; and isn't specific to a configuration or altsetting.
 */
static int ep_matches(
	struct usb_gadget		*gadget,
	struct usb_ep			*ep,
	struct usb_endpoint_descriptor	*desc
)
{
	u8		type;
	const char	*tmp;
	u16		max;

	/* endpoint already claimed? */
	if (NULL != ep->driver_data)
		return 0;

	/* only support ep0 for portable CONTROL traffic */
	type = desc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;
	if (USB_ENDPOINT_XFER_CONTROL == type)
		return 0;

	/* some other naming convention */
	if ('e' != ep->name[0])
		return 0;

	/* type-restriction:  "-iso", "-bulk", or "-int".
	 * direction-restriction:  "in", "out".
	 */
	if ('-' != ep->name[2]) {
		tmp = strrchr(ep->name, '-');
		if (tmp) {
			switch (type) {
			case USB_ENDPOINT_XFER_INT:
				/* bulk endpoints handle interrupt transfers,
				 * except the toggle-quirky iso-synch kind
				 */
				if ('s' == tmp[2])	/* == "-iso" */
					return 0;
				break;
			case USB_ENDPOINT_XFER_BULK:
				if ('b' != tmp[1])	/* != "-bulk" */
					return 0;
				break;
			case USB_ENDPOINT_XFER_ISOC:
				if ('s' != tmp[2])	/* != "-iso" */
					return 0;
			}
		} else {
			tmp = ep->name + strlen(ep->name);
		}

		/* direction-restriction:  "..in-..", "out-.." */
		tmp--;
		if (!isdigit(*tmp)) {
			if (desc->bEndpointAddress & USB_DIR_IN) {
				if ('n' != *tmp)
					return 0;
			} else {
				if ('t' != *tmp)
					return 0;
			}
		}
	}

	/* endpoint maxpacket size is an input parameter, except for bulk
	 * where it's an output parameter representing the full speed limit.
	 * the usb spec fixes high speed bulk maxpacket at 512 bytes.
	 */
	max = 0x7ff & le16_to_cpu(get_unaligned(&desc->wMaxPacketSize));
	switch (type) {
	case USB_ENDPOINT_XFER_INT:
		/* INT:  limit 64 bytes full speed, 1024 high speed */
		if (!gadget->is_dualspeed && max > 64)
			return 0;
		/* FALLTHROUGH */

	case USB_ENDPOINT_XFER_ISOC:
		/* ISO:  limit 1023 bytes full speed, 1024 high speed */
		if (ep->maxpacket < max)
			return 0;
		if (!gadget->is_dualspeed && max > 1023)
			return 0;

		/* BOTH:  "high bandwidth" works only at high speed */
		if ((get_unaligned(&desc->wMaxPacketSize) &
					__constant_cpu_to_le16(3<<11))) {
			if (!gadget->is_dualspeed)
				return 0;
			/* configure your hardware with enough buffering!! */
		}
		break;
	}

	/* MATCH!! */

	/* report address */
	if (isdigit(ep->name[2])) {
		u8	num = dectoul(&ep->name[2], NULL);
		desc->bEndpointAddress |= num;
#ifdef	MANY_ENDPOINTS
	} else if (desc->bEndpointAddress & USB_DIR_IN) {
		if (++in_epnum > 15)
			return 0;
		desc->bEndpointAddress = USB_DIR_IN | in_epnum;
#endif
	} else {
		if (++epnum > 15)
			return 0;
		desc->bEndpointAddress |= epnum;
	}

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

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

	if (gadget->ops->ep_conf)
		return gadget->ops->ep_conf(gadget, ep, desc);

	return 1;
}

/**
 * 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 un-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.  To prevent
 * the endpoint from being returned by a later autoconfig call, claim it
 * by assigning ep->driver_data to some non-null value.
 *
 * 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;

	if (gadget->ops->match_ep) {
		ep = gadget->ops->match_ep(gadget, desc, NULL);
		if (ep && ep_matches(gadget, ep, desc))
			return ep;
	}

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

	/* Fail */
	return NULL;
}

/**
 * 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->driver_data 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->driver_data = NULL;
	}
#ifdef	MANY_ENDPOINTS
	in_epnum = 0;
#endif
	epnum = 0;
}