source: mainline/uspace/drv/bus/usb/xhci/trb_ring.h@ 5cbccd4

/*
 * Copyright (c) 2017 Ondrej Hlavaty
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup drvusbxhci
 * @{
 */
/** @file
 * TRB Ring is a data structure for communication between HC and software.
 *
 * Despite this description, it is not used as an hardware structure - all but
 * the Event ring is used as buffer of the TRBs itself, linked by Link TRB to
 * form a (possibly multi-segment) circular buffer.
 *
 * This data structure abstracts this behavior.
 */

#ifndef XHCI_TRB_RING_H
#define XHCI_TRB_RING_H

#include <adt/list.h>
#include <libarch/config.h>
#include "hw_struct/trb.h"

typedef struct trb_segment trb_segment_t;

/**
 * A TRB ring of which the software is a producer - command / transfer.
 */
typedef struct xhci_trb_ring {
        list_t segments;                /* List of assigned segments */

        /*
         * As the link TRBs connect physical addresses, we need to keep track of
         * active segment in virtual memory. The enqueue ptr should always belong
         * to the enqueue segment.
         */
        trb_segment_t *enqueue_segment;
        xhci_trb_t *enqueue_trb;

        uintptr_t dequeue;              /* Last reported position of the dequeue pointer */
        bool pcs;                       /* Producer Cycle State: section 4.9.2 */
} xhci_trb_ring_t;

/**
 * Initializes the ring.
 * Allocates one page as the first segment.
 */
int trb_ring_init(xhci_trb_ring_t *ring);
int trb_ring_fini(xhci_trb_ring_t *ring);

/**
 * Enqueue a TD composed of TRBs.
 *
 * This will copy all TRBs chained together into the ring. The cycle flag in
 * TRBs may be changed.
 *
 * The chained TRBs must be contiguous in memory, and must not contain Link TRBs.
 *
 * We cannot avoid the copying, because the TRB in ring should be updated atomically.
 *
 * @param td the first TRB of TD
 * @return EOK on success,
 *         EAGAIN when the ring is too full to fit all TRBs (temporary)
 */
int trb_ring_enqueue(xhci_trb_ring_t *ring, xhci_trb_t *td);

/**
 * When an event is received by the upper layer, it needs to update the dequeue
 * pointer inside the ring. Otherwise, the ring will soon show up as full.
 */
void trb_ring_update_dequeue(xhci_trb_ring_t *ring, uintptr_t dequeue);


#endif