source: mainline/uspace/lib/usbhost/src/bandwidth.c@ d0db4a0

/*
 * Copyright (c) 2011 Jan Vesely
 * 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 libusbhost
 * @{
 */
/** @file
 *
 * Bandwidth calculation functions. Shared among uhci, ohci and ehci drivers.
 */

#include <usb/host/bandwidth.h>

#include <assert.h>
#include <stdlib.h>

/** Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 1.1 specification.
 * @param speed Device's speed.
 * @param type Type of the transfer.
 * @param size Number of byte to transfer.
 * @param max_packet_size Maximum bytes in one packet.
 */
size_t bandwidth_count_usb11(usb_speed_t speed, usb_transfer_type_t type,
    size_t size, size_t max_packet_size)
{
        /* We care about bandwidth only for interrupt and isochronous. */
        if ((type != USB_TRANSFER_INTERRUPT)
            && (type != USB_TRANSFER_ISOCHRONOUS)) {
                return 0;
        }

        const unsigned packet_count =
            (size + max_packet_size - 1) / max_packet_size;
        /* TODO: It may be that ISO and INT transfers use only one packet per
         * transaction, but I did not find text in USB spec to confirm this */
        /* NOTE: All data packets will be considered to be max_packet_size */
        switch (speed)
        {
        case USB_SPEED_LOW:
                assert(type == USB_TRANSFER_INTERRUPT);
                /* Protocol overhead 13B
                 * (3 SYNC bytes, 3 PID bytes, 2 Endpoint + CRC bytes, 2
                 * CRC bytes, and a 3-byte interpacket delay)
                 * see USB spec page 45-46. */
                /* Speed penalty 8: low speed is 8-times slower*/
                return packet_count * (13 + max_packet_size) * 8;
        case USB_SPEED_FULL:
                /* Interrupt transfer overhead see above
                 * or page 45 of USB spec */
                if (type == USB_TRANSFER_INTERRUPT)
                        return packet_count * (13 + max_packet_size);

                assert(type == USB_TRANSFER_ISOCHRONOUS);
                /* Protocol overhead 9B
                 * (2 SYNC bytes, 2 PID bytes, 2 Endpoint + CRC bytes, 2 CRC
                 * bytes, and a 1-byte interpacket delay)
                 * see USB spec page 42 */
                return packet_count * (9 + max_packet_size);
        default:
                return 0;
        }
}

/** Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 2.0 specification.
 * @param speed Device's speed.
 * @param type Type of the transfer.
 * @param size Number of byte to transfer.
 * @param max_packet_size Maximum bytes in one packet.
 */
size_t bandwidth_count_usb20(usb_speed_t speed, usb_transfer_type_t type,
    size_t size, size_t max_packet_size)
{
        /* We care about bandwidth only for interrupt and isochronous. */
        if ((type != USB_TRANSFER_INTERRUPT)
            && (type != USB_TRANSFER_ISOCHRONOUS)) {
                return 0;
        }
        //TODO Implement
        return 0;
}