/***************************************************************************
 * Copyright (c) 2024 Microsoft Corporation
 * Copyright (c) 2026-present Eclipse ThreadX contributors
 *
 * This program and the accompanying materials are made available under the
 * terms of the MIT License which is available at
 * https://opensource.org/licenses/MIT.
 *
 * SPDX-License-Identifier: MIT
 **************************************************************************/


/**************************************************************************/
/**************************************************************************/
/**                                                                       */
/** USBX Component                                                        */
/**                                                                       */
/**   EHCI Controller Driver                                              */
/**                                                                       */
/**************************************************************************/
/**************************************************************************/


/* Include necessary system files.  */

#define UX_SOURCE_CODE

#include "ux_api.h"
#include "ux_hcd_ehci.h"
#include "ux_host_stack.h"


/**************************************************************************/
/*                                                                        */
/*  FUNCTION                                               RELEASE        */
/*                                                                        */
/*    _ux_hcd_ehci_ed_obtain                              PORTABLE C      */
/*                                                           6.1          */
/*  AUTHOR                                                                */
/*                                                                        */
/*    Chaoqiong Xiao, Microsoft Corporation                               */
/*                                                                        */
/*  DESCRIPTION                                                           */
/*                                                                        */
/*    This function obtains a free ED from the ED list.                   */
/*                                                                        */
/*  INPUT                                                                 */
/*                                                                        */
/*    hcd_ehci                              Pointer to EHCI controller    */
/*                                                                        */
/*  OUTPUT                                                                */
/*                                                                        */
/*    UX_EHCI_ED *                          Pointer to ED                 */
/*                                                                        */
/*  CALLS                                                                 */
/*                                                                        */
/*    _ux_utility_memory_set                Set memory block              */
/*                                                                        */
/*  CALLED BY                                                             */
/*                                                                        */
/*    EHCI Controller Driver                                              */
/*                                                                        */
/**************************************************************************/
UX_EHCI_ED  *_ux_hcd_ehci_ed_obtain(UX_HCD_EHCI *hcd_ehci)
{

UX_EHCI_ED      *ed;
ULONG           ed_index;


    /* Start the search from the beginning of the list.  */
    ed =  hcd_ehci -> ux_hcd_ehci_ed_list;
    for (ed_index = 0; ed_index < _ux_system_host -> ux_system_host_max_ed; ed_index++)
    {

        /* Check the ED status, a free ED is marked with the UNUSED flag.  */
        if (ed -> ux_ehci_ed_status == UX_UNUSED)
        {

            /* The ED may have been used, so we reset all fields.  */
            _ux_utility_memory_set(ed, 0, sizeof(UX_EHCI_ED)); /* Use case of memset is verified. */

            /* This ED is now marked as USED.  */
            ed -> ux_ehci_ed_status =  UX_USED;

            /* We initialize the type of ED and mark its TD terminator to be safe.  */
            ed -> ux_ehci_ed_queue_head =     (UX_EHCI_ED *) UX_EHCI_QH_TYP_QH;
            ed -> ux_ehci_ed_queue_element =  (UX_EHCI_TD *) UX_EHCI_TD_T;

            /* Success, return ED pointer.  */
            return(ed);
        }

        /* Point to the next ED.  */
        ed++;
    }

    /* There is no available ED in the ED list.  */
    return(UX_NULL);
}