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common/usbx_stm32_host_controllers/ux_hcd_stm32_least_traffic_list_get.c
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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** USBX Component */
/** */
/** STM32 Controller Driver */
/** */
/**************************************************************************/
/**************************************************************************/
/* Include necessary system files. */
#define UX_SOURCE_CODE
#define UX_HCD_STM32_SOURCE_CODE
#include "ux_api.h"
#include "ux_hcd_stm32.h"
#include "ux_host_stack.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _ux_hcd_stm32_least_traffic_list_get PORTABLE C */
/* 6.0 */
/* AUTHOR */
/* */
/* Chaoqiong Xiao, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function return a pointer to the first ED in the periodic */
/* tree that has the least traffic registered. */
/* */
/* INPUT */
/* */
/* hcd_stm32 Pointer to STM32 controller */
/* */
/* OUTPUT */
/* */
/* UX_HCD_STM32_ED * Pointer to STM32 ED */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* STM32 Controller Driver */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Chaoqiong Xiao Initial Version 6.0 */
/* */
/**************************************************************************/
UINT _ux_hcd_stm32_least_traffic_list_get(UX_HCD_STM32 *hcd_stm32)
{
UX_HCD_STM32_ED *ed;
UINT list_index;
ULONG min_bandwidth_used;
ULONG bandwidth_used;
UINT min_bandwidth_slot;
/* Set the min bandwidth used to a arbitrary maximum value. */
min_bandwidth_used = 0xffffffff;
/* The first ED is the list candidate for now. */
min_bandwidth_slot = 0;
/* All list will be scanned. */
for (list_index = 0; list_index < 32; list_index++)
{
/* Reset the bandwidth for this list. */
bandwidth_used = 0;
/* Get the ED of the beginning of the list we parse now. */
ed = hcd_stm32 -> ux_hcd_stm32_periodic_ed_head;
/* Parse the eds in the list. */
while (ed != UX_NULL)
{
if ((list_index & ed -> ux_stm32_ed_interval_mask) == ed -> ux_stm32_ed_interval_position)
{
/* Add to the bandwidth used the max packet size pointed by this ED. */
bandwidth_used += (ULONG) ed -> ux_stm32_ed_endpoint -> ux_endpoint_descriptor.wMaxPacketSize;
}
/* Move to next ED. */
ed = ed -> ux_stm32_ed_next_ed;
}
/* We have processed a list, check the bandwidth used by this list.
If this bandwidth is the minimum, we memorize the ED. */
if (bandwidth_used < min_bandwidth_used)
{
/* We have found a better list with a lower used bandwidth, memorize the bandwidth
for this list. */
min_bandwidth_used = bandwidth_used;
/* Memorize the begin ED for this list. */
min_bandwidth_slot = list_index;
}
}
/* Return the ED list with the lowest bandwidth. */
return(min_bandwidth_slot);
}