Source code of Windows XP (NT5)
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/*++
Copyright (c) 1995,1996 Microsoft Corporation
:ts=4
Module Name:
bandwdth.c
Abstract:
This module contains code to calculate
bandwidth usage.
Environment:
kernel mode only
Notes:
Revision History:
2-15-95 : created
--*/
#include "wdm.h"
#include "stdarg.h"
#include "stdio.h"
#include "usbdi.h"
#include "hcdi.h"
#include "uhcd.h"
VOID
UHCD_InitBandwidthTable(
IN PDEVICE_OBJECT DeviceObject
)
/*++
Routine Description:
Initialize our array that tracks the bw in use.
Arguments:
DeviceObject - pointer to a device object
Return Value:
None.
--*/
{
ULONG i;
PDEVICE_EXTENSION deviceExtension;
deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
//
// Note: BwTable stores bytes per frame
//
for (i=0; i<MAX_INTERVAL; i++) {
//
// max bytes per frame - bw reaerved for bulk and control
//
deviceExtension->BwTable[i] =
UHCD_TOTAL_USB_BW - UHCD_BULK_CONTROL_BW;
}
}
#if DBG
ULONG UHCD_PnpTest = 0;
#endif
BOOLEAN
UHCD_ManageBandwidth(
IN PDEVICE_OBJECT DeviceObject,
IN PUHCD_ENDPOINT Endpoint,
IN ULONG Offset,
IN BOOLEAN AllocateFlag
)
/*++
Routine Description:
Calculate bandwidth required to open an endpoint
with the given input characteristics.
Arguments:
DeviceObject - pointer to a device object
Offset - offset in to table to start, allows load balancing
for interrupt endpoints.
Interval - interval for endoint (1 for iso).
AllocateFlag - TRUE if we are requesting BW, false if we
are releasing it.
Return Value:
TRUE if enough bandwidth available open the
endpoint.
--*/
{
ULONG i;
PDEVICE_EXTENSION deviceExtension;
BOOLEAN ok=TRUE;
ULONG interval, need;
ASSERT_ENDPOINT(Endpoint);
deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
//UHCD_KdPrint((2, "BWTable = %x\n", &deviceExtension->BwTable[0]));
//UHCD_KdBreak();
//
// claculate what we'll need based on endpoint
// type and max packet size
//
need =
USBD_CalculateUsbBandwidth(Endpoint->MaxPacketSize,
Endpoint->Type,
(BOOLEAN) (Endpoint->EndpointFlags & EPFLAG_LOWSPEED));
interval = Endpoint->Interval;
LOGENTRY(LOG_MISC, 'aBW1',
interval,
Offset,
need);
UHCD_ASSERT(interval<=MAX_INTERVAL);
UHCD_ASSERT(Offset<interval);
UHCD_ASSERT(MAX_INTERVAL % interval == 0);
if (AllocateFlag) {
for (i=Offset; i<MAX_INTERVAL; i+=interval) {
if (deviceExtension->BwTable[i] < need) {
ok = FALSE;
break;
}
}
}
#if DBG
if (UHCD_PnpTest == 1) {
ok = FALSE;
}
#endif
if (ok) {
//
// there is enough, go ahead and allocate
//
Endpoint->Offset = (USHORT) Offset;
for (i=Offset; i<MAX_INTERVAL; i+=interval) {
if (AllocateFlag) {
deviceExtension->BwTable[i] -= need;
} else {
deviceExtension->BwTable[i] += need;
}
UHCD_ASSERT(deviceExtension->BwTable[i] <=
UHCD_TOTAL_USB_BW - UHCD_BULK_CONTROL_BW);
}
}
LOGENTRY(LOG_MISC, 'aBW2',
AllocateFlag,
ok,
&deviceExtension->BwTable[0]);
#ifdef MAX_DEBUG
if (!ok) {
UHCD_KdBreak((2, "'no bandwidth\n"));
}
#endif
return ok;
}