USBD_CalculateUsbBandwidth - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers 
// usbdlib.h

ULONG USBD_CalculateUsbBandwidth(
  [in] ULONG   MaxPacketSize,
  [in] UCHAR   EndpointType,
  [in] BOOLEAN LowSpeed
);
View the official Windows Driver Kit DDI reference

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Windows Driver Kit DDI reference (nf-usbdlib-usbd_calculateusbbandwidth)

USBD_CalculateUsbBandwidth function

Description

The USBD_CalculateUsbBandwidth routine has been deprecated in Windows XP and later operating systems. Do not use.

Parameters

MaxPacketSize [in]

Specifies the maximum packet size.

EndpointType [in]

Contains a value of type USBD_PIPE_TYPE that specifies the pipe type.

LowSpeed [in]

Indicates, when TRUE, that the device is a low speed device. When FALSE, this member indicates that the device is a hi-speed device.

Return value

The USBD_CalculateUsbBandwidth routine returns zero for bulk and control endpoints and the bandwidth consumed in bits per millisecond. returns for all other endpoints.

Remarks

The USBD_CalculateUsbBandwidth routine approximates the bandwidth using the following procedure. First, USBD_CalculateUsbBandwidth adds the largest possible packet size, specified in MaxPacketSize, to the overhead associated with the type of end point specified in EndpointType. Next, USBD_CalculateUsbBandwidth multiplies this sum by 8 to convert the units from bytes per millisecond into bits per millisecond. Finally, USBD_CalculateUsbBandwidth multiplies this quantity by 7/6 to account for filler bits. In a worst case scenario, there will be one bit of filler data stuffed into the data stream for every six bits of data. USBD_CalculateUsbBandwidth uses worst-case assumptions to calculate the bandwidth required by the pipe.

See also

USB device driver programming reference

USBD_PIPE_TYPE

View the official Windows Driver Kit DDI reference

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