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IRB_REQ_ISOCH_ALLOCATE_BANDWIDTH structure (1394.h)

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This structure contains the fields necessary in order for the Bus driver to carry out an IsochAllocateBandwidth request.

Syntax

typedef struct _IRB_REQ_ISOCH_ALLOCATE_BANDWIDTH {
  ULONG  nMaxBytesPerFrameRequested;
  ULONG  fulSpeed;
  HANDLE hBandwidth;
  ULONG  BytesPerFrameAvailable;
  ULONG  SpeedSelected;
  ULONG  nBandwidthUnitsRequired;
} IRB_REQ_ISOCH_ALLOCATE_BANDWIDTH;

Members

nMaxBytesPerFrameRequested

Specifies the bandwidth requested, in bytes per isochronous frame. If the host controller is configured to strip away the packet headers, the device driver does not need to include the packet header size in the number of bytes requested. The driver also does not need to round the value up to the nearest quadlet.

fulSpeed

Specifies the connection speed to use in allocating bandwidth. The possible speed values are SPEED_FLAGS_xxx, where xxx is the (approximate) transfer rate in megabits per second. Existing hardware supports transfer rates of 100, 200, and 400 Mb/sec.

Transfer Rate Description
SPEED_FLAGS_100 100 Mb/s
SPEED_FLAGS_200 200 Mb/s
SPEED_FLAGS_400 400 Mb/s
 
Note  In Windows 7 and later versions of Windows, you can specify new values higher speed and greater sized payloads. For more information, see New Flags for Speed and Payload Size and IEEE 1394 IOCTL Changes in Device Driver Interface (DDI) Changes in Windows 7.
 

hBandwidth

Specifies the handle to use to refer to the bandwidth resource. The caller can set the IRB_FLAG_ALLOW_REMOTE_FREE flag in Flags member of the IRB structure to indicate that the system should free the memory allocated for this handle. If caller does not set this flag, then caller will have to free the bandwidth handle.

BytesPerFrameAvailable

Specifies the bytes per frame that are available after the allocation attempt. Drivers should not rely on this bandwidth being available, since another device may allocate or deallocate bandwidth at any time. The bus driver fills in this member, even if the request fails.

SpeedSelected

Specifies the actual speed selected in allocating bandwidth. The value is one of SPEED_FLAGS_xxx (see the fulSpeed member description above).

Note  In Windows 7 and later versions of Windows, you can specify new values higher speed and greater sized payloads. For more information, see New Flags for Speed and Payload Size and IEEE 1394 IOCTL Changes in Device Driver Interface (DDI) Changes in Windows 7.
 

nBandwidthUnitsRequired

This is a pre-calculated value.

Requirements

Requirement Value
Header 1394.h