Edit

IRB_REQ_ISOCH_ALLOCATE_RESOURCES_W2K structure (1394.h)

  • Article

This structure contains the fields necessary for the 1394 bus driver to carry out a IsochAllocateResources request.

Syntax

typedef struct _IRB_REQ_ISOCH_ALLOCATE_RESOURCES_W2K {
  ULONG  fulSpeed;
  ULONG  fulFlags;
  ULONG  nChannel;
  ULONG  nMaxBytesPerFrame;
  ULONG  nNumberOfBuffers;
  ULONG  nMaxBufferSize;
  ULONG  nQuadletsToStrip;
  HANDLE hResource;
} IRB_REQ_ISOCH_ALLOCATE_RESOURCES_W2K;

Members

fulSpeed

Specifies the connection speed to use for communication on the channel. 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.
 

fulFlags

Specifies how the bus driver should use any buffers attached to the resource handle. Many of the flags specify how the bus driver should configure the IEEE host controller for DMA from or to attached buffers.

Flag Description
RESOURCE_USED_IN_LISTENING Attached buffers are used to read data from an isochronous channel. Set this if the resource handle will be used in a REQUEST_ISOCH_LISTEN request.
RESOURCE_USED_IN_TALKING Attached buffers are used to write data to an isochronous channel. Set this if the resource handle will be used in a REQUEST_ISOCH_TALK request.
RESOURCE_STRIP_ADDITIONAL_QUADLETS The bus driver configures the host controller to strip additional quadlets from incoming isochronous packets. The number of quadlets to be stripped is specified in nQuadletsToStrip.
RESOURCE_SYNCH_ON_TIME The bus driver configures the host controller to synchronize the beginning of the isochronous transaction to the CYCLE_TIME specified in the StartTime member of the request's IRB. See REQUEST_ISOCH_LISTEN or REQUEST_ISOCH_TALK.
RESOURCE_USE_PACKET_BASED Used to switch to packet-based transfer, rather than the default. The default is stream-based transfer, unless the host controller only supports packet-based DMA.
RESOURCE_USE_MULTICHANNEL The driver owning this resource listens on multiple channels.
RESOURCE_VARIABLE_ISOCH_PAYLOAD The driver owning this resource transfers frames of variable size.

nChannel

Specifies the isochronous channel for all transactions involving the resource handle allocated by this request.

nMaxBytesPerFrame

Specifies the expected maximum isochronous frame size while transmitting and receiving on the channel.

nNumberOfBuffers

Specifies one more than the maximum expected number of buffers that are attached to the resource handle at any given time.

nMaxBufferSize

Specifies the maximum size of the buffers that are attached to the resource handle.

nQuadletsToStrip

Specifies the number of quadlets to strip from the beginning of every packet in an incoming isochronous stream. This parameter is ignored unless the device driver sets the RESOURCE_STRIP_ADDITIONAL_QUADLETS flag in u.IsochAllocateResources.fulFlags.

hResource

Specifies a handle to the resource.

Requirements

Requirement Value
Header 1394.h