REQUEST_GET_SPEED_BETWEEN_DEVICES control code

The REQUEST_GET_SPEED_BETWEEN_DEVICES request returns the maximum (simultaneous) transfer speed that can be used from one source device to a set of destination devices.

The relevant members of the IRB for this request are:


typedef struct _IRB {
  ULONG FunctionNumber;
    .
    .
    .
  union {
    struct {
      ULONG             fulFlags;
      ULONG             ulNumberOfDestinations;
      PDEVICE_OBJECT    hDestinationDeviceObjects[64];
      ULONG             fulSpeed;
    } GetMaxSpeedBetweenDevices;
    .
    .
    .
  } u;
} IRB;

IRB Input

FunctionNumber

REQUEST_GET_SPEED_BETWEEN_DEVICES

u.GetMaxSpeedBetweenDevices.fulFlags

Specifies the source device. Zero indicates the calling device. USE_LOCAL_NODE indicates the computer itself.

Note  In Windows 7, the new 1394 bus driver returns only the speed between the local node and the device. The USE_LOCAL_NODE flag must be set in the u.GetMaxSpeedBetweenDevices.fulFlags parameter.

u.GetMaxSpeedBetweenDevices.ulNumberOfDestinations

Specifies the number of destination devices.

u.GetMaxSpeedBetweenDevices.hDestinationDeviceObjects

Points to an array of the device objects of the destination devices.

IRB Output

u.GetMaxSpeedBetweenDevices.fulSpeed

Specifies the maximum possible transaction speed between the source device and the set of destination devices. The value returned is the maximum speed supported by all the devices simultaneously. 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 RateDescription

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.

I/O Status Block

If successful, the bus driver sets Irp->IoStatus.Status to STATUS_SUCCESS.

See Also

IOCTL_IEEE1394_API_REQUEST

Requirements

Header

1394.h (include 1394.h)

 

 

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