WMI sends this IRP to query for a single instance of a given data block.
WMI sends an IRP_MN_QUERY_SINGLE_INSTANCE prior to sending an IRP_MN_EXECUTE_METHOD. If a driver supports IRP_MN_EXECUTE_METHOD, it must have an IRP_MN_QUERY_SINGLE_INSTANCE handler for the same data block whose method is being executed.
WMI sends this IRP at IRQL = PASSIVE_LEVEL in an arbitrary thread context.
Parameters.WMI.ProviderId points to the device object of the driver that should respond to the request. This pointer is located in the driver's I/O stack location in the IRP.
Parameters.WMI.DataPath points to a GUID that identifies the data block to query.
Parameters.WMI.BufferSize indicates the maximum size of the nonpaged buffer at Parameters.WMI.Buffer, which points to a WNODE_SINGLE_INSTANCE structure that identifies the instance to query.
Otherwise, the driver fills in the WNODE_SINGLE_INSTANCE structure at Parameters.WMI.Buffer as follows:
Updates WnodeHeader.BufferSize with the size, in bytes, of the output WNODE_SINGLE_INSTANCE structure, including instance data. This value should include the length of the instance name (padded such that the instance data begins on a quad word boundary), even if the class being queried registered static instance names and the driver writer is not explicitly supplying the name when servicing this IRP.
Sets SizeDataBlock to the size, in bytes, of the instance data. If static instance names are in use, this value should not include the size of the instance name.
Writes the instance data to Parameters.WMI.Buffer starting at DataBlockOffset. The driver must not change the input value of DataBlockOffset.
If the buffer at Parameters.WMI.Buffer is too small to receive all of the data, the driver fills in the needed size in a WNODE_TOO_SMALL structure at Parameters.WMI.Buffer. If the buffer is smaller than sizeof(WNODE_TOO_SMALL), the driver fails the IRP and returns STATUS_BUFFER_TOO_SMALL.
I/O Status Block
If the driver handles the IRP by calling WmiSystemControl, WMI sets Irp->IoStatus.Status and Irp->IoStatus.Information in the I/O status block.
Otherwise, the driver sets Irp->IoStatus.Status to STATUS_SUCCESS or to an appropriate error status such as the following:
On success, a driver sets Irp->IoStatus.Information to the value entered into WnodeHeader.BufferSize. This value includes the length of the static instance name.
If a driver handles an IRP_MN_QUERY_SINGLE_INSTANCE request itself, it should do so only if Parameters.WMI.ProviderId points to the same device object as the pointer that the driver passed in its call to IoWMIRegistrationControl. Otherwise, the driver must forward the request to the next lower driver in the device stack.
Before handling the request, the driver must determine whether Parameters.WMI.DataPath points to a GUID that the driver supports. If not, the driver must fail the IRP and return STATUS_WMI_GUID_NOT_FOUND.
The driver is responsible for validating all input values. Specifically, the driver must do the following if it handles the IRP request itself:
For static names, verify that the InstanceIndex member of the WNODE_SINGLE_INSTANCE structure is within the range of instance indexes supported by the driver for the data block.
For dynamic names, verify that the instance name string identifies a data block instance supported by the driver.
Verify that Parameters.WMI.BufferSize specifies a buffer that is large enough to receive all the data that the driver will return.
If the driver supports the data block, it checks the input WNODE_SINGLE_INSTANCE at Parameters.WMI.Buffer for the instance name, as follows:
If WNODE_FLAG_STATIC_INSTANCE_NAMES is set in WnodeHeader.Flags, the driver uses InstanceIndex as an index into the driver's list of static instance names for that block. WMI obtains the index from registration data provided by the driver when it registered the block.
If WNODE_FLAG_STATIC_INSTANCE_NAMES is clear in WnodeHeader.Flags, the driver uses the offset at OffsetInstanceName to locate the instance name string in the input WNODE_SINGLE_INSTANCE. OffsetInstanceName is the offset, in bytes, from the beginning of the structure to a USHORT, which is the length of the instance name string in bytes (not characters), including the terminating null if present, followed by the instance name string in Unicode.
If the driver cannot locate the specified instance, it must fail the IRP and return STATUS_WMI_INSTANCE_NOT_FOUND. For an instance with a dynamic instance name, this status indicates that the driver does not support the instance. WMI can therefore continue to query other data providers, and return an appropriate error to the data consumer if another provider finds the instance but cannot handle the request for some other reason.
If the driver locates the instance and can handle the request, it fills in the WNODE_SINGLE_INSTANCE structure at Parameters.WMI.Buffer with data for the instance.
If the instance is valid but the driver cannot handle the request, it can return any appropriate error status.