KsSetMajorFunctionHandler function (ks.h)

Article
03/15/2022

The KsSetMajorFunctionHandler function sets the handler for a specified major function to use the internal dispatching. It routes through a KSDISPATCH_TABLE contained in the opaque object header to be the first element within a structure pointed to by a FsContext within a file object. The dispatching assumes the table and FsContext structure are initialized by the device using KsAllocateObjectHeader.

Syntax

KSDDKAPI NTSTATUS KsSetMajorFunctionHandler(
  [in] PDRIVER_OBJECT DriverObject,
  [in] ULONG          MajorFunction
);

Parameters

[in] DriverObject

Specifies the driver object whose major function is to be handled.

[in] MajorFunction

Specifies the major function identifier to be handled. This sets the major function pointer in the driver object to an internal function that then dispatches to the KSDISPATCH_TABLE function. The pointer to this table is assumed to be the first element in a structure pointed to by FsContext in the file object of the specific IRP being dispatched. The valid major function identifiers are as listed.

Identifier	Description
IRP_MJ_CREATE	Create IRP. In this instance, a create request could be used for either creating a new instance of a filter, or for creating some object such as a pin under a filter or a clock under a pin. This assumes that the first element in the driver object's extent contains a KSDEVICE_HEADER structure that is used to find the type of object to create, based on the name passed. If a parent file object is specified, then that object's KSDISPATCH_TABLE.ChildCreateHandlerTable in the FsContext is looked at to determine what handler to use for the create, or use the device object's table.
IRP_MJ_CLOSE	Close IRP.
IRP_MJ_DEVICE_CONTROL	Device control IRP.
IRP_MJ_READ	Read IRP.
IRP_MJ_WRITE	Write IRP.
IRP_MJ_FLUSH_BUFFERS	Flush IRP.
IRP_MJ_QUERY_SECURITY	Query security information.
IRP_MJ_SET_SECURITY	Set security information.
KSDISPATCH_FASTIO	This flag may be added to the MajorFunction identifier in order to specify that the entry refers to the fast I/O dispatch table, rather than the typical major function entry. This is valid only with IRP_MJ_READ, IRP_MJ_WRITE or IRP_MJ_DEVICE_CONTROL. The driver is responsible for creating the DriverObject->FastIoDispatch table. As with normal dispatching, if a handler is set for the driver object, all file objects must handle that fast I/O, even if the entry just points to DispatchFastIoDeviceControlFailure or a similar function.

Return value

Returns STATUS_SUCCESS if the MajorFunction identifier is valid.

Remarks

If a major function handler is set for a driver object, all file objects must handle that major function, even if the entry just points to KsDispatchInvalidDeviceRequest.

KSDISPATCH_FASTIO

This flag may be used to specify that the fast I/O entry should be set rather than the IRP-based entry.

Requirements

Requirement	Value
Target Platform	Universal
Header	ks.h (include Ks.h)
Library	Ks.lib

Share via