Deskripsi Buffer untuk Kode Kontrol I/O

I/O control codes are contained in IRP_MJ_DEVICE_CONTROL and IRP_MJ_INTERNAL_DEVICE_CONTROL requests. The I/O manager creates these requests as a result of calls to DeviceIoControl and IoBuildDeviceIoControlRequest.

Because DeviceIoControl and IoBuildDeviceIoControlRequest accept both an input buffer and an output buffer as arguments, all IRP_MJ_DEVICE_CONTROL and IRP_MJ_INTERNAL_DEVICE_CONTROL requests supply both an input buffer and an output buffer. Cara sistem menjelaskan buffer ini tergantung pada jenis transfer data. The transfer type is specified by the TransferType value in the CTL_CODE macro that creates IOCTL code values.

The system describes buffers for each TransferType value as follows.

METHOD_BUFFERED

For this transfer type, IRPs supply a pointer to a buffer at Irp->AssociatedIrp.SystemBuffer. This buffer represents both the input buffer and the output buffer that are specified in calls to DeviceIoControl and IoBuildDeviceIoControlRequest. Driver mentransfer data keluar dari, dan kemudian ke dalam, buffer ini.

For input data, the buffer size is specified by Parameters.DeviceIoControl.InputBufferLength in the driver's IO_STACK_LOCATION structure. For output data, the buffer size is specified by Parameters.DeviceIoControl.OutputBufferLength in the driver's IO_STACK_LOCATION structure.

Ukuran ruang yang dialokasikan sistem untuk buffer input/output tunggal adalah yang lebih besar dari dua nilai panjang.

METHOD_IN_DIRECT atau METHOD_OUT_DIRECT

For these transfer types, IRPs supply a pointer to a buffer at Irp->AssociatedIrp.SystemBuffer. This represents the first buffer that is specified in calls to DeviceIoControl and IoBuildDeviceIoControlRequest. The buffer size is specified by Parameters.DeviceIoControl.InputBufferLength in the driver's IO_STACK_LOCATION structure.

For these transfer types, IRPs also supply a pointer to an MDL at Irp->MdlAddress. This represents the second buffer that is specified in calls to DeviceIoControl and IoBuildDeviceIoControlRequest. Buffer ini dapat digunakan sebagai buffer input atau buffer output, sebagai berikut:

• METHOD_IN_DIRECT ditentukan jika driver yang menangani IRP menerima data di buffer saat dipanggil. MDL menjelaskan buffer input, dan menentukan METHOD_IN_DIRECT memastikan bahwa utas yang dieksekusi memiliki akses baca ke buffer.

• METHOD_OUT_DIRECT ditentukan jika driver yang menangani IRP menulis data ke dalam buffer sebelum menyelesaikan IRP. MDL menjelaskan buffer output, dan menentukan METHOD_OUT_DIRECT memastikan bahwa utas yang dieksekusi memiliki akses tulis ke buffer.

For both of these transfer types, Parameters.DeviceIoControl.OutputBufferLength specifies the size of the buffer that is described by the MDL.

METHOD_NEITHER

Manajer I/O tidak menyediakan buffer sistem atau MDL apa pun. The IRP supplies the user-mode virtual addresses of the input and output buffers that were specified to DeviceIoControl or IoBuildDeviceIoControlRequest, without validating or mapping them.

The input buffer's address is supplied by Parameters.DeviceIoControl.Type3InputBuffer in the driver's IO_STACK_LOCATION structure, and the output buffer's address is specified by Irp->UserBuffer.

Buffer sizes are supplied by Parameters.DeviceIoControl.InputBufferLength and Parameters.DeviceIoControl.OutputBufferLength in the driver's IO_STACK_LOCATION structure.

For more information about the CTL_CODE macro and the transfer types listed above, see Defining I/O Control Codes.