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MTP_COMMAND_DATA_IN (deprecated)

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This is preliminary documentation and subject to change.

This topic documents a feature of the Windows Media Device Manager SDK. We recommend that you migrate your application to use the Windows Portable Devices API. For more information, see the Windows Portable Devices SDK.

The MTP_COMMAND_DATA_IN structure contains Media Transport Protocol (MTP) custom commands that are sent to the device by using the IWMDMDevice3::DeviceIoControl method.

Syntax

typedef struct _MTP_COMMAND_DATA_IN{
  WORD  OpCode;
  DWORD  NumParams;
  DWORD  Params[MTP_COMMAND_MAX_PARAMS];
  DWORD  NextPhase;
  DWORD  CommandWriteDataSize;
  BYTE   CommandWriteData[1];
} MTP_COMMAND_DATA_IN, *PMTP_COMMAND_DATA_IN;

Members

OpCode

Operation code.

NumParams

Number of parameters passed in.

Params

Parameters to the command. MTP_COMMAND_MAX_PARAMS is a defined constant with a value of 5.

NextPhase

Indicates whether the command has a read data phase, a write data phase, or no data phase. The valid values are defined in the following table.

Value Description
MTP_NEXTPHASE_READ_DATA Read data phase.
MTP_NEXTPHASE_WRITE_DATA Write data phase.
MTP_NEXTPHASE_NO_DATA No data phase.

CommandWriteDataSize

Data size of CommandWriteData[1], in bytes.

CommandWriteData[1]

Optional, first byte of data to write to the device if NextPhase is MTP_NEXTPHASE_WRITE_DATA.

Remarks

The input buffer is expected to contain an appropriately filled out MTP_COMMAND_DATA_IN structure. On exit, the device driver will fill out the MTP_COMMAND_DATA_OUT structure and save it to the output buffer. Therefore, any request must have an input buffer of at least SIZEOF_REQUIRED_COMMAND_DATA_IN bytes, which is defined as

#define SIZEOF_REQUIRED_COMMAND_DATA_IN (sizeof(MTP_COMMAND_DATA_IN)-1)

and an output buffer of at least SIZEOF_REQUIRED_COMMAND_DATA_OUT bytes, which is defined as

#define SIZEOF_REQUIRED_COMMAND_DATA_OUT (sizeof(MTP_COMMAND_DATA_OUT)-1)

It is assumed that all commands are self-contained, that is, they can be processed completely in one call. This has implications on lengthy data transfers, because chunking in the traditional sense is not supported. (For example, to issue a read for 3megabytes, the caller would have to ensure that it allocates an output buffer of 3 MB plus SIZEOF_REQUIRED_COMMAND_DATA_OUT bytes.) Lengthy data transfers should not be done with this method, but rather through normal data-transfer APIs.

Requirements

Header: Defined in MtpExt.h.

Library: mssachlp.lib

See Also