MTP_COMMAND_DATA_IN

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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;BYTECommandWriteData[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