MTP_COMMAND_DATA_OUT

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The MTP_COMMAND_DATA_OUT structure contains Media Transport Protocol (MTP) responses that are filled by the device driver on exiting a call to IWMDMDevice3::DeviceIoControl.

Syntax

typedef struct _MTP_COMMAND_DATA_OUT{WORD  ResponseCode;DWORD  NumParams;DWORD  Params[MTP_RESPONSE_MAX_PARAMS];DWORD  CommandReadDataSize;BYTECommandReadData[1];} MTP_COMMAND_DATA_OUT, *PMTP_COMMAND_DATA_OUT;

Members

ResponseCode

Response code.

NumParams

Number of parameters for this response.

Params

Parameters of the response. MTP_RESPONSE_MAX_PARAMS is a defined constant with a value of 5.

CommandReadDataSize

Data size of CommandReadData[1], in bytes.

CommandReadData[1]

Optional, first byte of data to read from the device if MTP_COMMAND_DATA_IN.NextPhase is MTP_NEXTPHASE_READ_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 the following:

#define SIZEOF_REQUIRED_COMMAND_DATA_IN (sizeof(MTP_COMMAND_DATA_IN)-1)

Any request must also have an output buffer of at least SIZEOF_REQUIRED_COMMAND_DATA_OUT bytes, which is defined as the following:

#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