EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE callback function

Description

The EvtSerCx2CustomTransmitTransactionInitialize event callback function is called by version 2 of the serial framework extension (SerCx2) to prepare the serial controller driver to perform a custom-transmit transaction.

Parameters

CustomTransmitTransaction [in]

A SERCX2CUSTOMTRANSMITTRANSACTION handle to a custom-transmit object. The serial controller driver previously called the SerCx2CustomTransmitTransactionCreate method to create this object.

Mdl [in]

A pointer to an MDL that describes the memory pages that are spanned by the write buffer for the custom-transmit transaction. The scatter/gather list for the DMA transfer will use the region of this memory that is specified by the Offset and Length parameters.

Offset [in]

The starting offset for the data transfer. This parameter is a byte offset from the start of the buffer region described by the MDL. If the MDL specifies a total of N bytes of buffer space, possible values of Offset are in the range 0 to N–1.

Length [in]

The size, in bytes, of the data transfer. If the MDL specifies a total of N bytes of buffer space, possible values of Length are in the range 1 to N–Offset.

Remarks

Your serial controller driver can, as an option, implement this function. If implemented, the driver registers the function in the SerCx2CustomTransmitTransactionCreate call that creates the custom-transmit object.

Your driver should implement an EvtSerCx2CustomTransmitTransactionInitialize function if it needs to initialize the serial controller and associated hardware in preparation for a new custom-transmit transaction. SerCx2 calls this function, if it is implemented, before starting the custom-transmit transaction. In response to this call, the serial controller driver must call the SerCx2CustomTransmitTransactionInitializeComplete method to notify SerCx2 after the initialization is finished.

For more information, see SerCx2 Custom-Transmit Transactions.

Examples

To define an EvtSerCx2CustomTransmitTransactionInitialize callback function, you must first provide a function declaration that identifies the type of callback function you're defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it's a requirement for writing drivers for the Windows operating system.

For example, to define an EvtSerCx2CustomTransmitTransactionInitialize callback function that is named MyCustomTransmitTransactionInitialize, use the EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE function type, as shown in this code example:

EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE  MyCustomTransmitTransactionInitialize;

Then, implement your callback function as follows:

_Use_decl_annotations_
VOID
  MyCustomTransmitTransactionInitialize(
    SERCX2CUSTOMTRANSMITTRANSACTION  CustomTransmitTransaction,
    WDFREQUEST  Request,
    PMDL  Mdl,
    ULONG  Offset,
    ULONG  Length
    )
  {...}

The EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE function type is defined in the Sercx.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the _Use_decl_annotations_ annotation to your function definition. The _Use_decl_annotations_ annotation ensures that the annotations that are applied to the EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for KMDF Drivers. For more information about _Use_decl_annotations_, see Annotating Function Behavior.

See also

IRP_MJ_WRITE

MDL

SERCX2CUSTOMTRANSMITTRANSACTION

SerCx2CustomTransmitTransactionCreate