EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE callback function (sercx.h)

Article
10/21/2021

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.

Syntax

EVT_SERCX2_CUSTOM_TRANSMIT_TRANSACTION_INITIALIZE EvtSercx2CustomTransmitTransactionInitialize;

void EvtSercx2CustomTransmitTransactionInitialize(
  [in] SERCX2CUSTOMTRANSMITTRANSACTION CustomTransmitTransaction,
  [in] PMDL Mdl,
  [in] ULONG Offset,
  [in] ULONG Length
)
{...}

Parameters

[in] CustomTransmitTransaction

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

[in] Mdl

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.

[in] Offset

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.

[in] Length

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.

Return value

None

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.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows 8.1.
Target Platform	Desktop
Header	sercx.h
IRQL	Called at IRQL <= DISPATCH_LEVEL.