EVT_SERCX2_PURGE_FIFOS callback function (sercx.h)

Article
10/21/2021

The EvtSerCx2PurgeFifos event callback function is called by version 2 of the serial framework extension (SerCx2) to purge the FIFO buffers in the serial controller hardware.

Syntax

EVT_SERCX2_PURGE_FIFOS EvtSercx2PurgeFifos;

void EvtSercx2PurgeFifos(
  [in] WDFDEVICE Device,
  [in] BOOLEAN PurgeRxFifo,
  [in] BOOLEAN PurgeTxFifo
)
{...}

Parameters

[in] Device

A WDFDEVICE handle to the framework device object that represents the serial controller. The serial controller driver created this object in its EvtDriverDeviceAdd callback function. For more information, see SerCx2InitializeDevice.

[in] PurgeRxFifo

Whether to purge the receive FIFO. If this parameter is set to TRUE, purge the receive FIFO. If FALSE, do not purge the receive FIFO.

[in] PurgeTxFifo

Whether to purge the transmit FIFO. If this parameter is set to TRUE, purge the transmit FIFO. If FALSE, do not purge the transmit FIFO.

Return value

None

Remarks

Your serial controller driver must implement this function. The driver registers the function in the call to the SerCx2InitializeDevice method that finishes the initialization of the framework device object for the serial controller.

SerCx2 calls the EvtSerCx2PurgeFifos function when a client (peripheral driver) sends an IOCTL_SERIAL_PURGE control request that requires either one or both of the FIFO buffers in the serial controller hardware to be purged. If the IOCTL_SERIAL_PURGE control request requires pending read or write (IRP_MJ_READ or IRP_MJ_WRITE) requests to be canceled, SerCx2 cancels these requests before it calls the EvtSerCx2PurgeFifos function.

SerCx2 also calls the EvtSerCx2PurgeFifos function when a client opens a logical connection to the serial controller device and obtains a file handle to this connection. For more information, see Framework File Objects.

Examples

To define an EvtSerCx2PurgeFifos 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 EvtSerCx2PurgeFifos callback function that is named MyPurgeFifos, use the EVT_SERCX2_PURGE_FIFOS function type, as shown in this code example:

EVT_SERCX2_PURGE_FIFOS  MyPurgeFifos;

Then, implement your callback function as follows:

_Use_decl_annotations_
VOID
  MyPurgeFifos(
    WDFDEVICE  Device,
    BOOLEAN PurgeRxFifo,
    BOOLEAN PurgeTxFifo
    )
  {...}

The EVT_SERCX2_PURGE_FIFOS 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_PURGE_FIFOS 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 PASSIVE_LEVEL.