GPIO_CLIENT_CONNECT_IO_PINS callback function (gpioclx.h)

Article
02/22/2024

The CLIENT_ConnectIoPins event callback function opens a logical connection to a set of general-purpose I/O (GPIO) pins and configures these pins for data read or write operations.

Syntax

GPIO_CLIENT_CONNECT_IO_PINS GpioClientConnectIoPins;

NTSTATUS GpioClientConnectIoPins(
  [in] PVOID Context,
  [in] PGPIO_CONNECT_IO_PINS_PARAMETERS ConnectParameters
)
{...}

Parameters

[in] Context

A pointer to the GPIO controller driver's device context.

[in] ConnectParameters

A pointer to a GPIO_CONNECT_IO_PINS_PARAMETERS structure that describes a connection to a set of GPIO pins and that specifies whether to configure these pins as data inputs or outputs.

Return value

The CLIENT_ConnectIoPins function returns STATUS_SUCCESS if the call is successful. Otherwise, it returns an appropriate error code.

Remarks

This callback function is implemented by the GPIO controller driver. The GPIO framework extension (GpioClx) calls this function to open a connection to a set of GPIO pins. These pins are specified in the PinNumberTable array in the GPIO_CONNECT_IO_PINS_PARAMETERS structure pointed to by ConnectParameters. The ConnectMode member of this structure indicates whether to configure the pins as inputs or outputs.

To close the connection, GpioClx calls the CLIENT_DisconnectIoPins callback function.

To register your driver's CLIENT_ConnectIoPins callback function, call the GPIO_CLX_RegisterClient method. This method accepts, as an input parameter, a pointer to a GPIO_CLIENT_REGISTRATION_PACKET structure that contains a CLIENT_ConnectIoPins function pointer.

Examples

To define a CLIENT_ConnectIoPins 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 a CLIENT_ConnectIoPins callback function that is named MyEvtGpioConnectIoPins, use the GPIO_CLIENT_CONNECT_IO_PINS function type, as shown in this code example:

GPIO_CLIENT_CONNECT_IO_PINS MyEvtGpioConnectIoPins;

Then, implement your callback function as follows:

_Use_decl_annotations_
NTSTATUS
  MyEvtGpioConnectIoPins(
    PVOID Context,
    PGPIO_CONNECT_IO_PINS_PARAMETERS ConnectParameters
    )
{ ... }

The GPIO_CLIENT_CONNECT_IO_PINS function type is defined in the Gpioclx.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 GPIO_CLIENT_CONNECT_IO_PINS 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	Supported starting with Windows 8.
Target Platform	Desktop
Header	gpioclx.h
IRQL	Called at PASSIVE_LEVEL.

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