GPIO_CLIENT_READ_PINS callback function (gpioclx.h)

Article
10/21/2021

The CLIENT_ReadGpioPins event callback function reads a set of general-purpose I/O (GPIO) pins that are configured as data inputs.

Syntax

GPIO_CLIENT_READ_PINS GpioClientReadPins;

NTSTATUS GpioClientReadPins(
  [in]      PVOID Context,
  [in, out] PGPIO_READ_PINS_PARAMETERS ReadParameters
)
{...}

Parameters

[in] Context

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

[in, out] ReadParameters

A pointer to a GPIO_READ_PINS_PARAMETERS structure that, on entry, describes the GPIO pins to read, and, on exit, contains the data that was read from the GPIO pins.

Return value

The CLIENT_ReadGpioPins 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. GpioClx calls this function.

All of the pins in the PinNumberTable array belong to the bank identified by the BankId parameter.

To register your driver's CLIENT_ReadGpioPins 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_ReadGpioPins function pointer.

The CLIENT_ReadGpioPins function can be called from the interrupt service routine (ISR) in GpioClx. This ISR runs either at PASSIVE_LEVEL or DIRQL, depending on the device information that the CLIENT_QueryControllerBasicInformation callback function supplies to GpioClx. The CLIENT_QueryControllerBasicInformation function provides device information in the form of a CLIENT_CONTROLLER_BASIC_INFORMATION structure. If the MemoryMappedController flag bit is set in the Flags member of this structure, the GpioClx ISR runs at DIRQL and calls the CLIENT_ReadGpioPins function at DIRQL. Otherwise, the ISR runs at PASSIVE_LEVEL and calls the function at PASSIVE_LEVEL. For more information about this flag bit, see Optional and Required GPIO Callback Functions.

Examples

To define a CLIENT_ReadGpioPins 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_ReadGpioPins callback function that is named MyEvtGpioReadGpioPins, use the GPIO_CLIENT_READ_PINS function type, as shown in this code example:

GPIO_CLIENT_READ_PINS MyEvtGpioReadPins;

Then, implement your callback function as follows:

_Use_decl_annotations_
NTSTATUS
  MyEvtGpioReadPins(
    PVOID Context,
    PGPIO_READ_PINS_PARAMETERS ReadParameters
    )
{ ... }

The GPIO_CLIENT_READ_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_READ_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	See Remarks.

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