Windows Phone 8.1 驱动开发——GPIO Device
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在上一节 Windows Phone 8.1 驱动开发——GPIO 简介 中，我们了解了Windows 8系统中GPIO驱动的大体架构，由于在工作中手机驱动开发人员很少涉及到GPIO Controller驱动的开发，该部分都由平台厂商开发完成，所以这里给大家讲解一下GPIO Peripheral Device Driver的开发步骤。
本文以微软官方提供的GPIO Sample为例进行讲解，你也可以到MSDN官网进行源码下载：GPIO Sample Drivers
电路示意图
根据该Sample Code，本人画了一张电路示意图，如下：
ACPI资源配置
编写驱动之前，我们首先看一下在ACPI配置表中，GPIO I/O Resource的分配：
// // Sample peripheral device // Device (DEV1) { Name (_HID, "TEST0001") Name (_CID, "TEST0001") Name (_UID, 1) Method (_CRS, 0x0, NotSerialized) { Name (RBUF, ResourceTemplate () { // GPIO Interrupt Resources GpioInt(Edge, ActiveHigh, Shared, PullUp, 0, "\\_SB.GPIO", 0, ResourceConsumer,, RawDataBuffer() {1}) {1} // GPIO IO Resources GpioIo(Exclusive, PullUp, 0, 0,, "\\_SB.GPIO",0, ResourceConsumer, , RawDataBuffer() {1}) {10} GpioIo(Exclusive, PullUp, 0, 0,, "\\_SB.GPIO",0, ResourceConsumer, , RawDataBuffer() {1}) {11} }) Return (RBUF) } Method (_STA, 0x0, NotSerialized) { Return(0xf) } }从资源表中可以看到，该设备DEV1使用了GPIO10、GPIO11和GPIO1三个引脚，其中GPIO10/11用作普通IO口，而GPIO1则用作中断输入引脚。至于这里对GPIO10/11的引脚配置到底作输入还是输出，是否上拉等，其实大家并不用关心，因为在电源管理中，也就是加载PEP模块的时候，会重新根据电源管理中的配置文件（pep_common.asl）进行相应设置，这里的GpioIo方法只是告诉Peripheral Driver该设备使用到了哪些I/O引脚。同样，GpioInt方法也只是告诉驱动当前设备使用到那个GPIO作外部中断引脚，至于具体的配置细节也是在电源管理配置文件中进行描述的。
获取I/O资源
当PnP Manager加载设备时，会在EvtDevicePrepareHardware回调函数中，去读取I/O资源：
NTSTATUSSampleDrvEvtDevicePrepareHardware ( _In_ WDFDEVICE Device, _In_ WDFCMRESLIST ResourcesRaw, _In_ WDFCMRESLIST ResourcesTranslated ){ PCM_PARTIAL_RESOURCE_DESCRIPTOR Descriptor; PSAMPLE_DRV_DEVICE_EXTENSION SampleDrvExtension; ULONG Index; ULONG ResourceCount; ... SampleDrvExtension = SampleDrvGetDeviceExtension(Device); // // Walk through the resource list and map all the resources. Only two // I/O resource and one interrupt is expected. // ResourceCount = WdfCmResourceListGetCount(ResourcesTranslated); for (Index = 0; Index < ResourceCount; Index += 1) { Descriptor = WdfCmResourceListGetDescriptor(ResourcesTranslated, Index); switch(Descriptor->Type) { // // GPIO I/O descriptors // case CmResourceTypeConnection: // // Check against expected connection type // if ((Descriptor->u.Connection.Class == CM_RESOURCE_CONNECTION_CLASS_GPIO) && (Descriptor->u.Connection.Type == CM_RESOURCE_CONNECTION_TYPE_GPIO_IO)) { SampleDrvExtension->ConnectionIds[IoResourceIndex].LowPart = Descriptor->u.Connection.IdLowPart; SampleDrvExtension->ConnectionIds[IoResourceIndex].HighPart = Descriptor->u.Connection.IdHighPart; } break; // // Interrupt resource // case CmResourceTypeInterrupt: SampleDrvExtension->InterruptCount++; default: break; } } ...}在以上代码中需要注意的是，函数WdfCmResourceListGetDescriptor()是按照ACPI资源表中的顺序依次读取的，所以这里SampleDrvExtension->ConnectionIds[0]对应GPIO10，SampleDrvExtension->ConnectionIds[1]对应GPIO11，顺序不能弄错了。
创建IO Target
当获取到I/O资源后，就可以使用该资源ID号创建一个IO Target来操作对应的GPIO口。这里对原始Sample Code做了点修改，增加了结构体SAMPLE_DRV_DEVICE_EXTENSION成员变量ReadIoTarget和WriteIoTarget，分别用于保存读、写IO TARGET的句柄。
创建一个读操作的IO Target：
NTSTATUS ReadIoTargetInitialize(WDFDEVICE Device){ NTSTATUS Status; PSAMPLE_DRV_DEVICE_EXTENSION SampleDrvExtension; UNICODE_STRING ReadString; WCHAR ReadStringBuffer[100]; WDF_OBJECT_ATTRIBUTES ObjectAttributes; WDF_IO_TARGET_OPEN_PARAMS OpenParams ... SampleDrvExtension = SampleDrvGetDeviceExtension(Device); WDF_OBJECT_ATTRIBUTES_INIT(&ObjectAttributes); ObjectAttributes.ParentObject = Device; WdfIoTargetCreate(Device, &ObjectAttributes, &SampleDrvExtension->ReadIoTarget); RtlInitEmptyUnicodeString(&ReadString, ReadStringBuffer, sizeof(ReadStringBuffer)); RESOURCE_HUB_CREATE_PATH_FROM_ID(&ReadString, SampleDrvExtension->ConnectionIds[0].LowPart, SampleDrvExtension->ConnectionIds[0].HighPart); WDF_IO_TARGET_OPEN_PARAMS_INIT_OPEN_BY_NAME(&OpenParams, ReadString, FILE_GENERIC_READ); WdfIoTargetOpen(SampleDrvExtension->ReadIoTarget, &OpenParams); ...}创建一个写操作的IO Target：
NTSTATUS WriteIoTargetInitialize(WDFDEVICE Device){ NTSTATUS Status; PSAMPLE_DRV_DEVICE_EXTENSION SampleDrvExtension; UNICODE_STRING WriteString; WCHAR WriteStringBuffer[100]; WDF_OBJECT_ATTRIBUTES ObjectAttributes; WDF_IO_TARGET_OPEN_PARAMS OpenParams ... SampleDrvExtension = SampleDrvGetDeviceExtension(Device); WDF_OBJECT_ATTRIBUTES_INIT(&ObjectAttributes); ObjectAttributes.ParentObject = Device; WdfIoTargetCreate(Device, &ObjectAttributes, &SampleDrvExtension->WriteIoTarget); RtlInitEmptyUnicodeString(&WriteString, WriteStringBuffer, sizeof(WriteStringBuffer)); RESOURCE_HUB_CREATE_PATH_FROM_ID(&WriteString, SampleDrvExtension->ConnectionIds[1].LowPart, SampleDrvExtension->ConnectionIds[1].HighPart); WDF_IO_TARGET_OPEN_PARAMS_INIT_OPEN_BY_NAME(&OpenParams, WriteString, FILE_GENERIC_WRITE); WdfIoTargetOpen(SampleDrvExtension->WriteIoTarget, &OpenParams); ...}发送IO请求
当创建并打开了一个IO TARGET后，就可以通过对该IO TARGET发送IOCTL请求来实现I/O引脚的读写操作。发送IOCTL_GPIO_READ_PINS进行读操作，发送IOCTL_GPIO_WRITE_PINS进行写操作。
NTSTATUSReadWriteGPIO ( _In_ WDFDEVICE Device, _In_ BOOLEAN ReadOperation, _Inout_ PUCHAR Data, _In_ _In_range_(>, 0) ULONG Size, ){ WDF_OBJECT_ATTRIBUTES RequestAttributes; WDF_OBJECT_ATTRIBUTES Attributes; WDFIOTARGET IoTarget; WDFREQUEST IoctlRequest; WDFMEMORY WdfMemory; WDF_REQUEST_SEND_OPTIONS SendOptions; PSAMPLE_DRV_DEVICE_EXTENSION SampleDrvExtension; NTSTATUS Status; SampleDrvExtension = SampleDrvGetDeviceExtension(Device); if(ReadOperation != FALSE) IoTarget = SampleDrvExtension->ReadIoTarget; else IoTarget = SampleDrvExtension->WriteIoTarget; WDF_OBJECT_ATTRIBUTES_INIT(&RequestAttributes); WdfRequestCreate(&RequestAttributes, IoTarget, &IoctlRequest); WDF_OBJECT_ATTRIBUTES_INIT(&Attributes); Attributes.ParentObject = IoctlRequest; WdfMemoryCreatePreallocated(&Attributes, Data, Size, &WdfMemory); if (ReadOperation != FALSE) { WdfIoTargetFormatRequestForIoctl(IoTarget, IoctlRequest, IOCTL_GPIO_READ_PINS, NULL, 0, WdfMemory, 0); } else { WdfIoTargetFormatRequestForIoctl(IoTarget, IoctlRequest, IOCTL_GPIO_WRITE_PINS, WdfMemory, 0, WdfMemory, 0); } WDF_REQUEST_SEND_OPTIONS_INIT(&SendOptions, WDF_REQUEST_SEND_OPTION_SYNCHRONOUS); WdfRequestSend(IoctlRequest, IoTarget, &SendOptions); ...}设备初始化
实现以上函数后，就可以对设备进行初始化了。一般设备的初始化操作在PnP Manager的回调函数EvtDeviceD0Entry中完成：
NTSTATUSSampleDrvEvtDeviceD0Entry ( _In_ WDFDEVICE Device, _In_ WDF_POWER_DEVICE_STATE PreviousPowerState ){ BYTE Data; NTSTATUS Status; ReadIoTargetInitialize(Device); Data = 0x0; Status = ReadWriteGPIO(Device, TRUE, &Data, sizeof(Data)); if (!NT_SUCCESS(Status)) { goto Cleanup; } WriteIoTargetInitialize(Device); Data = 0x1; Status = ReadWriteGPIO(Device, FALSE, &Data, sizeof(Data)); if (!NT_SUCCESS(Status)) { goto Cleanup; } ...}至此，GPIO外设驱动就完成了。关于GPIO外设驱动更多详细信息，请参考MSDN官方文档：Connecting a KMDF Driver to GPIO I/O Pins
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