Windows驱动资源的使用一

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              上次讲到了，Windows驱动中的资源，今天着重讲一下，Windows资源，如何使用。关于中断，内存，IO这些，以后再讲。今天重点讲一下，总线驱动的引用。我们知道，在设备驱动中，经常会使用I2C，GPIO这些资源，但是我们如何进行操作了，当然，我们可以直接进行IO映射。直接I2C，GPIO地址进行操作，但是这种方式不安全，且MSFT不推荐。所以，MSFT在后来的CM_PARTIAL_RESOURCE_DESCRIPTOR结构体中，加上了如下结构体：

95.        struct { 
96.                  UCHAR Class; 
97.                  UCHAR Type; 
98.                  UCHAR Reserved1; 
99.                  UCHAR Reserved2; 
100.               ULONG IdLowPart; 
101.               ULONG IdHighPart; 
102.              } Connection;

              我们通过这个结构体，可以得到一个对我们配置资源总线的一个引用。即通过这个域，我们可以把它组成了一ID，通过这个ID，就可以和我们设备驱动底层的GPIO，I2C这些驱动进行通讯。

              下面贴出MSDN中的一个实例。

             

NTSTATUS  EvtDevicePrepareHardware(    _In_ WDFDEVICE Device,    _In_ WDFCMRESLIST ResourcesRaw,    _In_ WDFCMRESLIST ResourcesTranslated    ){    int ResourceCount, Index;    PCM_PARTIAL_RESOURCE_DESCRIPTOR Descriptor;    XYZ_DEVICE_CONTEXT *DeviceExtension;    ...    DeviceExtension = XyzDrvGetDeviceExtension(Device);    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)) {                DeviceExtension->ConnectionId.LowPart = Descriptor->u.Connection.IdLowPart;                DeviceExtension->ConnectionId.HighPart = Descriptor->u.Connection.IdHighPart;        ...}

我们得到这个描述符。就可以进行和目标IO进行通讯了，继续看：

NTSTATUS IoRoutine(WDFDEVICE Device) {    XYZ_DEVICE_CONTEXT *DeviceExtension;    UNICODE_STRING ReadString;    WCHAR ReadStringBuffer[100];    WDF_OBJECT_ATTRIBUTES ObjectAttributes;    WDF_IO_TARGET_OPEN_PARAMS OpenParams;    WDFIOTARGET IoTarget;    BOOL DesiredAccess;    NTSTATUS Status;    DeviceExtension = XyzDrvGetDeviceExtension(Device);    RtlInitEmptyUnicodeString(&ReadString,                              ReadStringBuffer,                              sizeof(ReadStringBuffer));    Status = RESOURCE_HUB_CREATE_PATH_FROM_ID(&ReadString,                                              DeviceExtension->ConnectionId.LowPart,                                              DeviceExtension->ConnectionId.HighPart);    NT_ASSERT(NT_SUCCESS(Status));    WDF_OBJECT_ATTRIBUTES_INIT(&ObjectAttributes);    ObjectAttributes.ParentObject = Device;    Status = WdfIoTargetCreate(Device, &ObjectAttributes, &IoTarget);    if (!NT_SUCCESS(Status)) {        goto IoErrorEnd;    }       if (ReadOperation != FALSE) {        DesiredAccess = FILE_GENERIC_READ;    } else {        DesiredAccess = FILE_GENERIC_WRITE;    }    WDF_IO_TARGET_OPEN_PARAMS_INIT_OPEN_BY_NAME(&OpenParams, ReadString, DesiredAccess);    Status = WdfIoTargetOpen(IoTarget, &OpenParams);    if (!NT_SUCCESS(Status)) {        goto IoErrorEnd;    }    ...

再看实际的GPIO读写状态：

WDF_OBJECT_ATTRIBUTES RequestAttributes;    WDF_OBJECT_ATTRIBUTES Attributes;    WDF_REQUEST_SEND_OPTIONS SendOptions;    WDFREQUEST IoctlRequest;    WDFIOTARGET IoTarget;    WDFMEMORY WdfMemory;    NTSTATUS Status;    WDF_OBJECT_ATTRIBUTES_INIT(&RequestAttributes);    Status = WdfRequestCreate(&RequestAttributes, IoTarget, &IoctlRequest);    if (!NT_SUCCESS(Status)) {        goto RwErrorExit;    }    //    // Set up a WDF memory object for the IOCTL request.    //    WDF_OBJECT_ATTRIBUTES_INIT(&Attributes);    Attributes.ParentObject = IoctlRequest;    Status = WdfMemoryCreatePreallocated(&Attributes, Data, Size, &WdfMemory);    if (!NT_SUCCESS(Status)) {        goto RwErrorExit;    }    //    // Format the request.    //    if (ReadOperation != FALSE) {        Status = WdfIoTargetFormatRequestForIoctl(IoTarget,                                                  IoctlRequest,                                                  IOCTL_GPIO_READ_PINS,                                                  NULL,                                                  0,                                                  WdfMemory,                                                  0);    } else {        Status = WdfIoTargetFormatRequestForIoctl(IoTarget,                                                  IoctlRequest,                                                  IOCTL_GPIO_WRITE_PINS,                                                  WdfMemory,                                                  0,                                                  WdfMemory,                                                  0);    }    if (!NT_SUCCESS(Status)) {        goto RwErrorExit;    }    //    // Send the request synchronously (with a 60-second time-out).    //    WDF_REQUEST_SEND_OPTIONS_INIT(&SendOptions,                                  WDF_REQUEST_SEND_OPTION_SYNCHRONOUS);    WDF_REQUEST_SEND_OPTIONS_SET_TIMEOUT(&SendOptions,                                         WDF_REL_TIMEOUT_IN_SEC(60));    Status = WdfRequestAllocateTimer(IoctlRequest);    if (!NT_SUCCESS(Status)) {        goto RwErrorExit;    }    if (!WdfRequestSend(IoctlRequest, IoTarget, &SendOptions)) {        Status = WdfRequestGetStatus(IoctlRequest);    }    ...

       我们再来看下Connection的MSDN的说明：

      先看Class:

     CM_RESOURCE_CONNECTION_CLASS_GPIO或者CM_RESOURCE_CONNECTION_CLASS_SERIAL

     再看Type：

    CM_RESOURCE_CONNECTION_TYPE_GPIO_IO或者CM_RESOURCE_CONNECTION_TYPE_SERIAL_I2C，CM_RESOURCE_CONNECTION_TYPE_SERIAL_SPI，CM_RESOURCE_CONNECTION_TYPE_SERIAL_UART

    IdLowPart：64位连接ID的低32位。

    IdHighPart：64位连接ID的高32位。

    我们可以举一反三，在I2C， SPI中都可以这样用，当然，有使用，MSFT为我们封装了后序的IOCTL的操作，比如，直接提供I2CReadRegister,或者I2CWriteRegister.