Windows Phone 8.1 驱动开发——如何调用ACPI Method

今天给大家讲解一下，在KMDF(Kernel-Mode Driver Framework)中是如何调用ACPI配置表中用户定义的Method。在ACPI中，凡是以下划线开头的Method（如_STA）都系统预定义的Method，它们都由Windows OS自己调用，其他用户自定义Method则由驱动程序调用。

ACPI Method

首先我们来看一段在ACPI中定义的Method：

//Global Buffer
Name(DATA, Buffer(0x4) { 0x00, 0x00, 0x00, 0x00})

Device (TEST)
{
    Name (_HID, "TEST001")
    Name (_UID, 1)

	...
	
    Method(GETD, 0x0, NotSerialized)
    {
        return (DATA)
    }

    Method(SETD, 0x1, NotSerialized)
    {
        Store(Arg0, DATA)
    }
	
	...
}

从代码中可以看到，该TEST设备提供了2个Method：GETD()和SETD()。全局变量DATA为4字节数组，GETD()方法用于读取DATA的数据并传给驱动程序，SETD()则用于将驱动程序传过来的数据写入DATA中去。用C语言的表现形式来描述它们的话，就可以写成这样：uchar* GETD(void); 和 void SETD(uchar* data);

IOCTL_ACPI_EVAL_METHOD 请求

驱动程序可以通过调用WdfIoTargetSendIoctlSynchronously()函数发送IOCTL_ACPI_EVAL_METHOD请求给ACPI驱动来调用ACPI Method。关于该IOCTL更详细的信息，请查阅MSDN文档：IOCTL_ACPI_EVAL_METHOD control code

在编写KMDF驱动之前，我们需要先了解一下以下4个结构体：

ACPI_EVAL_INPUT_BUFFER

ACPI_EVAL_INPUT_BUFFER_COMPLEX

ACPI_EVAL_OUTPUT_BUFFER

ACPI_METHOD_ARGUMENT

ACPI_EVAL_INPUT_BUFFER结构体

结构体定义如下：

typedef struct _ACPI_EVAL_INPUT_BUFFER {
  ULONG Signature;
  union {
    UCHAR MethodName[4];
    ULONG MethodNameAsUlong;
  };
} ACPI_EVAL_INPUT_BUFFER, *PACPI_EVAL_INPUT_BUFFER;

该结构体用于调用一个不带输入参数的ACPI Method，假设要访问的Method为GETD()，在发送IOCTL_ACPI_EVAL_METHOD请求之前，需要对其成员变量进行如下设置：

设置Signature为ACPI_EVAL_INPUT_BUFFER_SIGNATURE
设置MethodName为 'GETD' 或设置MethodNameAsUlong为 (ULONG)('DTEG')

关于该结构体更详细的信息，请查阅MSDN文档： ACPI_EVAL_INPUT_BUFFER structure

ACPI_EVAL_INPUT_BUFFER_COMPLEX结构体

结构体定义如下：

typedef struct _ACPI_EVAL_INPUT_BUFFER_COMPLEX {
  ULONG                Signature;
  union {
    UCHAR MethodName[4];
    ULONG MethodNameAsUlong;
  };
  ULONG                Size;
  ULONG                ArgumentCount;
  ACPI_METHOD_ARGUMENT Argument[ANYSIZE_ARRAY];
} ACPI_EVAL_INPUT_BUFFER_COMPLEX, *PACPI_EVAL_INPUT_BUFFER_COMPLEX;

该结构体用于调用一个带输入参数的ACPI Method，用来传递输入参数，假设要访问的Method为SETD()，在发送IOCTL_ACPI_EVAL_METHOD请求之前，需要对其成员变量进行如下设置：

设置Signature为ACPI_EVAL_INPUT_BUFFER_COMPLEX_SIGNATURE
设置MethodName为 'SETD' 或设置MethodNameAsUlong为 (ULONG)('DTES')
设置Size的值，该值表示Argument[ANYSIZE_ARRAY]整个数组的字节大小
设置ArgumentCount的值，这里为1
给结构体成员Argument赋值，设置输入参数

关于该结构体更详细的信息，请查阅MSDN文档： ACPI_EVAL_INPUT_BUFFER_COMPLEX structure

ACPI_EVAL_OUTPUT_BUFFER结构体

结构体定义如下：

typedef struct _ACPI_EVAL_OUTPUT_BUFFER {
  ULONG                Signature;
  ULONG                Length;
  ULONG                Count;
  ACPI_METHOD_ARGUMENT Argument[ANYSIZE_ARRAY];
} ACPI_EVAL_OUTPUT_BUFFER;

该结构体用于返回ACPI Method执行后的输出参数，输出参数将被保存在Argument成员变量中，Signature的值必须为ACPI_EVAL_OUTPUT_BUFFER_SIGNATURE，Length表示整个ACPI_EVAL_OUTPUT_BUFFER结构体的字节大小，Count记录了有多少个Argument成员。关于该结构体更详细的信息，请查阅MSDN文档：ACPI_EVAL_OUTPUT_BUFFER structure

ACPI_METHOD_ARGUMENT结构体

结构体定义如下：

typedef struct _ACPI_METHOD_ARGUMENT
  USHORT Type;
  USHORT DataLength;
  union {
    ULONG Argument;
    UCHAR Data[ANYSIZE_ARRAY];
  };
} ACPI_METHOD_ARGUMENT;

该结构体才是真正存储输入、输出参数的地方。其中

Type定义了参数的类型，它的值有以下几种：

ACPI_METHOD_ARGUMENT_INTEGER

ACPI_METHOD_ARGUMENT_STRING

ACPI_METHOD_ARGUMENT_BUFFER

ACPI_METHOD_ARGUMENT_PACKAGE

DataLength为数组Data的字节大小。

关于该结构体更详细的信息，请查阅MSDN文档：ACPI_METHOD_ARGUMENT structure

Sample Code

访问不带输入参数的ACPI Method：

NTSTATUS ACPIGetData(WDFDEVICE FxDevice, void *pBuffer)
{
    NTSTATUS                 Status;
    WDF_MEMORY_DESCRIPTOR    InputDescriptor;
    WDF_MEMORY_DESCRIPTOR    OutputDescriptor;
    ACPI_EVAL_INPUT_BUFFER   InputBuffer;
    ACPI_EVAL_OUTPUT_BUFFER  OutputBuffer;
    WDFIOTARGET              IoTarget;
    ULONG                    SizeReturned;
    USHORT                   DataLength;

    PAGED_CODE();
	
    //
    // Signature and Method name in reverse
    //
    InputBuffer.Signature = ACPI_EVAL_INPUT_BUFFER_SIGNATURE;
    InputBuffer.MethodNameAsUlong = (ULONG) ('DTEG');

    //
    // Use following WDF method to initialize memory descriptor
    // The memory descriptor is initialized with the input buffer we have defined.
    //
    WDF_MEMORY_DESCRIPTOR_INIT_BUFFER(&InputDescriptor,
                                     (PVOID)&InputBuffer,
                                     sizeof(ACPI_EVAL_INPUT_BUFFER));

    RtlZeroMemory(&OutputBuffer, sizeof(OutputBuffer));
    WDF_MEMORY_DESCRIPTOR_INIT_BUFFER(&OutputDescriptor,
                                     (PVOID)&OutputBuffer,
                                     sizeof(ACPI_EVAL_OUTPUT_BUFFER));

    //
    // Get handle for underlying ACPI layer
    //
    IoTarget = WdfDeviceGetIoTarget(FxDevice);

    //
    // Send synchronous request
    //
    Status = WdfIoTargetSendIoctlSynchronously(IoTarget,
	                                       NULL,
                                               IOCTL_ACPI_EVAL_METHOD,
                                               &InputDescriptor,
                                               &OutputDescriptor,
                                               NULL,
                                               &SizeReturned);

    if (!NT_SUCCESS(Status)) {
       return Status;
    }

    //
    // Verify output signature and length
    //
    if ((OutputBuffer.Signature == ACPI_EVAL_OUTPUT_BUFFER_SIGNATURE)
	    && (OutputBuffer.Argument[0].Type == ACPI_METHOD_ARGUMENT_BUFFER))
    {
	//
	// Extract data from buffer
	//
	DataLength =  OutputBuffer.Argument[0].DataLength;
	memcpy_s((UINT8*)pBuffer,
                 (DataLength * sizeof(UINT8)),
                 (UINT8*)OutputBuffer.Argument[0].Data,
                 (DataLength * sizeof(UINT8)));

        Status = STATUS_SUCCESS;
    }
    else
    {
        Status = STATUS_ACPI_INVALID_DATA;
    }

exit:
    return Status;
}

访问带输入参数的ACPI Method：

NTSTATUS ACPISetData(WDFDEVICE FxDevice, void *pBuffer)
{
    NTSTATUS                        Status;
    WDF_MEMORY_DESCRIPTOR            InputDescriptor;
    WDF_MEMORY_DESCRIPTOR            OutputDescriptor;
    ACPI_EVAL_INPUT_BUFFER_COMPLEX   InputBuffer;
    ACPI_EVAL_OUTPUT_BUFFER        OutputBuffer;
    WDFIOTARGET                        IoTarget;
    ULONG                            SizeReturned;

    PAGED_CODE();
    //
    // Signature and Method name in reverse
    //
    InputBuffer.MethodNameAsUlong = (ULONG)('DTES');
    InputBuffer.Signature = ACPI_EVAL_INPUT_BUFFER_COMPLEX_SIGNATURE;
    InputBuffer.ArgumentCount = 1;
    InputBuffer.Size = InputBuffer.ArgumentCount * sizeof(ACPI_METHOD_ARGUMENT);
    InputBuffer.Argument[0].Type = ACPI_METHOD_ARGUMENT_BUFFER;
    InputBuffer.Argument[0].DataLength = 4;
	memcpy_s(InputBuffer.Argument[0].Data, InputBuffer.Argument[0].DataLength, 
		     pBuffer, InputBuffer.Argument[0].DataLength);

    //
    // Use following WDF method to initialize memory descriptor
    // The memory descriptor is initialized with the input buffer we have defined.
    //
    WDF_MEMORY_DESCRIPTOR_INIT_BUFFER(&InputDescriptor,
        (PVOID)&InputBuffer,
        sizeof(ACPI_EVAL_INPUT_BUFFER_COMPLEX));

    RtlZeroMemory(&OutputBuffer, sizeof(OutputBuffer));
    WDF_MEMORY_DESCRIPTOR_INIT_BUFFER(&OutputDescriptor,
        (PVOID)&OutputBuffer,
        sizeof(ACPI_EVAL_OUTPUT_BUFFER));

    //
    // Get handle for underlying ACPI layer
    //
    IoTarget = WdfDeviceGetIoTarget(FxDevice);

    //
    // Send synchronous request
    //
    Status = WdfIoTargetSendIoctlSynchronously(IoTarget,
        NULL,
        IOCTL_ACPI_EVAL_METHOD,
        &InputDescriptor,
        &OutputDescriptor,
        NULL,
        &SizeReturned);
	
    if (!NT_SUCCESS(Status))
    {
		goto exit;
    }
    else
    {
        //
        // Verify output signature and length
        //
        if ( (OutputBuffer.Signature == ACPI_EVAL_OUTPUT_BUFFER_SIGNATURE)
            && (OutputBuffer.Argument[0].Type == ACPI_METHOD_ARGUMENT_BUFFER))
        {
            Status = STATUS_SUCCESS;
        }
        else
        {
            Status = STATUS_ACPI_INVALID_DATA;
        }
    }
	
exit:
    return Status;
}

关于ACPI Control Method更详细的用法，请查阅MSDN官方文档：Evaluating ACPI Control Methods Synchronously

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Windows Phone 8.1 驱动开发——如何调用ACPI Method

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