MyFSD_DeviceIoControl

This function sends a control code directly to a specified device driver, causing the corresponding device to perform the specified operation. The application does not call this function directly. Instead, use the corresponding standard Win32 function DeviceIoControl. The file system driver (FSD) Manager determines the file system type and calls the MyFSD_DeviceIoControl implementation of the function.

At a Glance

Header file:	Fsdmgr.h
Windows CE versions:	2.10 and later

Syntax

BOOL MyFSD_DeviceIoControl( PFILE pFile, DWORD dwIoControlCode, PVOID pInBuf, DWORD nInBufSize, PVOID pOutBuf, DWORD nOutBufSize, PDWORD pBytesReturned, OVERLAPPED *pOverlapped);

Parameters

pFile

[in] Pointer to the value that the file system driver (FSD) passes to the FSDMGR_CreateFileHandle function when creating the file handle.

dwIoControlCode

[in] Specifies the control code for the operation. This value identifies the specific operation to be performed and the type of device on which the operation is to be performed.

pInBuffer

[in] Pointer to a buffer that contains the data required to perform the operation.

This parameter can be NULL if the dwIoControlCode parameter specifies an operation that does not require input data.

nInBufSize

[in] Size, in bytes, of the buffer pointed to by pInBuf.

pOutBuf

[out] Pointer to a buffer that receives the operation’s output data.

This parameter can be NULL if the dwIoControlCode parameter specifies an operation that does not produce output data.

nOutBufSize

[in] Size, in bytes, of the buffer pointed to by pOutBuf.

pBytesReturned

[out] Pointer to a variable that receives the size, in bytes, of the data stored into the buffer pointed to by pOutBuf.

The pBytesReturned parameter cannot be NULL. Even when an operation produces no output data and pOutBuf can be NULL, the DeviceIoControl function makes use of the variable pointed to by pBytesReturned. After such an operation, the value of the variable is without meaning.

pOverlapped

Ignored; set to NULL.

Return Values

Nonzero indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Remarks

An FSD exports this function if it wants to support the DeviceIoControl function. All FSD functions can be called reentryly, therefore, FSD developers must take this into account when developing an FSD.

The Fsdmgr component is a dynamic-link library (DLL) that manages all operating system interaction with installable files systems. Each installable file system requires an FSD, which is a DLL that exports an API needed to support an installable file system. The name of the DLL for the FSD and the names of the functions it exports start with the name of the associated installable file system. For example, if the name of file system is MyFSD, then its DLL is MyFSD.dll and its exported functions are prefaced with MyFSD_*.

Fsdmgr provides service functions to FSDs. The FSDMGR_RegisterVolume, FSDMGR_CreateFileHandle, and FSDMGR_CreateSearchHandle functions record a DWORD of volume-specific data the FSD needs to keep associated with volume. This volume-specific data is passed as the first parameter of these three functions.

Applications that access an installable file system use standard Win32 functions. For example, when an application wants to create a folder on a device that contains an installable file system, it calls CreateDirectory. Fsdmgr recognizes that the path is to a device containing an installable file system and calls the appropriate function, which in the case of the MyFSD file system is MyFSD_CreateDirectoryW. That is, the application calls CreateDirectory, causing Fsdmgr to call MyFSD_CreateDirectoryW.