File System Driver Loading
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8/28/2008
A file system driver (FSD) is loaded automatically when storage hardware that is registered for an FSD is inserted into a device. Alternatively, FSDs can be auto-loaded at startup.
When a PC card, such as a storage card, is inserted into a device, the card's device driver reads the PC card driver registry entry. A PC card registry entry specifies the name of the FSD for the card, such as MyFSD.dll.
When a user inserts a PC card, a notification is sent to Storage Manager. Storage Manager mounts the appropriate partition driver, and then loads the corresponding file system for the partition. While loading the file system, Storage Manager verifies that the file system, in this case MyFSD.dll, defines the FSD_MountDisk entry point, which is the generic exported entry point for MyFSD_MountDisk.
FSD Manager calls the MyFSD_MountDisk function that MyFSD.dll exports. The following table shows the two methods for loading an FSD.
| File system | Method |
|---|---|
Automatically loaded file systems |
The HKEY_LOCAL_MACHINE\System\StorageManager\AutoLoad registry key specifies these file systems. They do not necessarily need a block driver. |
Block driver based file systems |
If the block driver registry key contains the IClass registry subkey, which means that Storage Manager manages it, Storage Manager loads the specified partition driver. For an example of the IClass registry subkey, see the ATADISK and ATAPI registry keys. Using the specified partition driver, Storage Manager enumerates partitions and loads file systems. For more information, see Storage Management. |
For more specific information about registry values that control file system driver loading, see File System Driver Registry Settings.
Because there are two methods of loading a file system, the file system is loaded multiple times with Storage Manager, and you only need to call FSDMGR_RegisterVolume once per instance of an FSD.
FSD Manager displays all volumes as directories in the built-in file system and makes them accessible to applications, using the file system functions. Similarly, when the FSD MyFSD_UnmountDisk entry point is called, it deregisters the volumes on the target device. The following illustration shows how an FSD is loaded.
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