Device Operations

The ultimate purpose of a file system device is to hold data. Consequently, two major operations that can occur on a device are the reading and writing of individual sectors. Five additional operations can be performed which affect not just individual sectors, but the whole device:

A device can be opened. During the opening of a device, it is initialized and its characteristics are determined (sector size, number of sectors, vendor).

A device can be partitioned. Partitioning divides the final unallocated portion of the device into two parts, so that a volume could be located on each (see section 7-5 “Partitions”).

A device can be low-level formatted. Some device must be low-level formatted before being used.

A device can be (high-level) formatted. (High-level) formatting writes the control information for a file system to a device so that a volume on it can be mounted. Essentially, (high-level) formatting is the process of creating a volume on an empty device or partition.

A device can be closed. During the closing of a device, it is uninitialized (if necessary) and associated structures are freed.

These operations and the corresponding API functions are discussed in this section. For information about using device names, see section 4-2 “μ C/FS Device and Volume Names”.

Function	Description
FSDev_AccessLock()	Acquire exclusive access to a device.
FSDev_AccessUnlock()	Release exclusive access to a device.
`FSDev_Close()`	Remove device from file system.
`FSDev_GetNbrPartitions()`	Get number of partitions on a device.
FSDev_Invalidate()	Invalidate files and volumes open on a device.
`FSDev_IO_Ctrl()`	Perform device I/O control operation.
`FSDev_Open()`	Add device to file system.
`FSDev_PartitionAdd()`	Add partition to device.
`FSDev_PartitionFind()`	Find partition on device and get information about partition.
`FSDev_PartitionInit()`	Initialize partition on device.
`FSDev_Query()`	Get device information.
`FSDev_Rd()`	Read sector on device.
`FSDev_Refresh()`	Refresh device in file system.
`FSDev_Wr()`	Write sector on device.

Table 7-1 Device API functions