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68 lines
2.7 KiB
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=======
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Preface
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=======
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This document describes the implementation of the RTEMS filesystem
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infrastructure. This infrastructure supports the following
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capabilities:
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- Mountable file systems
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- Hierarchical file system directory structure
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- POSIX compliant set of routines for the manipulation of files and directories
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- Individual file and directory support for the following:
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# Permissions for read, write and execute
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# User ID
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# Group ID
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# Access time
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# Modification time
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# Creation time
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- Hard links to files and directories
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- Symbolic links to files and directories
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This has been implemented to provide the framework for a UNIX-like
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file system support. POSIX file and directory functions have been
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implemented that allow a standard method of accessing file, device and
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directory information within file systems. The file system concept that
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has been implemented allows for expansion and adaptation of the file
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system to a variety of existing and future data storage devices. To this
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end, file system mount and unmount capabilities have been included in this
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RTEMS framework.
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This framework slightly alters the manner in which devices are handled
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under RTEMS from that of public release 4.0.0 and earlier. Devices that
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are defined under a given RTEMS configuration will now be registered as
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files in a mounted file system. Access to these device drivers and their
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associated devices may now be performed through the traditional file system
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open(), read(), write(), lseek(), fstat() and ioctl() functions in addition
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to the interface provided by the IO Manager in the RTEMS Classic API.
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An In-Memory File System (IMFS) is included which provides full POSIX
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filesystem functionality yet is RAM based. The IMFS maintains a
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node structure for each file, device, and directory in each mounted
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instantiation of its file system. The node structure is used to
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manage ownership, access rights, access time, modification time,
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and creation time. A union of structures within the IMFS nodal
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structure provide for manipulation of file data, device selection,
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or directory content as required by the nodal type. Manipulation of
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these properties is accomplished through the POSIX set of file and
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directory functions. In addition to being useful in its own right,
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the IMFS serves as a full featured example filesystem.
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The intended audience for this document is those persons implementing
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their own filesystem. Users of the filesystem may find information
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on the implementation useful. But the user interface to the filesystem
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is through the ISO/ANSI C Library and POSIX 1003.1b file and directory
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APIs.
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.. COMMENT: COPYRIGHT (c) 1988-2002.
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.. COMMENT: On-Line Applications Research Corporation (OAR).
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.. COMMENT: All rights reserved.
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