Subversion Repositories or1k

@c

@c  COPYRIGHT (c) 1988-2002.

@c  On-Line Applications Research Corporation (OAR).

@c  All rights reserved.

@c

@c  preface.texi,v 1.6 2002/01/17 21:47:45 joel Exp

@c

@ifinfo

@node Preface, , Top, Top

@end ifinfo

@unnumbered Preface

This document describes the implementation of the RTEMS filesystem

infrastructure.  This infrastructure supports the following

capabilities:

@itemize @bullet

@item Mountable file systems

@item Hierarchical file system directory structure

@item POSIX compliant set of routines for the manipulation of files and directories

@item Individual file and directory support for the following:

@enumerate

@item Permissions for read, write and execute

@item User ID

@item Group ID

@item Access time

@item Modification time

@item Creation time

@end enumerate

@item Hard links to files and directories

@item Symbolic links to files and directories

@end itemize

This has been implemented to provide the framework for a UNIX-like

file system support. POSIX file and directory functions have been

implemented that allow a standard method of accessing file, device and

directory information within file systems. The file system concept that

has been implemented allows for expansion and adaptation of the file

system to a variety of existing and future data storage devices. To this

end, file system mount and unmount capabilities have been included in this

RTEMS framework.

This framework slightly alters the manner in which devices are handled

under RTEMS from that of public release 4.0.0 and earlier.  Devices that

are defined under a given RTEMS configuration will now be registered as

files in a mounted file system.  Access to these device drivers and their

associated devices may now be performed through the traditional file system

open(), read(), write(), lseek(), fstat() and ioctl() functions in addition

to the interface provided by the IO Manager in the RTEMS Classic API.

An In-Memory File System (IMFS) is included which provides full POSIX

filesystem functionality yet is RAM based.  The IMFS maintains a

node structure for each file, device, and directory in each mounted

instantiation of its file system. The node structure is used to

manage ownership, access rights, access time, modification time,

and creation time.  A union of structures within the IMFS nodal

structure provide for manipulation of file data, device selection,

or directory content as required by the nodal type. Manipulation of

these properties is accomplished through the POSIX set of file and

directory functions.  In addition to being useful in its own right,

the IMFS serves as a full featured example filesystem.

The intended audience for this document is those persons implementing

their own filesystem.  Users of the filesystem may find information

on the implementation useful.  But the user interface to the filesystem

is through the ISO/ANSI C Library and POSIX 1003.1b file and directory

APIs.