Subversion Repositories or1k

@c

@c  COPYRIGHT (c) 1988-2002.

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

@c  All rights reserved.

@c

@c  init.t,v 1.8 2002/01/17 21:47:45 joel Exp

@c

@chapter System Initialization

After the RTEMS initialization is performed, the application's

initialization will be performed. Part of initialization is a call to

rtems_filesystem_initialize(). This routine will mount the `In Memory File

System' as the base filesystem.  Mounting the base filesystem consists

of the following:

@itemize @bullet

@item Initialization of mount table chain control structure

@item Allocation of a @code{jnode} structure that will server as the root node

of the `In Memory Filesystem'

@item Initialization of the allocated @code{jnode} with the appropriate OPS,

directory handlers and pathconf limits and options.

@item Allocation of a memory region for filesystem specific global

management variables

@item Creation of first mount table entry for the base filesystem

@item Initialization of the first mount table chain entry to indicate that

the mount point is NULL and the mounted filesystem is the base file

system

@end itemize

After the base filesystem has been mounted, the following operations are

performed under its directory structure:

@itemize @bullet

@item Creation of the /dev directory

@item Registration of devices under /dev directory

@end itemize

@section Base Filesystem

RTEMS initially mounts a RAM based file system known as the base file system.

The root directory of this file system tree serves as the logical root of the

directory hierarchy (Figure 3). Under the root directory a `/dev' directory

is created under which all I/O device directories and files are registered as

part of the file system hierarchy.

@example

Figure of the tree structure goes here.

@end example

A RAM based file system draws its management resources from memory. File and

directory nodes are simply allocated blocks of memory. Data associated with

regular files is stored in collections of memory blocks. When the system is

turned off or restarted all memory-based components of the file system are

lost.

The base file system serves as a starting point for the mounting of file

systems that are resident on semi-permanent storage media. Examples of such

media include non- volatile memory, flash memory and IDE hard disk drives

(Figure 3). File systems of other types will be mounted onto mount points

within the base file system or other file systems that are subordinate to the

base file system. The framework set up under the base file system will allow

for these new file system types and the unique data and functionality that is

required to manage the future file systems.

@subsection Base Filesystem Mounting

At present, the first file system to be mounted is the `In Memory File

System'. It is mounted using a standard MOUNT() command in which the mount

point is NULL.  This flags the mount as the first file system to be

registered under the operating system and appropriate initialization of file

system management information is performed (See figures 4 and 5). If a

different file system type is desired as the base file system, alterations

must be made to base_fs.c. This routine handles the mount of the base file

system.

@example

Figure of the mount table chain goes here.

@end example

Once the root of the base file system has been established and it has been

recorded as the mount point of the base file system, devices are integrated

into the base file system. For every device that is configured into the

system (See ioman.c) a device registration process is performed. Device

registration produces a unique dev_t handle that consists of a major and

minor device number. In addition, the configuration information for each

device contains a text string that represents the fully qualified pathname to

that device's place in the base file system's hierarchy. A file system node

is created for the device along the specified registration path.

@example

Figure  of the Mount Table Processing goes here.

@end example

Note: Other file systems can be mounted but they are mounted onto points

(directory mount points) in the base file system.