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skrzyp |
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FAT Filesystem README
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+++++++++++++++++++++
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This file serves as documentation for the FAT filesystem until full
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documentation can be generated.
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Configuring FAT
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===============
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The FAT filesystem support consists of several packages:
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CYGPKG_FS_FAT
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The FAT filesystem itself.
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CYGPKG_BLOCK_LIB
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Block library. This actually implements the block cache. It
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depends on the Linux compatibility library
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(CYGPKG_LINUX_COMPAT) for support.
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CYGPKG_IO_DISK
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Disk device IO support. This provides the top level disk
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driver functions. It also interprets partition tables and
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provides a separate access channel for each partition.
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CYGPKG_DEVS_DISK_ECOSYNTH
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This is the only low level device driver currently known to
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work. This driver treats a file in the Linux filesystem as a
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disk image.
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CYGPKG_DEVS_DISK_V85X_EDB_V850
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This is a device driver for an IDE compatible Compact Flash
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device on a platform that is otherwise unsupported. It has not
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been tested.
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and other disk drivers which have been added in the mean time.
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In addition the above new packages, FAT support also relies on the
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following existing packages:
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CYGPKG_IO_FILEIO
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The File IO package. This provides the API by which the FAT
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filesystem is accessed.
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CYGPKG_IO
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Device IO package. This provides all the infrastructure for
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the disk devices.
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CYGPKG_LIBC_STRING
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Strings library. This provides the string and memory move and
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compare routines used by the filesystem.
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CYGPKG_MEMALLOC
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The FAT filesystem currently uses malloc() to allocate
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its memory resources, so this package is required.
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The doc directory that contains this file contains a number of .ecm
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files that will add the FAT filesystem to most configurations. These
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should be used as a basis for creating new configurations.
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Device Drivers
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==============
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The disk device interface is divided into a generic layer in the
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CYGPKG_IO_DISK package and drivers for each device.
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Each disk driver provides a number of device files. The drivers use a
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naming convention to ensure they are unique. The convention is
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/dev/XXXdiskY/Z. XXX is the name of the device driver, eg ide, mmc,
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synth etc. The DISK packages provide support for disk partitions. They
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interpret the on-disk data structures and provides an independent
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channel to access each partition independently. Partitions are
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referenced using an additional element to the device name. If the
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device is named "/dev/XXXdisk0" then "/dev/XXXdisk0/1" refers to
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partition 1, "/dev/XXXdisk0/2" to partition 2 and so on. If the disk
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is not partitioned, for example a floppy disk, then "/dev/XXXdisk0/0"
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refers to the whole disk.
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Testing
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=======
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There is currently just one test available for the FAT filesystem,
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fileio1. This test will currently only run on the Linux synthetic
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target and needs a special disk image. However, with some work it
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should be possible to make this test run on other disk drivers, if the
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image can be installed and the configury set appropriately.
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To run the test you first need to configure the synthetic disk driver
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to access the disk image. This is most easily done by importing the
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fat16.ecm file. A complete build would look like this:
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$ mkdir linux.fat16
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$ cd linux.fat16
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$ ecosconfig new linux
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$ ecosconfig import $ECOS_REPOSITORY/fs/fat/current/doc/fat16.ecm
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$ ecosconfig tree
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$ make tests
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To make the disk image, first ensure that there is at least 10MB of
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space available in your /tmp directory. Add the following two lines to
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your ~/.mtoolsrc file (you may need to create it):
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drive z: file="/tmp/disk0.img" partition=1
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drive y: file="/tmp/disk0.img" partition=2
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Now run the mkdisk0 shell script from the fs/fat/doc directory:
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$ source $ECOS_REPOSITORY/fs/fat/current/doc/mkdisk0
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20000+0 records in
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20000+0 records out
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Warning: no active (bootable) partition present
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$
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Ignore the warning, we are not interested in booting this disk.
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It should now be possible to run the fileio1 test program.
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