Samsung V1.3.0 User manual

Linux RFS v1.3.0 Porting Guide
May 20-2008, Version 1.13

Copyright notice
Copyright 200ⓒ8 Flash Software Group, Samsung Electronics, Co., Ltd..
All rights reserved.
Trademarks
RFS is trademark of Flash Software Group, Samsung Electronics Co., Ltd.. in Korea and other
countries
Restrictions on Use and Transfer
All software and documents of RFS are commercial software.
Therefore, you must install, use, redistribute, modify and purchase only in accordance with the
terms of the license agreement you entered into with Flash Software Group, Samsung Electronics
Co., Ltd.
All advertising materials mentioning features or use of this software must display the following
acknowledgement:
“This product includes RFS written by Flash Software Group, Samsung Electronics Co., Ltd.”
Contact Information:
Flash Software Group
Samsung Electronics Co., Ltd
Address: San #16 BanWol- Dong, Hwasung-City,
Gyeonggi-Do, Korea, 445-701
I LinuxRFSv1.3.0PortingGuide

II Linux RFS v1.3.0 Porting Guide
Preface
SEC-FSG-RFS1.2-POG
This document is a porting guide of RFS developed by Flash Software Group, Memory
Division, Samsung Electronics. It describes Linux RFS porting procedure to user's target platform.
Purpose
This document is RFS Porting Guide. This document explains the definition,
architecture, system requirement, and porting tutorial of RFS. This document also
provides the features and API of each module that a user should know well to port RFS.
Combine the above two paragraphs for one into a meaningful one
Scope
This document is for Project Manager, Project Leader, Application Programmers, etc.
Definitions and Acronyms
FTL (Flash
Translation Layer) A software module which maps between logical addresses and physical addresses when accessing to
flash memory
IDE Integrated Development Environment
CRAMFS Compressed ROM File System
RFS Robust FAT File System
VFS Virtual File System
XSR eXtended Sector Remapper
MTD Memory Technology Device
LLD Low Level Device Driver
Sector The file system performs read/write operations in a
512-byte unit called sector.
Page NAND flash memory is partitioned into fixed-sized
pages. A page is (512+16) bytes or (2048 + 64) bytes.
Block NAND flash memory is partitioned into fixed-sized
blocks. A block is 16K bytes or 128K bytes.
NAND flash device NAND flash device is a device that contains NAND flash
memory or NAND flash controller.
NAND flash memory NAND-type flash memory
Deferred Check
Operation The method that can increase time and device operation performance. Every operation function of LLD
defers the check routine to the next operation.
OneNAND Samsung NAND flash device that includes NAND flash
memory and NAND flash controller.

Related Documents
- RFS v1.3.0 Programmer’s Guide, Samsung Electronics, Co., Ltd.
- LinuStoreII Utility Guide, Samsung Electronics Co., Ltd.
- LinuStoreII Porting Guide, Samsung Electronics Co., Ltd.
History Version Date Comment Author
0.1 2006.01.05 Initial Flash Software Group
0.8 2006.01.13 1st draft Flash Software Group
1.4 2006.02.13 Release Thomas
1.5 2006.03.16 Release Amit
1.6 2006.03.23 Release Amit
1.7 2006.04.19 RFS1.2.1 release Amit
1.8 2006.05.10 DPM porting added Seung-Jin Jung
1.9 2006.09.27 NLS added Ha-Young Kim
1.10 2006-09-29 H/W int added Kyu-Hyung Kim
1.11 2006.12.26 Review comments Vishu Kumar
1.12 2007.03.19 SAM factor modifications Seung-Jin Jung
1.13 2008-05-20 Change version to 1.3.0
Delete sections about xsr Hayoung Kim
III Linux RFS v1.3.0 Porting Guide

IV Linux RFS v1.3.0 Porting Guide
Table of Contents
1 Introduction .........................................................................................1
1.1 Overview........................................................................................1
1.2 Features.........................................................................................1
1.3 Architecture....................................................................................1
2 Prerequisites ........................................................................................4
2.1 Host Environment..............................................................................4
2.2 Software Environment ........................................................................4
2.2.1 Directory Structure of Linux RFS Package............................................4
2.2.2 Source Files List ..........................................................................5
2.2.3 RFS Memory Usage .......................................................................6
2.3 Hardware Environment .......................................................................6
3 Porting Linux RFS...................................................................................7
3.1 Porting Overview ..............................................................................7
3.2 Porting Procedure .............................................................................7
3.2.1 Installation of Linux RFS Sources ......................................................7
3.2.2 Kernel Configuration for RFS ...........................................................8
3.2.3 Building Linux Kernel and RFS Kernel Module .......................................9
3.3 Using the NLS (Native Language Support) ............................................... 12
3.3.1 Kernel Configuration for NLS......................................................... 12
3.3.2 Mounting RFS with codepage......................................................... 14
Appendix................................................................................................. 16

Tables
Table 1 Host System Requirements.........................................................................4
Table 2 RFS Static Memory Usage (in bytes) ..............................................................6
Table 3 Hardware information of OMAP2420..............................................................6
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VI Linux RFS v1.3.0 Porting Guide
Figures
Figure 1-1 Linux RFS Architecture ..........................................................................2
Figure 2-1 Directory Structure of Linux RFS Package....................................................4
Figure 2-2 Linux RFS Source Files (Annotated on the Source Tree) ...................................5
Figure 3-1 Linux RFS Porting Procedure....................................................................7
Figure 3-2 Main screen of Kernel menu ....................................................................8
Figure 3-3 File system screen of Kernel menu ............................................................9
Figure 3-6 Code maturity level............................................................................ 10
Figure 3-7 CRMAFS OPTION Settings...................................................................... 11
Figure 3-9 RFS Filesystem configuration for VFAT...................................................... 12
Figure 3-10 NLS(Native Language Support) configuration............................................. 13
Figure 3-11 RFS Filesystem configuration for FAT16................................................... 14

1Introduction
This chapter describes the overview and system architecture of RFS. It also covers the
information about low-level flash memory partitions.
1.1 Overview
Linux RFS (Linux Robust FAT File System) is a FAT compatible file system to use
OneNAND/NAND flash memory as storage on any consumer electronic devices. As its name
implies, Linux RFS runs in the Linux kernel and is fully compatible with FAT file system
standards (FAT16/32). For ‘robustness’, it provides a journaling based error recovery
mechanism, which guarantees that the file system runs at all times even if there is a sudden
power loss.
Currently, there are a few open-source projects that implement NAND based flash file systems
such as JFFS2, YAFFS and YAFFS2. However, they have a limited applicability to brand-new
OneNAND flash memory devices that feature advanced technologies to improve performance.
RFS supports all of the OneNAND flash memory devices in the market and is optimized for those
devices. RFS can deliver much better read/write performance compared to the existing
solutions.
1.2 Features
The following are RFS features.
•FAT compatible file system which supports FAT16/32
•Robust error-recovery system based on journaling
•Provide POSIX-compatible interface
•Supports Linux kernel 2.4.X and 2.6.X (tested on MontaVista Linux)
•Supports demand paging
•Packaged as a loadable kernel module
1.3 Architecture
Figure 1-1 shows typical file system architecture where RFS is used for OneNAND flash memory.
Linux RFS flash file system has been divided into different layers based on their operations. It
consists of following layers: FAT file system layer, flash block device driver layer, sector
translation layer, block management layer, and low level device driver layer.
Low level device driver layer code for OneNANDTM is provided with RFS package and is tested
on OMAP2420 board. For other chipsets, you need to write your own low level driver code. A
brief description about each of these components is given here.
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2 Linux RFS v1.3.0 Porting Guide
Figure 1-1 Linux RFS Architecture
File Systems
Linux file system for flash devices is managed by two file systems: CRAMFS and RFS. Both of
these file systems run under Linux VFS (Virtual File System).
•CRAMFS: This is a read-only file system included in a standard Linux kernel distribution.
CRAMFS is used to manage the read-only part of Linux file system directories, i.e. execution
code, libraries, and ROM data files. Because CRAMFS supports run-time code decompression,
you can store code in a compressed form, which results in high space efficiency. CRAMFS
runs on top of the BML Block Device Driver.
•RFS: This is a read-write Samsung’s file system and is used to manage the modifiable data
part of the Linux file system directories, i.e. configuration files and applications data files.
It does not support compression feature. RFS runs on top of the STL Block Device Driver.
XSR Block Device Drivers
Block device drivers are used to provide common block device APIs to file systems. For each of
the block device drivers, separate block device files provide device interface methods like
mount and format to applications. RFS needs two kinds of block device driver interface.
•BML Block Device Driver: This block device driver is used to provide driver functions for
the device files /dev/bml0/*. This block device driver acts right upon the BML. There is no
logical to physical address translation because there is no FTL-like software layer between
BML and this driver layer. For example, logical sector number n directly maps to physical
sector number n. Data write to a sector involves following sequence of low-level flash
operations:
1. Block copy for back-up
2. Block erase
3. Copy back for non-modified pages