Embedded Linux And Device Driver Lecture

Fall 2012SILICON VALLEY UNIVERSITY

CONFIDENTIAL 1

Embedded Linux and Linux Device Drivers

Simon Au, Silicon Valley University

SILICON VALLEY UNIVERSITY CONFIDENTIAL 2

Course Description

Concepts of Embedded Linux Development. Bootloader (i.e. Redboot, uBoot). Linux Library uclibc for microcontrollers (Kernel APIs or system calls). Understand Linux File System and RamDisk. Crossplatform GNU toolchain to compile Linux Kernel and uclibc for

target. Concepts of Linux Device Driver Development.

Loadable Kernel modules (device drivers) and load/unload the Kernel modules.

Char/Block/Network Device drivers and /Proc File System Drivers. Linux Library APIs (i.e. System Calls) and IOCTL calls.

Hands-On Lab Build Embedded Linux System for Cirrus Logic ARM Microcontroller. Develop Char/Block Device Driver for RAM Filesystem. Develop /Proc File System Drivers. Cirrus Logic Microcontroller chip 9302 ARM 9 Core. 32 MByte RAM, 16

MByte Flash memory, network and serial ports. Redhat Linux Host Development System to develop and download

embedded Linux/RamDisk target systems.

Fall 2012

SILICON VALLEY UNIVERSITY CONFIDENTIAL 3Fall 2012

Course Description

Class Evaluation: 30 %: Midterm. First half material. 40 %: Final. Second half material. 30 %: Homework + : Extra credit.

Lab Evaluation: 100 %: Lab 11 assignments.

References: Building Embedded Linux Systems 2nd Edition, O’Reilly Media, 2008 Materials included from Suleman Saya, UC Santa Cruz Linux Device Drivers 3rd Edition, Rubini & Corbet Materials included from Raghav Vinjamuri, UC Santa Cruz http://class.svuca.edu/~sau/CE562/

Homework Assignments LinuxDeviceDrivers3rdEdition


Course Description

Cross Development Build Environment Assignment 1:

Build RAMDisk on Host Linux. RedBoot BootLoader TFTP/Serial From Host Linux To Target Platform

(Cirrus Microcontroller). Assignment 2:

Compile Linux Toolchain For Cirrus Logic EP9302 ARM Platform. Compile C Application With Linux Toolchain and Place In RAMDisk.

Assignment 3: Compile Embedded Linux Kernel 2.6.29. Compile uclibc For Embedded Linux System.

Assignment 4: Compile BusyBox Application and Create RAMDisk. Create Linux initialization file.

Assignment 5: Use /proc File System driver. Install Loadable Modules.


Course DescriptionLinux Device Driver DevelopmentAssignment 6:

Create /dev char Device Driver. Create /proc File System driver. Read/Write /proc File RAM file and Read/Write /dev RAM file.

Assignment 7: Create /dev char Device Driver. Use semaphores and spinlocks. Read/Write /dev device.

Assignment 8: Create /dev char Device Driver with multiple minor numbers. Read/Write multiple /dev devices.

Assignment 9: Create Interrupt Handler. Register Interrupt Handler with IRQ and create

workqueue for bottom-half. Assignment 10:

Create /dev char Device Driver with mmapped kernel to user memory. User application access kernel memory.

Assignment 11: Export Kernel Symbols. Install Kernel Thread.


Embedded Linux Course Outline Section 1 Embedded Linux Introduction

Linux At the Beginning GNU and GNU Public License (GPL) Embedded Linux Criterias Embedded Linux Development Linux Kernel Infrastructure Cross-Platform Development

Section 2 Embedded Linux Development Embedded Linux Development Requirements For Host System

Setup Host System For Cross-Development Setup Target Board For Cross-Development

Target Board Boot Process Target Board / Host System Communication RAM Disk


Embedded Linux Course Outline Section 3 Embedded Linux ToolChain

ARM Tool-Chain Binutils Kernel Headers Cross Compiler First / Second Stage Glibc Library

Section 4 Linux File System Linux File System

Linux Source Directory Hierarchy Root File System

File System Concepts Inodes Virtual File System

/proc File System


Embedded Linux Course Outline Section 5 Kernel Internals

Kernel Modules Module Organization Module Installation (Insmod) and Removal (rmmod)

Linux Device Drivers Character Drivers Block Drivers Major and Minor Number

Section 6 Kernel Scheduling Process Fundamentals

Process States Process Scheduling

Preemptive / Cooperative Multitasking Scheduling Policy Process Classification

Interactive Processes Batch Processes


Embedded Linux Course Outline Section 7 Kernel Process / Treads

Process VS Threads InterProcess Communications (IPC) Memory Constraints

Thread Management User Level Threads Kernel Level Threads

Clone() / Fork() / VFork() Threads

Section 8 Linux Interrupt Handlers Linux Interrupt Handlers

Fast Interrupt Handlers Slow Interrupt Handlers Top Half Handlers Bottom Half Handlers

Tasklets Workqueues


Embedded Linux Course Outline Section 9 Character/Block Device Drivers

Device Data Structures Character Driver Registration Block Driver Registation File Operations and ioctl

File Operations Init/Open/Read/Write/Release/Mmap ioctl

Race Conditions Semaphores and Mutexes Spinlocks

Memory Management in Linux Memory Mapping and DMA The mmap Device Operation

Section 10 Network/USB/PCI Drivers Device Data Structures

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Section 1 Embedded Linux Introduction 1991 University Of Helsinki in Finland by Linus B. Torvalds. Originally Minux, alternative to DOS.

Minux developed by Andrew Tanenbaum to teach Unix. Minux supported protected mode. Minux rewrote for additional funtionality and features as

Linux. Currently all code in Minux has been replaced. Minux file system format supported under Linux. Core is the

Virtual File System (VFS). Linux built with GNU compiler and library. Released on

10/1991. Linux is POSIX compliant. Compatiable with Unix System V. GNU utilities and tools (compiler, assembler, loader, etc) are

freeware. GNU Public License (GPL) specifies any modifications to Linux

has to be freely published. Linux is open source because of GNU utilities and tools.

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Section 1 Embedded Linux Introduction Embedded System Definition

Computer system integrated into a larger applicances that is not a computer (i.e. oven, gas station pump, ATM machine) or small devices (i.e. cell phone, PDA

Physcial size is small. The computer system is on a small board. CPU, RAM, and low power consumption.

Based on concept of the microcontroller, single integrated circuit that contains all the technology required to run an application. Combined onto a chip. Reduces chips and wiring to control a device. Reduce complexity, size, and cost.

CPU RAM for program and data storage. Flash memory for program storage. Input/Output interfaces (i.e. serial, USB, ethernet, USB). Timers.

Embedded system designed to perform simple, repeatable tasks. Simpliying tasks reduces complexity, minimize CPU processing power, and minimize RAM/Flash requirements. Maximum performance for minimum size and weight.

Not apparent to user. Provide device with network-ability, available as modem, ethernet port, USB, or

wireless. Provide device with user Interaction, likely (i.e. cell phone, PDA, gas pumps,

ATMs). Some run without human intervention, but might be required to respond to realtime events (i.e. LEDs).

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Section 1 Embedded Linux Introduction Users of Embedded System

Manufacturing – Replaces general purpose computers to control equipment. Drive down manufacturing costs and subsequently drives down end user prices.

Solution for complex problems in product design. Car has embedded systems to control brakes,

ariconditioning, ignition systems. Without embedded systems, need complicated and fault prone electronics or general purpose PC.

Consumer electronics – Cell phones, digital cameras, pagers, PDAs, DVD players, copiers, printers, scanners, fax machines, Network switches/routers, stereo systems, televisions, game consoles, electronic instruments, electronic toys.

Consumer products – Ovens, dishwashers, washer, dryers, home security systems.

Business products – automobile electronics (i.e. audio system, anti-lock brakes), ATMs, hospital life-support systems, hospital medical testing systems, airplane on-board electronic monitors.

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Section 1 Embedded Linux Introduction Linux as Embedded System

Why use Linux? Other Embedded OS options (i.e. VxWorks by WindRiver, pSOS by WindRiver, QNX, Nucleus by Accelerated Technologies, RTKernel, Symbian OS, Microware OS-9 by RadiSys, Windows CE by Microsoft, OSE by Enea, MicroC by OS-II).

Linux quality and reliability. Large community support (i.e. Google). No need to pay for customer support.

Open source. GNU utilities and tools made Linux appealing. Even condensed version of Linux on dedicated system has many solutions.

Linux Custom Distributions: Monta Vista, TimeSys, Linux Free Distirbutions: Redhat, Degian, and Suse.

Multitasking scheduler allows many processes/threads to run at the same time.

Symmetric Multi Processor (SMP) Memory protection between processes, prevents one process from bringing

down system. Multiplatform solution since Linux runs on many CPUs (ARM, x386,

PowerPC, MIPS). Networking protocols (TCP/IP, IP services, Netware, AppleTalk, Supports Virtual File System (VFS) for transparent access to many file

systems. Dynamic loadable kernel modules.

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Section 1 Embedded Linux Introduction

Linux Kernel Architecture Linux is modular, monolithic kernel. Kernel is single process with one

address and memory space. Services (i.e. scheduler, file manager, memory manager) made through direct function calls.

User space, each process (i.e. application) protected by their own user memory. Invalid memory access will crash only the process.

Kernel space, memory space is not protected. Invalid memory access will

crash the system. User Space

App1 . . .

Kernel Space File Manager

Networking uclibc Memory Manager

Device DriversScheduler

Architecture / Platform

X386 PowerPC ARM MIPS . . .

App2

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API (Libraries, System Call Interfaces)


Section 1 Embedded Linux Introduction Linux Monolithic Kernel

Linux is modular, monolithic kernel. Kernel is single process with one address and memory space. Services (i.e. scheduler, file manager, memory manager) made through direct function calls.

Linux Kernel modules exported symbols and functions are directly callable by other modules.

Linux Kernel makes invalid memory reference, the kernel and all user processes crashes.

Contrast micro-Kernel. Services are separate processes. IPC between services to request service. QNX example of micro-Kernel. When QNX service makes invalid memory reference, the kernel does not crash, only that service crashes.

struct_task data structure used by every process and thread. Allows Kernel to schedule both process and threads together. First process created is the init process and all other processes are child processes.

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Section 1 Embedded Linux Introduction

Linux Directory Structure

vmlinux

inittabfstab

passwd

bin mount

usr

/boot

etc

bingrep

varlog

devtty0

mntcdrom

home student1

/boot – Linux bootup files (i.e. Linux Kernel)

/etc – Linux system configuration files.

/etc/inittab – Processes started at bootup (i.e. Runlevel)

/etc/fstab – File systems and mount points.

/etc/passwd – Users are defined and user accounts.

/bin – Linux system binaries.

/sbin/init – Process runned during boot process.

/usr/bin – Applications for the users.

/lib – The shared libraries for dynamically linked modules.

/var – Data changes when the Linux system is running.

/var/log – The running Linux system updated log files.

/dev – Devices that are available to Linux system. Devices are treated like files and devices can be read/written as files.

/mnt – Storage devices (i.e. hard disk, CD-ROMs) must be attached to some directory before accessing. Directores are the mount points.

/home – Each users have own directory and only place normal users are allowed to write.

/proc – Special directory containing information about the kernel.

/proc/devices – List of devices configured into current kernel.proc

devices

lib

sbin init


Section 1 Embedded Linux Introduction Soft Real-Time Embedded System

Time tolerance for an event to occur. ATM machine. Transaction occurs after 10 seconds or 20 seconds, but

not critical to occur at the same time every time. At least the transaction completes.

Video streaming. Best effort and minimized latency from event. Linux latency in scheduler and memory manager makes Linux Soft

Real-Time. For Hard Real-Time, Linux Kernel must be rewritten. Hard Real-Time Embedded System

Absolute deadline must be met and no deadline missed. Airline computers controls radar, alarm indicators, airplane controls. Nuclear reactor temperator gauges and sensors must trigger cool down

action immediately or disaster will occur. Absolute deterministic response to an event. OS that provides required service in bounded response time. In

bounded response time, need to know when event must occur. VxWorks provides the most real-time critical events.

Real-time event is measured and response time is tested repeatedly.


Section 1 Embedded Linux Introduction Real Time Linux 2.6

Preemption Linux 2.4 nonpreemptive. System call (uclibc library) completed before

the CPU was released. Higher priority process or interrupt prevented from running.

For example, keyboard not responsive until system call was completed.

Linux 2.6 system call was preemptable. A process forced to release CPU.

Real Time Scheduler Linux 2.6 scheduler determined time slice for each process and which

process to run based on runqueue per priority level. Active and Expired priority arrays.

Linux 2.4 scheduler uses one global runqueue. Traverse entire runqueue to determine next process to run.

Scheduling Policies (NORMAL, FIFO, RR, BATCH) Process Class (Interactive, Batch, Real-Time)

Interactive spends time performing I/O (i.e. editors). Batch do not need user interaction (i.e. compiler). Real-Time provide deterministic response time (i.e. robot controllers).


Section 1 Embedded Linux Introduction Linux Development Requirements Cross Development Platform on Linux Host

Development is done on a different platform than the target platform.

Microcontrollers has limited resources, CPU is not powerful enough to run compiler, a file system, or a development environment.

Host system running Linux 2.4, but the target system is Linux 2.6. The Linux 2.4 GCC compiler will be used to compile the Linux 2.6 GCC cross compiler.

Host system is x86 processor, but the target system has ARM 9 based microcontroller.

Cross compiler used to build toolchain (i.e. assembler, linker, utilties) for target system.

Cross compiler and toolchain used to build Linux 2.6 Kernel for target system.

Advantage of Linux based host. Target simulators on host allow testing before loading target

system.


Section 2 Embedded Linux Development Cirus Logic EP-9302 Microcontroller

200 MHz Cirrus Logic EP-9302 ARM920T core processor with math co-processor and MMU

ARM stands for Advanced RISC Machine (Reduced Instruction Set Computer Instruction Set Architecture).

Simplicity suitable for low power applications in mobile and embedded electronics.

90% of all embedded 32-bit RISC processors. 10/100 MBps Ethernet 2 USB Ports RS232 Serial Port Real-time clock and watch-dog timer A/D, D/A converter 32 MByte 100 MHz SDRAM, 16 MByte Flash Marverick Math Engine

SILICON VALLEY UNIVERSITY CONFIDENTIALFall 2012

Section 2 Embedded Linux Development

Cross Development Environment Host System will send bootloader commands over Target

System serial port. Host system ethernet port send Linux Kernel image and

RAMDisk to target system RAM.

Switch

Host System

TargetSystem Serial Port

Ethernet Port

1) Bootload commands.2) Target System console log.

Transfer Kernel image and RAMDisk (ext2 File System) to Target System RAM or Flash.

1) Host Linux Distribution, RedHat Linux.2)Target System Linux 2.63) GNU Cross Development.4) Root permission.5) tftp Server.6) tftpboot directory.7) IPNetwork8) Minicom communicate to target over serial cable.192.168.1.100

192.168.1.101

22


Section 2 Embedded Linux Development Linux Boot Process – Bootloader

Reset Microcontroller First stage bootloader located in small ROM (2K or 4K Bytes). Initializes CPU, MMU, on-chip devices, configures memory map. ROM bootloader loads second stage bootloader (i.e. Redboot) from fixed address from

flash to RAM. ROM bootloader must have flash driver. NAND Flash –large, less cost, cannot execute-in-place. NOR Flash – smaller, execute-in-place (i.e. Second Stage Bootloader execute

from NOR). Second stage bootloader will load the Linux Kernel and RAMDisk from:

Automatically decompress the Linux Kernel and RAMDisk from flash to RAM. Manually interrupt bootloader (<cntrl> <c>) and use tftp to load Linux Kernel from

server. After Linux Kernel starts running, bootloader is no longer in RAM.

Bootloader configuration (i.e. IP address, host system (server) IP address) saved in high address space in flash. Only for development and testing.

Bootloader configured with the starting address space in flash where Linux is located and where RAMDisk is located.

During development, bootloader will load Kernel and RAMDisk from host system. Bootloader executes a jump to the Kernel code to configure the microprocessor

registers and start_kernel() function. Bootloader architecture specific. Bootloader has memory map for the flash and for

loading Kernel and RAMDisk and will be different for another microcontroller.


Section 2 Embedded Linux Development Linux Boot Process – Kernel

Kernel initializes cache, hardware devices, and mounts root file system (i.e. RAMDisk). Without root file system, Kernel will hang.

/etc directory contains Kernel configuration files (i.e. inittab, rc.d, fstab).

Kernel executes the init process, reading its configuration file, /etc/inittab, and executes scripts dependent on selected runlevel.

Init process executes startup script, /etc/rc.d/rc.sysinit, configuring and starting networking and other system services (i.e. /etc/rc.d/init.d contains service scripts).

Init process enters a runlevel, where different processes are started by scripts to run activate the resources for that runlevel (default in /etc/inittab).

Runlevel 5 used for graphical interface (used for PC). Starts services in /etc/rc.d/rc5.d.

Runlevel 3 brings up the system console window (used for embedded system). Starts services in /etc/rc.d/rc3.d.

Local initialization, /etc/rc.local.



Linux Boot Process – /etc/inittab

# inittab This file describes how the INIT # process should setup the system# in a certain run-level.Id:5:initdefault:#System initializationsi::sysinit:/etc/rc.d/rc.sysinit

l0:0:wait:/etc/rc.d/rc 0l1:1:wait/etc/rc.d/rc 1l2:2:wait/etc/rc.d/rc 2l3:3:wait:/etc/rc.d/rc 3l4:4:wait:/etc/rc.d/rc 4l5:5:wait:/etc/rc.d/rc 5l6:6:wait/etc/rc.d/rc 6

#Run gettys in standard runlevels1:2345:respawn:/sbin/mingetty tty1…#Run xdm in runlevel 5X:5:respawn:/etc/X11/prefdm - nodaemon

Format of inittab file entries:

id:runlevels:action:process

Id: unique sequence of 1-4 characters.

runlevels: 0-6 runlevels for the specified action.

action:

-- initdefault: runlevel to enter (i.e. scripts in /etc/rc.d/rcx.d directory, where x=0 to 6) after system boot.

-- sysinit: process executed during system boot before any boot or bootwait actions.

-- boot: process executed during system boot.

-- bootwait: process executed during system boot while init waits for its termination (i.e. /etc/rc).

-- wait: process started when runlevel is entered and init will wait for termination.

-- respawn: process will restart whenever it terminates.


Section 2 Embedded Linux Development Linux Boot Process – Root File System

Embedded system, RAMDisk is used for file system. No hard disk in embedded system. RAMDisk is in system memory and acts like a block device. Supports different kinds of file systems (i.e. FAT, ext2, ext3). Default file system is ext2.

Before loaded from flash or tftp from host system, root file system is a compressed file. Decompressed into RAM as ext2 file system.

Root file system must contain everything needed to support a full Linux system. The basic file system structure:

Directories: /dev, /proc, /bin, /etc, /lib, /usr, /tmp Set of utilties (/bin): sh, ls, cp, mv, etc. System config files (/etc): rc.d, inittab, fstab, etc. Devices (/dev): hda, tty<x>, fd, etc. Runtime library used by utilities.

Root file system is mounted in RAM from RAMDisk, persists in RAM until system reboots.

Development option: NFS-mount the root file system from the host system. Using NFS need configuration options enabled when Kernel is built.

Linux interface through Virtual File System (VFS), standard set of I/O interfaces that can be used over different devices (i.e. hard disk, CDROM, NFS, NTFS, Apple File System).

Physical device abstacted away from the user. Common Open/Read/Write/Close APIs are used regardless of underlying file system.


Section 2 Embedded Linux Development Linux Boot Process – Host System Requirements

Host Linux distribution (i.e. Redhat Linux). GNU Cross Development environment. tftpboot directory (root level) contains the Kernel image and root file

system (i.e. RAMDisk). NOTE: chmod –R 777 /tftpboot /etc/init.d directory contains start/stop scripts for services in the

system. /etc/init.d/xinetd (extended InterNet Daemon) must be running.

Manages all Internet-based connectivity (i.e. ftp, tftp, telnet, …). /etc/init.d/xinetd <start|stop|status|restart> /etc/xinetd.d directory contains the configuration files for all applications

managed by xinetd (i.e. tftp configuration file is here). Included in the xinetd configuration file.

Each xinetd application has separate file, organized per application for security reason and allow easier customization.

IP addresses assigned to Host System and assigned to Embedded System must be on same subnet.

/etc/services file contain the protocol/port number used by a service.



Linux Boot Process – Host System Requirements For /etc/xinetd.d/tftp configuration file, tftp service must be

enabled. /etc/xinetd.d/tftp

service tftp { socket_type = dgram

protocol = udpwait = yesuser = root

server = /usr/sbin/in.tftpdserver_args = -s /opt/tftpbootdisable = noper_source = 11cps = 100 2flags = IPv4 }


Section 2 Embedded Linux Development Linux Boot Process – Host System Requirements

Minicom application to communicate with target system. minicom –s (minicom setup mode).

Set “BPS to 57600”, “No Flow Control”, “Data Bits 8, Parity None, Stop Bits 1.

Set Hardware Flow Control to “No”. USB serial device allows user access, otherwise only root

permission can initialize minicom. chmod 666 /dev/ttyUSB0 (command in /etc/rc.d/rc.sysinit). /etc/rc.local has local startup commands. Cirrus Logic Microcontroller with RS232 serial use Serial-to-

USB converter. NOTE: Cirrus Logic Microcontroller USB not active until after

Linux boots. Bootloader must have USB driver to use during boot.



Linux Boot Process – Host System Requirements

minicom -s

Filenames and pathFile transfer protocolsSerial port setupModem and dialingScreen and keyboardSave setup as dflSave setup as …ExitExit from Minicom

[configuration]

A – Serial Device: /dev/ttyS1 /dev/ttyUSB0B – Lockfile Location: /var/lockC – Callin Program:D – Callout Program:E – Bps/Par/Bits: 38400 8N1 57600 8N1F – Hardware Flow Control: Yes NoG – Software Flow Control: NoChange which setting?


Section 2 Embedded Linux Development Linux In Desktop PC

During powerup, BIOS in host (X86 system) access the hard drive Master Boot Record.

In MBR is GRUB, Linux bootloader in Linux distributions. GRUB provides choice to boot one of multiple OS (i.e. Linux or Windows).

/boot/grub/grub.conf contains GRUB configuration file with menu selection (i.e. which OS) and disk partition containing Linux Kernel and the root file system.

GRUB loads Linux Kernel from /boot directory ( contains Linux Kernel(s), Kernel System Map(s), initrd (initial Ramdisk with drivers), Kernel config file(s) from Kernel build ).

Initrd is temporary root file system with executables (i.e. insmod) and drivers to mount the root file system on disk. After mounting, initrd is unmounted and memory freed.

NOTE: In embedded Linux systems, initrd is the final root file system.

Linux Kernel starts init process. Init process is the root/parent process of all other process executing on Linux.

Init process runs script, /etc/rc.d/rc.sysinit. Init process runs script, /etc/inittab, to execute scripts to start processes

based on the runlevel.


Section 2 Embedded Linux Development Target System Flash Boot – minicom console

Power cycle target, when “+” sign on console appear, execute <ctrl> <c> to interrupt bootloader (Redboot) from continuing with autoboot. The bootloader prompt “Redboot> ” will appear.

Redboot> fconfig –lRun script at boot: trueBoot script:.. fis load ramdisk.. fis load zImage.. exec –r 0x800000 –x 0x300000Boot script timeout (1000ms resolution): 1Use BOOTP for network configuration: falseGateway IP address: 0.0.0.0Local IP address: 192.168.1.200Local IP address mask: 0.0.0.0Default server IP address: 0.0.0.0DNS servier IP address: 0.0.0.0Set eth0 network hardware address [MAC]: trueEth0 network hardware address [MAC]: 0x00:0x00:0x00:0x00:0x4c:0x33GDB connection port: 9000Force console for special debug messages: falseNetwork debug at boot time: false


Section 2 Embedded Linux Development Target System TFTP Boot – minicom console

Power cycle target, when “+” sign on console appear, execute <ctrl> <c> to interrupt bootloader (Redboot) from continuing with autoboot. The bootloader prompt “Redboot> ” will appear.

Redboot> load –r –v –b 0x800000 –h 192.168.1.230 ramdisk.gz Loads data to the target RAM or flash file system. The IP address of

Redboot (i.e. fconfig Local IP Address) must be in same subnet as tftp server IP address, 192.168.1.230.

-r: Raw or binary data. Requires –b option to specify the location in RAM.

-v: Display small spinner when the download is in progress. -b 0x800000: Address in RAM to load the data. This is the location of

the RAMDisk as configured internally in Redboot. -h 192.168.1.230: IP address of the tftp server. ramdisk.gz: The name of the file on the tftp server.

Redboot> fis load zImage Flash Image System. Loads the file, zImage, from the FIS directory.

Once loaded, image can be executed. Redboot> exec –r 0x800000 –s 0x300000

Execute the Linux kernel from Redboot internal configuration. -r 0x800000: Address in RAM of the RAMDisk (i.e. Root File System). -s 0x300000: Length of the RAMDisk image.

Embedded Linux And Device Driver Lecture

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