Embedded Linux Primer

s1axter writes "Embedded system development is crucial in this day of high tech specialized appliances and devices. However much of the knowledge of embedded development resides in the heads of engineers who have been doing it for years. The hardware aspect of embedded systems is now available to the smaller startup companies, however many specialized, proprietary operating systems are not. This is where Linux and the book Embedded Linux Primer: A Practical Real-World Approach enters. Embedded Linux Primer is written to introduce engineers and designers to using the Linux operating systems for embedded applications." Read on for s1axter's review.

Embedded Linux Primer
author	Christopher Hallinan
pages	537
publisher	Prentice Hall
rating	9
reviewer	s1axter
ISBN	0-13-167984-8
summary	A Practical Real-World Approach to Embedded Linux

Prentice Hall's Embedded Linux Primer by Christopher Hallinan was published September 18th, 2006 as part of their Open Source Software Development Series. Very much like a textbook, Embedded Linux Primer is very informative and an excellent source of information for an engineer looking to enter or move to the embedded Linux field. The text is a decent size, with 537 pages spanning 17 chapters and 6 appendices; it retails for around $45 USD.

I had some reservations on reviewing a detailed technical book since most of the ones I have are dry and have a very segmented structure. However after taking a look at the sample chapter, chapter 7 "Bootloaders", available on the Prentice Hall website along with the table of contents for the text I figured I would give it a look and I am very glad I did.

Many technical books focus on a specific demographic in the technology world, mostly beginners or professionals expanding their knowledge base. I was quite pleased to see this text is written for both professional developers and emerging embedded engineers.

Professional engineers will find the text informative on the Linux operating system and how flexible it is to implement on even the most custom hardware. The author understands that a large number of embedded system engineers work with proprietary systems and explains items that might be new and different than these systems. For example Chapters 4-6 detail the Linux boot sequence and describe common pitfalls engineers new to the embedded Linux methodology might make. Chapters 8-11 dive further into the operating system and explain device driver creation, the important file system and how Linux handles volatile and non-volatile memory systems using the MTD subsystem.

Engineers starting in the field of embedded systems will find information on what an embedded system is in Chapter 1, processor and board comparisons in Chapter 2 and setting up an embedded environment for development in Chapter 12.

It is quite obvious throughout the text the author has an extensive in depth understanding of embedded systems and the inner workings of the Linux operating system. With such a deep understanding of the material an author many times explains items in such detail it clouds the mind of the reader. The first line in Chapter 2 says (paraphrasing) that the best way understand something is to understand the 'big picture' . This is exactly the approach the author takes through out the text, first explaining the theory and high level aspect of the system, then diving into the detail of how it is done on the low level. Also, rather than get sidetracked in chapters by explaining every processor attribute or software package, the author suggests external sources mid-text and in the "Suggestions for Additional Reading" at the end of each chapter.

For the first edition of a book, Embedded Linux Primer is rather complete, with the only exception being chapter 8, Device Driver Basics, which is...well, rather basic. I started the chapter expecting to finish with a detailed understanding of how the Linux kernel processes driver requests and a look into some common drivers. This is not the case; for a second edition of this text I would suggest beefing up this chapter to provide more of an insight into kernel-driver interaction.

Overall Embedded Linux Primer is an excellent source of information for both the seasoned professional and aspiring embedded engineer. I know that when I dive fully into the world of embedded Linux this book will have a permanent place on the bench right next to the spec sheets.

s1axter is the main poster for Geeksinside.com, which is a hardware hacking, technology blog that showcases projects, reviews and technical links.

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Sounds promising.

Looks like a good book. I've dabbled in embedded systems before. For anyone who has had reflashed their router with DD-WRT or think programming your toaster could be fun, this could be a good read.

primer

Sweet. I'll head down to Home Depot after work and see if they have any.

Why worry about embedded driver development?

For the first edition of a book, Embedded Linux Primer is rather complete, with the only exception being chapter 8, Device Driver Basics, which is...well, rather basic. I started the chapter expecting to finish with a detailed understanding of how the Linux kernel processes driver requests and a look into some common drivers. This is not the case; for a second edition of this text I would suggest beefing up this chapter to provide more of an insight into kernel-driver interaction.

Embedded or not, Linux uses the same driver structure. Most often, the same drivers as well. That's the main advantage of "embedded" Linux - it's no different than any other Linux. Just smaller. Try running a Windows XP program on Windows CE to see what I mean.

If you want to chase driver development, read Linux Device Drivers [oreilly.com], by O'Reilly. It's IMHO the definitive book, and works just the same for embedded Linux. A single chapter in an embedded how-to book could hardly be expected to capture everything you'd need.

Re:Why worry about embedded driver development?

If you want to chase driver development, read Linux Device Drivers, by O'Reilly. It's IMHO the definitive book, and works just the same for embedded Linux. A single chapter in an embedded how-to book could hardly be expected to capture everything you'd need.

I didn't like this book; it stuck to basic network, char and block devices, and while it provided a good deal of detail on these, it completely avoided actual hardware interfacing: PCI (e/x too), PCMCIA, USB, basic memory/interrupt allocation, etc. Unfortunately, those are the trickier bits to driver writing.

Embedded

The smallest Linux computer in the world: Picotux! [picotux.com]

Routers, Phones, Now What?

Am I the only one that read that subject, initially, as "Embedded Linux Printer"? Not that that's a totally uncool idea, now that I'm thinking about it...

@yg

Device Drivers issue

Device Driver Basics, which is...well, rather basic. I started the chapter expecting to finish with a detailed understanding of how the Linux kernel processes driver requests and a look into some common drivers

Detailed understanding requires a whole bookshelf, and several years hacking away at a couple of drivers, but here is a good start.
http://lwn.net/Kernel/LDD3/ [lwn.net]

elinux.org

Great review and great book. Just wanted to also point out that http://www.elinux.org/ [elinux.org] (a site I edit) is a fantastic wiki for information regarding embedded linux and it's only getting better. We recently merged content from elinux.org (the original) and the CELF Public Wiki. Also, the wiki will be relaunched officially at OLS.

HW recommendations?

Does this book supply any HW recommendations? For me that has been one of the stumbling blocks... what architecture, what device, how much memory etc. to get going.

I've seen a lot of embedded developer kits but I don't know where to start as none really list what kind of OS they'll support.

Any suggestions on HW would be welcome!

What is an embedded system?

I do embedded systems for a living, and was asked this question during my intervuiew. My answer: "a system that is the brains of something else, and is not necessarily visible as a computer". They thought that was an interesting answer, and I got the job.

I think embedded systems are interesting. The challenge is obvious: it's easy to make a system with a multi-GHz processor, gigabytes of RAM and terabytes of disk do something interesting and/or useful. Can you make a computer the size of a stick of gum do something interesting and/or useful? That is the challenge.

The other challenge is that your embedded system must be reliable. People will not tolerate toasters that won't boot. The testing requirements can be interesting, and nerve-wracking too. How do you report "I'm broken" when all you can do is flash an LED?

This is where you get to find creative new abuses for mmap(), learn what those MTD device drivers in the kernel do, find just what JFFS2 will (and won't) do, and so on.

...laura, embedded Linux on 68k and StrongARM

Good Embedded Linux Starter Kit

Atmel has put out a nice and cheap (80 bucks!!) kit called NGW100 for developing embedded linux devices on their AVR32 series. There is a lot of open community support around it and it seems like a great place to start. I've been thinking about getting into embedded linux for a while.

Am reading the book now

I'm on a project building a router using the freescale mpc8548e on a custom board - a pretty powerful processor for embedded work. This is my first embedded project, though I'm a long time linux user and had an early career doing primarily electronics work.

This book is uneven, but largely its a good book. The bootloader chapters are a very good intro - it even has a porting section going into the ppc assembly part of u-boot. The init sections of the kernel are also a good intro. The chapter describing gdb and kernel debugging is good, as I learned several tricks using macros with gdb that I think will help me a lot. Lots of tools like cpp are explained that I didn't know about.

However, where it comes short is that I still really need help with early debugging the bootloader and kernel init using the bdi-2000 (a hardware debugger that connects to the jtag interface that most boards have). It barely mentions the bdi-2000, which is a fundamental tool as its pretty much the only way to debug very early booting problems when porting.

I also think the flash section has too much of a jffs2 focus, and not ext2 focused to match most users. The driver section is very module focused and so bare it could be omitted.

Overall, I'm happy with the book in that it does have a lot of info that I haven't found elsewhere. It really convinced me I need to read the manuals of my hardware more as there is no alternative. The book has helped, and I think its a great intro.

First hand experience: Books not enough

I recently began a coop at an embeded systems company, doing, whatelse, linux development for their platforms. I've read everything I could get my hands on about linux on embedded systems. For they most part, they're all redundant. Orielly's Understanding the Linux Kernel and Linux Device Drivers have been the two most useful books.

That said, neither is the "linux is the same embedded or not" argument all that good. I sure wish it was. Most information out there is about the x86 system, which embedded applications tend to avoid. On the other hand, books that target themselves towards the embedded market tend to mix and match different architectures. What I needed was comprehensive coverage of different processes specific to all the different platforms, because this is where kernel documentation or other resources tend to be rather skim.

Long story short: there was no quick substitute for paging through assembly code, and the very beginings of c code, to learn what I needed to know. For example, bootstrapping elfs verses non bootstrapping elfs, figuring out which code is which, the addresses that code executes at, etc. is all different for different platforms. In the least, it was only well explained for x86, and there was no explinations for the different standards and structures used in the boot process. (Mips, for example, uses an argv/c boot standard, ppc looks for the begining and end of a string address).

Re:Engineers doing it? Yeah, plenty of them.

Dood, where I work they have been porting a *nix OS to printers for years, like 10 years. It's voodoo and the results are often spooky. It's actually pretty cool to be able to use typical Unix commands to work in the printer's OS. I work in the test department and we spend a lot of time logging in and working on the printer. I can compile new 'firmware' and load it when I need to, and I have sometimes looked at the source for failure analysis reasons.

I will probably buy a book like this one to help me understand the issues. I have a little familiarity with low-level Unix workings, and it would be instructive to get an overview of the subject.

Re:Embedded Linux? No thanks.

While your post was trollish. There is an embedded form of OS X/darwin. What do you think powers the iPhone. :)

Re:Embedded Linux? No thanks.

A lot of people will see EMBEDDED and think ooh scary! But nowadays there are very cheap $100 small boards with enough ram and flash to code in plain old C. This stuff has come so far that these boards are NOT a big step from desktop programming.
 
Just a reminder.

Re:Won't GPL3 kill embedding?

Tivoisation doesn't mean "no embedding", instead it's more like "no need of a hardware key to run".

Re:Linux is too heavy

I agree. Traditional OS's aren't the best choice for true embedded systems, but if what you're really building is a general purpose computer in a smaller form-=factor, they make sense.