Essential Linux device drivers / Sreekrishnan Venkateswaran. Short Cuts are short, concise, PDF documents designed specifically for busy. Automatically exported from - amitkumar/ tech-books-pdf. Essential Linux Device Drivers by Sreekrishnan Venkateswaran Publisher: Prentice Hall Pub Date: March 27, Print IS.

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PREFACE This is, on the surface, a book about writing device drivers for the Linux system. That is a worthy goal, of c LINUX Device Drivers. PREFACE This is. reekrishnan. Venkateswaran, who holds a master's degree in computer science from the Indian Institute of. Technology, Kanpur, has exhibited his profound. Essential Linux Device Drivers [Sreekrishnan Venkateswaran] on * FREE* shipping on qualifying offers. “Probably the most wide ranging and.

The book ends by pondering What next? Device drivers sometimes need to implement code snippets in assembly, so Appendix A, "Linux Assembly," takes a look at the different facets of assembly programming on Linux.

Appendix C, "Seq Files," describes seq files, a kernel helper interface introduced in the 2. The book is generally organized according to device and bus complexity, coupled with practical reasons of dependencies between chapters.

So, we start off with basic device classes such as character, serial, and input. The next portions of the book are oriented toward embedded Linux and cover technologies such as wireless networking and flash memory.

User-space drivers are discussed toward the end of the book. Kernel Version This book is generally up to date as of the 2. Most code listings in this book have been tested on a 2. If you are using a later version, look at Linux websites such as lwn. Book Website I've set up a website at elinuxdd. Conventions Used Source code, function names, and shell commands are written like this. Filename are written in italics, like this.

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Italics are also used to introduce new terms. Some chapters modify original kernel source files while implementing code examples. Sometimes, for simplicity, the book uses generic references. The symbol is sometimes inserted between command or kernel output to attach explanations. Simple regular expressions are occasionally used to compactly list function prototypes.

Several chapters refer you to user-space configuration files. The exact names and locations of such files might, however, vary according to the Linux distribution you use. Without their supporting work, this book would not have materialized. I thank Mark Taub for his interest in this project and for initiating it. Several sources have contributed to my learning in the past decade: the many teammates with whom I worked on Linux projects, the mighty kernel sources, mailing lists, and the Internet.

All these have played a part in helping me write this book. Martin Streicher of Linux Magazine changed me from a full-time coder to a spare-time writer when he offered me the magazine's "Gearheads" kernel column. I gratefully acknowledge the many lessons in technical writing that I've learned from him.

I owe a special debt of gratitude to my technical reviewers. Vamsi Krishna patiently read through each chapter of the manuscript. His numerous suggestions have made this a better book. Jim Lieb provided valuable feedback on several chapters. Arnold Robbins reviewed the first few chapters and provided insightful comments. Finally, I thank my parents and my wife for their love and support. And thanks to my baby daughter for constantly reminding me to spend cycles on the book by her wobbly walk that bears an uncanny resemblance to that of a penguin.

During the past 12 years that he has been working for IBM, he has ported Linux to various embedded devices such as a wristwatch, handheld, music player, VoIP phone, pacemaker programmer, and remote patient monitoring system.

Essential Linux Device Drivers

Sreekrishnan was a contributing editor and kernel columnist to the Linux Magazine for more than 2 years. Currently, he manages the embedded solutions group at IBM India. Chapter 1. It has the enticing aroma of an internationalist project where people of all nationalities, creed, and gender collaborate. Free availability of source code and a well-understood UNIX-like application programming environment have contributed to its runaway success.

Highquality support from experts available instantly over the Internet at no charge has also played a major role in stitching together a huge Linux community. Developers get incredibly excited about working on technologies where they have access to all the sources because that lets them create innovative solutions.

You can, for example, hack the sources and customize Linux to boot in a few seconds on your device, a feat that is hard to achieve with a proprietary operating system. Evolution Linux started as the hobby of a Finnish college student named Linus Torvalds in , but quickly metamorphed into an advanced operating system popular all over the planet.

From its first release for the Intel processor, the kernel has gradually grown in complexity to support numerous architectures, multiprocessor hardware, and high-performance clusters. Linux has been ported to hundreds of hardware platforms built around these processors. The kernel is continuously getting better, and the evolution is progressing at a frantic pace. Although it started life as a desktop-operating system, Linux has penetrated the embedded and enterprise worlds and is touching our daily lives.

When you push the buttons on your handheld, flip your remote to the weather channel, or visit the hospital for a physical checkup, it's increasingly likely that some Linux code is being set into motion to come to your service.

Linux's free availability is helping its evolution as much as its technical superiority. A complete GNU operating system is powered by the Linux kernel but also contains components such as libraries, compilers, and utilities. There are different flavors of free software.

One such flavor is called public domain software. Software released under the public domain is not copyrighted, and no restrictions are imposed on its usage.

You can use it for free, make changes to it, and even restrict the distribution of your modified sources. As you can see, the "no restrictions" clause introduces the power to introduce restrictions downstream. Those who modify copylefted software are required to also copyleft their derived work.

So, if you make modifications to the kernel, you have to return your changes back to the community. Essentially, you have to pass on the rights vested on you by the copyleft. The Linux kernel is licensed under GPL version 2. There is an ongoing debate in the kernel community about whether the kernel should move to GPLv3, the latest version of the GPL.

The current tide seems to be against relicensing the kernel to adopt GPLv3. Linux applications that invoke system calls to access kernel services are not considered derived work, however, and won't be restricted by the GPL. Proprietary software is permitted to dynamically link with libraries released under the LGPL. The website contains all released kernel versions.

A number of websites around the world mirror the contents of kernel.

In addition to released kernels, kernel. A patch is a text file containing source code differences between a development tree and the original snapshot from which the developer started work. A popular patch-set available at kernel. You will find experimental features in the -mm patch that have not yet made it to the mainline source tree. Another patch-set periodically released on kernel. Several —rt features have been merged into the mainline kernel.

You can find a real-time feed of the mailing list at www. The kernel now contains several million lines of code contributed by thousands of developers all over the world. LKML acts as the thread that ties all these developers together. LKML is not for general Linux questions. The basic rule is to post only questions pertaining to kernel development that have not been previously answered in the mailing list or in popularly available documentation.

If the C compiler crashed while compiling your Linux application, you should post that question elsewhere. Spend a few hours browsing LKML archives to get an insight into the philosophy behind the Linux kernel. Most subprojects in the kernel have their own specific mailing lists. So, subscribe to the linux-mtd mailing list if you are developing a Linux flash memory driver or initiate a thread in the linux-usb-devel mailing list if you think you have found a bug in the USB mass storage driver.

We refer to relevant mailing lists at the end of several chapters. In various forums, kernel experts from around the globe gather under one roof. The Linux Symposium held annually at Ottawa, Canada, is one such conference. Others include the Linux Kongress that takes place in Germany and linux. There are also numerous commercial Linux forums where industry leaders meet and share their insights. If you want to glean the highlights of the latest kernel release without many cryptic references to kernel internals, this might be a good place to look.

With every major kernel release, you will see sweeping improvements, be it kernel preemption, lock-free readers, new services to offload work from interrupt handlers, or support for new architectures.

Stay in constant touch with the mailing lists, websites, and forums, to keep yourself in the thick of things. Linux distributions come to the rescue by classifying the components and bundling them into packages in an orderly fashion. A typical distribution contains thousands of ready-made packages. You need not worry about downloading the right program versions or fixing dependency issues. Because packaging is a way to make a lot of money within the ambit of the GNU license, there are several Linux distributions in the market today.

[PDF Download] Essential Linux Device Drivers (Prentice Hall Open Source Software Development)

Embedded Linux distributions also include a dynamically configurable compact application-set to tailor the system's footprint to suit resource constraints. In addition to packaging, distributions offer value-adds for kernel development.

Many projects start development based on kernels supplied by a distribution rather than a kernel released officially at kernel. Reasons for this include the following: Linux distributions that comply with standards relevant to your device's industry domain are often better starting points for development. The CELF specification defines the support level of features such as scalable footprint, fast boot, execute in place, and power management, desirable on consumer electronics devices. OSDL's Carrier Grade Linux CGL specification codifies value additions such as reliability, high availability, runtime patching, and enhanced error recovery, important in the telecom space.

The mainline kernel might not include full support for the embedded controller of your choice even if the controller is built around a kernel-supported CPU core. A Linux distribution might offer device drivers for all the peripheral modules inside the controller, however.

Debugging tools that you plan to use during kernel development may not be part of the mainline kernel. For example, the kernel has no built-in debugger support. If you want to use a kernel debugger during development, you have to separately download and apply the corresponding patches. You have to endure more hassles if tested patches are not readily available for your kernel version. Distributions prepackage many useful debugging features, so you can start using them right away.

Some distributions provide legal indemnification so that your company won't be liable for lawsuits arising out of kernel bugs. Distributions tend to do a lot of testing on the kernels they release. You can download service and support packages from distribution vendors for kernels that they supply. Looking at the Sources Before we start wetting our toes in the kernel, let's download the sources, learn to apply a patch, and look at the layout of the code tree. First, go to www.

The sources are archived as tar files compressed in both gzip. Obtain the source files by uncompressing and untarring the zipped tar ball. In the following commands, replace X. Z with the latest kernel version, such as 2. This is piped to the patch utility, which applies changes to each modified file in the code tree.

If you need to apply multiple patches, do so in the right sequence. To generate a kernel enabled with the X. Z-aa-bb patch, first download the full X. Z kernel sources, apply the X.

Z-aa patch, and then apply the X. Z-aa-bb patch. As per 2. You are now all set to post your patch to the relevant mailing list, such as LKML. Go to the root of the source tree and list its contents. The directories branching out from the root of the code tree are as follows: 1. This directory contains architecture-specific files. This directory implements cipher operations and the cryptographic API, used, for example, by some WiFi device drivers for implementing encryption algorithms.

This directory has brief descriptions of various kernel subsystems. This can be your first stop to dig for answers to kernel-related queries. Device drivers for numerous device classes and peripheral controllers reside in this directory. Kernel header files live here.

Subdirectories prefixed with asm contain headers specific to the particular architecture. This directory contains high-level initialization and startup code. This contains support for Inter-Process Communication IPC mechanisms such as message queues, semaphores, and shared memory. The architecture-independent portions of the base kernel can be found here.

Library routines such as generic kernel object kobject handlers and Cyclic Redundancy Code CRC computation functions stay here. The memory management implementation lives here. Networking protocols reside under this directory. Scripts used during kernel build reside here.

This directory contains the framework for security. The Linux audio subsystem is based in this directory. This currently contains the initramfs implementation. Unified x86 Architecture Tree Starting with the 2. If you are using a pre Some filenames within these directories have also changed. Wading through these large directories in search of symbols and other code elements can be a tough task.

The tools in Table 1. Table 1. Cscope might not be as versatile as lxr, but it gives you the flexibility of using the search features of your favorite text editor rather than a browser. From the root of your kernel tree, issue the cscope -qkRv command to build the cross-reference database.

The -q option generates more indexing information, so searches become noticeably faster at the expense of extra initial startup time. The —k option requests cscope to tune its behavior to suit kernel sources, -R asks for recursive subdirectory traversal, and —v appeals for verbose messages.

You can obtain the detailed invocation syntax from the man page. Do make tags from the root of your kernel tree to ctag all source files.

The etags utility generates similar indexing information understood by the emacs editor. Issue make TAGS to etag your kernel source files. Utilities Tools such as grep, find, sdiff, strace, od, dd, make, tar, file, and objdump.

Preprocessed code contains header file expansions and reduces the need to hop-skip through nested include files to expand multiple levels of macros. GCC generates assembly listings if you use the -S option. To generate an assembly listing in mydrv.

Essential Linux Device Drivers

This is when you pick and choose the pieces that form part of the operating system. Use make xconfig to get a graphical interface. The configuration information that you choose is saved in a file named.

Distributions generally package a minimal kernel image and supply the rest of the functionalities in the form of kernel modules.

During runtime, the necessary modules are dynamically loaded on demand. The following utilities are available to manipulate modules: insmod, rmmod, lsmod, modprobe, modinfo, and depmod. The first two are utilities to insert and remove modules, whereas lsmod lists the modules that are currently loaded.

Use modprobe to load the VFAT filesystem driver:[2] [2] This example assumes that the module is not autoloaded by the kernel. You'll learn about module autoloading in Chapter 4, "Laying the Groundwork.

Most of the device driver examples in this book are implemented as kernel modules. To build a module mymodule. You only need to recompile the particular module and reinsert it to effect a change. We look at module debugging techniques in Chapter 21, "Debugging Device Drivers.

Unlike built-in drivers, modules cannot reserve resources during boot time, when success is more or less guaranteed. Before Starting Linux has trekked many a terrain and is now state of the art, so you can use it as a vehicle to understand operating system concepts, processor architectures, and even industry domains. When you learn a technique used by a device driver subsystem, look one level deeper and probe the underlying reasons behind that design choice. Wherever not explicitly stated, the text assumes the bit x86 architecture.

The book is, however, mindful of the fact that you are more likely to write device drivers for embedded devices than for conventional PCcompatible systems. The chapter on serial drivers, for example, examines two devices: a touch controller on a PC derivative and a UART on a cell phone.

The book also teaches you about the core infrastructure that the kernel provides for most driver classes, which hides architecture dependencies from device drivers. Device driver debugging techniques are discussed near the end of the book in Chapter 21, so you might find it worthwhile to forward to that chapter as you develop drivers while reading the book. This book is based on the 2. Hopefully, you have installed a 2.

Each chapter takes the liberty of profusely pointing you to relevant kernel source files for two main reasons: 1. Because each driver subsystem in the kernel is tens of thousands of lines long, it's only possible to take a relatively simplistic view in a book.

Looking at real drivers in the sources along with the example code in this book will give you the bigger picture. So, to derive maximum benefit from this book, familiarize yourself with the kernel by frequently browsing the source tree and staring hard at the code.

And in tandem with your code explorations, follow the goings-on in the kernel mailing list. Chapter 2. We learn about kernel timers, synchronization mechanisms, and memory allocation. Do you want to remove all your recent searches? For You Explore. All recent searches will be deleted. Cancel Remove. Watch fullscreen. Browse more videos.

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French taxi drivers trap Uber driver and attack him in the street. Russian drivers are the worst ever! Hot Uber drivers: Lyon, France Uber office offers sexy driver promotion to passengers.Use make xconfig to get a graphical interface. However, when there are too many programs demanding memory resources, the kernel frees up some used RAM pages by storing them in a disk partition called swap space.

What took thousands of lines of code and a year in development back then can be accomplished in a few days with the current kernels.

In this chapter, you also learn to use trace tools, kernel probes, crash-dump, and profilers. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. Linux Kernel Development,, 3rd Edition. Sreekrishnan Venkateswaran focuses on the essentials, bringing together all the concepts and techniques you need, while avoiding topics that only matter in highly specialized situations.

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