About the AuthorChristopher Hallinan is a technical marketing engineer for the Embedded Sys-tems Division of Mentor Graphics, living and working in Florida. He has spentmore than 25 years in the networking and communications industry, mostly in vari-ous product development, management, and marketing roles, where he developeda strong background in the space where hardware meets software.Prior to joiningMentor Graphics, he spent nearly seven years as a field applications engineer forMonta Vista Software.Before that,Hallinan spent four years as an independentLinux consultant, providing custom Linux board ports, device drivers, and boot-loaders.His introduction to the open source community was through contributionsto the popular U-Boot bootloader. When not messing about with Linux, he is oftenfound singing and playing a Taylor or Martin.xovi
ptg xxxvi About the Author Christopher Hallinan is a technical marketing engineer for the Embedded Systems Division of Mentor Graphics, living and working in Florida. He has spent more than 25 years in the networking and communications industry, mostly in various product development, management, and marketing roles, where he developed a strong background in the space where hardware meets software. Prior to joining Mentor Graphics, he spent nearly seven years as a field applications engineer for Monta Vista Software. Before that, Hallinan spent four years as an independent Linux consultant, providing custom Linux board ports, device drivers, and bootloaders. His introduction to the open source community was through contributions to the popular U-Boot bootloader. When not messing about with Linux, he is often found singing and playing a Taylor or Martin
ChapterIntroductionInThis Chapter2■ 1.1Why Linux?3■ 1.2Embedded Linux Today31.3OpenSourceandtheGPL■ 1.4Standards and Relevant Bodies8■1.5Summary1
ptg 1 1 Introduction In This Chapter ■ 1.1 Why Linux? 2 ■ 1.2 Embedded Linux Today 3 ■ 1.3 Open Source and the GPL 3 ■ 1.4 Standards and Relevant Bodies 5 ■ 1.5 Summary 8
hemove away from proprietary embedded operating systems is causingquite a stir in the corporate boardrooms of many traditional embeddedoperating system (OS)companies.For many well-founded reasons, Linux isbeing adopted as the operating system in many products beyond its traditionalstronghold in server applications. Examples of these embedded systems includecellular phones,DVD players,video games, digital cameras,network switches,and wireless networking gear. It is quite likely that Linux is already in your homeor automobile. Linux has been commonly selected as the embedded operatingsystem in devices including set-top boxes, high-definition televisions, Blu-rayDVD players, automobile infotainment centers, and many other devices en-countered ineverydaylife.1.1Why Linux?Because of the numerous economic and technical benefits, we are seeing stronggrowth in the adoption of Linux for embedded devices. This trend has crossed virtu-ally all markets and technologies. Linux has been adopted for embedded products inthe worldwide public switched telephone network,global data networks, and wire-less cellular handsets, as well as radio node controllers and backhaul infrastructurethat operates these networks. Linux has enjoyed success in automobile applications,consumer products such as games and PDAs, printers, enterprise switches and rout-ers, and many other products.Tens of millions of cell phones are now shippingworldwide with Linux as the operating system of choice.The adoption rate of em-bedded Linux continues to grow, with no end in sight.Here are some of the reasons for thegrowth of embedded Linux:. Linux supports a vast variety of hardware devices, probably more than anyotherOs.Linux supports a huge variery of applications and networking protocols..Linux is scalable, from small consumer-oriented devices to large, heavy-iron,carrier-class switches and routers.2
ptg 2 The move away from proprietary embedded operating systems is causing quite a stir in the corporate boardrooms of many traditional embedded operating system (OS) companies. For many well-founded reasons, Linux is being adopted as the operating system in many products beyond its traditional stronghold in server applications. Examples of these embedded systems include cellular phones, DVD players, video games, digital cameras, network switches, and wireless networking gear. It is quite likely that Linux is already in your home or automobile. Linux has been commonly selected as the embedded operating system in devices including set-top boxes, high-definition televisions, Blu-ray DVD players, automobile infotainment centers, and many other devices encountered in everyday life. 1.1 Why Linux? Because of the numerous economic and technical benefits, we are seeing strong growth in the adoption of Linux for embedded devices. This trend has crossed virtually all markets and technologies. Linux has been adopted for embedded products in the worldwide public switched telephone network, global data networks, and wireless cellular handsets, as well as radio node controllers and backhaul infrastructure that operates these networks. Linux has enjoyed success in automobile applications, consumer products such as games and PDAs, printers, enterprise switches and routers, and many other products. Tens of millions of cell phones are now shipping worldwide with Linux as the operating system of choice. The adoption rate of embedded Linux continues to grow, with no end in sight. Here are some of the reasons for the growth of embedded Linux: • Linux supports a vast variety of hardware devices, probably more than any other OS. • Linux supports a huge variety of applications and networking protocols. • Linux is scalable, from small consumer-oriented devices to large, heavy-iron, carrier-class switches and routers. Download at www.wowebook.com
1.3Open SourceandtheGPL3 Linux can be deployed without the royalties required by traditional proprietaryembeddedoperatingsystems.·Linux has attracted a huge numberofactivedevelopers,enabling rapid supportofnewhardwarearchitectures,platforms,and devices.·An increasing number of hardware and software vendors, including virtuallyallthe top-tier chip manufacturers and independent software vendors (ISVs), nowsupport Linux.For these and other reasons, we are seeing an accelerated adoption rate of Linux inmany common household items, ranging from high-definition televisions to cellularhandsets.1.2EmbeddedLinuxTodayIt may come as no surprise that Linux has experienced significant growth in the em-bedded space. Indeed, the fact that you are reading this book indicates that Linux hastouched your life.It is difficult to estimate themarket size,because many companiescontinue to build their own embedded Linux distributions.LinuxDevices.com,thepopular news and informationportal foundedbyRick Leh-rbaum, now owned by Ziff Davis, conducts an annual survey oftheembedded Linuxmarket.In its latest survey, it reports that Linux has emerged as the dominant operat-ing system used in thousands of new designs each year. In fact, nearly half the respon-dents reported using Linux in an embedded design. The next most popular operatingsystem reportedly was used by only about one in eight respondents. Commercial op-erating systems that once dominated the embedded market were reportedly used byfewer than one in ten respondents.Even if you find reason to dispute these results, noone can ignorethe momentum in the embedded Linux marketplacetoday.1.3OpenSourceandtheGPLOne of thefundamental factors driving the adoption of Linux is thefact that it is opensource.For a fascinating and insightful look at the history and culture of the opensourcemovement, read Eric S.Raymond's book, referenced at the end of this chapter.The Linux kernel is licensed under the terms of the GNU GPL(General Pub-lic License), which leads to the popular myth that Linux is free. In fact, the second See http:/www.gnu.org/licenses/gpl.html for complete text of the license
ptg 1.3 Open Source and the GPL 3 • Linux can be deployed without the royalties required by traditional proprietary embedded operating systems. • Linux has attracted a huge number of active developers, enabling rapid support of new hardware architectures, platforms, and devices. • An increasing number of hardware and software vendors, including virtually all the top-tier chip manufacturers and independent software vendors (ISVs), now support Linux. For these and other reasons, we are seeing an accelerated adoption rate of Linux in many common household items, ranging from high-definition televisions to cellular handsets. 1.2 Embedded Linux Today It may come as no surprise that Linux has experienced significant growth in the embedded space. Indeed, the fact that you are reading this book indicates that Linux has touched your life. It is difficult to estimate the market size, because many companies continue to build their own embedded Linux distributions. LinuxDevices.com, the popular news and information portal founded by Rick Lehrbaum, now owned by Ziff Davis, conducts an annual survey of the embedded Linux market. In its latest survey, it reports that Linux has emerged as the dominant operating system used in thousands of new designs each year. In fact, nearly half the respondents reported using Linux in an embedded design. The next most popular operating system reportedly was used by only about one in eight respondents. Commercial operating systems that once dominated the embedded market were reportedly used by fewer than one in ten respondents. Even if you find reason to dispute these results, no one can ignore the momentum in the embedded Linux marketplace today. 1.3 Open Source and the GPL One of the fundamental factors driving the adoption of Linux is the fact that it is open source. For a fascinating and insightful look at the history and culture of the open source movement, read Eric S. Raymond’s book, referenced at the end of this chapter. The Linux kernel is licensed under the terms of the GNU GPL1 (General Public License), which leads to the popular myth that Linux is free. In fact, the second 1 See http://www.gnu.org/licenses/gpl.html for complete text of the license. Download at www.wowebook.com
Chapter1 Introduction4.paragraph of the GNU GPL Version 3 declares: “When we speak of free software, weare referring to freedom,not price."Most professional developmentmanagers agree:You can download Linux without charge, but development and deployment with anyOS on an embeddedplatform carries an (often substantial)cost.Linux is no differentin this regard.TheGPLis remarkably shortand easytoread.Hereare some of its most importantcharacteristics:.The license is self-perpetuating..The license grants the user freedom to run the program..The license grants the user the right to study and modify the source code..The license grants the user permission to distribute the original code and hismodifications..The license is viral. In other words, it grants these same rights to anyone towhomyoudistributeGPLsoftware.When software is released under the terms of the GPL, it must forever carry thatlicense.2Even if the code is highly modified, which is allowed and even encouraged bythe license, the GPL mandates that it must be released under the same license.Theintentof this feature is to guarantee freedom ofaccess to the software, including modi-fied versions of the software (or derived works, as they are commonly called).Nomatter how the software was obtained, the GPL grants the licensee unlimiteddistribution rights, without the obligation to pay royalties or per-unit fees.This doesnot mean thatvendors can't charge for their GPL software-this is a reasonable andcommon business practice.It means thatonce in possession of GPL software,it is per-missible to modify and redistribute it, whether or not it is a derived (modifed) work.However, as dictated bytheGPL,the authors of themodified workare obligated torelease the work under the terms of the GPL if they decide to do so. Any distributionof a derived work, such as shipment to a customer, triggers this obligation.1.3.1FreeVersusFreedomTwopopularphrasesareoften repeated inthediscussion aboutthefree natureofopensource:“free as in freedom"and“free as in beer."(The author is particularly fond ofthe latter.)The GPL exists to guarantee“free as in freedom"of a particular body offalthecopyright holders aged, hesofwarecouldinthory bereleasedunderanewlienseThis wouldbeaeryunlikelyscenario indeed, especially for a large software base with thousands of contributors
ptg 4 Chapter 1 Introduction paragraph of the GNU GPL Version 3 declares: “When we speak of free software, we are referring to freedom, not price.” Most professional development managers agree: You can download Linux without charge, but development and deployment with any OS on an embedded platform carries an (often substantial) cost. Linux is no different in this regard. The GPL is remarkably short and easy to read. Here are some of its most important characteristics: • The license is self-perpetuating. • The license grants the user freedom to run the program. • The license grants the user the right to study and modify the source code. • The license grants the user permission to distribute the original code and his modifications. • The license is viral. In other words, it grants these same rights to anyone to whom you distribute GPL software. When software is released under the terms of the GPL, it must forever carry that license.2 Even if the code is highly modified, which is allowed and even encouraged by the license, the GPL mandates that it must be released under the same license. The intent of this feature is to guarantee freedom of access to the software, including modi- fied versions of the software (or derived works, as they are commonly called). No matter how the software was obtained, the GPL grants the licensee unlimited distribution rights, without the obligation to pay royalties or per-unit fees. This does not mean that vendors can’t charge for their GPL software—this is a reasonable and common business practice. It means that once in possession of GPL software, it is permissible to modify and redistribute it, whether or not it is a derived (modified) work. However, as dictated by the GPL, the authors of the modified work are obligated to release the work under the terms of the GPL if they decide to do so. Any distribution of a derived work, such as shipment to a customer, triggers this obligation. 1.3.1 Free Versus Freedom Two popular phrases are often repeated in the discussion about the free nature of open source: “free as in freedom” and “free as in beer.” (The author is particularly fond of the latter.) The GPL exists to guarantee “free as in freedom” of a particular body of 2 If all the copyright holders agreed, the software could in theory be released under a new license. This would be a very unlikely scenario indeed, especially for a large software base with thousands of contributors. Download at www.wowebook.com