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diff --git a/qemu/dtc/Documentation/dtc-paper.tex b/qemu/dtc/Documentation/dtc-paper.tex deleted file mode 100644 index 4494226d8..000000000 --- a/qemu/dtc/Documentation/dtc-paper.tex +++ /dev/null @@ -1,597 +0,0 @@ -\documentclass[a4paper,twocolumn]{article} - -\usepackage{abstract} -\usepackage{xspace} -\usepackage{amssymb} -\usepackage{latexsym} -\usepackage{tabularx} -\usepackage[T1]{fontenc} -\usepackage{calc} -\usepackage{listings} -\usepackage{color} -\usepackage{url} - -\title{Device trees everywhere} - -\author{David Gibson \texttt{<{dwg}{@}{au1.ibm.com}>}\\ - Benjamin Herrenschmidt \texttt{<{benh}{@}{kernel.crashing.org}>}\\ - \emph{OzLabs, IBM Linux Technology Center}} - -\newcommand{\R}{\textsuperscript{\textregistered}\xspace} -\newcommand{\tm}{\textsuperscript{\texttrademark}\xspace} -\newcommand{\tge}{$\geqslant$} -%\newcommand{\ditto}{\textquotedbl\xspace} - -\newcommand{\fixme}[1]{$\bigstar$\emph{\textbf{\large #1}}$\bigstar$\xspace} - -\newcommand{\ppc}{\mbox{PowerPC}\xspace} -\newcommand{\of}{Open Firmware\xspace} -\newcommand{\benh}{Ben Herrenschmidt\xspace} -\newcommand{\kexec}{\texttt{kexec()}\xspace} -\newcommand{\dtbeginnode}{\texttt{OF\_DT\_BEGIN\_NODE\xspace}} -\newcommand{\dtendnode}{\texttt{OF\_DT\_END\_NODE\xspace}} -\newcommand{\dtprop}{\texttt{OF\_DT\_PROP\xspace}} -\newcommand{\dtend}{\texttt{OF\_DT\_END\xspace}} -\newcommand{\dtc}{\texttt{dtc}\xspace} -\newcommand{\phandle}{\texttt{linux,phandle}\xspace} -\begin{document} - -\maketitle - -\begin{abstract} - We present a method for booting a \ppc{}\R Linux\R kernel on an - embedded machine. To do this, we supply the kernel with a compact - flattened-tree representation of the system's hardware based on the - device tree supplied by Open Firmware on IBM\R servers and Apple\R - Power Macintosh\R machines. - - The ``blob'' representing the device tree can be created using \dtc - --- the Device Tree Compiler --- that turns a simple text - representation of the tree into the compact representation used by - the kernel. The compiler can produce either a binary ``blob'' or an - assembler file ready to be built into a firmware or bootwrapper - image. - - This flattened-tree approach is now the only supported method of - booting a \texttt{ppc64} kernel without Open Firmware, and we plan - to make it the only supported method for all \texttt{powerpc} - kernels in the future. -\end{abstract} - -\section{Introduction} - -\subsection{OF and the device tree} - -Historically, ``everyday'' \ppc machines have booted with the help of -\of (OF), a firmware environment defined by IEEE1275 \cite{IEEE1275}. -Among other boot-time services, OF maintains a device tree that -describes all of the system's hardware devices and how they're -connected. During boot, before taking control of memory management, -the Linux kernel uses OF calls to scan the device tree and transfer it -to an internal representation that is used at run time to look up -various device information. - -The device tree consists of nodes representing devices or -buses\footnote{Well, mostly. There are a few special exceptions.}. -Each node contains \emph{properties}, name--value pairs that give -information about the device. The values are arbitrary byte strings, -and for some properties, they contain tables or other structured -information. - -\subsection{The bad old days} - -Embedded systems, by contrast, usually have a minimal firmware that -might supply a few vital system parameters (size of RAM and the like), -but nothing as detailed or complete as the OF device tree. This has -meant that the various 32-bit \ppc embedded ports have required a -variety of hacks spread across the kernel to deal with the lack of -device tree. These vary from specialised boot wrappers to parse -parameters (which are at least reasonably localised) to -CONFIG-dependent hacks in drivers to override normal probe logic with -hardcoded addresses for a particular board. As well as being ugly of -itself, such CONFIG-dependent hacks make it hard to build a single -kernel image that supports multiple embedded machines. - -Until relatively recently, the only 64-bit \ppc machines without OF -were legacy (pre-POWER5\R) iSeries\R machines. iSeries machines often -only have virtual IO devices, which makes it quite simple to work -around the lack of a device tree. Even so, the lack means the iSeries -boot sequence must be quite different from the pSeries or Macintosh, -which is not ideal. - -The device tree also presents a problem for implementing \kexec. When -the kernel boots, it takes over full control of the system from OF, -even re-using OF's memory. So, when \kexec comes to boot another -kernel, OF is no longer around for the second kernel to query. - -\section{The Flattened Tree} - -In May 2005 \benh implemented a new approach to handling the device -tree that addresses all these problems. When booting on OF systems, -the first thing the kernel runs is a small piece of code in -\texttt{prom\_init.c}, which executes in the context of OF. This code -walks the device tree using OF calls, and transcribes it into a -compact, flattened format. The resulting device tree ``blob'' is then -passed to the kernel proper, which eventually unflattens the tree into -its runtime form. This blob is the only data communicated between the -\texttt{prom\_init.c} bootstrap and the rest of the kernel. - -When OF isn't available, either because the machine doesn't have it at -all or because \kexec has been used, the kernel instead starts -directly from the entry point taking a flattened device tree. The -device tree blob must be passed in from outside, rather than generated -by part of the kernel from OF. For \kexec, the userland -\texttt{kexec} tools build the blob from the runtime device tree -before invoking the new kernel. For embedded systems the blob can -come either from the embedded bootloader, or from a specialised -version of the \texttt{zImage} wrapper for the system in question. - -\subsection{Properties of the flattened tree} - -The flattened tree format should be easy to handle, both for the -kernel that parses it and the bootloader that generates it. In -particular, the following properties are desirable: - -\begin{itemize} -\item \emph{relocatable}: the bootloader or kernel should be able to - move the blob around as a whole, without needing to parse or adjust - its internals. In practice that means we must not use pointers - within the blob. -\item \emph{insert and delete}: sometimes the bootloader might want to - make tweaks to the flattened tree, such as deleting or inserting a - node (or whole subtree). It should be possible to do this without - having to effectively regenerate the whole flattened tree. In - practice this means limiting the use of internal offsets in the blob - that need recalculation if a section is inserted or removed with - \texttt{memmove()}. -\item \emph{compact}: embedded systems are frequently short of - resources, particularly RAM and flash memory space. Thus, the tree - representation should be kept as small as conveniently possible. -\end{itemize} - -\subsection{Format of the device tree blob} -\label{sec:format} - -\begin{figure}[htb!] - \centering - \footnotesize - \begin{tabular}{r|c|l} - \multicolumn{1}{r}{\textbf{Offset}}& \multicolumn{1}{c}{\textbf{Contents}} \\\cline{2-2} - \texttt{0x00} & \texttt{0xd00dfeed} & magic number \\\cline{2-2} - \texttt{0x04} & \emph{totalsize} \\\cline{2-2} - \texttt{0x08} & \emph{off\_struct} & \\\cline{2-2} - \texttt{0x0C} & \emph{off\_strs} & \\\cline{2-2} - \texttt{0x10} & \emph{off\_rsvmap} & \\\cline{2-2} - \texttt{0x14} & \emph{version} \\\cline{2-2} - \texttt{0x18} & \emph{last\_comp\_ver} & \\\cline{2-2} - \texttt{0x1C} & \emph{boot\_cpu\_id} & \tge v2 only\\\cline{2-2} - \texttt{0x20} & \emph{size\_strs} & \tge v3 only\\\cline{2-2} - \multicolumn{1}{r}{\vdots} & \multicolumn{1}{c}{\vdots} & \\\cline{2-2} - \emph{off\_rsvmap} & \emph{address0} & memory reserve \\ - + \texttt{0x04} & ...& table \\\cline{2-2} - + \texttt{0x08} & \emph{len0} & \\ - + \texttt{0x0C} & ...& \\\cline{2-2} - \vdots & \multicolumn{1}{c|}{\vdots} & \\\cline{2-2} - & \texttt{0x00000000}- & end marker\\ - & \texttt{00000000} & \\\cline{2-2} - & \texttt{0x00000000}- & \\ - & \texttt{00000000} & \\\cline{2-2} - \multicolumn{1}{r}{\vdots} & \multicolumn{1}{c}{\vdots} & \\\cline{2-2} - \emph{off\_strs} & \texttt{'n' 'a' 'm' 'e'} & strings block \\ - + \texttt{0x04} & \texttt{~0~ 'm' 'o' 'd'} & \\ - + \texttt{0x08} & \texttt{'e' 'l' ~0~ \makebox[\widthof{~~~}]{\textrm{...}}} & \\ - \vdots & \multicolumn{1}{c|}{\vdots} & \\\cline{2-2} - \multicolumn{1}{r}{+ \emph{size\_strs}} \\ - \multicolumn{1}{r}{\vdots} & \multicolumn{1}{c}{\vdots} & \\\cline{2-2} - \emph{off\_struct} & \dtbeginnode & structure block \\\cline{2-2} - + \texttt{0x04} & \texttt{'/' ~0~ ~0~ ~0~} & root node\\\cline{2-2} - + \texttt{0x08} & \dtprop & \\\cline{2-2} - + \texttt{0x0C} & \texttt{0x00000005} & ``\texttt{model}''\\\cline{2-2} - + \texttt{0x10} & \texttt{0x00000008} & \\\cline{2-2} - + \texttt{0x14} & \texttt{'M' 'y' 'B' 'o'} & \\ - + \texttt{0x18} & \texttt{'a' 'r' 'd' ~0~} & \\\cline{2-2} - \vdots & \multicolumn{1}{c|}{\vdots} & \\\cline{2-2} - & \texttt{\dtendnode} \\\cline{2-2} - & \texttt{\dtend} \\\cline{2-2} - \multicolumn{1}{r}{\vdots} & \multicolumn{1}{c}{\vdots} & \\\cline{2-2} - \multicolumn{1}{r}{\emph{totalsize}} \\ - \end{tabular} - \caption{Device tree blob layout} - \label{fig:blob-layout} -\end{figure} - -The format for the blob we devised, was first described on the -\texttt{linuxppc64-dev} mailing list in \cite{noof1}. The format has -since evolved through various revisions, and the current version is -included as part of the \dtc (see \S\ref{sec:dtc}) git tree, -\cite{dtcgit}. - -Figure \ref{fig:blob-layout} shows the layout of the blob of data -containing the device tree. It has three sections of variable size: -the \emph{memory reserve table}, the \emph{structure block} and the -\emph{strings block}. A small header gives the blob's size and -version and the locations of the three sections, plus a handful of -vital parameters used during early boot. - -The memory reserve map section gives a list of regions of memory that -the kernel must not use\footnote{Usually such ranges contain some data -structure initialised by the firmware that must be preserved by the -kernel.}. The list is represented as a simple array of (address, -size) pairs of 64 bit values, terminated by a zero size entry. The -strings block is similarly simple, consisting of a number of -null-terminated strings appended together, which are referenced from -the structure block as described below. - -The structure block contains the device tree proper. Each node is -introduced with a 32-bit \dtbeginnode tag, followed by the node's name -as a null-terminated string, padded to a 32-bit boundary. Then -follows all of the properties of the node, each introduced with a -\dtprop tag, then all of the node's subnodes, each introduced with -their own \dtbeginnode tag. The node ends with an \dtendnode tag, and -after the \dtendnode for the root node is an \dtend tag, indicating -the end of the whole tree\footnote{This is redundant, but included for -ease of parsing.}. The structure block starts with the \dtbeginnode -introducing the description of the root node (named \texttt{/}). - -Each property, after the \dtprop, has a 32-bit value giving an offset -from the beginning of the strings block at which the property name is -stored. Because it's common for many nodes to have properties with -the same name, this approach can substantially reduce the total size -of the blob. The name offset is followed by the length of the -property value (as a 32-bit value) and then the data itself padded to -a 32-bit boundary. - -\subsection{Contents of the tree} -\label{sec:treecontents} - -Having seen how to represent the device tree structure as a flattened -blob, what actually goes into the tree? The short answer is ``the -same as an OF tree''. On OF systems, the flattened tree is -transcribed directly from the OF device tree, so for simplicity we -also use OF conventions for the tree on other systems. - -In many cases a flat tree can be simpler than a typical OF provided -device tree. The flattened tree need only provide those nodes and -properties that the kernel actually requires; the flattened tree -generally need not include devices that the kernel can probe itself. -For example, an OF device tree would normally include nodes for each -PCI device on the system. A flattened tree need only include nodes -for the PCI host bridges; the kernel will scan the buses thus -described to find the subsidiary devices. The device tree can include -nodes for devices where the kernel needs extra information, though: -for example, for ISA devices on a subsidiary PCI/ISA bridge, or for -devices with unusual interrupt routing. - -Where they exist, we follow the IEEE1275 bindings that specify how to -describe various buses in the device tree (for example, -\cite{IEEE1275-pci} describe how to represent PCI devices). The -standard has not been updated for a long time, however, and lacks -bindings for many modern buses and devices. In particular, embedded -specific devices such as the various System-on-Chip buses are not -covered. We intend to create new bindings for such buses, in keeping -with the general conventions of IEEE1275 (a simple such binding for a -System-on-Chip bus was included in \cite{noof5} a revision of -\cite{noof1}). - -One complication arises for representing ``phandles'' in the flattened -tree. In OF, each node in the tree has an associated phandle, a -32-bit integer that uniquely identifies the node\footnote{In practice -usually implemented as a pointer or offset within OF memory.}. This -handle is used by the various OF calls to query and traverse the tree. -Sometimes phandles are also used within the tree to refer to other -nodes in the tree. For example, devices that produce interrupts -generally have an \texttt{interrupt-parent} property giving the -phandle of the interrupt controller that handles interrupts from this -device. Parsing these and other interrupt related properties allows -the kernel to build a complete representation of the system's -interrupt tree, which can be quite different from the tree of bus -connections. - -In the flattened tree, a node's phandle is represented by a special -\phandle property. When the kernel generates a flattened tree from -OF, it adds a \phandle property to each node, containing the phandle -retrieved from OF. When the tree is generated without OF, however, -only nodes that are actually referred to by phandle need to have this -property. - -Another complication arises because nodes in an OF tree have two -names. First they have the ``unit name'', which is how the node is -referred to in an OF path. The unit name generally consists of a -device type followed by an \texttt{@} followed by a \emph{unit -address}. For example \texttt{/memory@0} is the full path of a memory -node at address 0, \texttt{/ht@0,f2000000/pci@1} is the path of a PCI -bus node, which is under a HyperTransport\tm bus node. The form of -the unit address is bus dependent, but is generally derived from the -node's \texttt{reg} property. In addition, nodes have a property, -\texttt{name}, whose value is usually equal to the first path of the -unit name. For example, the nodes in the previous example would have -\texttt{name} properties equal to \texttt{memory} and \texttt{pci}, -respectively. To save space in the blob, the current version of the -flattened tree format only requires the unit names to be present. -When the kernel unflattens the tree, it automatically generates a -\texttt{name} property from the node's path name. - -\section{The Device Tree Compiler} -\label{sec:dtc} - -\begin{figure}[htb!] - \centering - \begin{lstlisting}[frame=single,basicstyle=\footnotesize\ttfamily, - tabsize=3,numbers=left,xleftmargin=2em] -/memreserve/ 0x20000000-0x21FFFFFF; - -/ { - model = "MyBoard"; - compatible = "MyBoardFamily"; - #address-cells = <2>; - #size-cells = <2>; - - cpus { - #address-cells = <1>; - #size-cells = <0>; - PowerPC,970@0 { - device_type = "cpu"; - reg = <0>; - clock-frequency = <5f5e1000>; - timebase-frequency = <1FCA055>; - linux,boot-cpu; - i-cache-size = <10000>; - d-cache-size = <8000>; - }; - }; - - memory@0 { - device_type = "memory"; - memreg: reg = <00000000 00000000 - 00000000 20000000>; - }; - - mpic@0x3fffdd08400 { - /* Interrupt controller */ - /* ... */ - }; - - pci@40000000000000 { - /* PCI host bridge */ - /* ... */ - }; - - chosen { - bootargs = "root=/dev/sda2"; - linux,platform = <00000600>; - interrupt-controller = - < &/mpic@0x3fffdd08400 >; - }; -}; -\end{lstlisting} - \caption{Example \dtc source} - \label{fig:dts} -\end{figure} - -As we've seen, the flattened device tree format provides a convenient -way of communicating device tree information to the kernel. It's -simple for the kernel to parse, and simple for bootloaders to -manipulate. On OF systems, it's easy to generate the flattened tree -by walking the OF maintained tree. However, for embedded systems, the -flattened tree must be generated from scratch. - -Embedded bootloaders are generally built for a particular board. So, -it's usually possible to build the device tree blob at compile time -and include it in the bootloader image. For minor revisions of the -board, the bootloader can contain code to make the necessary tweaks to -the tree before passing it to the booted kernel. - -The device trees for embedded boards are usually quite simple, and -it's possible to hand construct the necessary blob by hand, but doing -so is tedious. The ``device tree compiler'', \dtc{}\footnote{\dtc can -be obtained from \cite{dtcgit}.}, is designed to make creating device -tree blobs easier by converting a text representation of the tree -into the necessary blob. - -\subsection{Input and output formats} - -As well as the normal mode of compiling a device tree blob from text -source, \dtc can convert a device tree between a number of -representations. It can take its input in one of three different -formats: -\begin{itemize} -\item source, the normal case. The device tree is described in a text - form, described in \S\ref{sec:dts}. -\item blob (\texttt{dtb}), the flattened tree format described in - \S\ref{sec:format}. This mode is useful for checking a pre-existing - device tree blob. -\item filesystem (\texttt{fs}), input is a directory tree in the - layout of \texttt{/proc/device-tree} (roughly, a directory for each - node in the device tree, a file for each property). This is useful - for building a blob for the device tree in use by the currently - running kernel. -\end{itemize} - -In addition, \dtc can output the tree in one of three different -formats: -\begin{itemize} -\item blob (\texttt{dtb}), as in \S\ref{sec:format}. The most - straightforward use of \dtc is to compile from ``source'' to - ``blob'' format. -\item source (\texttt{dts}), as in \S\ref{sec:dts}. If used with blob - input, this allows \dtc to act as a ``decompiler''. -\item assembler source (\texttt{asm}). \dtc can produce an assembler - file, which will assemble into a \texttt{.o} file containing the - device tree blob, with symbols giving the beginning of the blob and - its various subsections. This can then be linked directly into a - bootloader or firmware image. -\end{itemize} - -For maximum applicability, \dtc can both read and write any of the -existing revisions of the blob format. When reading, \dtc takes the -version from the blob header, and when writing it takes a command line -option specifying the desired version. It automatically makes any -necessary adjustments to the tree that are necessary for the specified -version. For example, formats before 0x10 require each node to have -an explicit \texttt{name} property. When \dtc creates such a blob, it -will automatically generate \texttt{name} properties from the unit -names. - -\subsection{Source format} -\label{sec:dts} - -The ``source'' format for \dtc is a text description of the device -tree in a vaguely C-like form. Figure \ref{fig:dts} shows an -example. The file starts with \texttt{/memreserve/} directives, which -gives address ranges to add to the output blob's memory reserve table, -then the device tree proper is described. - -Nodes of the tree are introduced with the node name, followed by a -\texttt{\{} ... \texttt{\};} block containing the node's properties -and subnodes. Properties are given as just {\emph{name} \texttt{=} - \emph{value}\texttt{;}}. The property values can be given in any -of three forms: -\begin{itemize} -\item \emph{string} (for example, \texttt{"MyBoard"}). The property - value is the given string, including terminating NULL. C-style - escapes (\verb+\t+, \verb+\n+, \verb+\0+ and so forth) are allowed. -\item \emph{cells} (for example, \texttt{<0 8000 f0000000>}). The - property value is made up of a list of 32-bit ``cells'', each given - as a hex value. -\item \emph{bytestring} (for example, \texttt{[1234abcdef]}). The - property value is given as a hex bytestring. -\end{itemize} - -Cell properties can also contain \emph{references}. Instead of a hex -number, the source can give an ampersand (\texttt{\&}) followed by the -full path to some node in the tree. For example, in Figure -\ref{fig:dts}, the \texttt{/chosen} node has an -\texttt{interrupt-controller} property referring to the interrupt -controller described by the node \texttt{/mpic@0x3fffdd08400}. In the -output tree, the value of the referenced node's phandle is included in -the property. If that node doesn't have an explicit phandle property, -\dtc will automatically create a unique phandle for it. This approach -makes it easy to create interrupt trees without having to explicitly -assign and remember phandles for the various interrupt controller -nodes. - -The \dtc source can also include ``labels'', which are placed on a -particular node or property. For example, Figure \ref{fig:dts} has a -label ``\texttt{memreg}'' on the \texttt{reg} property of the node -\texttt{/memory@0}. When using assembler output, corresponding labels -in the output are generated, which will assemble into symbols -addressing the part of the blob with the node or property in question. -This is useful for the common case where an embedded board has an -essentially fixed device tree with a few variable properties, such as -the size of memory. The bootloader for such a board can have a device -tree linked in, including a symbol referring to the right place in the -blob to update the parameter with the correct value determined at -runtime. - -\subsection{Tree checking} - -Between reading in the device tree and writing it out in the new -format, \dtc performs a number of checks on the tree: -\begin{itemize} -\item \emph{syntactic structure}: \dtc checks that node and property - names contain only allowed characters and meet length restrictions. - It checks that a node does not have multiple properties or subnodes - with the same name. -\item \emph{semantic structure}: In some cases, \dtc checks that - properties whose contents are defined by convention have appropriate - values. For example, it checks that \texttt{reg} properties have a - length that makes sense given the address forms specified by the - \texttt{\#address-cells} and \texttt{\#size-cells} properties. It - checks that properties such as \texttt{interrupt-parent} contain a - valid phandle. -\item \emph{Linux requirements}: \dtc checks that the device tree - contains those nodes and properties that are required by the Linux - kernel to boot correctly. -\end{itemize} - -These checks are useful to catch simple problems with the device tree, -rather than having to debug the results on an embedded kernel. With -the blob input mode, it can also be used for diagnosing problems with -an existing blob. - -\section{Future Work} - -\subsection{Board ports} - -The flattened device tree has always been the only supported way to -boot a \texttt{ppc64} kernel on an embedded system. With the merge of -\texttt{ppc32} and \texttt{ppc64} code it has also become the only -supported way to boot any merged \texttt{powerpc} kernel, 32-bit or -64-bit. In fact, the old \texttt{ppc} architecture exists mainly just -to support the old ppc32 embedded ports that have not been migrated -to the flattened device tree approach. We plan to remove the -\texttt{ppc} architecture eventually, which will mean porting all the -various embedded boards to use the flattened device tree. - -\subsection{\dtc features} - -While it is already quite usable, there are a number of extra features -that \dtc could include to make creating device trees more convenient: -\begin{itemize} -\item \emph{better tree checking}: Although \dtc already performs a - number of checks on the device tree, they are rather haphazard. In - many cases \dtc will give up after detecting a minor error early and - won't pick up more interesting errors later on. There is a - \texttt{-f} parameter that forces \dtc to generate an output tree - even if there are errors. At present, this needs to be used more - often than one might hope, because \dtc is bad at deciding which - errors should really be fatal, and which rate mere warnings. -\item \emph{binary include}: Occasionally, it is useful for the device - tree to incorporate as a property a block of binary data for some - board-specific purpose. For example, many of Apple's device trees - incorporate bytecode drivers for certain platform devices. \dtc's - source format ought to allow this by letting a property's value be - read directly from a binary file. -\item \emph{macros}: it might be useful for \dtc to implement some - sort of macros so that a tree containing a number of similar devices - (for example, multiple identical ethernet controllers or PCI buses) - can be written more quickly. At present, this can be accomplished - in part by running the source file through CPP before compiling with - \dtc. It's not clear whether ``native'' support for macros would be - more useful. -\end{itemize} - -\bibliographystyle{amsplain} -\bibliography{dtc-paper} - -\section*{About the authors} - -David Gibson has been a member of the IBM Linux Technology Center, -working from Canberra, Australia, since 2001. Recently he has worked -on Linux hugepage support and performance counter support for ppc64, -as well as the device tree compiler. In the past, he has worked on -bringup for various ppc and ppc64 embedded systems, the orinoco -wireless driver, ramfs, and a userspace checkpointing system -(\texttt{esky}). - -Benjamin Herrenschmidt was a MacOS developer for about 10 years, but -ultimately saw the light and installed Linux on his Apple PowerPC -machine. After writing a bootloader, BootX, for it in 1998, he -started contributing to the PowerPC Linux port in various areas, -mostly around the support for Apple machines. He became official -PowerMac maintainer in 2001. In 2003, he joined the IBM Linux -Technology Center in Canberra, Australia, where he ported the 64 bit -PowerPC kernel to Apple G5 machines and the Maple embedded board, -among others things. He's a member of the ppc64 development ``team'' -and one of his current goals is to make the integration of embedded -platforms smoother and more maintainable than in the 32-bit PowerPC -kernel. - -\section*{Legal Statement} - -This work represents the view of the author and does not necessarily -represent the view of IBM. - -IBM, \ppc, \ppc Architecture, POWER5, pSeries and iSeries are -trademarks or registered trademarks of International Business Machines -Corporation in the United States and/or other countries. - -Apple and Power Macintosh are a registered trademarks of Apple -Computer Inc. in the United States, other countries, or both. - -Linux is a registered trademark of Linus Torvalds. - -Other company, product, and service names may be trademarks or service -marks of others. - -\end{document} |