dtc/Documentation/dtc-paper.tex

48   The ``blob'' representing the device tree can be created using \dtc
51   the kernel.  The compiler can produce either a binary ``blob'' or an
74 The device tree consists of nodes representing devices or
77 information about the device.  The values are arbitrary byte strings,
81 \subsection{The bad old days}
102 The device tree also presents a problem for implementing \kexec.  When
107 \section{The Flattened Tree}
114 compact, flattened format.  The resulting device tree ``blob'' is then
121 directly from the entry point taking a flattened device tree.  The
131 The flattened tree format should be easy to handle, both for the
203 The format for the blob we devised, was first described on the
204 \texttt{linuxppc64-dev} mailing list in \cite{noof1}.  The format has
216 The memory reserve map section gives a list of regions of memory that
219 kernel.}.  The list is represented as a simple array of (address,
220 size) pairs of 64 bit values, terminated by a zero size entry.  The
225 The structure block contains the device tree proper.  Each node is
230 their own \dtbeginnode tag.  The node ends with an \dtendnode tag, and
233 ease of parsing.}.  The structure block starts with the \dtbeginnode
240 of the blob.  The name offset is followed by the length of the
248 blob, what actually goes into the tree?  The short answer is ``the
254 device tree.  The flattened tree need only provide those nodes and
260 described to find the subsidiary devices.  The device tree can include
267 \cite{IEEE1275-pci} describe how to represent PCI devices).  The
299 referred to in an OF path.  The unit name generally consists of a
303 bus node, which is under a HyperTransport\tm bus node.  The form of
314 \section{The Device Tree Compiler}
384 The device trees for embedded boards are usually quite simple, and
386 so is tedious.  The ``device tree compiler'', \dtc{}\footnote{\dtc can
398 \item source, the normal case.  The device tree is described in a text
413 \item blob (\texttt{dtb}), as in \S\ref{sec:format}.  The most
438 The ``source'' format for \dtc is a text description of the device
440 example.  The file starts with \texttt{/memreserve/} directives, which
447   \emph{value}\texttt{;}}.  The property values can be given in any
450 \item \emph{string} (for example, \texttt{"MyBoard"}).  The property
453 \item \emph{cells} (for example, \texttt{<0 8000 f0000000>}).  The
456 \item \emph{bytestring} (for example, \texttt{[1234abcdef]}).  The
473 The \dtc source can also include ``labels'', which are placed on a
481 the size of memory.  The bootloader for such a board can have a device
516 The flattened device tree has always been the only supported way to