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+
+==================
+QEMU Documentation
+==================
+
+QEMU's documentation is written in reStructuredText format and
+built using the Sphinx documentation generator. We generate both
+the HTML manual and the manpages from the some documentation sources.
+
+hxtool and .hx files
+--------------------
+
+The documentation for QEMU command line options and Human Monitor Protocol
+(HMP) commands is written in files with the ``.hx`` suffix. These
+are processed in two ways:
+
+ * ``scripts/hxtool`` creates C header files from them, which are included
+   in QEMU to do things like handle the ``--help`` option output
+ * a Sphinx extension in ``docs/sphinx/hxtool.py`` generates rST output
+   to be included in the HTML or manpage documentation
+
+The syntax of these ``.hx`` files is simple. It is broadly an
+alternation of C code put into the C output and rST format text
+put into the documention. A few special directives are recognised;
+these are all-caps and must be at the beginning of the line.
+
+``HXCOMM`` is the comment marker. The line, including any arbitrary
+text after the marker, is discarded and appears neither in the C output
+nor the documentation output.
+
+``SRST`` starts a reStructuredText section. Following lines
+are put into the documentation verbatim, and discarded from the C output.
+
+``ERST`` ends the documentation section started with ``SRST``,
+and switches back to a C code section.
+
+``DEFHEADING()`` defines a heading that should appear in both the
+``--help`` output and in the documentation. This directive should
+be in the C code block. If there is a string inside the brackets,
+this is the heading to use. If this string is empty, it produces
+a blank line in the ``--help`` output and is ignored for the rST
+output.
+
+``ARCHHEADING()`` is a variant of ``DEFHEADING()`` which produces
+the heading only if the specified guest architecture was compiled
+into QEMU. This should be avoided in new documentation.
+
+Within C code sections, you should check the comments at the top
+of the file to see what the expected usage is, because this
+varies between files. For instance in ``qemu-options.hx`` we use
+the ``DEF()`` macro to define each option and specify its ``--help``
+text, but in ``hmp-commands.hx`` the C code sections are elements
+of an array of structs of type ``HMPCommand`` which define the
+name, behaviour and help text for each monitor command.
+
+In the file ``qemu-options.hx``, do not try to define a
+reStructuredText label within a documentation section. This file
+is included into two separate Sphinx documents, and some
+versions of Sphinx will complain about the duplicate label
+that results.