/usr/share/doc/xorg/reference/dependencies.html is in xserver-xorg 1:7.6+12ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
<meta name="generator" content="AsciiDoc 8.6.6" />
<title>Dependencies between server and drivers</title>
<link rel="stylesheet" href="../xsf.css" type="text/css" />
<script type="text/javascript" src="../asciidoc-xhtml11.js"></script>
<script type="text/javascript">
/*<![CDATA[*/
asciidoc.install(2);
/*]]>*/
</script>
</head>
<body class="article">
<div id="header">
<h1><a href="../index.html">XSF</a> / Dependencies between server and drivers</h1>
<span id="author">Cyril Brulebois</span><br />
<span id="email"><tt><<a href="mailto:kibi@debian.org">kibi@debian.org</a>></tt></span><br />
<div id="toc">
<div id="toctitle">Table of Contents</div>
<noscript><p><b>JavaScript must be enabled in your browser to display the table of contents.</b></p></noscript>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_upstream_side_abi_version_numbers">Upstream-side: ABI version numbers</h2>
<div class="sectionbody">
<div class="paragraph"><p>The X server defines several
<a href="http://en.wikipedia.org/wiki/Application_binary_interface">ABI</a> version numbers in the
<tt>hw/xfree86/common/xf86Module.h</tt> header, through the
<tt>SET_ABI_VERSION(maj,min)</tt> macro. In this document, the focus is on
<tt>ABI_VIDEODRV_VERSION</tt> and <tt>ABI_XINPUT_VERSION</tt>, which are
respectively about <tt>video</tt> drivers and <tt>input</tt> drivers.</p></div>
<div class="paragraph"><p>An example of input ABI is <tt>12.1</tt>, <tt>12</tt> being the <tt>major</tt>, <tt>1</tt> being
the <tt>minor</tt>.</p></div>
<div class="paragraph"><p>Like in usual shared libraries, the major is bumped when interfaces
are broken. There’s no compatibility at all in that case.</p></div>
<div class="paragraph"><p>The minor gets bumped when interfaces are added. In other words, if a
driver is working with <tt>x.y</tt>, it should also work with higher minors:
<tt>x.z</tt>; <tt>z>y</tt>. The converse is not true, if a driver requires a given
minor (for example because it needs a new feature, like MultiTouch),
it won’t work with lower minors (which didn’t provide the needed
feature). Put another way: we have ascending compatibility with the
minors.</p></div>
<div class="paragraph"><p>Conclusion: We need to keep track of both major and minor.</p></div>
<div class="paragraph"><p>Thanks to <tt>pkg-config</tt> we can query them:</p></div>
<div class="listingblock">
<div class="content">
<pre><tt>$ pkg-config --variable=abi_videodrv xorg-server
9.0
$ pkg-config --variable=abi_xinput xorg-server
12.1</tt></pre>
</div></div>
<div style="page-break-after:always"></div>
</div>
</div>
<div class="sect1">
<h2 id="_debian_side_using_virtual_packages">Debian-side: Using virtual packages</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_server_s_build_system">Server’s build system</h3>
<div class="paragraph"><p>When <tt>xorg-server</tt> gets built, we use <tt>pkg-config</tt>’s output to
determine the current major. Through substitution variables, we add
two virtual packages in the <tt>Provides</tt> field of the server (for both
<tt>xserver-xorg-core</tt> and <tt>xserver-xorg-core-udeb</tt>): <tt>xorg-input-abi-$x</tt>
and <tt>xorg-video-abi-$y</tt>, where <tt>$x</tt> and <tt>$y</tt> are the major part of the
version queried through <tt>pkg-config</tt> variables.</p></div>
<div class="paragraph"><p>To handle ascending compatibility for minors, we maintain in
<tt>debian/serverminver</tt> the minimal version of <tt>xserver-xorg-core</tt> which
is needed. When a minor is bumped, we store the server version in that
file. This way, drivers built afterwards will depend on a <strong>minimal</strong>
version of the driver, the last which saw a minor version bump. In
other words: they will “depend on the server version they were built
against, or a higher/compatible one”.</p></div>
<div class="paragraph"><p>Both ABI and minimal server version are recorded in two files shipped
in <tt>xserver-xorg-dev</tt>, to be used while building drivers:</p></div>
<div class="ulist"><ul>
<li>
<p>
<tt>/usr/share/xserver-xorg/xinputdep</tt>
</p>
</li>
<li>
<p>
<tt>/usr/share/xserver-xorg/videodrvdep</tt>
</p>
</li>
</ul></div>
<div class="paragraph"><p>Example for <tt>xinputdep</tt>:</p></div>
<div class="listingblock">
<div class="content">
<pre><tt>xorg-input-abi-11, xserver-xorg-core (>= 2:1.8.99.904)</tt></pre>
</div></div>
<div class="paragraph"><p>To make sure we bump the <tt>debian/serverminver</tt> when there’s a minor
ABI change, there’s a <tt>abibumpcheck</tt> target (on which <tt>clean</tt>
depends), which extracts input and video ABI from the upstream header,
and compares them to the previous ones stored in
<tt>debian/serverminver</tt>, failing and diffing is something changed.</p></div>
</div>
<div class="sect2">
<h3 id="_driver_s_control_file">Driver’s control file</h3>
<div class="paragraph"><p>Drivers also use substitution variables in their control file,
replaced at build time.</p></div>
<div class="listingblock">
<div class="content">
<pre><tt># Input driver:
Depends: ${xinpdriver:Depends}, …
Provides: ${xinpdriver:Provides}
# Video driver:
Depends: ${xviddriver:Depends}, …
Provides: ${xviddriver:Provides}</tt></pre>
</div></div>
<div class="paragraph"><p>For now, <tt>${xinpdriver:Provides}</tt> is always replaced with
<tt>xorg-driver-input</tt>, and <tt>${xviddriver:Provides}</tt> is always replaced
with <tt>xorg-driver-video</tt>. Hopefully provided packages will not change,
but using substitution variables is cheap, and makes it easy to add
tweaks afterwards if needed.</p></div>
</div>
<div class="sect2">
<h3 id="_driver_s_build_system">Driver’s build system</h3>
<div class="paragraph"><p>To set those variables, we ship a <tt>dh_xsf_substvars</tt> script in
<tt>xserver-xorg-dev</tt> starting with <tt>2:1.9.4</tt>, to be run before
<tt>dh_gencontrol</tt>. It iterates on the packages listed by
<tt>dh_listpackages</tt> (very old <tt>debhelper</tt> command) and does the
following work:</p></div>
<div class="ulist"><ul>
<li>
<p>
It reads variables from the files mentioned above.
</p>
</li>
<li>
<p>
If a package name ends with <tt>-udeb</tt>, it replaces
<tt>xserver-xorg-core</tt> with <tt>xserver-xorg-core-udeb</tt>.
</p>
</li>
<li>
<p>
If a package name ends with <tt>-dbg</tt>, it does nothing for this
package. Debug packages usually depend strictly on the non-debug
packages, which in turn have appropriate dependencies.
</p>
</li>
<li>
<p>
If a package name starts with <tt>xserver-xorg-input-</tt>, it appends
<tt>xinpdriver:Depends=…</tt> and <tt>xinpdriver:Provides=…</tt> to this
package’s substvars file.
</p>
</li>
<li>
<p>
If a package name starts with <tt>xserver-xorg-video-</tt>, it appends
<tt>xviddriver:Depends=…</tt> and <tt>xviddriver:Provides=…</tt> to this
package’s substvars file.
</p>
</li>
</ul></div>
<div class="paragraph"><p>Why such heuristics? The idea is to avoid getting “unused substitution
variable” warning messages while building. And since there’s a clear
<tt>xserver-xorg-{input,video}-*</tt> namespace, we can use that to specify
only input-related variables for input drivers, and only video-related
variables for video drivers.</p></div>
<div class="paragraph"><p>To make it easy to compute substvars when using <tt>dh</tt>, a <tt>dh</tt> sequence
(<tt>xsf.pm</tt>) is shipped. As of <tt>2:1.9.4-1</tt>, it inserts
<tt>dh_xsf_substvars</tt> right before the <tt>dh_gencontrol</tt> call. Other
repetitive tasks could also be automated this way.</p></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_sample_driver_packaging">Sample driver packaging</h2>
<div class="sectionbody">
<div class="paragraph"><p>The following assumes:</p></div>
<div class="ulist"><ul>
<li>
<p>
The upstream build system is sane enough, which lets us run
<tt>autoreconf</tt> at build time.
</p>
</li>
<li>
<p>
It is a <tt>video</tt> driver. For an <tt>input</tt> driver, replace both
<tt>xviddriver</tt> occurrences with <tt>xinpdriver</tt>.
</p>
</li>
</ul></div>
<div class="sect2">
<h3 id="_sample_debian_control_file">Sample debian/control file</h3>
<div class="listingblock">
<div class="content">
<pre><tt>Build-Depends:
debhelper (>= 8),
dh-autoreconf,
quilt,
xserver-xorg-dev (>= 2:1.9.4),</tt></pre>
</div></div>
<div class="listingblock">
<div class="content">
<pre><tt>Depends:
${shlibs:Depends},
${misc:Depends},
${xviddriver:Depends},
Provides:
${xviddriver:Provides}</tt></pre>
</div></div>
</div>
<div class="sect2">
<h3 id="_sample_debian_rules_file">Sample debian/rules file</h3>
<div class="listingblock">
<div class="content">
<pre><tt>#!/usr/bin/make -f
# Configuration:
#override_dh_auto_configure:
# dh_auto_configure -- --with-FOO --without-BAR
# Install in debian/tmp to retain control through dh_install:
override_dh_auto_install:
dh_auto_install --destdir=debian/tmp
# Kill *.la files, and forget no-one:
override_dh_install:
find debian/tmp -name '*.la' -delete
dh_install --fail-missing
## Debug package:
#override_dh_strip:
# dh_strip --dbg-package=xserver-xorg-video-DRIVER-dbg
# That's a plugin, use appropriate warning level:
override_dh_shlibdeps:
dh_shlibdeps -- --warnings=6
%:
dh $@ --with quilt,autoreconf,xsf --builddirectory=build/</tt></pre>
</div></div>
<div class="paragraph"><p>Some comments:</p></div>
<div class="ulist"><ul>
<li>
<p>
<tt>dh_auto_configure</tt>: Commented out since there’s usually no
specific option to pass when building drivers. Sometimes needed to
get a related utility built.
</p>
</li>
<li>
<p>
<tt>dh_auto_install</tt>: It behaves differently when operating on a
single package (it installs under <tt>debian/PACKAGE</tt> instead of
<tt>debian/tmp</tt>), so make it use <tt>debian/tmp</tt> in all cases. This way,
<tt>dh_install</tt> has to be used (see below). That also means that a
binary package (<em>e.g.</em> a debug package) can be added without
changing this part.
</p>
</li>
<li>
<p>
<tt>dh_install</tt>: No point in keeping the <tt>.la</tt> files. Also, using
<tt>--fail-missing</tt> makes sure every file installed by upstream is
installed in some package, or explicitly ignored.
</p>
</li>
<li>
<p>
<tt>dh_strip</tt>: Commented out, there’s only a few drivers shipping a
debug package.
</p>
</li>
<li>
<p>
<tt>dh_shlibdeps</tt>: The comment really says it all.
</p>
</li>
<li>
<p>
<tt>dh</tt>: The order is important! We want patching to happen before
autoreconfiguring (both <tt>quilt</tt> and <tt>autoreconf</tt> insert commands
before <tt>dh_auto_configure</tt>, and after <tt>dh_clean</tt>). Also, we build
out-of-tree. The <tt>xsf</tt> sequence is explained in the previous part.
</p>
</li>
</ul></div>
<div class="paragraph"><p>If one needs to build several flavours,
<a href="http://git.debian.org/?p=pkg-xorg/driver/xserver-xorg-video-fbdev.git;a=blob;f=debian/rules"><tt>fbdev</tt>’s rules file</a>
can be used as an example.</p></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_staying_tuned">Staying tuned</h2>
<div class="sectionbody">
<div class="paragraph"><p>Staying informed of driver-related changes can be a bit difficult in
the following cases:</p></div>
<div class="ulist"><ul>
<li>
<p>
If one maintains a single driver within the X Strike Force, one
might not notice the few mails about drivers in the heavy mail flow
on <tt>debian-x@</tt>.
</p>
</li>
<li>
<p>
If one maintains a driver outside the X Strike Force, one is
probably not subscribed to the mailing list at all.
</p>
</li>
</ul></div>
<div class="paragraph"><p>For those reasons, a mail alias is being set up to gather all
maintainers interested in receiving driver-related mails.</p></div>
</div>
</div>
</div>
<div id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
Last updated 2011-06-06 07:22:56 UTC
</div>
</div>
</body>
</html>
|