Index: chapter07/udev.xml
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-<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
+<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
+  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
   <!ENTITY % general-entities SYSTEM "../general.ent">
   %general-entities;
 ]>
+
 <sect1 id="ch-scripts-udev">
-<title>Device and Module Handling on an LFS System</title>
-<?dbhtml filename="udev.html"?>
-
-<indexterm zone="ch-scripts-udev">
-<primary sortas="a-Udev">Udev</primary>
-<secondary>usage</secondary></indexterm>
-
-<para>In <xref linkend="chapter-building-system"/>, we installed the Udev
-package. Before we go into the details regarding how this works,
-a brief history of previous methods of handling devices is in
-order.</para>
-
-<para>Linux systems in general traditionally use a static device creation
-method, whereby a great many device nodes are created under <filename
-class="directory">/dev</filename> (sometimes literally thousands of nodes),
-regardless of whether the corresponding hardware devices actually exist. This is
-typically done via a <command>MAKEDEV</command> script, which contains a number
-of calls to the <command>mknod</command> program with the relevant major and
-minor device numbers for every possible device that might exist in the world.
-Using the Udev method, only those devices which are detected by the kernel get
-device nodes created for them. Because these device nodes will be created each
-time the system boots, they will be stored on a <systemitem
-class="filesystem">tmpfs</systemitem> file system (a virtual file system that
-resides entirely in system memory). Device nodes do not require much space, so
-the memory that is used is negligible.</para>
-
-<sect2>
-<title>History</title>
-
-<para>In February 2000, a new filesystem called <systemitem
-class="filesystem">devfs</systemitem> was merged into the 2.3.46
-kernel and was made available during the 2.4 series of
-stable kernels.  Although it was present in the kernel source itself,
-this method of creating devices dynamically never received
-overwhelming support from the core kernel developers.</para>
-
-<para>The main problem with the approach adopted by <systemitem
-class="filesystem">devfs</systemitem> was the way it handled
-device detection, creation, and naming. The latter issue, that of
-device node naming, was perhaps the most critical. It is generally
-accepted that if device names are allowed to be configurable, then
-the device naming policy should be up to a system administrator, not
-imposed on them by any particular developer(s). The <systemitem
-class="filesystem">devfs</systemitem> file system also suffers from race
-conditions that are inherent in its design and cannot be fixed
-without a substantial revision to the kernel. It has also been marked
-as deprecated due to a lack of recent maintenance.</para>
-
-<para>With the development of the unstable 2.5 kernel tree, later released as
-the 2.6 series of stable kernels, a new virtual filesystem called <systemitem
-class="filesystem">sysfs</systemitem> came to be. The job of <systemitem
-class="filesystem">sysfs</systemitem> is to export a view of the system's
-hardrware configuration to userspace processes. With this userspace-visible
-representation, the possibility of seeing a userspace replacement for
-<systemitem class="filesystem">devfs</systemitem> became much more
-realistic.</para>
-
-</sect2>
-
-<sect2>
-<title>Udev Implementation</title>
-
-<para>The <systemitem class="filesystem">sysfs</systemitem> filesystem was
-mentioned briefly above. One may wonder how <systemitem
-class="filesystem">sysfs</systemitem> knows about the devices present on a
-system and what device numbers should be used for them. Drivers that have been
-compiled into the kernel directly register their objects with <systemitem
-class="filesystem">sysfs</systemitem> as they are detected by the kernel. For
-drivers compiled as modules, this registration will happen when the module is
-loaded. Once the <systemitem class="filesystem">sysfs</systemitem> filesystem is
-mounted (on <filename class="directory">/sys</filename>), data which the
-built-in drivers registered with <systemitem
-class="filesystem">sysfs</systemitem> are available to userspace processes and
-to <command>udev</command> for device node creation.</para>
-
-<para>The <command>S10udev</command> initscript takes care of creating these
-device nodes when Linux is booted. This script starts by registering
-<command>/sbin/udevsend</command> as a hotplug event handler. Hotplug events
-(discussed below) are not usually generated during this stage, but
-<command>udev</command> is registered just in case they do occur. The
-<command>udevstart</command> program then walks through the <systemitem
-class="filesystem">/sys</systemitem> filesystem and creates devices under
-<filename class="directory">/dev</filename> that match the descriptions. For
-example, <filename>/sys/class/tty/vcs/dev</filename> contains the string
-<quote>7:0</quote> This string is used by <command>udevstart</command> to create
-<filename>/dev/vcs</filename> with major number <emphasis>7</emphasis> and minor
-<emphasis>0</emphasis>. The names and permissions of the nodes created under
-the <filename class="directory">/dev</filename> directory are configured
-according to the rules specified in the files within the <filename
-class="directory">/etc/udev/rules.d/</filename> directory. These are numbered in
-a similar fashion to the LFS-Bootscripts package. If <command>udev</command>
-can't find a rule for the device it is creating, it will default permissions to
-<emphasis>660</emphasis> and ownership to <emphasis>root:root</emphasis>.</para>
-
-<para>Once the above stage is complete, all devices that were already present
-and have compiled-in drivers will be available for use. This leads us to the
-devices that have modular drivers.</para>
-
-<para>Earlier, we mentioned the concept of a <quote>hotplug event
-handler.</quote> When a new device connection is detected by the kernel, the
-kernel will generate a hotplug event and look at the file
-<filename>/proc/sys/kernel/hotplug</filename> to determine the userspace program
-that handles the device's connection. The <command>udev</command> bootscript
-registered <command>udevsend</command> as this handler. When these hotplug
-events are generated, the kernel will tell <command>udev</command> to check the
-<filename class="directory">/sys</filename> filesystem for the information
-pertaining to this new device and create the <filename
-class="directory">/dev</filename> entry for it.</para>
-
-<para>This brings us to one problem that exists with <command>udev</command>,
-and likewise with <systemitem class="filesystem">devfs</systemitem> before it.
-It is commonly referred to as the <quote>chicken and egg</quote> problem. Most
-Linux distributions handle loading modules via entries in
-<filename>/etc/modules.conf</filename>. Access to a device node causes the
-appropriate kernel module to load. With <command>udev</command>, this method
-will not work because the device node does not exist until the module is loaded.
-To solve this, the <command>S05modules</command> bootscript was added to the
-LFS-Bootscripts package, along with the
-<filename>/etc/sysconfig/modules</filename> file. By adding module names to the
-<filename>modules</filename> file, these modules will be loaded when the
-computer starts up. This allows <command>udev</command> to detect the devices
-and create the appropriate device nodes.</para>
-
-<para>Note that on slower machines or for drivers that create a lot
-of device nodes, the process of creating devices may take a few
-seconds to complete. This means that some device nodes may not be
-immediately accessible.</para>
-</sect2>
-
-<sect2>
-<title>Handling Hotpluggable/Dynamic Devices</title>
-
-<para>When you plug in a device, such as a Universal Serial Bus (USB) MP3 player, the kernel
-recognizes that the device is now connected and generates a hotplug
-event. If the driver is already loaded (either because it was compiled
-into the kernel or because it was loaded via the
-<command>S05modules</command> bootscript), <command>udev</command> will
-be called upon to create the relevant device node(s) according to the
-<systemitem class="filesystem">sysfs</systemitem> data available in
-<filename class="directory">/sys</filename>.</para>
-
-<para>If the driver for the just plugged in device is available as a module but
-currently unloaded, the Hotplug package will load the appropriate module
-and make this device available by creating the device node(s) for it.</para>
-</sect2>
-
-<sect2>
-<title>Problems with Creating Devices</title>
-
-<para>There are a few known problems when it comes to automatically creating
-device nodes:</para>
-
-<para>1) A kernel driver may not export its data to <systemitem
-class="filesystem">sysfs</systemitem>.</para>
-   
-<para>This is most common with third party drivers from outside the kernel tree.
-Udev will be unable to automatically create device nodes for such drivers. Use
-the <filename>/etc/sysconfig/createfiles</filename> configuration file to
-manually create the devices. Consult the <filename>devices.txt</filename> file
-inside the kernel documentation or the documentation for that driver to find the
-proper major/minor numbers.</para>
-
-<para>2) A non-hardware device is required.  This is most common with
-the Advanced Linux Sound Architecture (ALSA) project's Open Sound
-System (OSS) compatibility module.  These types of devices can be
-handled in one of two ways:</para>
-
-<itemizedlist>
-
-<listitem><para>Adding the module names to
-<filename>/etc/sysconfig/modules</filename></para></listitem>
-<listitem><para>Using an
-<quote>install</quote> line in
-<filename>/etc/modprobe.conf</filename>. This tells the
-<command>modprobe</command> command <quote>when loading this module, 
-also load this other module, at the same time.</quote>  For example:</para>
+  <?dbhtml filename="udev.html"?>
+
+  <title>Device and Module Handling on an LFS System</title>
+
+  <indexterm zone="ch-scripts-udev">
+    <primary sortas="a-Udev">Udev</primary>
+    <secondary>usage</secondary>
+  </indexterm>
+
+  <para>In <xref linkend="chapter-building-system"/>, we installed the Udev
+  package. Before we go into the details regarding how this works,
+  a brief history of previous methods of handling devices is in
+  order.</para>
+
+  <para>Linux systems in general traditionally use a static device creation
+  method, whereby a great many device nodes are created under <filename
+  class="directory">/dev</filename> (sometimes literally thousands of nodes),
+  regardless of whether the corresponding hardware devices actually exist. This is
+  typically done via a <command>MAKEDEV</command> script, which contains a number
+  of calls to the <command>mknod</command> program with the relevant major and
+  minor device numbers for every possible device that might exist in the world.
+  Using the Udev method, only those devices which are detected by the kernel get
+  device nodes created for them. Because these device nodes will be created each
+  time the system boots, they will be stored on a <systemitem
+  class="filesystem">tmpfs</systemitem> file system (a virtual file system that
+  resides entirely in system memory). Device nodes do not require much space, so
+  the memory that is used is negligible.</para>
+
+  <sect2>
+    <title>History</title>
+
+    <para>In February 2000, a new filesystem called <systemitem
+    class="filesystem">devfs</systemitem> was merged into the 2.3.46 kernel
+    and was made available during the 2.4 series of stable kernels. Although
+    it was present in the kernel source itself, this method of creating devices
+    dynamically never received overwhelming support from the core kernel
+    developers.</para>
+
+    <para>The main problem with the approach adopted by <systemitem
+    class="filesystem">devfs</systemitem> was the way it handled device
+    detection, creation, and naming. The latter issue, that of device node
+    naming, was perhaps the most critical. It is generally accepted that if
+    device names are allowed to be configurable, then the device naming policy
+    should be up to a system administrator, not imposed on them by any
+    particular developer(s). The <systemitem class="filesystem">devfs</systemitem>
+    file system also suffers from race conditions that are inherent in its design
+    and cannot be fixed without a substantial revision to the kernel. It has also
+    been marked as deprecated due to a lack of recent maintenance.</para>
+
+    <para>With the development of the unstable 2.5 kernel tree, later released as
+    the 2.6 series of stable kernels, a new virtual filesystem called <systemitem
+    class="filesystem">sysfs</systemitem> came to be. The job of <systemitem
+    class="filesystem">sysfs</systemitem> is to export a view of the system's
+    hardrware configuration to userspace processes. With this userspace-visible
+    representation, the possibility of seeing a userspace replacement for
+    <systemitem class="filesystem">devfs</systemitem> became much more
+    realistic.</para>
+
+  </sect2>
+
+  <sect2>
+    <title>Udev Implementation</title>
+
+    <para>The <systemitem class="filesystem">sysfs</systemitem> filesystem was
+    mentioned briefly above. One may wonder how <systemitem
+    class="filesystem">sysfs</systemitem> knows about the devices present on
+    a system and what device numbers should be used for them. Drivers that have
+    been compiled into the kernel directly register their objects with
+    <systemitem class="filesystem">sysfs</systemitem> as they are detected by
+    the kernel. For drivers compiled as modules, this registration will happen
+    when the module is loaded. Once the <systemitem
+    class="filesystem">sysfs</systemitem> filesystem is mounted (on <filename
+    class="directory">/sys</filename>), data which the built-in drivers
+    registered with <systemitem class="filesystem">sysfs</systemitem> are
+    available to userspace processes and to <command>udev</command> for device
+    node creation.</para>
+
+    <para>The <command>S10udev</command> initscript takes care of creating
+    these device nodes when Linux is booted. This script starts by registering
+    <command>/sbin/udevsend</command> as a hotplug event handler. Hotplug events
+    (discussed below) are not usually generated during this stage, but
+    <command>udev</command> is registered just in case they do occur. The
+    <command>udevstart</command> program then walks through the <systemitem
+    class="filesystem">/sys</systemitem> filesystem and creates devices under
+    <filename class="directory">/dev</filename> that match the descriptions.
+    For example, <filename>/sys/class/tty/vcs/dev</filename> contains the
+    string <quote>7:0</quote> This string is used by <command>udevstart</command>
+    to create <filename>/dev/vcs</filename> with major number
+    <emphasis>7</emphasis> and minor <emphasis>0</emphasis>. The names and
+    permissions of the nodes created under the <filename
+    class="directory">/dev</filename> directory are configured according to the
+    rules specified in the files within the <filename
+    class="directory">/etc/udev/rules.d/</filename> directory. These are
+    numbered in a similar fashion to the LFS-Bootscripts package. If
+    <command>udev</command> can't find a rule for the device it is creating,
+    it will default permissions to <emphasis>660</emphasis> and ownership to
+    <emphasis>root:root</emphasis>.</para>
+
+    <para>Once the above stage is complete, all devices that were already present
+    and have compiled-in drivers will be available for use. This leads us to the
+    devices that have modular drivers.</para>
+
+    <para>Earlier, we mentioned the concept of a <quote>hotplug event
+    handler.</quote> When a new device connection is detected by the kernel,
+    the kernel will generate a hotplug event and look at the file
+    <filename>/proc/sys/kernel/hotplug</filename> to determine the userspace
+    program that handles the device's connection. The <command>udev</command>
+    bootscript registered <command>udevsend</command> as this handler. When
+    these hotplug events are generated, the kernel will tell
+    <command>udev</command> to check the <filename
+    class="directory">/sys</filename> filesystem for the information pertaining
+    to this new device and create the <filename class="directory">/dev</filename>
+    entry for it.</para>
+
+    <para>This brings us to one problem that exists with <command>udev</command>,
+    and likewise with <systemitem class="filesystem">devfs</systemitem> before it.
+    It is commonly referred to as the <quote>chicken and egg</quote> problem. Most
+    Linux distributions handle loading modules via entries in
+    <filename>/etc/modules.conf</filename>. Access to a device node causes the
+    appropriate kernel module to load. With <command>udev</command>, this method
+    will not work because the device node does not exist until the module is loaded.
+    To solve this, the <command>S05modules</command> bootscript was added to the
+    LFS-Bootscripts package, along with the
+    <filename>/etc/sysconfig/modules</filename> file. By adding module names to the
+    <filename>modules</filename> file, these modules will be loaded when the
+    computer starts up. This allows <command>udev</command> to detect the devices
+    and create the appropriate device nodes.</para>
+
+    <para>Note that on slower machines or for drivers that create a lot of device
+    nodes, the process of creating devices may take a few seconds to complete.
+    This means that some device nodes may not be immediately accessible.</para>
+
+  </sect2>
+
+  <sect2>
+    <title>Handling Hotpluggable/Dynamic Devices</title>
+
+    <para>When you plug in a device, such as a Universal Serial Bus (USB) MP3
+    player, the kernel recognizes that the device is now connected and generates
+    a hotplug event. If the driver is already loaded (either because it was
+    compiled into the kernel or because it was loaded via the
+    <command>S05modules</command> bootscript), <command>udev</command> will be
+    called upon to create the relevant device node(s) according to the
+    <systemitem class="filesystem">sysfs</systemitem> data available in
+    <filename class="directory">/sys</filename>.</para>
+
+    <para>If the driver for the just plugged in device is available as a module but
+    currently unloaded, the Hotplug package will load the appropriate module
+    and make this device available by creating the device node(s) for it.</para>
+
+  </sect2>
+
+  <sect2>
+    <title>Problems with Creating Devices</title>
+
+    <para>There are a few known problems when it comes to automatically creating
+    device nodes:</para>
+
+    <para>1) A kernel driver may not export its data to <systemitem
+    class="filesystem">sysfs</systemitem>.</para>
+
+    <para>This is most common with third party drivers from outside the kernel
+    tree. Udev will be unable to automatically create device nodes for such
+    drivers. Use the <filename>/etc/sysconfig/createfiles</filename>
+    configuration file to manually create the devices. Consult the
+    <filename>devices.txt</filename> file inside the kernel documentation or
+    the documentation for that driver to find the proper major/minor
+    numbers.</para>
+
+    <para>2) A non-hardware device is required.  This is most common with
+    the Advanced Linux Sound Architecture (ALSA) project's Open Sound
+    System (OSS) compatibility module.  These types of devices can be
+    handled in one of two ways:</para>
+
+    <itemizedlist>
+
+      <listitem>
+        <para>Adding the module names to
+        <filename>/etc/sysconfig/modules</filename></para>
+      </listitem>
+
+      <listitem>
+        <para>Using an <quote>install</quote> line in
+        <filename>/etc/modprobe.conf</filename>. This tells the
+        <command>modprobe</command> command <quote>when loading this module,
+        also load this other module, at the same time.</quote>
+        For example:</para>
 
 <screen role="nodump"><userinput>install snd-pcm modprobe -i snd-pcm ; modprobe \
     snd-pcm-oss ; true</userinput></screen>
 
-<para>This will cause the system to load both the
-<emphasis>snd-pcm</emphasis> and <emphasis>snd-pcm-oss</emphasis>
-modules when any request is made to load the driver
-<emphasis>snd-pcm</emphasis>.</para></listitem>
-</itemizedlist>
-</sect2>
-
-<sect2>
-<title>Useful Reading</title>
-
-<para>Additional helpful documentation is available at the following
-sites:</para>
-
-<itemizedlist>
-<listitem><para>A Userspace Implementation of <systemitem class="filesystem">devfs</systemitem>
-<ulink url="http://www.kroah.com/linux/talks/ols_2003_udev_paper/Reprint-Kroah-Hartman-OLS2003.pdf"/></para></listitem>
-
-<listitem><para>udev FAQ
-<ulink url="http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev-FAQ"/></para></listitem>
-
-<listitem><para>The Linux Kernel Driver Model
-<ulink url="http://public.planetmirror.com/pub/lca/2003/proceedings/papers/Patrick_Mochel/Patrick_Mochel.pdf"/></para></listitem>
-</itemizedlist>
-</sect2>
+        <para>This will cause the system to load both the
+        <emphasis>snd-pcm</emphasis> and <emphasis>snd-pcm-oss</emphasis>
+        modules when any request is made to load the driver
+        <emphasis>snd-pcm</emphasis>.</para>
+      </listitem>
+
+    </itemizedlist>
+
+  </sect2>
+
+  <sect2>
+    <title>Useful Reading</title>
+
+    <para>Additional helpful documentation is available at the following
+    sites:</para>
+
+    <itemizedlist>
+
+      <listitem>
+        <para>A Userspace Implementation of <systemitem class="filesystem">devfs</systemitem>
+        <ulink url="http://www.kroah.com/linux/talks/ols_2003_udev_paper/Reprint-Kroah-Hartman-OLS2003.pdf"/></para>
+      </listitem>
+
+      <listitem>
+        <para>udev FAQ
+        <ulink url="http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev-FAQ"/></para>
+      </listitem>
+
+      <listitem>
+        <para>The Linux Kernel Driver Model
+        <ulink url="http://public.planetmirror.com/pub/lca/2003/proceedings/papers/Patrick_Mochel/Patrick_Mochel.pdf"/></para>
+      </listitem>
+
+    </itemizedlist>
+
+  </sect2>
 
 </sect1>
-
