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authorDavid Bryant <david@davidcbryant.net>2022-12-21 16:13:16 -0600
committerDavid Bryant <david@davidcbryant.net>2022-12-21 16:13:16 -0600
commit6ef50538b2bf9d57c9856ea002a1efa12204e7a4 (patch)
tree51a523b02aa3c177bf254c046998b5df324ea698 /chapter09/udev.xml
parentc1fec3a92268a67d06233d9fe093c02d0e3f6dfc (diff)
Correct capitalization, patch up grammar and idiom.
Regularized capital letters in <title> lines. Changed a dependent clause and made it independent. Smoothed out some bumpy verbiage in the "History" section. Removed superfluous verbiage. Clarified some trounbleshooting advice.
Diffstat (limited to 'chapter09/udev.xml')
-rw-r--r--chapter09/udev.xml76
1 files changed, 38 insertions, 38 deletions
diff --git a/chapter09/udev.xml b/chapter09/udev.xml
index 396f2b389..4bcb52dfe 100644
--- a/chapter09/udev.xml
+++ b/chapter09/udev.xml
@@ -16,23 +16,23 @@
</indexterm>
<para>In <xref linkend="chapter-building-system"/>, we installed the udev
- package when <phrase revision="sysv">eudev</phrase>
+ daemon when <phrase revision="sysv">eudev</phrase>
<phrase revision="systemd">systemd</phrase> was built. Before we go into the
- details regarding how this works, a brief history of previous methods of
+ details regarding how udev works, a brief history of previous methods of
handling devices is in order.</para>
<para>Linux systems in general traditionally used a static device creation
method, whereby a great many device nodes were created under <filename
class="directory">/dev</filename> (sometimes literally thousands of nodes),
regardless of whether the corresponding hardware devices actually existed. This
- was typically done via a <command>MAKEDEV</command> script, which contains a
+ was typically done via a <command>MAKEDEV</command> script, which contained 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.</para>
- <para>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
+ <para>Using the udev method, device nodes are only created for those devices
+ which are detected by the kernel. These device nodes are
+ created each time the system boots; they are stored in a <systemitem
class="filesystem">devtmpfs</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>
@@ -51,23 +51,23 @@
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
+ device names are configurable, the device naming policy
+ should be chosen by system administrators, and not imposed on them by the
+ developer(s). The <systemitem
class="filesystem">devfs</systemitem> file system also suffered from race
- conditions that were inherent in its design and could not be fixed without a
- substantial revision to the kernel. It was marked as deprecated for a long
- period &ndash; due to a lack of maintenance &ndash; and was finally removed
+ conditions that were inherent in its design; these could not be fixed without a
+ substantial revision of the kernel. <systemitem class="filesystem">devfs</systemitem>
+ was marked as deprecated for a long
+ time, and was finally removed
from the kernel in June, 2006.</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
+ <systemitem class="filesystem">sysfs</systemitem> is to provide information about
the system's hardware configuration to userspace processes. With this
- userspace-visible representation, the possibility of developing a userspace
- replacement for <systemitem class="filesystem">devfs</systemitem> became
- much more realistic.</para>
+ userspace-visible representation, it became possible to develop a userspace
+ replacement for <systemitem class="filesystem">devfs</systemitem>.</para>
</sect2>
@@ -81,12 +81,12 @@
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 a
+ have been compiled into the kernel register their objects in
<systemitem class="filesystem">sysfs</systemitem> (devtmpfs internally)
- as they are detected by the kernel. For drivers compiled as modules, this
- registration will happen when the module is loaded. Once the <systemitem
+ as they are detected by the kernel. For drivers compiled as modules,
+ registration happens when the module is loaded. Once the <systemitem
class="filesystem">sysfs</systemitem> filesystem is mounted (on /sys),
- data which the drivers register with <systemitem
+ data which the drivers have registered with <systemitem
class="filesystem">sysfs</systemitem> are available to userspace
processes and to udevd for processing (including modifications to device
nodes).</para>
@@ -96,13 +96,13 @@
<sect3 id='ch-config-udev-device-node-creation'>
<title>Device Node Creation</title>
- <para>Device files are created by the kernel by the <systemitem
- class="filesystem">devtmpfs</systemitem> filesystem. Any driver that
- wishes to register a device node will go through the <systemitem
+ <para>Device files are created by the kernel in the <systemitem
+ class="filesystem">devtmpfs</systemitem> file system. Any driver that
+ wishes to register a device node will use the <systemitem
class="filesystem">devtmpfs</systemitem> (via the driver core) to do it.
When a <systemitem class="filesystem">devtmpfs</systemitem> instance is
mounted on <filename class="directory">/dev</filename>, the device node
- will initially be created with a fixed name, permissions, and
+ will initially be exposed to userspace with a fixed name, permissions, and
owner.</para>
<para>A short time later, the kernel will send a uevent to <command>
@@ -172,7 +172,7 @@
creating device nodes.</para>
<sect3>
- <title>A kernel module is not loaded automatically</title>
+ <title>A Kernel Module Is Not Loaded Automatically</title>
<para>Udev will only load a module if it has a bus-specific alias and the
bus driver properly exports the necessary aliases to <systemitem
@@ -206,8 +206,8 @@
</sect3>
<sect3>
- <title>A kernel module is not loaded automatically, and udev is not
- intended to load it</title>
+ <title>A Kernel Module Is Not Loaded Automatically, and Udev Is Not
+ Intended to Load It</title>
<para>If the <quote>wrapper</quote> module only enhances the
functionality provided by some other module (e.g.,
@@ -236,7 +236,7 @@
</sect3>
<sect3>
- <title>Udev loads some unwanted module</title>
+ <title>Udev Loads Some Unwanted Module</title>
<para>Either don't build the module, or blacklist it in a
<filename>/etc/modprobe.d/blacklist.conf</filename> file as done with the
@@ -250,7 +250,7 @@
</sect3>
<sect3>
- <title>Udev creates a device incorrectly, or makes a wrong symlink</title>
+ <title>Udev Creates a Device Incorrectly, or Makes the Wrong Symlink</title>
<para>This usually happens if a rule unexpectedly matches a device. For
example, a poorly-written rule can match both a SCSI disk (as desired)
@@ -261,7 +261,7 @@
</sect3>
<sect3>
- <title>Udev rule works unreliably</title>
+ <title>Udev Rule Works Unreliably</title>
<para>This may be another manifestation of the previous problem. If not,
and your rule uses <systemitem class="filesystem">sysfs</systemitem>
@@ -275,15 +275,15 @@
</sect3>
<sect3>
- <title>Udev does not create a device</title>
+ <title>Udev Does Not Create a Device</title>
- <para>Further text assumes that the driver is built statically into the
- kernel or already loaded as a module, and that you have already checked
- that udev doesn't create a misnamed device.</para>
+ <para>First, be certain that the driver is built into the
+ kernel or already loaded as a module, and that
+ udev isn't creating a misnamed device.</para>
- <para>Udev has no information needed to create a device node if a kernel
- driver does not export its data to
- <systemitem class="filesystem">sysfs</systemitem>. This is most common
+ <para>If a kernel driver does not export its data to
+ <systemitem class="filesystem">sysfs</systemitem>, udev lacks the
+ information needed to create a device node. This is most likely to happen
with third party drivers from outside the kernel tree. Create a static
device node in <filename>/usr/lib/udev/devices</filename> with the
appropriate major/minor numbers (see the file
@@ -295,7 +295,7 @@
</sect3>
<sect3>
- <title>Device naming order changes randomly after rebooting</title>
+ <title>Device Naming Order Changes Randomly After Rebooting</title>
<para>This is due to the fact that udev, by design, handles uevents and
loads modules in parallel, and thus in an unpredictable order. This will