nightmorph 11/03/12 05:44:15 Modified: udev-guide.xml Log: update udev guide to remove sysfs, add uevents and rules.d, new profiles, and remove conf.d-rc; patch from swift on bug 358409
Revision Changes Path 1.53 xml/htdocs/doc/en/udev-guide.xml file : http://sources.gentoo.org/viewvc.cgi/gentoo/xml/htdocs/doc/en/udev-guide.xml?rev=1.53&view=markup plain: http://sources.gentoo.org/viewvc.cgi/gentoo/xml/htdocs/doc/en/udev-guide.xml?rev=1.53&content-type=text/plain diff : http://sources.gentoo.org/viewvc.cgi/gentoo/xml/htdocs/doc/en/udev-guide.xml?r1=1.52&r2=1.53 Index: udev-guide.xml =================================================================== RCS file: /var/cvsroot/gentoo/xml/htdocs/doc/en/udev-guide.xml,v retrieving revision 1.52 retrieving revision 1.53 diff -u -r1.52 -r1.53 --- udev-guide.xml 26 Dec 2010 19:21:44 -0000 1.52 +++ udev-guide.xml 12 Mar 2011 05:44:14 -0000 1.53 @@ -1,6 +1,6 @@ <?xml version='1.0' encoding="UTF-8"?> <!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> -<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/udev-guide.xml,v 1.52 2010/12/26 19:21:44 nightmorph Exp $ --> +<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/udev-guide.xml,v 1.53 2011/03/12 05:44:14 nightmorph Exp $ --> <guide> <title>Gentoo udev Guide</title> @@ -23,8 +23,8 @@ <!-- See http://creativecommons.org/licenses/by-sa/2.5 --> <license/> -<version>7</version> -<date>2010-12-26</date> +<version>8</version> +<date>2011-03-11</date> <chapter> <title>What is udev?</title> @@ -71,103 +71,14 @@ </ul> <p> -To provide these features, udev is developed in three separate projects: -<e>namedev</e>, <e>libsysfs</e> and, of course, <e>udev</e>. -</p> - -</body> -</section> -<section> -<title>namedev</title> -<body> - -<p> -Namedev allows you to define the device naming separately from the udev program. -This allows for flexible naming policies and naming schemes developed by -separate entities. This device naming subsystem provides a standard interface -that udev can use. -</p> - -<p> -Currently only a single naming scheme is provided by namedev; the one provided -by LANANA, used by the majority of Linux systems currently and therefore very -suitable for the majority of Linux users. -</p> - -<p> -Namedev uses a 5-step procedure to find out the name of a given device. If the -device name is found in one of the given steps, that name is used. The steps -are: -</p> - -<ul> - <li>label or serial number</li> - <li>bus device number</li> - <li>bus topology</li> - <li>statically given name</li> - <li>kernel provided name</li> -</ul> - -<p> -The <e>label or serial number</e> step checks if the device has a unique -identifier. For instance USB devices have a unique USB serial number; SCSI -devices have a unique UUID. If namedev finds a match between this unique number -and a given configuration file, the name provided in the configuration file is -used. -</p> - -<p> -The <e>bus device number</e> step checks the device bus number. For -non-hot-swappable environments this procedure is sufficient to -identify a hardware device. For instance PCI bus numbers rarely change in the -lifetime of a system. Again, if namedev finds a match between this position and -a given configuration file, the name provided in that configuration file is -used. -</p> - -<p> -Likewise the <e>bus topology</e> is a rather static way of defining devices as -long as the user doesn't switch devices. When the position of the device matches -a given setting provided by the user, the accompanying name is used. -</p> - -<p> -The fourth step, <e>statically given name</e>, is a simple string replacement. -When the kernel name (the default name) matches a given replacement string, the -substitute name will be used. -</p> - -<p> -The final step (<e>kernel provided name</e>) is a catch-all: this one takes -the default name provided by the kernel. In the majority of cases this is -sufficient as it matches the device naming used on current Linux systems. -</p> - -</body> -</section> -<section> -<title>libsysfs</title> -<body> - -<p> -udev interacts with the kernel through the sysfs pseudo filesystem. The libsysfs -project provides a common API to access the information given by the sysfs -filesystem in a generic way. This allows for querying all kinds of hardware -without having to make assumptions on the kind of hardware. -</p> - -</body> -</section> -<section> -<title>udev</title> -<body> - -<p> -Every time the kernel gets an event in the device structure, it asks udev to -take a look. udev follows the rules in the <path>/etc/udev/rules.d/</path> -directory. udev then uses the information given by the kernel to perform the -necessary actions on the <path>/dev</path> structure (creating or deleting -device files). +Every time a change happens within the device structure, the kernel emits a +<e>uevent</e> which gets picked up by udev. udev then follows the rules as +declared in the <path>/etc/udev/rules.d</path> and +<path>/lib/udev/rules.d</path> directories. Based on the information contained +within the uevent, it finds the rule or rules it needs to trigger and performs +the required actions. These actions can be creating or deleting device files, +but can also trigger the loading of particular firmware files into the +kernel memory. </p> </body> @@ -182,9 +93,11 @@ <p> udev is meant to be used in combination with a 2.6 kernel (like -<c>gentoo-sources</c> with the default 2007.0 profile). If you're using such a -kernel then you just have to make sure that you have a recent -<c>sys-apps/baselayout</c> version. That's all you need. +<c>gentoo-sources</c> with the default 10.0 profile). If you're using such a +kernel then you just should have no issues whatsoever with using udev as the +necessary support is built-in in all stable <c>sys-apps/baselayout</c> +versions. Normally, udev should already be installed on your system, but if +this is not the case, then it is easy to install: </p> <pre caption="Installing udev"> @@ -196,11 +109,13 @@ </p> <pre caption="Required kernel options"> -File systems ---> - [*] Inotify file change notification support - [*] Inotify support for userspace +General Setup ---> + <comment>(Make sure the following item is *not* enabled)</comment> + [ ] enable deprecated sysfs features to support old userspace tools + +File Systems ---> + [*] Inotify support for userspace Pseudo filesystems ---> - [*] /proc file system support [*] Virtual memory file system support (former shm fs) </pre> @@ -211,43 +126,6 @@ </body> </section> -<section> -<title>Configuration</title> -<body> - -<p> -If you want to use the udev settings Gentoo provides to make your life -comfortable, then read no more. Gentoo will use udev but keep a static -<path>/dev</path> so that you will never have any missing device nodes. -The Gentoo init scripts won't run the devfsd daemon and will deactivate devfs -when you boot up. -</p> - -<p> -But if you are a die-hard and want to run a udev-only, unmodified system as is -intended by the udev development (including the difficulties of missing device -nodes because udev doesn't support them yet), by all means, read on :) -</p> - -<p> -We'll deactivate the rules that save the device file nodes: edit the -<c>RC_DEVICE_TARBALL</c> variable in <path>/etc/conf.d/rc</path> and set it to -<c>no</c>: -</p> - -<pre caption="/etc/conf.d/rc"> -RC_DEVICE_TARBALL="no" -</pre> - -<p> -If you have included devfs support in your kernel, you can deactivate it in -the bootloader configuration: add <c>gentoo=nodevfs</c> as a kernel parameter. -If you want to use devfs and deactivate udev, add <c>gentoo=noudev</c> as kernel -parameter. -</p> - -</body> -</section> </chapter> <chapter>
