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authorPascal Bach <pascal.bach@siemens.com>2015-01-16 16:01:06 -0800
committerRichard Purdie <richard.purdie@linuxfoundation.org>2015-02-17 15:16:50 +0000
commitda47cb736b06ebbebd9c0ee4a39805809c22ace2 (patch)
tree9b9e0805e6e719e819e47ea8f46bfc0a2d22da22 /documentation/dev-manual
parenta23e76dbce98458f21fe9fa32941827207681cab (diff)
downloadpoky-da47cb736b06ebbebd9c0ee4a39805809c22ace2.tar.gz
dev-manual: New section on choosing a device manager added.
This patch was modified to fit in with the style of the book. (From yocto-docs rev: 7c6c7ac573f92bfc844977e0d7a97ca4aac9bc70) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'documentation/dev-manual')
-rw-r--r--documentation/dev-manual/dev-manual-common-tasks.xml109
1 files changed, 108 insertions, 1 deletions
diff --git a/documentation/dev-manual/dev-manual-common-tasks.xml b/documentation/dev-manual/dev-manual-common-tasks.xml
index 5cfc8bec44..c2a361c6bb 100644
--- a/documentation/dev-manual/dev-manual-common-tasks.xml
+++ b/documentation/dev-manual/dev-manual-common-tasks.xml
@@ -946,7 +946,7 @@
946 Furthermore, you must use <filename>_append</filename> instead 946 Furthermore, you must use <filename>_append</filename> instead
947 of the <filename>+=</filename> operator if you want to avoid 947 of the <filename>+=</filename> operator if you want to avoid
948 ordering issues. 948 ordering issues.
949 The reason for this is because doing so unconditionally appends 949 The reason for this is because doing so un>+conditionally appends
950 to the variable and avoids ordering problems due to the 950 to the variable and avoids ordering problems due to the
951 variable being set in image recipes and 951 variable being set in image recipes and
952 <filename>.bbclass</filename> files with operators like 952 <filename>.bbclass</filename> files with operators like
@@ -7587,6 +7587,113 @@
7587 </section> 7587 </section>
7588 </section> 7588 </section>
7589 7589
7590 <section id="selecting-dev-manager">
7591 <title>Selecting a Device Manager</title>
7592
7593 <para>
7594 The Yocto Project provides multiple ways to manage the device
7595 manager (<filename>/dev</filename>):
7596 <itemizedlist>
7597 <listitem><para><emphasis>Persistent and Pre-Populated<filename>/dev</filename>:</emphasis>
7598 For this case, the <filename>/dev</filename> directory
7599 is persistent and the required device nodes are created
7600 during the build.
7601 </para></listitem>
7602 <listitem><para><emphasis>Use <filename>devtmps</filename> with a Device Manager:</emphasis>
7603 For this case, the <filename>/dev</filename> directory
7604 is provided by the kernel as an in-memory file system and
7605 is automatically populated by the kernel at runtime.
7606 Additional configuration of device nodes is done in user
7607 space by a device manager like
7608 <filename>udev</filename> or
7609 <filename>busybox-mdev</filename>.
7610 </para></listitem>
7611 </itemizedlist>
7612 </para>
7613
7614 <section id="static-dev-management">
7615 <title>Using Persistent and Pre-Populated<filename>/dev</filename></title>
7616
7617 <para>
7618 To use the static method for device population, you need to
7619 set the
7620 <ulink url='&YOCTO_DOCS_REF_URL;#var-USE_DEVFS'><filename>USE_DEVFS</filename></ulink>
7621 variable to "0" as follows:
7622 <literallayout class='monospaced'>
7623 USE_DEVFS = "0"
7624 </literallayout>
7625 </para>
7626
7627 <para>
7628 The content of the resulting <filename>/dev</filename>
7629 directory is defined in a Device Table file.
7630 The
7631 <ulink url='&YOCTO_DOCS_REF_URL;#var-IMAGE_DEVICE_TABLES'><filename>IMAGE_DEVICE_TABLES</filename></ulink>
7632 variable defines the Device Table to use and should be set
7633 in the machine or distro configuration file.
7634 Alternatively, you can set this variable in your
7635 <filename>local.conf</filename> configuration file.
7636 </para>
7637
7638 <para>
7639 If you do not define the
7640 <filename>IMAGE_DEVICE_TABLES</filename> variable, the default
7641 <filename>device_table-minimal.txt</filename> is used:
7642 <literallayout class='monospaced'>
7643 IMAGE_DEVICE_TABLES = "device_table-mymachine.txt"
7644 </literallayout>
7645 </para>
7646
7647 <para>
7648 The population is handled by the <filename>makedevs</filename>
7649 utility during image creation:
7650 </para>
7651 </section>
7652
7653 <section id="devtmps-dev-management">
7654 <title>Using <filename>devtmpfs</filename> and a Device Manager</title>
7655
7656 <para>
7657 To use the dynamic method for device population, you need to
7658 use (or be sure to set) the
7659 <ulink url='&YOCTO_DOCS_REF_URL;#var-USE_DEVFS'><filename>USE_DEVFS</filename></ulink>
7660 variable to "1", which is the default:
7661 <literallayout class='monospaced'>
7662 USE_DEVFS = "1"
7663 </literallayout>
7664 With this setting, the resulting <filename>/dev</filename>
7665 is populated by the kernel using <filename>devtmpfs</filename>.
7666 Make sure the corresponding kernel configuration variable
7667 <filename>CONFIG_DEVTMPFS</filename> is set when building
7668 you build a linux kernel.
7669 </para>
7670
7671 <para>
7672 All devices created by <filename>devtmpfs</filename> will be
7673 owned by <filename>root</filename> and have permissions
7674 <filename>0600</filename>.
7675 </para>
7676
7677 <para>
7678 To have more control over the device nodes, you can use a
7679 device manager like <filename>udev</filename> or
7680 <filename>busybox-mdev</filename>.
7681 You choose the device manager by defining the
7682 <filename>VIRTUAL-RUNTIME_dev_manager</filename> variable
7683 in your machine or distro configuration file.
7684 Alternatively, you can set this variable in your
7685 <filename>local.conf</filename> configuration file:
7686 <literallayout class='monospaced'>
7687 VIRTUAL-RUNTIME_dev_manager = "udev"
7688
7689 # Some alternative values
7690 # VIRTUAL-RUNTIME_dev_manager = "busybox-mdev"
7691 # VIRTUAL-RUNTIME_dev_manager = "systemd"
7692 </literallayout>
7693 </para>
7694 </section>
7695 </section>
7696
7590 <section id="platdev-appdev-srcrev"> 7697 <section id="platdev-appdev-srcrev">
7591 <title>Using an External SCM</title> 7698 <title>Using an External SCM</title>
7592 7699