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kernel-dev: Added new "Building Out-of-Tree Modules on the Target" section.

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Fixes [YOCTO #3729]

I have made an attempt at understanding this and creating
a section that describes the steps the user needs to take in
order to build out-of-tree modules on the target device when
running an SDK image.  I created a new section called
"Building Out-of-Tree Modules on the Target".  Basically,
the user needs to be on the target and change to a directory
and then create some scripts before attempting to build these
types of modules on the target.

(From yocto-docs rev: e0754ae6dbc5dc07fb6707fe4b71ecd95c8180dc)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2014-06-03 10:51:09 +03:00
committed by Richard Purdie
parent 3cb04638b4
commit 65cf76cc1c
1 changed files with 144 additions and 97 deletions
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241
documentation/kernel-dev/kernel-dev-common.xml
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@@ -625,55 +625,100 @@
</para> </para>
</section> </section>
<section id='incorporating-out-of-tree-modules'> <section id='working-with-out-of-tree-modules'>
<title>Incorporating Out-of-Tree Modules</title> <title>Working with Out-of-Tree Modules</title>
<para> <para>
While it is always preferable to work with sources integrated This section describes steps you need to take to be able
into the Linux kernel sources, if you need an external kernel to build out-of-tree modules on your target and how to
module, the <filename>hello-mod.bb</filename> recipe is available incorporate out-of-tree modules in the build.
as a template from which you can create your own out-of-tree
Linux kernel module recipe.
</para> </para>
<para> <section id='building-out-of-tree-modules-on-the-target'>
This template recipe is located in the <title>Building Out-of-Tree Modules on the Target</title>
<filename>poky</filename> Git repository of the
Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink> <para>
at: If you want to be able to build out-of-tree modules on
<literallayout class="monospaced"> the target, there are some steps you need to take
on the target that has your SDK image running.
Briefly, the <filename>kernel-dev</filename> package
is installed by default on all
<filename>*.sdk</filename> images.
However, you need to create some scripts prior to
attempting to build the out-of-tree modules on the target
that is running that image.
</para>
<para>
Prior to attempting to build the out-of-tree modules,
you need to be on the target as root and change to the
<filename>/usr/src/kernel</filename> directory and
then <filename>make</filename> the scripts:
<literallayout class='monospaced'>
# cd /usr/src/kernel
# make scripts
</literallayout>
Because all SDK image recipes include
<filename>dev-pkgs</filename> the
<filename>kernel-dev</filename> packages will be installed
as part of the SDK image.
The SDK uses the scripts when building out-of-tree
modules.
Once you have switched to that directory and created the
scripts, you should be able to build your out-of-tree modules
on the target.
</para>
</section>
<section id='incorporating-out-of-tree-modules'>
<title>Incorporating Out-of-Tree Modules</title>
<para>
While it is always preferable to work with sources integrated
into the Linux kernel sources, if you need an external kernel
module, the <filename>hello-mod.bb</filename> recipe is available
as a template from which you can create your own out-of-tree
Linux kernel module recipe.
</para>
<para>
This template recipe is located in the
<filename>poky</filename> Git repository of the
Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink>
at:
<literallayout class="monospaced">
poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
</literallayout> </literallayout>
</para> </para>
<para> <para>
To get started, copy this recipe to your layer and give it a To get started, copy this recipe to your layer and give it a
meaningful name (e.g. <filename>mymodule_1.0.bb</filename>). meaningful name (e.g. <filename>mymodule_1.0.bb</filename>).
In the same directory, create a directory named In the same directory, create a directory named
<filename>files</filename> where you can store any source files, <filename>files</filename> where you can store any source files,
patches, or other files necessary for building patches, or other files necessary for building
the module that do not come with the sources. the module that do not come with the sources.
Finally, update the recipe as appropriate for the module. Finally, update the recipe as appropriate for the module.
Typically you will need to set the following variables: Typically you will need to set the following variables:
<itemizedlist> <itemizedlist>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-DESCRIPTION'><filename>DESCRIPTION</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-DESCRIPTION'><filename>DESCRIPTION</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE*</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE*</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>
</para></listitem> </para></listitem>
</itemizedlist> </itemizedlist>
</para> </para>
<para> <para>
Depending on the build system used by the module sources, you might Depending on the build system used by the module sources, you might
need to make some adjustments. need to make some adjustments.
For example, a typical module <filename>Makefile</filename> looks For example, a typical module <filename>Makefile</filename> looks
much like the one provided with the <filename>hello-mod</filename> much like the one provided with the <filename>hello-mod</filename>
template: template:
<literallayout class='monospaced'> <literallayout class='monospaced'>
obj-m := hello.o obj-m := hello.o
SRC := $(shell pwd) SRC := $(shell pwd)
@@ -684,68 +729,70 @@
modules_install: modules_install:
$(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
... ...
</literallayout> </literallayout>
</para> </para>
<para> <para>
The important point to note here is the The important point to note here is the
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_SRC'><filename>KERNEL_SRC</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_SRC'><filename>KERNEL_SRC</filename></ulink>
variable. variable.
The class <filename>module.bbclass</filename> sets this variable, The class <filename>module.bbclass</filename> sets this variable,
as well as the as well as the
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_PATH'><filename>KERNEL_PATH</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_PATH'><filename>KERNEL_PATH</filename></ulink>
variable to variable to
<filename>${<ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink>}</filename> <filename>${<ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink>}</filename>
with the necessary Linux kernel build information to build modules. with the necessary Linux kernel build information to build modules.
If your module <filename>Makefile</filename> uses a different If your module <filename>Makefile</filename> uses a different
variable, you might want to override the variable, you might want to override the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile()</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile()</filename></ulink>
step, or create a patch to step, or create a patch to
the <filename>Makefile</filename> to work with the more typical the <filename>Makefile</filename> to work with the more typical
<filename>KERNEL_SRC</filename> or <filename>KERNEL_PATH</filename> <filename>KERNEL_SRC</filename> or <filename>KERNEL_PATH</filename>
variables. variables.
</para> </para>
<para> <para>
After you have prepared your recipe, you will likely want to After you have prepared your recipe, you will likely want to
include the module in your images. include the module in your images.
To do this, see the documentation for the following variables in To do this, see the documentation for the following variables in
the Yocto Project Reference Manual and set one of them as the Yocto Project Reference Manual and set one of them as
appropriate in your machine configuration file: appropriate in your machine configuration file:
<itemizedlist> <itemizedlist>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink>
</para></listitem> </para></listitem>
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink> <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink>
</para></listitem> </para></listitem>
</itemizedlist> </itemizedlist>
</para> </para>
<para> <para>
modules are often not required for boot and can be excluded from modules are often not required for boot and can be excluded from
certain build configurations. certain build configurations.
The following allows for the most flexibility: The following allows for the most flexibility:
<literallayout class='monospaced'> <literallayout class='monospaced'>
MACHINE_EXTRA_RRECOMMENDS += "kernel-module-mymodule" MACHINE_EXTRA_RRECOMMENDS += "kernel-module-mymodule"
</literallayout> </literallayout>
Where the value is derived by appending the module filename without Where the value is derived by appending the module filename without
the <filename>.ko</filename> extension to the string the <filename>.ko</filename> extension to the string
"kernel-module-". "kernel-module-".
</para> </para>
<para> <para>
Because the variable is Because the variable is
<ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink>
and not a and not a
<ulink url='&YOCTO_DOCS_REF_URL;#var-RDEPENDS'><filename>RDEPENDS</filename></ulink> <ulink url='&YOCTO_DOCS_REF_URL;#var-RDEPENDS'><filename>RDEPENDS</filename></ulink>
variable, the build will not fail if this module is not available variable, the build will not fail if this module is not available
to include in the image. to include in the image.
</para> </para>
</section>
</section> </section>
<section id='inspecting-changes-and-commits'> <section id='inspecting-changes-and-commits'>
<title>Inspecting Changes and Commits</title> <title>Inspecting Changes and Commits</title>