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dev-manual, kernel-dev: Working kernel flow process using devtool

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A work-in-progress of an example that modifies the kernel
using the devtool.  The procedure is not complete yet as it
does not run properly.

(From yocto-docs rev: 462ba2e46f237c294f05805ad5044291a085975d)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2017-08-30 13:34:52 -07:00
committed by Richard Purdie
parent 2a1bdf7416
commit ea256df2a8
3 changed files with 408 additions and 369 deletions
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13
documentation/dev-manual/dev-manual-start.xml
View File

@@ -123,6 +123,19 @@
section in the Yocto Project Reference Manual. section in the Yocto Project Reference Manual.
</para></listitem> </para></listitem>
</orderedlist> </orderedlist>
Once you have completed the previous steps, you are ready to
continue using a given development path on your native Linux
machine.
If you are going to use BitBake, see the
"<link linkend='cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</link>"
section.
If you are going to use the Extensible SDK, see the
"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-extensible'>Using the Extensible SDK</ulink>"
Chapter in the Yocto Project Software Development Kit (SDK)
Developer's Guide.
If you are going to use Toaster, see the
"<ulink url='&YOCTO_DOCS_TOAST_URL;#toaster-manual-setup-and-use'>Setting Up and Using Toaster</ulink>"
section in the Toaster User Manual.
</para> </para>
</section> </section>

742
documentation/kernel-dev/kernel-dev-common.xml
View File

@@ -45,6 +45,67 @@
information. information.
</note> </note>
</para> </para>
<para>
Following is a detailed example showing how to create a layer
without the aid of tools for building the kernel:
<orderedlist>
<listitem><para>
<emphasis>Create additional structure</emphasis>:
Create the additional layer structure:
<literallayout class='monospaced'>
$ cd ~/poky/meta-mylayer
$ mkdir conf
$ mkdir recipes-kernel
$ mkdir recipes-kernel/linux
$ mkdir recipes-kernel/linux/linux-yocto
</literallayout>
The <filename>conf</filename> directory holds your configuration files, while the
<filename>recipes-kernel</filename> directory holds your append file and
your patch file.
</para></listitem>
<listitem><para>
<emphasis>Create the layer configuration file</emphasis>:
Move to the <filename>meta-mylayer/conf</filename>
directory and create the <filename>layer.conf</filename>
file as follows:
<literallayout class='monospaced'>
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"
# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
BBFILE_COLLECTIONS += "mylayer"
BBFILE_PATTERN_mylayer = "^${LAYERDIR}/"
BBFILE_PRIORITY_mylayer = "5"
</literallayout>
Notice <filename>mylayer</filename> as part of the last three
statements.</para></listitem>
<listitem><para>
<emphasis>Create the kernel recipe append file</emphasis>:
Move to the <filename>meta-mylayer/recipes-kernel/linux</filename> directory and create
the <filename>linux-yocto_3.4.bbappend</filename> file as follows:
<literallayout class='monospaced'>
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
</literallayout>
The <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
and <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
statements enable the OpenEmbedded build system to find the patch file.
For more information on using append files, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Manual.
</para></listitem>
<listitem><para>
<emphasis>Put the patch file in your layer</emphasis>:
Move the <filename>0001-calibrate-Add-printk-example.patch</filename> file to
the <filename>meta-mylayer/recipes-kernel/linux/linux-yocto</filename>
directory.</para></listitem>
</orderedlist>
</para>
</section> </section>
<section id='modifying-an-existing-recipe'> <section id='modifying-an-existing-recipe'>
@@ -72,11 +133,9 @@
<para> <para>
Before modifying an existing recipe, be sure that you have created Before modifying an existing recipe, be sure that you have created
a minimal, custom layer from which you can work. a minimal, custom layer from which you can work.
See the "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>" See the
section for some general resources. "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>"
You can also see the section for information.
"<link linkend='set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</link>"
section for a detailed example.
</para> </para>
<section id='creating-the-append-file'> <section id='creating-the-append-file'>
@@ -452,63 +511,51 @@
<section id="using-devtool-to-patch-the-kernel"> <section id="using-devtool-to-patch-the-kernel">
<title>Using <filename>devtool</filename> to Patch the Kernel</title> <title>Using <filename>devtool</filename> to Patch the Kernel</title>
<para role='writernotes'> <para role='writernotes'>
Some stuff here for the using devtool from the wiki. This procedure currently does not work.
This whole section is WIP. It is WIP.
<orderedlist>
<listitem><para role='writernotes'>
If you are dealing with real hardware, you can flash the
new kernel image to a USB stick and boot the hardware to
see it run.
</para></listitem>
<listitem><para role='writernotes'>
Checkout and modify the kernel source.
This is where you make your changes to the image.
</para></listitem>
<listitem><para role='writernotes'>
Create a new image that uses the altered kernel.
</para></listitem>
<listitem><para role='writernotes'>
If you are working with actual hardware, you can flash
the new image to a USB stick and use it to boot up the
hardware.
You can see your changes in action.
</para></listitem>
</orderedlist>
</para> </para>
<para> <para>
Patching the kernel involves changing or adding configurations to an existing kernel, The steps in this procedure show you how you can patch the
changing or adding recipes to the kernel that are needed to support specific hardware features, kernel using the extensible SDK and <filename>devtool</filename>.
or even altering the source code itself.
<note> <note>
You can use the <filename>yocto-kernel</filename> script Before attempting this procedure, be sure you have performed
the steps to get ready for updating the kernel as described
in the
"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>"
section.
</note>
</para>
<para>
Patching the kernel involves changing or adding configurations
to an existing kernel, changing or adding recipes to the kernel
that are needed to support specific hardware features, or even
altering the source code itself.
<note>
You can also use the <filename>yocto-kernel</filename> script
found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
under <filename>scripts</filename> to manage kernel patches and configuration. under <filename>scripts</filename> to manage kernel patches and configuration.
See the "<ulink url='&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel'>Managing kernel Patches and Config Items with yocto-kernel</ulink>" See the "<ulink url='&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel'>Managing kernel Patches and Config Items with yocto-kernel</ulink>"
section in the Yocto Project Board Support Packages (BSP) Developer's Guide for section in the Yocto Project Board Support Packages (BSP)
more information.</note> Developer's Guide for more information.
</note>
</para> </para>
<para> <para>
This example creates a simple patch by adding some QEMU emulator console This example creates a simple patch by adding some QEMU emulator
output at boot time through <filename>printk</filename> statements in the kernel's console output at boot time through <filename>printk</filename>
<filename>calibrate.c</filename> source code file. statements in the kernel's <filename>calibrate.c</filename> source
code file.
Applying the patch and booting the modified image causes the added Applying the patch and booting the modified image causes the added
messages to appear on the emulator's console. messages to appear on the emulator's console.
</para> <note>
The example is a continuation of the setup procedure found in
<para> the
The example builds an extensible SDK, which is then used to "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop using <filename>devtool</filename></link>"
build, using <filename>devtool</filename>, a clean image for the Section.
default <filename>qemux86</filename> machine in a </note>
<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
named <filename>poky</filename>.
In the example, the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
is <filename>build</filename> and is located in the default
<filename>poky_sdk</filename> directory.
</para> </para>
<para> <para>
@@ -517,159 +564,93 @@
section. section.
</para> </para>
<section id='patch-kernel-set-up-the-build-host'> <orderedlist>
<title>Set Up the Build Host</title> <listitem><para>
<emphasis>Check Out the Kernel Source Files:</emphasis>
<para> First you must use <filename>devtool</filename> to checkout
Prior to creating any actual patches for your kernel, you the kernel source code in its workspace.
need to prepare the build host. Be sure you are in the terminal set up to do work
This example builds an extensible SDK. with the extensible SDK.
Follow these steps: <note>
<itemizedlist> See this
<listitem><para> <link linkend='setting-up-the-esdk-terminal'>step</link>
<emphasis>Set Up the Build Environment:</emphasis> in the
Be sure you are set up to use BitBake in a shell. "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>"
See the section for more information.
"<ulink url='&YOCTO_DOCS_DEV_URL;#setting-up-the-development-host-to-use-the-yocto-project'>Setting Up the Development Host to Use the Yocto Project</ulink>" </note>
section in the Yocto Project Development Manual for information Use the following <filename>devtool</filename> command
on how to get a build host ready that is either a native to check out the code:
Linux machine or a machine that uses CROPS.
</para></listitem>
<listitem><para>
<emphasis>Clone the <filename>poky</filename> Repository:</emphasis>
You need to have a local copy of the Yocto Project
<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
(i.e. a local <filename>poky</filename> repository).
See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</ulink>"
and possibly the
"<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking Out by Branch in Poky</ulink>"
and
"<ulink url='&YOCTO_DOCS_DEV_URL;#checkout-out-by-tag-in-poky'>Checking Out by Tag in Poky</ulink>"
sections all in the Yocto Project Development Manual for
information on how to clone the <filename>poky</filename>
repository and check out the appropriate branch for your work.
</para></listitem>
<listitem><para>
<emphasis>Initialize the Build Environment:</emphasis>
While in the root directory of the Source Directory (i.e.
<filename>poky</filename>), run the
<ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
environment setup script to define the OpenEmbedded
build environment on your build host.
<literallayout class='monospaced'>
$ source &OE_INIT_FILE;
</literallayout>
Among other things, the script creates the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
which is <filename>build</filename> in this case
and is located in the
<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
After the script runs, your current working directory
is set to the <filename>build</filename> directory.
<note>
For information on running a memory-resident
<ulink url='&YOCTO_DOCS_REF_URL;#usingpoky-components-bitbake'>BitBake</ulink>,
see the
<ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>
setup script.
</note>
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='create-a-layer-for-your-changes'>
<title>Create a Layer for your Changes</title>
<para>
The first step is to create a layer so you can isolate your
changes to the kernel.
Rather than use the <filename>yocto-layer</filename> script
to create the layer, this example steps through the process
by hand.
If you want information on the script that creates a general
layer, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-yocto-layer-script'>Creating a General Layer Using the yocto-layer Script</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
These two commands create a directory you can use for your
layer:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ cd ~/poky $ devtool modify linux-yocto
$ mkdir meta-mylayer Loading cache: 100% |#######################################################################| Time: 0:00:00
Loaded 1300 entries from dependency cache.
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
Summary: There was 1 WARNING message shown.
Loading cache: 100% |########################################################################| Time: 0:00:00
Loaded 1300 entries from dependency cache.
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
Summary: There was 1 WARNING message shown.
NOTE: Executing RunQueue Tasks
NOTE: Executing do_fetch...
NOTE: Executing do_unpack...
NOTE: Tasks Summary: Attempted 2 tasks of which 0 didn't need to be rerun and all succeeded.
NOTE: Executing RunQueue Tasks
NOTE: Executing do_kernel_checkout...
NOTE: Tasks Summary: Attempted 3 tasks of which 2 didn't need to be rerun and all succeeded.
NOTE: Patching...
NOTE: Executing RunQueue Tasks
NOTE: Executing do_validate_branches...
NOTE: Executing do_kernel_metadata...
NOTE: Executing do_patch...
NOTE: Tasks Summary: Attempted 6 tasks of which 3 didn't need to be rerun and all succeeded.
NOTE: Generating kernel config
NOTE: Executing RunQueue Tasks
NOTE: Executing do_kernel_configme...
NOTE: Executing do_prepare_recipe_sysroot...
NOTE: Executing do_configure...
NOTE: Tasks Summary: Attempted 9 tasks of which 6 didn't need to be rerun and all succeeded.
NOTE: Copying kernel config to srctree
NOTE: Source tree extracted to /home/scottrif/poky_sdk/workspace/sources/linux-yocto
NOTE: Recipe linux-yocto now set up to build from /home/scottrif/poky_sdk/workspace/sources/linux-yocto
</literallayout> </literallayout>
Creating a directory that follows the Yocto Project layer naming <note>
conventions sets up the layer for your changes. During the checkout operation, a bug exists that could
The layer is where you place your configuration files, append cause errors such as the following to appear:
files, and patch files. <literallayout class='monospaced'>
To learn more about creating a layer and filling it with the ERROR: Taskhash mismatch 2c793438c2d9f8c3681fd5f7bc819efa versus
files you need, see the be3a89ce7c47178880ba7bf6293d7404 for
"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" /path/to/esdk/layers/poky/meta/recipes-kernel/linux/linux-yocto_4.10.bb.do_unpack
section in the Yocto Project Development Manual. </literallayout>
</para> You can safely ignore these messages.
</section> The source code is correctly checked out.
</note>
<section id='finding-the-kernel-source-code'> </para></listitem>
<title>Finding the Kernel Source Code</title> <listitem><para>
<emphasis>Edit the Source Files</emphasis>
<para> Follow these steps to make some simple changes to the source
Each time you build a kernel image, the kernel source code files:
is fetched and unpacked into the following directory:
<literallayout class='monospaced'>
${S}/linux
</literallayout>
See the "<ulink url='&YOCTO_DOCS_DEV_URL;#finding-the-temporary-source-code'>Finding Temporary Source Code</ulink>"
section in the Yocto Project Development Manual and the
<ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink>
variable for more information about where source is kept
during a build.
</para>
<para>
For this example, we are going to patch the
<filename>init/calibrate.c</filename> file
by adding some simple console <filename>printk</filename> statements that we can
see when we boot the image using QEMU.
</para>
</section>
<section id='creating-the-patch'>
<title>Creating the Patch</title>
<para>
Two methods exist by which you can create the patch:
<ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink>
and
<ulink url='&YOCTO_DOCS_DEV_URL;#using-a-quilt-workflow'>Quilt</ulink>.
For kernel patches, the Git workflow is more appropriate.
This section assumes the Git workflow and shows the steps
specific to this example.
<orderedlist> <orderedlist>
<listitem><para> <listitem><para>
<emphasis>Change the working directory</emphasis>: <emphasis>Change the working directory</emphasis>:
In the previous step, the output noted where you can find
the source files (e.g.
<filename>~/poky_sdk/workspace/sources/linux-yocto</filename>).
Change to where the kernel source code is before making Change to where the kernel source code is before making
your edits to the <filename>calibrate.c</filename> file: your edits to the <filename>calibrate.c</filename> file:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ cd ~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-${PV}-${PR}/linux $ cd ~/poky_sdk/workspace/sources/linux-yocto
</literallayout> </literallayout>
Because you are working in an established Git repository, </para></listitem>
you must be in this directory in order to commit your changes
and create the patch file.
<note>The <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink> and
<ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink> variables
represent the version and revision for the
<filename>linux-yocto</filename> recipe.
The <filename>PV</filename> variable includes the Git meta and machine
hashes, which make the directory name longer than you might
expect.
</note></para></listitem>
<listitem><para> <listitem><para>
<emphasis>Edit the source file</emphasis>: <emphasis>Edit the source file</emphasis>:
Edit the <filename>init/calibrate.c</filename> file to have the Edit the <filename>init/calibrate.c</filename> file to have
following changes: the following changes:
<literallayout class='monospaced'> <literallayout class='monospaced'>
void calibrate_delay(void) void calibrate_delay(void)
{ {
@@ -687,202 +668,239 @@
. .
. .
. .
</literallayout></para></listitem>
<listitem><para><emphasis>Stage and commit your changes</emphasis>:
These Git commands display the modified file, stage it, and then
commit the file:
<literallayout class='monospaced'>
$ git status
$ git add init/calibrate.c
$ git commit -m "calibrate: Add printk example"
</literallayout></para></listitem>
<listitem><para><emphasis>Generate the patch file</emphasis>:
This Git command creates the a patch file named
<filename>0001-calibrate-Add-printk-example.patch</filename>
in the current directory.
<literallayout class='monospaced'>
$ git format-patch -1
</literallayout> </literallayout>
</para></listitem> </para></listitem>
</orderedlist> </orderedlist>
</para> </para></listitem>
</section> <listitem><para>
<emphasis>Build the Updated Kernel Source:</emphasis>
To build the updated kernel source, use
<filename>devtool</filename>:
<literallayout class='monospaced'>
$ devtool build linux-yocto
Parsing recipes: 100% |####################################################################################| Time: 0:00:31
Parsing of 831 .bb files complete (0 cached, 831 parsed). 1300 targets, 48 skipped, 0 masked, 0 errors.
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
NOTE: There are 1 recipes to be removed from sysroot qemux86, removing...
NOTE: Resolving any missing task queue dependencies
Initialising tasks: 100% |#################################################################################| Time: 0:00:00
Checking sstate mirror object availability: 100% |#########################################################| Time: 0:00:00
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
linux-yocto-4.10.17+git999-r0 do_compile: NOTE: linux-yocto: compiling from external source tree /home/scottrif/poky_sdk/workspace/sources/linux-yocto
NOTE: Tasks Summary: Attempted 471 tasks of which 454 didn't need to be rerun and all succeeded.
<section id='set-up-your-layer-for-the-build'> Summary: There was 1 WARNING message shown.
<title>Set Up Your Layer for the Build</title> </literallayout>
</para></listitem>
<!--
<listitem><para>
<para>These steps get your layer set up for the build: NOTE: This stuff is how it would have been if a *.wic file was created
when the image was built earlier. That is the method used by the
example in the wiki (https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk).
I am leaving it here for now.
<emphasis>Create the Image With the New Kernel:</emphasis>
Normally, you would create a new image using the
<filename>devtool build-image</filename> command.
However, this method can take some time and alters the
kernel source folder.
A faster option is to use
<ulink url='https://linux.die.net/man/8/kpartx'><filename>kpartx</filename></ulink>
to splice the new kernel into the image you have already built.
<note>
You might have to install <filename>kpartx</filename>
onto your build host.
</note>
Follow these steps to create the image with the new kernel:
<orderedlist> <orderedlist>
<listitem><para><emphasis>Create additional structure</emphasis>:
Create the additional layer structure:
<literallayout class='monospaced'>
$ cd ~/poky/meta-mylayer
$ mkdir conf
$ mkdir recipes-kernel
$ mkdir recipes-kernel/linux
$ mkdir recipes-kernel/linux/linux-yocto
</literallayout>
The <filename>conf</filename> directory holds your configuration files, while the
<filename>recipes-kernel</filename> directory holds your append file and
your patch file.</para></listitem>
<listitem><para><emphasis>Create the layer configuration file</emphasis>:
Move to the <filename>meta-mylayer/conf</filename> directory and create
the <filename>layer.conf</filename> file as follows:
<literallayout class='monospaced'>
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"
# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
BBFILE_COLLECTIONS += "mylayer"
BBFILE_PATTERN_mylayer = "^${LAYERDIR}/"
BBFILE_PRIORITY_mylayer = "5"
</literallayout>
Notice <filename>mylayer</filename> as part of the last three
statements.</para></listitem>
<listitem><para><emphasis>Create the kernel recipe append file</emphasis>:
Move to the <filename>meta-mylayer/recipes-kernel/linux</filename> directory and create
the <filename>linux-yocto_3.4.bbappend</filename> file as follows:
<literallayout class='monospaced'>
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
</literallayout>
The <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
and <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
statements enable the OpenEmbedded build system to find the patch file.
For more information on using append files, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Manual.
</para></listitem>
<listitem><para> <listitem><para>
<emphasis>Put the patch file in your layer</emphasis>: <emphasis>Make a Copy of Your Wic File:</emphasis>
Move the <filename>0001-calibrate-Add-printk-example.patch</filename> file to Create a copy of your Wic from into the
the <filename>meta-mylayer/recipes-kernel/linux/linux-yocto</filename> <filename>/tmp</filename> directory:
directory.</para></listitem>
</orderedlist>
</para>
</section>
<section id='set-up-for-the-build'>
<title>Set Up for the Build</title>
<para>
Do the following to make sure the build parameters are set up for the example.
Once you set up these build parameters, they do not have to change unless you
change the target architecture of the machine you are building:
<itemizedlist>
<listitem><para><emphasis>Build for the correct target architecture:</emphasis> Your
selected <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink>
definition within the <filename>local.conf</filename> file in the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
specifies the target architecture used when building the Linux kernel.
By default, <filename>MACHINE</filename> is set to
<filename>qemux86</filename>, which specifies a 32-bit
<trademark class='registered'>Intel</trademark> Architecture
target machine suitable for the QEMU emulator.</para></listitem>
<listitem><para><emphasis>Identify your <filename>meta-mylayer</filename>
layer:</emphasis> The
<ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
variable in the
<filename>bblayers.conf</filename> file found in the
<filename>poky/build/conf</filename> directory needs to have the path to your local
<filename>meta-mylayer</filename> layer.
By default, the <filename>BBLAYERS</filename> variable contains paths to
<filename>meta</filename>, <filename>meta-poky</filename>, and
<filename>meta-yocto-bsp</filename> in the
<filename>poky</filename> Git repository.
Add the path to your <filename>meta-mylayer</filename> location:
<literallayout class='monospaced'> <literallayout class='monospaced'>
BBLAYERS ?= " \ $ cp tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic /tmp
$HOME/poky/meta \
$HOME/poky/meta-poky \
$HOME/poky/meta-yocto-bsp \
$HOME/poky/meta-mylayer \
"
</literallayout></para></listitem>
</itemizedlist>
</para>
</section>
<section id='build-the-modified-qemu-kernel-image'>
<title>Build the Modified QEMU Kernel Image</title>
<para>
The following steps build your modified kernel image:
<orderedlist>
<listitem><para><emphasis>Be sure your build environment is initialized</emphasis>:
Your environment should be set up since you previously sourced
the
<ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
script.
If it is not, source the script again from <filename>poky</filename>.
<literallayout class='monospaced'>
$ cd ~/poky
$ source &OE_INIT_FILE;
</literallayout> </literallayout>
</para></listitem> </para></listitem>
<listitem><para> <listitem><para>
<emphasis>Clean up</emphasis>: <emphasis>Create Loopback Devices for Partitions:</emphasis>
Be sure to clean the shared state out by using BitBake Next, create loopback devices for each partition in
to run from within the Build Directory the the Wic file.
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink> <note>
task as follows: The first unused loopback device is automatically
allocated.
</note>
In this example, the command's output uses a variable
"<replaceable>X</replaceable>" to indicate the loopback
device.
The actual output you get when you run the command lists
the actual loopback devices (e.g. "loop0p1", "loop0p2",
and "loop0p3"):
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ bitbake -c cleansstate linux-yocto $ sudo kpartx -v -a /tmp/core-image-minimal-qemux86.wic
</literallayout></para> add map loop<replaceable>X</replaceable>p1 (253:6): 0 47446 linear /dev/loopX 2048
<para> add map loop<replaceable>X</replaceable>p2 (253:7): 0 119356 linear /dev/loopX 51200
<note> add map loop<replaceable>X</replaceable>p3 (253:8): 0 90112 linear /dev/loopX 170556
Never remove any files by hand from the </literallayout>
<filename>tmp/deploy</filename>
directory inside the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>.
Always use the various BitBake clean tasks to
clear out previous build artifacts.
For information on the clean tasks, see the
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-clean'><filename>do_clean</filename></ulink>",
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>do_cleanall</filename></ulink>",
and
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink>"
sections all in the Yocto Project Reference
Manual.
</note>
</para></listitem> </para></listitem>
<listitem><para> <listitem><para>
<emphasis>Build the image</emphasis>: <emphasis>Mount the First Device:</emphasis>
Next, build the kernel image using this command: The kernel is in the first device, so mount
<filename>/dev/mapper/loop</filename><replaceable>X</replaceable><filename>p1</filename>:
<note>
Be sure to replace the "<replaceable>X</replaceable>"
in "loop<replaceable>X</replaceable>p1" with the
automatically allocated loopback device
(e.g loop0p1).
</note>
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ bitbake -k linux-yocto $ sudo mkdir /mnt/wic-p1
</literallayout></para></listitem> $ sudo mount /dev/mapper/loop<replaceable>X</replaceable>p1 /mnt/wic-p1
</literallayout>
</para></listitem>
<listitem><para>
<emphasis>Copy Over the New Kernel:</emphasis>
Now copy over new kernel using the following:
<literallayout class='monospaced'>
$ sudo cp workspace/sources/linux-yocto/arch/x86/boot/bzImage /mnt/wic-p1
</literallayout>
</para></listitem>
<listitem><para>
Finally, unmount the device and use
<filename>kpartx</filename> to delete the partition
mappings:
<note>
Replace the "<replaceable>X</replaceable>" in
"loop<replaceable>X</replaceable>" with the
automatically allocated loopback device from
earlier (e.g "loop0").
</note>
<literallayout class='monospaced'>
$ sudo umount /mnt/wic-p1
$ sudo kpartx -d /dev/loop<replaceable>X</replaceable>
</literallayout>
</para></listitem>
</orderedlist> </orderedlist>
</para> </para></listitem>
</section> -->
<listitem><para>
<emphasis>Create the Image With the New Kernel:</emphasis>
Use the <filename>devtool build-image</filename> command
to create a new image that has the new kernel.
<note>
If the image you originally created resulted in a Wic
file, you can use an alternate method to create the new
image with the updated kernel.
For an example, see the steps in the
<ulink url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk'>TipsAndTricks/KernelDevelopmentWithEsdk</ulink>
Wiki Page.
</note>
<literallayout class='monospaced'>
$ cd ~
$ devtool build-image core-image-minimal
Loading cache: 100% |###########################################################################| Time: 0:00:00
Loaded 1299 entries from dependency cache.
Parsing recipes: 100% |#########################################################################| Time: 0:00:00
Parsing of 831 .bb files complete (830 cached, 1 parsed). 1300 targets, 48 skipped, 0 masked, 0 errors.
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
<section id='boot-the-image-and-verify-your-changes'> Summary: There was 1 WARNING message shown.
<title>Boot the Image and Verify Your Changes</title> WARNING: Skipping recipe linux-yocto as it doesn't produce a package with the same name
WARNING: No recipes in workspace, building image core-image-minimal unmodified
Loading cache: 100% |###########################################################################| Time: 0:00:00
Loaded 1299 entries from dependency cache.
Parsing recipes: 100% |#########################################################################| Time: 0:00:00
Parsing of 831 .bb files complete (830 cached, 1 parsed). 1300 targets, 48 skipped, 0 masked, 0 errors.
WARNING: No bb files matched BBFILE_PATTERN_my-kernel '^/home/scottrif/poky_sdk/layers/meta-my-kernel/'
NOTE: Resolving any missing task queue dependencies
Initialising tasks: 100% |######################################################################| Time: 0:00:06
Checking sstate mirror object availability: 100% |##############################################| Time: 0:00:00
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
NOTE: Tasks Summary: Attempted 2393 tasks of which 2375 didn't need to be rerun and all succeeded.
<para> Summary: There was 1 WARNING message shown.
These steps boot the image and allow you to see the changes NOTE: Successfully built core-image-minimal. You can find output files in /home/scottrif/poky_sdk/tmp/deploy/images/qemux86
</literallayout>
</para></listitem>
<listitem><para>
<emphasis>Test the New Image:</emphasis>
For this example, you can run the new image using QEMU
to verify your changes:
<orderedlist> <orderedlist>
<listitem><para><emphasis>Boot the image</emphasis>: <listitem><para>
<emphasis>Boot the image</emphasis>:
Boot the modified image in the QEMU emulator Boot the modified image in the QEMU emulator
using this command: using this command:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ runqemu qemux86 $ runqemu qemux86
</literallayout></para></listitem> </literallayout>
<listitem><para><emphasis>Verify the changes</emphasis>: </para></listitem>
Log into the machine using <filename>root</filename> with no password and then <listitem><para>
use the following shell command to scroll through the console's boot output. <emphasis>Verify the changes</emphasis>:
Log into the machine using <filename>root</filename>
with no password and then use the following shell
command to scroll through the console's boot output.
<literallayout class='monospaced'> <literallayout class='monospaced'>
# dmesg | less # dmesg | less
</literallayout> </literallayout>
You should see the results of your <filename>printk</filename> statements You should see the results of your
as part of the output.</para></listitem> <filename>printk</filename> statements
as part of the output when you scroll down the
console window.
</para></listitem>
</orderedlist> </orderedlist>
</para> </para></listitem>
</section> <listitem><para>
<emphasis>Stage and commit your changes</emphasis>:
Within your eSDK terminal, change your working directory to
where you modified the <filename>calibrate.c</filename>
file and use these Git commands to stage and commit your
changes:
<literallayout class='monospaced'>
$ cd ~/poky_sdk/workspace/sources/linux-yocto
$ git status
$ git add init/calibrate.c
$ git commit -m "calibrate: Add printk example"
</literallayout>
</para></listitem>
<listitem><para>
<emphasis>Export the Patches and Create a <filename>.bbappend</filename>:</emphasis>
To export your commits as patches and create a
<filename>.bbappend</filename> file, use the following
command in the terminal used to work with the extensible
SDK.
This example uses the previously established layer named
<filename>meta-my-kernel</filename>.
<note>
See Step 3 of the
"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop using devtool</link>"
section for information on setting up this layer.
</note>
<literallayout class='monospaced'>
$ devtool finish linux-yocto /path/to/meta-my-kernel
</literallayout>
Once the command finishes, the patches and the
<filename>.bbappend</filename> file are located in the
<filename>~/meta-my-kernel/recipes-kernel/linux</filename>
directory.
</para></listitem>
<listitem><para>
<emphasis>Build the Image With Your Modified Kernel:</emphasis>
You can now build an image that includes your kernel
patches.
Execute the following command from your
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
in the terminal set up to run BitBake:
<literallayout class='monospaced'>
$ cd ~/poky/build
$ bitbake core-image-minimal
</literallayout>
</para></listitem>
</orderedlist>
</section> </section>
<section id='using-an-iterative-development-process'> <section id='using-an-iterative-development-process'>
@@ -1174,7 +1192,7 @@
are very time consuming. are very time consuming.
</para> </para>
<para> <para role='writernotes'>
Once you are satisfied with your source code modifications, Once you are satisfied with your source code modifications,
you can make them permanent by generating patches and you can make them permanent by generating patches and
applying them to the applying them to the
@@ -1183,7 +1201,7 @@
"<link linkend='applying-patches'>Applying Patches</link>" "<link linkend='applying-patches'>Applying Patches</link>"
section. section.
If you are not familiar with generating patches, refer to the If you are not familiar with generating patches, refer to the
"<link linkend='creating-the-patch'>Creating the Patch</link>" "I need a linked section here for the patch stuff"
section. section.
</para> </para>
</section> </section>

22
documentation/kernel-dev/kernel-dev-intro.xml
View File

@@ -108,6 +108,16 @@
"<ulink url='&YOCTO_DOCS_DEV_URL;#cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</ulink>" "<ulink url='&YOCTO_DOCS_DEV_URL;#cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</ulink>"
section in the Yocto Project Development Manual to set up your section in the Yocto Project Development Manual to set up your
Source Directory. Source Directory.
<note>
Be sure you check out the appropriate development branch or
by tag to get the version of Yocto Project you want.
See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking Out by Branch in Poky</ulink>"
and
"<ulink url='&YOCTO_DOCS_DEV_URL;#checkout-out-by-tag-in-poky'>Checking Out by Tag in Poky</ulink>"
sections in the Yocto Project Development Manual for more
information.
</note>
</para> </para>
<para> <para>
@@ -156,7 +166,7 @@
building for the QEMU emulator in 32-bit mode. building for the QEMU emulator in 32-bit mode.
However, if you are not, you need to set the However, if you are not, you need to set the
<filename>MACHINE</filename> variable appropriately in <filename>MACHINE</filename> variable appropriately in
your <filename>local.conf</filename> file found in the your <filename>conf/local.conf</filename> file found in the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
(i.e. <filename>~/poky/build</filename> in this example). (i.e. <filename>~/poky/build</filename> in this example).
</para> </para>
@@ -208,6 +218,7 @@
Use BitBake to build the extensible SDK specifically for Use BitBake to build the extensible SDK specifically for
the Minnowboard: the Minnowboard:
<literallayout class='monospaced'> <literallayout class='monospaced'>
$ cd ~/poky/build
$ bitbake core-image-minimal -c populate_sdk_ext $ bitbake core-image-minimal -c populate_sdk_ext
</literallayout> </literallayout>
Once the build finishes, you can find the SDK installer Once the build finishes, you can find the SDK installer
@@ -290,12 +301,9 @@
If you were building for actual hardware and not for If you were building for actual hardware and not for
emulation, you could flash the image to a USB stick emulation, you could flash the image to a USB stick
on <filename>/dev/sdd</filename> and boot your device. on <filename>/dev/sdd</filename> and boot your device.
Use a command similar to the following command to flash For an example that uses a Minnowboard, see the
the image: <ulink url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk'>TipsAndTricks/KernelDevelopmentWithEsdk</ulink>
<literallayout class='monospaced'> Wiki page.
$ sudo dd if=tmp/deploy/images/<replaceable>architecture</replaceable>/core-image-minimal-<replaceable>architecture</replaceable>.wic of=/dev/sdd bs=1MB
$ sync
</literallayout>
</para></listitem> </para></listitem>
</orderedlist> </orderedlist>
</para> </para>