[gnome-continuous-yocto/gnomeostree-3.28-rocko: 7694/8267] kernel-dev: Added the host prep for kernel dev to the chapter.
- From: Emmanuele Bassi <ebassi src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [gnome-continuous-yocto/gnomeostree-3.28-rocko: 7694/8267] kernel-dev: Added the host prep for kernel dev to the chapter.
- Date: Sun, 17 Dec 2017 06:36:28 +0000 (UTC)
commit ccbfdd795e36ca421b1c169343c1e9a886f515a7
Author: Scott Rifenbark <srifenbark gmail com>
Date: Wed Sep 6 14:52:41 2017 -0700
kernel-dev: Added the host prep for kernel dev to the chapter.
(From yocto-docs rev: 7343f1108808bb3be182af58325f9e3195ff4d8e)
Signed-off-by: Scott Rifenbark <srifenbark gmail com>
Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>
documentation/kernel-dev/kernel-dev-common.xml | 577 +++++++++++++++++++++++-
1 files changed, 565 insertions(+), 12 deletions(-)
---
diff --git a/documentation/kernel-dev/kernel-dev-common.xml b/documentation/kernel-dev/kernel-dev-common.xml
index de119c3..3af52eb 100644
--- a/documentation/kernel-dev/kernel-dev-common.xml
+++ b/documentation/kernel-dev/kernel-dev-common.xml
@@ -3,20 +3,391 @@
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<chapter id='kernel-dev-common'>
-
<title>Common Tasks</title>
-<para>
- This chapter presents several common tasks you perform when you
- work with the Yocto Project Linux kernel.
- These tasks include preparing a layer, modifying an existing recipe,
- iterative development, working with your own sources, and incorporating
- out-of-tree modules.
- <note>
- The examples presented in this chapter work with the Yocto Project
- 1.2.2 Release and forward.
- </note>
-</para>
+ <para>
+ This chapter presents several common tasks you perform when you
+ work with the Yocto Project Linux kernel.
+ These tasks include preparing your host development system for
+ kernel development, preparing a layer, modifying an existing recipe,
+ patching the kernel, iterative development, working with your own sources,
+ and incorporating out-of-tree modules.
+ <note>
+ The examples presented in this chapter work with the Yocto Project
+ 2.4 Release and forward.
+ </note>
+ </para>
+
+ <section id='preparing-the-build-host-to-work-on-the-kernel'>
+ <title>Preparing the Build Host to Work on the Kernel</title>
+
+ <para>
+ Before you can do any kernel development, you need to be
+ sure your build host is set up to use the Yocto Project.
+ For information on how to get set up, see the
+ "<ulink
url='&YOCTO_DOCS_DEV_URL;#setting-up-the-development-host-to-use-the-yocto-project'>Setting Up to Use the
Yocto Project</ulink>"
+ section in the Yocto Project Development Manual.
+ Part of preparing the system is creating a local Git
+ repository of the
+ <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
+ (<filename>poky</filename>) on your system.
+ Follow the steps in the
+ "<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
+ 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>
+ Kernel development is best accomplished using
+ <ulink
url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink>
+ and not through traditional kernel workflow methods.
+ The remainder of this section provides information for both
+ scenarios.
+ </para>
+
+ <section id='getting-ready-to-develop-using-devtool'>
+ <title>Getting Ready to Develop using <filename>devtool</filename></title>
+
+ <para>
+ Follow these steps to prepare to update the kernel image using
+ <filename>devtool</filename>.
+ Completing this procedure leaves you with a clean kernel image
+ and ready to make modifications as described in the
+ "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to
Patch the Kernel</link>"
+ section:
+ <orderedlist>
+ <listitem><para>
+ <emphasis>Initialize the BitBake Environment:</emphasis>
+ Before building an extensible SDK, you need to
+ initialize the BitBake build environment by sourcing a
+ build environment script
+ (i.e. <ulink
url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</filename></ulink>
+ or
+ <ulink
url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>):
+ <literallayout class='monospaced'>
+ $ cd ~/poky
+ $ source oe-init-build-env
+ </literallayout>
+ <note>
+ The previous commands assume the
+ <ulink url='&YOCTO_DOCS_REF_URL;#source-repositories'>Source Repositories</ulink>
+ (i.e. <filename>poky</filename>) have been cloned
+ using Git and the local repository is named
+ "poky".
+ </note>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Prepare Your <filename>local.conf</filename> File:</emphasis>
+ By default, the
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink>
+ variable is set to "qemux86", which is fine if you are
+ building for the QEMU emulator in 32-bit mode.
+ However, if you are not, you need to set the
+ <filename>MACHINE</filename> variable appropriately in
+ your <filename>conf/local.conf</filename> file found in
+ the
+ <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
+ (i.e. <filename>~/poky/build</filename> in this
+ example).</para>
+
+ <para>Also, since you are preparing to work on the
+ kernel image, you need to set the
+ <ulink
url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink>
+ variable to include kernel modules.</para>
+
+ <para>This example uses the default "qemux86" for the
+ <filename>MACHINE</filename> variable but needs to
+ add the "kernel-modules":
+ <literallayout class='monospaced'>
+ MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules"
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Create a Layer for Patches:</emphasis>
+ You need to create a layer to hold patches created
+ for the kernel image.
+ You can use the <filename>yocto-layer</filename> command
+ as follows:
+ <literallayout class='monospaced'>
+ $ cd ~/poky
+ $ yocto-layer create my-kernel -o ../meta-my-kernel
+ Please enter the layer priority you'd like to use for the layer: [default: 6]
+ Would you like to have an example recipe created? (y/n) [default: n]
+ Would you like to have an example bbappend file created? (y/n) [default: n]
+
+ New layer created in ../meta-my-kernel.
+
+ Don't forget to add it to your BBLAYERS (for details see ../meta-my-kernel/README).
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Inform the BitBake Build Environment About
+ Your Layer:</emphasis>
+ As directed when you created your layer, you need to
+ add the layer to the
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
+ variable in the <filename>bblayers.conf</filename> file
+ as follows:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build
+ $ bitbake-layers add-layer ../../meta-my-kernel
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Build the Extensible SDK:</emphasis>
+ Use BitBake to build the extensible SDK specifically for
+ the Minnowboard:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build
+ $ bitbake core-image-minimal -c populate_sdk_ext
+ </literallayout>
+ Once the build finishes, you can find the SDK installer
+ file (i.e. <filename>*.sh</filename> file) in the
+ following directory:
+ <literallayout class='monospaced'>
+ ~/poky/build/tmp/deploy/sdk
+ </literallayout>
+ For this example, the installer file is named
+
<filename>poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-&DISTRO;.sh</filename>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Install the Extensible SDK:</emphasis>
+ Use the following command to install the SDK.
+ For this example, install the SDK in the default
+ <filename>~/poky_sdk</filename> directory:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build/tmp/deploy/sdk
+ $ ./poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-&DISTRO;.sh
+ Poky (Yocto Project Reference Distro) Extensible SDK installer version &DISTRO;
+ ============================================================================
+ Enter target directory for SDK (default: ~/poky_sdk):
+ You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed[Y/n]? Y
+ Extracting SDK......................................done
+ Setting it up...
+ Extracting buildtools...
+ Preparing build system...
+ Parsing recipes: 100% |#################################################################| Time: 0:00:52
+ Initializing tasks: 100% |############## ###############################################| Time: 0:00:04
+ Checking sstate mirror object availability: 100% |######################################| Time: 0:00:00
+ Parsing recipes: 100% |#################################################################| Time: 0:00:33
+ Initializing tasks: 100% |##############################################################| Time: 0:00:00
+ done
+ SDK has been successfully set up and is ready to be used.
+ Each time you wish to use the SDK in a new shell session, you need to source the environment setup
script e.g.
+ $ . /home/scottrif/poky_sdk/environment-setup-i586-poky-linux
+ </literallayout>
+ </para></listitem>
+ <listitem><para id='setting-up-the-esdk-terminal'>
+ <emphasis>Set Up a New Terminal to Work With the
+ Extensible SDK:</emphasis>
+ You must set up a new terminal to work with the SDK.
+ You cannot use the same BitBake shell used to build the
+ installer.</para>
+
+ <para>After opening a new shell, run the SDK environment
+ setup script as directed by the output from installing
+ the SDK:
+ <literallayout class='monospaced'>
+ $ source ~/poky_sdk/environment-setup-i586-poky-linux
+ "SDK environment now set up; additionally you may now run devtool to perform development tasks.
+ Run devtool --help for further details.
+ </literallayout>
+ <note>
+ If you get a warning about attempting to use the
+ extensible SDK in an environment set up to run
+ BitBake, you did not use a new shell.
+ </note>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Build the Clean Image:</emphasis>
+ The final step in preparing to work on the kernel is to
+ build an initial image using
+ <filename>devtool</filename> in the new terminal you
+ just set up and initialized for SDK work:
+ <literallayout class='monospaced'>
+ $ devtool build-image
+ Parsing recipes: 100% |##########################################| Time: 0:00:05
+ Parsing of 830 .bb files complete (0 cached, 830 parsed). 1299 targets, 47 skipped, 0 masked, 0 errors.
+ WARNING: No packages to add, building image core-image-minimal unmodified
+ Loading cache: 100% |############################################| Time: 0:00:00
+ Loaded 1299 entries from dependency cache.
+ NOTE: Resolving any missing task queue dependencies
+ Initializing tasks: 100% |#######################################| Time: 0:00:07
+ Checking sstate mirror object availability: 100% |###############| Time: 0:00:00
+ NOTE: Executing SetScene Tasks
+ NOTE: Executing RunQueue Tasks
+ NOTE: Tasks Summary: Attempted 2866 tasks of which 2604 didn't need to be rerun and all succeeded.
+ NOTE: Successfully built core-image-minimal. You can find output files in
/home/scottrif/poky_sdk/tmp/deploy/images/qemux86
+ </literallayout>
+ If you were building for actual hardware and not for
+ emulation, you could flash the image to a USB stick
+ on <filename>/dev/sdd</filename> and boot your device.
+ For an example that uses a Minnowboard, see the
+ <ulink
url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk'>TipsAndTricks/KernelDevelopmentWithEsdk</ulink>
+ Wiki page.
+ </para></listitem>
+ </orderedlist>
+ </para>
+
+ <para>
+ At this point you have set up to start making modifications to
+ the kernel by using the extensible SDK.
+ For a continued example, see the
+ "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to
Patch the Kernel</link>"
+ section.
+ </para>
+ </section>
+
+ <section id='getting-ready-for-traditional-kernel-development'>
+ <title>Getting Ready for Traditional Kernel Development</title>
+
+ <para>
+ Getting ready for traditional kernel development using the Yocto
+ Project involves many of the same steps as described in the
+ previous section.
+ However, you need to establish a local copy of the kernel source
+ since you will be editing these files.
+ </para>
+
+ <para>
+ Follow these steps to prepare to update the kernel image using
+ traditional kernel development flow with the Yocto Project.
+ Completing this procedure leaves you ready to make modifications
+ to the kernel source as described in the
+ "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional
Kernel Development to Patch the Kernel</link>"
+ section:
+ <orderedlist>
+ <listitem><para>
+ <emphasis>Initialize the BitBake Environment:</emphasis>
+ Before you can do anything using BitBake, you need to
+ initialize the BitBake build environment by sourcing a
+ build environment script
+ (i.e. <ulink
url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</filename></ulink>
+ or
+ <ulink
url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>):
+ <literallayout class='monospaced'>
+ $ cd ~/poky
+ $ source oe-init-build-env
+ </literallayout>
+ <note>
+ The previous commands assume the
+ <ulink url='&YOCTO_DOCS_REF_URL;#source-repositories'>Source Repositories</ulink>
+ (i.e. <filename>poky</filename>) have been cloned
+ using Git and the local repository is named
+ "poky".
+ </note>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Prepare Your <filename>local.conf</filename>
+ File:</emphasis>
+ By default, the
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink>
+ variable is set to "qemux86", which is fine if you are
+ building for the QEMU emulator in 32-bit mode.
+ However, if you are not, you need to set the
+ <filename>MACHINE</filename> variable appropriately in
+ your <filename>conf/local.conf</filename> file found
+ in the
+ <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
+ (i.e. <filename>~/poky/build</filename> in this
+ example).</para>
+
+ <para>Also, since you are preparing to work on the
+ kernel image, you need to set the
+ <ulink
url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink>
+ variable to include kernel modules.</para>
+
+ <para>This example uses the default "qemux86" for the
+ <filename>MACHINE</filename> variable but needs to
+ add the "kernel-modules":
+ <literallayout class='monospaced'>
+ MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules"
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Create a Layer for Patches:</emphasis>
+ You need to create a layer to hold patches created
+ for the kernel image.
+ You can use the <filename>yocto-layer</filename> command
+ as follows:
+ <literallayout class='monospaced'>
+ $ cd ~/poky
+ $ yocto-layer create my-kernel -o ../meta-my-kernel
+ Please enter the layer priority you'd like to use for the layer: [default: 6]
+ Would you like to have an example recipe created? (y/n) [default: n]
+ Would you like to have an example bbappend file created? (y/n) [default: n]
+
+ New layer created in ../meta-my-kernel.
+
+ Don't forget to add it to your BBLAYERS (for details see ../meta-my-kernel/README).
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Inform the BitBake Build Environment About
+ Your Layer:</emphasis>
+ As directed when you created your layer, you need to add
+ the layer to the
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
+ variable in the <filename>bblayers.conf</filename> file
+ as follows:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build
+ $ bitbake-layers add-layer ../../meta-my-kernel
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Create a Local Copy of the Kernel Git
+ Repository:</emphasis>
+ You can find Git repositories of supported Yocto Project
+ kernels organized under "Yocto Linux Kernel" in the
+ Yocto Project Source Repositories at
+ <ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink>.
+ </para>
+
+ <para>
+ For simplicity, it is recommended that you create your
+ copy of the kernel Git repository outside of the
+ <ulink url='&YOCTO_DOCS_REF_URL;source-directory'>Source Directory</ulink>,
+ which is usually named <filename>poky</filename>.
+ </para>
+
+ <para>
+ The following command shows how to create a local copy
+ of the <filename>linux-yocto-4.9</filename> kernel:
+ <literallayout class='monospaced'>
+ $ git clone git://git.yoctoproject.org/linux-yocto-4.9 linux-yocto-4.9.git
+ Cloning into 'linux-yocto-4.9.git'...
+ remote: Counting objects: 5094108, done.
+ remote: Compressing objects: 100% (765113/765113), done.
+ remote: Total 5094108 (delta 4294009), reused 5088388 (delta 4288312)
+ Receiving objects: 100% (5094108/5094108), 1.02 GiB | 7.82 MiB/s, done.
+ Resolving deltas: 100% (4294009/4294009), done.
+ Checking connectivity... done.
+ Checking out files: 100% (56233/56233), done.
+ </literallayout>
+ </para></listitem>
+ </orderedlist>
+ </para>
+
+ <para>
+ At this point you have set up to start making modifications to
+ the kernel using traditional kernel development steps.
+ For a continued example, see the
+ "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional
Kernel Development to Patch the Kernel</link>"
+ section.
+ </para>
+ </section>
+ </section>
<section id='creating-and-preparing-a-layer'>
<title>Creating and Preparing a Layer</title>
@@ -824,6 +1195,188 @@ NOTE: This stuff is how it would have been if a *.wic file was created
</orderedlist>
</section>
+ <section id="using-traditional-kernel-development-to-patch-the-kernel">
+ <title>Using Traditional Kernel Development to Patch the Kernel</title>
+
+ <para>
+ The steps in this procedure show you how you can patch the
+ kernel using traditional kernel development (i.e. not using
+ <filename>devtool</filename> and the extensible SDK as
+ described in the
+ "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch
the Kernel</link>"
+ section).
+ <note>
+ 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-for-traditional-kernel-development'>Getting Ready for
Traditional Kernel Development</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>
+ 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>"
+ section in the Yocto Project Board Support Packages (BSP)
+ Developer's Guide for more information.
+ </note>
+ </para>
+
+ <para>
+ This example creates a simple patch by adding some QEMU emulator
+ console output at boot time through <filename>printk</filename>
+ statements in the kernel's <filename>calibrate.c</filename> source
+ code file.
+ Applying the patch and booting the modified image causes the added
+ messages to appear on the emulator's console.
+ <note>
+ The example is a continuation of the setup procedure found in
+ the
+ "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for
Traditional Kernel Development</link>"
+ Section.
+ </note>
+ </para>
+
+ <para>
+ Also, for more information on patching the kernel, see the
+ "<link linkend='applying-patches'>Applying Patches</link>"
+ section.
+ <orderedlist>
+ <listitem><para>
+ <emphasis>Know What Branch is Checked Out In Your Local
+ Kernel Git Repository:</emphasis>
+ Prior to this step, you should have used Git to create a
+ local copy of the repository for your kernel.
+ Assuming you created the repository as directed in the
+ "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for
Traditional Kernel Development</link>"
+ section, use the following commands to check out the
+ <filename>standard/base</filename> branch of the
+ Linux Yocto 4.9 kernel:
+ <literallayout class='monospaced'>
+ $ cd ~/linux-yocto-4.9
+ $ git checkout -b standard/base origin/standard/base
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Edit the Source Files</emphasis>
+ Follow these steps to make some simple changes to the source
+ files:
+ <orderedlist>
+ <listitem><para>
+ <emphasis>Change the working directory</emphasis>:
+ You need to locate the source files in the
+ local copy of the kernel Git repository:
+ Change to where the kernel source code is before making
+ your edits to the <filename>calibrate.c</filename> file:
+ <literallayout class='monospaced'>
+ $ cd ~/linux-yocto-4.9/init
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Edit the source file</emphasis>:
+ Edit the <filename>calibrate.c</filename> file to have
+ the following changes:
+ <literallayout class='monospaced'>
+ void calibrate_delay(void)
+ {
+ unsigned long lpj;
+ static bool printed;
+ int this_cpu = smp_processor_id();
+
+ printk("*************************************\n");
+ printk("* *\n");
+ printk("* HELLO YOCTO KERNEL *\n");
+ printk("* *\n");
+ printk("*************************************\n");
+
+ if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
+ .
+ .
+ .
+ </literallayout>
+ </para></listitem>
+ </orderedlist>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Stage and Commit Your Changes:</emphasis>
+ Use standard Git commands to stage and commit the changes
+ you just made:
+ <literallayout class='monospaced'>
+ $ git add calibrate.c
+ $ git commit -m "calibrate.c - Added some printk statements"
+ </literallayout>
+ If you do not stage and commit your changes, the OpenEmbedded
+ Build System will not pick up the changes.
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Update Your <filename>local.conf</filename> File to Point to Your Source
Files:</emphasis>
+ In addition to your <filename>local.conf</filename> file
+ specifying to use "kernel-modules" and the "qemux86" machine,
+ it must also point to the updated kernel source files.
+ Add the following commands to your
+ <filename>local.conf</filename>:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build/conf
+ <replaceable>Add the following:</replaceable>
+
+ SRC_URI_pn-linux-yocto =
"git:///$HOME/linux-yocto-4.9;protocol=file;name=machine;branch=standard/base; \
+
git:///home/scottrif/yocto-kernel-cache;protocol=file;type=kmeta;name=meta;branch=yocto-4.9;destsuffix=${KMETA}"
+SRCREV_meta_qemux86 = "${AUTOREV}"
+SRCREV_machine_qemux86 = "${AUTOREV}"
+ </literallayout>
+ You must be sure to specify the correct branch and machine
+ types.
+ For this example, the branch is
+ <filename>standard/base</filename> and the machine is
+ "qemux86".
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Build the Image:</emphasis>
+ With the source modified, staged, and committed, and
+ the <filename>local.conf</filename> file pointing to
+ the kernel files, you can now use BitBake to build the
+ image:
+ <literallayout class='monospaced'>
+ $ cd ~/poky/build
+ $ bitbake core-image-minimal
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Boot the image</emphasis>:
+ Boot the modified image in the QEMU emulator
+ using this command.
+ When prompted to login to the QEMU console, use "root"
+ with no password:
+ <literallayout class='monospaced'>
+ $ runqemu qemux86
+ </literallayout>
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Look for Your Changes:</emphasis>
+ As QEMU booted, you might have seen your changes rapidly
+ scroll by.
+ If not, use these commands to see your changes:
+ <literallayout class='monospaced'>
+ # dmesg | less
+ </literallayout>
+ You should see the results of your
+ <filename>printk</filename> statements
+ as part of the output when you scroll down the
+ console window.
+ </para></listitem>
+ </orderedlist>
+ </para>
+ </section>
+
<section id='using-an-iterative-development-process'>
<title>Using an Iterative Development Process</title>
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