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diff --git a/import-layers/yocto-poky/documentation/kernel-dev/kernel-dev-common.xml b/import-layers/yocto-poky/documentation/kernel-dev/kernel-dev-common.xml index aa40fc852a..b8fd870162 100644 --- a/import-layers/yocto-poky/documentation/kernel-dev/kernel-dev-common.xml +++ b/import-layers/yocto-poky/documentation/kernel-dev/kernel-dev-common.xml @@ -3,20 +3,466 @@ [<!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, configuring 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 Tasks 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 Tasks Manual to set up your + Source Directory. + <note> + Be sure you check out the appropriate development branch or + you create your local branch by checking out a specific tag + to get the desired version of Yocto Project. + 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 Tasks 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 the + build environment script + (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</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>bitbake-layers create-layer</filename> + command as follows: + <literallayout class='monospaced'> + $ cd ~/poky/build + $ bitbake-layers create-layer ../../meta-mylayer + NOTE: Starting bitbake server... + Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' + $ + </literallayout> + <note> + For background information on working with + common and BSP layers, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" + section in the Yocto Project Development Tasks + Manual and the + "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>" + section in the Yocto Project Board Support (BSP) + Developer's Guide, respectively. + For information on how to use the + <filename>bitbake-layers create-layer</filename> + command, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" + section in the Yocto Project Development Tasks + Manual. + </note> + </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-mylayer + NOTE: Starting bitbake server... + $ + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Build the Extensible SDK:</emphasis> + Use BitBake to build the extensible SDK specifically + for use with images to be run using QEMU: + <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 the + build environment script + (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</filename></ulink>). + Also, for this example, be sure that the local branch + you have checked out for <filename>poky</filename> is + the Yocto Project &DISTRO_NAME; branch. + If you need to checkout out the &DISTRO_NAME; branch, + see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking out by Branch in Poky</ulink>" + section in the Yocto Project Development Tasks Manual. + <literallayout class='monospaced'> + $ cd ~/poky + $ git branch + master + * &DISTRO_NAME; + $ 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>bitbake-layers create-layer</filename> + command as follows: + <literallayout class='monospaced'> + $ cd ~/poky/build + $ bitbake-layers create-layer ../../meta-mylayer + NOTE: Starting bitbake server... + Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' + </literallayout> + <note> + For background information on working with + common and BSP layers, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" + section in the Yocto Project Development Tasks + Manual and the + "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>" + section in the Yocto Project Board Support (BSP) + Developer's Guide, respectively. + For information on how to use the + <filename>bitbake-layers create-layer</filename> + command, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" + section in the Yocto Project Development Tasks + Manual. + </note> + </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-mylayer + NOTE: Starting bitbake server ... + $ + </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>. + Also, be sure you are in the + <filename>standard/base</filename> branch. + </para> + + <para> + The following commands show how to create a local copy + of the <filename>linux-yocto-4.12</filename> kernel and + be in the <filename>standard/base</filename> branch. + <note> + The <filename>linux-yocto-4.12</filename> kernel + can be used with the Yocto Project 2.4 release + and forward. + You cannot use the + <filename>linux-yocto-4.12</filename> kernel with + releases prior to Yocto Project 2.4: + </note> + <literallayout class='monospaced'> + $ cd ~ + $ git clone git://git.yoctoproject.org/linux-yocto-4.12 --branch standard/base + Cloning into 'linux-yocto-4.12'... + remote: Counting objects: 6097195, done. + remote: Compressing objects: 100% (901026/901026), done. + remote: Total 6097195 (delta 5152604), reused 6096847 (delta 5152256) + Receiving objects: 100% (6097195/6097195), 1.24 GiB | 7.81 MiB/s, done. + Resolving deltas: 100% (5152604/5152604), done. + Checking connectivity... done. + Checking out files: 100% (59846/59846), done. + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Create a Local Copy of the Kernel Cache Git + Repository:</emphasis> + For simplicity, it is recommended that you create your + copy of the kernel cache Git repository outside of the + <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>, + which is usually named <filename>poky</filename>. + Also, for this example, be sure you are in the + <filename>yocto-4.12</filename> branch. + </para> + + <para> + The following commands show how to create a local copy + of the <filename>yocto-kernel-cache</filename> and + be in the <filename>yocto-4.12</filename> branch: + <literallayout class='monospaced'> + $ cd ~ + $ git clone git://git.yoctoproject.org/yocto-kernel-cache --branch yocto-4.12 + Cloning into 'yocto-kernel-cache'... + remote: Counting objects: 22639, done. + remote: Compressing objects: 100% (9761/9761), done. + remote: Total 22639 (delta 12400), reused 22586 (delta 12347) + Receiving objects: 100% (22639/22639), 22.34 MiB | 6.27 MiB/s, done. + Resolving deltas: 100% (12400/12400), done. + Checking connectivity... done. + </literallayout> + </para></listitem> + </orderedlist> + </para> + + <para> + At this point, you are ready 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> @@ -26,25 +472,98 @@ that you create and prepare your own layer in which to do your work. Your layer contains its own - <ulink url='&YOCTO_DOCS_DEV_URL;#bitbake-term'>BitBake</ulink> - append files - (<filename>.bbappend</filename>) and provides a convenient - mechanism to create your own recipe files - (<filename>.bb</filename>). - For details on how to create and work with layers, see the + <ulink url='&YOCTO_DOCS_REF_URL;#bitbake-term'>BitBake</ulink> + append files (<filename>.bbappend</filename>) and provides a + convenient mechanism to create your own recipe files + (<filename>.bb</filename>) as well as store and use kernel + patch files. + For background information on working with layers, see the "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" - section in the Yocto Project Development Manual. + section in the Yocto Project Development Tasks Manual. <note><title>Tip</title> The Yocto Project comes with many tools that simplify tasks you need to perform. - One such tool is the <filename>yocto-layer create</filename> - script, which simplifies creating a new layer. + One such tool is the + <filename>bitbake-layers create-layer</filename> + command, which simplifies creating a new 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 for more - information. + "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" + section in the Yocto Project Development Tasks Manual for + information on how to use this script. </note> </para> + + <para> + To better understand the layer you create for kernel development, + the following section describes how to create a layer + without the aid of tools. + These steps assume creation of a layer named + <filename>mylayer</filename> in your home directory: + <orderedlist> + <listitem><para> + <emphasis>Create Structure</emphasis>: + Create the layer's structure: + <literallayout class='monospaced'> + $ cd $HOME + $ mkdir meta-mylayer + $ mkdir meta-mylayer/conf + $ mkdir meta-mylayer/recipes-kernel + $ mkdir meta-mylayer/recipes-kernel/linux + $ mkdir meta-mylayer/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 eventual patch files. + </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 kernel's append file. + This example uses the + <filename>linux-yocto-4.12</filename> kernel. + Thus, the name of the append file is + <filename>linux-yocto_4.12.bbappend</filename>: + <literallayout class='monospaced'> + FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + + SRC_URI_append += "file://<replaceable>patch-file-one</replaceable>" + SRC_URI_append += "file://<replaceable>patch-file-two</replaceable>" + SRC_URI_append += "file://<replaceable>patch-file-three</replaceable>" + </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 + patch files. + 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 Tasks Manual. + </para></listitem> + </orderedlist> + </para> </section> <section id='modifying-an-existing-recipe'> @@ -56,7 +575,7 @@ Each release of the Yocto Project provides a few Linux kernel recipes from which you can choose. These are located in the - <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> + <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> in <filename>meta/recipes-kernel/linux</filename>. </para> @@ -72,12 +591,9 @@ <para> Before modifying an existing recipe, be sure that you have created a minimal, custom layer from which you can work. - See the "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>" - section for some general resources. - You can also see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</ulink>" section - of the Yocto Project Development Manual for a detailed - example. + See the + "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>" + section for information. </para> <section id='creating-the-append-file'> @@ -88,11 +604,11 @@ You also name it accordingly based on the linux-yocto recipe you are using. For example, if you are modifying the - <filename>meta/recipes-kernel/linux/linux-yocto_4.4.bb</filename> + <filename>meta/recipes-kernel/linux/linux-yocto_4.12.bb</filename> recipe, the append file will typically be located as follows within your custom layer: <literallayout class='monospaced'> - <replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto_4.4.bbappend + <replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto_4.12.bbappend </literallayout> The append file should initially extend the <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink> @@ -123,7 +639,7 @@ As an example, consider the following append file used by the BSPs in <filename>meta-yocto-bsp</filename>: <literallayout class='monospaced'> - meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.4.bbappend + meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.12.bbappend </literallayout> The following listing shows the file. Be aware that the actual commit ID strings in this @@ -140,11 +656,12 @@ KBRANCH_beaglebone = "standard/beaglebone" KBRANCH_mpc8315e-rdb = "standard/fsl-mpc8315e-rdb" - SRCREV_machine_genericx86 ?= "ad8b1d659ddd2699ebf7d50ef9de8940b157bfc2" - SRCREV_machine_genericx86-64 ?= "ad8b1d659ddd2699ebf7d50ef9de8940b157bfc2" - SRCREV_machine_edgerouter ?= "cebe1ad56aebd89e0de29412e19433fb441bf13c" - SRCREV_machine_beaglebone ?= "cebe1ad56aebd89e0de29412e19433fb441bf13c" - SRCREV_machine_mpc8315e-rdb ?= "06c0dbdcba374ca7f92a53d69292d6bb7bc9b0f3" + SRCREV_machine_genericx86 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" + SRCREV_machine_genericx86-64 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" + SRCREV_machine_edgerouter ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" + SRCREV_machine_beaglebone ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" + SRCREV_machine_mpc8315e-rdb ?= "2d1d010240846d7bff15d1fcc0cb6eb8a22fc78a" + COMPATIBLE_MACHINE_genericx86 = "genericx86" COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64" @@ -152,11 +669,11 @@ COMPATIBLE_MACHINE_beaglebone = "beaglebone" COMPATIBLE_MACHINE_mpc8315e-rdb = "mpc8315e-rdb" - LINUX_VERSION_genericx86 = "4.4.41" - LINUX_VERSION_genericx86-64 = "4.4.41" - LINUX_VERSION_edgerouter = "4.4.53" - LINUX_VERSION_beaglebone = "4.4.53" - LINUX_VERSION_mpc8315e-rdb = "4.4.53" + LINUX_VERSION_genericx86 = "4.12.7" + LINUX_VERSION_genericx86-64 = "4.12.7" + LINUX_VERSION_edgerouter = "4.12.10" + LINUX_VERSION_beaglebone = "4.12.10" + LINUX_VERSION_mpc8315e-rdb = "4.12.10" </literallayout> This append file contains statements used to support several BSPs that ship with the Yocto Project. @@ -179,7 +696,7 @@ variable could be used to enable features specific to the kernel. The append file points to specific commits in the - <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> + <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> Git repository and the <filename>meta</filename> Git repository branches to identify the exact kernel needed to build the BSP. @@ -187,8 +704,8 @@ <para> One thing missing in this particular BSP, which you will - typically need when developing a BSP, is the kernel configuration - file (<filename>.config</filename>) for your BSP. + typically need when developing a BSP, is the kernel + configuration file (<filename>.config</filename>) for your BSP. When developing a BSP, you probably have a kernel configuration file or a set of kernel configuration files that, when taken together, define the kernel configuration for your BSP. @@ -196,7 +713,8 @@ in a file or a set of files inside a directory located at the same level as your kernel's append file and having the same name as the kernel's main recipe file. - With all these conditions met, simply reference those files in the + With all these conditions met, simply reference those files in + the <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> statement in the append file. </para> @@ -242,25 +760,31 @@ <note> <para> - Other methods exist to accomplish grouping and defining configuration options. - For example, if you are working with a local clone of the kernel repository, - you could checkout the kernel's <filename>meta</filename> branch, make your changes, - and then push the changes to the local bare clone of the kernel. - The result is that you directly add configuration options to the - <filename>meta</filename> branch for your BSP. - The configuration options will likely end up in that location anyway if the BSP gets - added to the Yocto Project. + Other methods exist to accomplish grouping and defining + configuration options. + For example, if you are working with a local clone of the + kernel repository, you could checkout the kernel's + <filename>meta</filename> branch, make your changes, and + then push the changes to the local bare clone of the + kernel. + The result is that you directly add configuration options + to the <filename>meta</filename> branch for your BSP. + The configuration options will likely end up in that + location anyway if the BSP gets added to the Yocto Project. </para> <para> - In general, however, the Yocto Project maintainers take care of moving the - <filename>SRC_URI</filename>-specified - configuration options to the kernel's <filename>meta</filename> branch. - Not only is it easier for BSP developers to not have to worry about putting those - configurations in the branch, but having the maintainers do it allows them to apply - 'global' knowledge about the kinds of common configuration options multiple BSPs in - the tree are typically using. - This allows for promotion of common configurations into common features. + In general, however, the Yocto Project maintainers take + care of moving the <filename>SRC_URI</filename>-specified + configuration options to the kernel's + <filename>meta</filename> branch. + Not only is it easier for BSP developers to not have to + worry about putting those configurations in the branch, + but having the maintainers do it allows them to apply + 'global' knowledge about the kinds of common configuration + options multiple BSPs in the tree are typically using. + This allows for promotion of common configurations into + common features. </para> </note> </section> @@ -295,9 +819,12 @@ </para> <para> - For a detailed example showing how to patch the kernel, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>" - section in the Yocto Project Development Manual. + For a detailed example showing how to patch the kernel using + <filename>devtool</filename>, see the + "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" + and + "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" + sections. </para> </section> @@ -383,8 +910,8 @@ <para> For a detailed example showing how to configure the kernel, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>" - section in the Yocto Project Development Manual. + "<link linkend='configuring-the-kernel'>Configuring the Kernel</link>" + section. </para> </section> @@ -416,15 +943,17 @@ <para> To specify an "in-tree" <filename>defconfig</filename> file, - edit the recipe that builds your kernel so that it has the - following command form: + use the following statement form: <literallayout class='monospaced'> - KBUILD_DEFCONFIG_KMACHINE ?= <replaceable>defconfig_file</replaceable> + KBUILD_DEFCONFIG_<replaceable>KMACHINE</replaceable> ?= <replaceable>defconfig_file</replaceable> + </literallayout> + Here is an example that appends the + <filename>KBUILD_DEFCONFIG</filename> variable with + "common-pc" and provides the path to the "in-tree" + <filename>defconfig</filename> file: + <literallayout class='monospaced'> + KBUILD_DEFCONFIG_common-pc ?= "/home/scottrif/configfiles/my_defconfig_file" </literallayout> - You need to append the variable with - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink> - and then supply the path to your "in-tree" - <filename>defconfig</filename> file. </para> <para> @@ -432,7 +961,8 @@ <filename>defconfig</filename> file, you need to be sure no files or statements set <filename>SRC_URI</filename> to use a <filename>defconfig</filename> other than your "in-tree" - file (e.g. a kernel's <filename>linux-</filename><replaceable>machine</replaceable><filename>.inc</filename> + file (e.g. a kernel's + <filename>linux-</filename><replaceable>machine</replaceable><filename>.inc</filename> file). In other words, if the build system detects a statement that identifies an "out-of-tree" @@ -449,115 +979,750 @@ </section> </section> - <section id='using-an-iterative-development-process'> - <title>Using an Iterative Development Process</title> + <section id="using-devtool-to-patch-the-kernel"> + <title>Using <filename>devtool</filename> to Patch the Kernel</title> <para> - If you do not have existing patches or configuration files, - you can iteratively generate them from within the BitBake build - environment as described within this section. - During an iterative workflow, running a previously completed BitBake - task causes BitBake to invalidate the tasks that follow the - completed task in the build sequence. - Invalidated tasks rebuild the next time you run the build using - BitBake. + The steps in this procedure show you how you can patch the + kernel using the extensible SDK and <filename>devtool</filename>. + <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-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" + section. + </note> </para> <para> - As you read this section, be sure to substitute the name - of your Linux kernel recipe for the term - "linux-yocto". + 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. </para> - <section id='tip-dirty-string'> - <title>"-dirty" String</title> + <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. + The example is a continuation of the setup procedure found in + the + "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" + Section. + <orderedlist> + <listitem><para> + <emphasis>Check Out the Kernel Source Files:</emphasis> + First you must use <filename>devtool</filename> to checkout + the kernel source code in its workspace. + Be sure you are in the terminal set up to do work + with the extensible SDK. + <note> + See this + <link linkend='setting-up-the-esdk-terminal'>step</link> + in the + "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" + section for more information. + </note> + Use the following <filename>devtool</filename> command + to check out the code: + <literallayout class='monospaced'> + $ devtool modify linux-yocto + </literallayout> + <note> + During the checkout operation, a bug exists that could + cause errors such as the following to appear: + <literallayout class='monospaced'> + ERROR: Taskhash mismatch 2c793438c2d9f8c3681fd5f7bc819efa versus + be3a89ce7c47178880ba7bf6293d7404 for + /path/to/esdk/layers/poky/meta/recipes-kernel/linux/linux-yocto_4.10.bb.do_unpack + </literallayout> + You can safely ignore these messages. + The source code is correctly checked out. + </note> + </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>: + 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 + your edits to the <filename>calibrate.c</filename> file: + <literallayout class='monospaced'> + $ cd ~/poky_sdk/workspace/sources/linux-yocto + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Edit the source file</emphasis>: + Edit the <filename>init/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>Build the Updated Kernel Source:</emphasis> + To build the updated kernel source, use + <filename>devtool</filename>: + <literallayout class='monospaced'> + $ devtool build linux-yocto + </literallayout> + </para></listitem> + <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 + </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> + <listitem><para> + <emphasis>Boot the image</emphasis>: + Boot the modified image in the QEMU emulator + using this command: + <literallayout class='monospaced'> + $ runqemu qemux86 + </literallayout> + </para></listitem> + <listitem><para> + <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'> + # 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></listitem> + <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 an Append File:</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-mylayer</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 ~/meta-mylayer + </literallayout> + Once the command finishes, the patches and the + <filename>.bbappend</filename> file are located in the + <filename>~/meta-mylayer/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> + </para> + </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. + </para> + + <para> + The example in this section 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. + 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. + </para> + + <para> + Although this example uses Git and shell commands to generate the + patch, you could 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 add and 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 on the + <filename>yocto-kernel</filename> script. + <orderedlist> + <listitem><para> + <emphasis>Edit the Source Files</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 edit the + <filename>calibrate.c</filename> file: + <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-4.12/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 + <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> + and + <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink> + statements similar to the following to your + <filename>local.conf</filename>: + <literallayout class='monospaced'> + $ cd ~/poky/build/conf + </literallayout> + Add the following to the <filename>local.conf</filename>: + <literallayout class='monospaced'> + SRC_URI_pn-linux-yocto = "git:///<replaceable>path-to</replaceable>/linux-yocto-4.12;protocol=file;name=machine;branch=standard/base; \ + git:///<replaceable>path-to</replaceable>/yocto-kernel-cache;protocol=file;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}" + SRCREV_meta_qemux86 = "${AUTOREV}" + SRCREV_machine_qemux86 = "${AUTOREV}" + </literallayout> + <note> + Be sure to replace + <replaceable>path-to</replaceable> with the pathname + to your local Git repositories. + Also, 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". + </note> + </para></listitem> + <listitem><para> + <emphasis>Build the Image:</emphasis> + With the source modified, your changes 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'> + $ cd ~/poky/build + $ 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> + <listitem><para> + <emphasis>Generate the Patch File:</emphasis> + Once you are sure that your patch works correctly, you + can generate a <filename>*.patch</filename> file in the + kernel source repository: + <literallayout class='monospaced'> + $ cd ~/linux-yocto-4.12/init + $ git format-patch -1 + 0001-calibrate.c-Added-some-printk-statements.patch + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Move the Patch File to Your Layer:</emphasis> + In order for subsequent builds to pick up patches, you + need to move the patch file you created in the previous + step to your layer <filename>meta-mylayer</filename>. + For this example, the layer created earlier is located + in your home directory as <filename>meta-mylayer</filename>. + When the layer was created using the + <filename>yocto-create</filename> script, no additional + hierarchy was created to support patches. + Before moving the patch file, you need to add additional + structure to your layer using the following commands: + <literallayout class='monospaced'> + $ cd ~/meta-mylayer + $ mkdir recipes-kernel + $ mkdir recipes-kernel/linux + $ mkdir recipes-kernel/linux/linux-yocto + </literallayout> + Once you have created this hierarchy in your layer, you can + move the patch file using the following command: + <literallayout class='monospaced'> + $ mv ~/linux-yocto-4.12/init/0001-calibrate.c-Added-some-printk-statements.patch ~/meta-mylayer/recipes-kernel/linux/linux-yocto + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Create the Append File:</emphasis> + Finally, you need to create the + <filename>linux-yocto_4.12.bbappend</filename> file and + insert statements that allow the OpenEmbedded build + system to find the patch. + The append file needs to be in your layer's + <filename>recipes-kernel/linux</filename> + directory and it must be named + <filename>linux-yocto_4.12.bbappend</filename> and have + the following contents: + <literallayout class='monospaced'> + FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + + SRC_URI_append = " file://0001-calibrate.c-Added-some-printk-statements.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.</para> + + <para>For more information on append files and patches, + see the + "<link linkend='creating-the-append-file'>Creating the Append File</link>" + and + "<link linkend='applying-patches'>Applying Patches</link>" + sections. + You can also see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer"</ulink>" + section in the Yocto Project Development Tasks Manual. + <note> + To build <filename>core-image-minimal</filename> + again and see the effects of your patch, you can + essentially eliminate the temporary source files + saved in <filename>poky/build/tmp/work/...</filename> + and residual effects of the build by entering the + following sequence of commands: + <literallayout class='monospaced'> + $ cd ~/poky/build + $ bitbake -c cleanall yocto-linux + $ bitbake core-image-minimal -c cleanall + $ bitbake core-image-minimal + $ runqemu qemux86 + </literallayout> + </note> + </para></listitem> + </orderedlist> + </para> + </section> + + <section id='configuring-the-kernel'> + <title>Configuring the Kernel</title> + + <para> + Configuring the Yocto Project kernel consists of making sure the + <filename>.config</filename> file has all the right information + in it for the image you are building. + You can use the <filename>menuconfig</filename> tool and + configuration fragments to make sure your + <filename>.config</filename> file is just how you need it. + You can also save known configurations in a + <filename>defconfig</filename> file that the build system can use + for kernel configuration. + </para> + + <para> + This section describes how to use <filename>menuconfig</filename>, + create and use configuration fragments, and how to interactively + modify your <filename>.config</filename> file to create the + leanest kernel configuration file possible. + </para> + + <para> + For more information on kernel configuration, see the + "<link linkend='changing-the-configuration'>Changing the Configuration</link>" + section. + </para> + + <section id='using-menuconfig'> + <title>Using <filename>menuconfig</filename></title> -<!-- <para> - <emphasis>AR - Darren Hart:</emphasis> This section - originated from the old Yocto Project Kernel Architecture - and Use Manual. - It was decided we need to put it in this section here. - Darren needs to figure out where we want it and what part - of it we want (all, revision???) + The easiest way to define kernel configurations is to set + them through the <filename>menuconfig</filename> tool. + This tool provides an interactive method with which + to set kernel configurations. + For general information on <filename>menuconfig</filename>, see + <ulink url='http://en.wikipedia.org/wiki/Menuconfig'></ulink>. </para> ---> <para> - If kernel images are being built with "-dirty" on the - end of the version string, this simply means that - modifications in the source directory have not been committed. + To use the <filename>menuconfig</filename> tool in the Yocto + Project development environment, you must launch it using + BitBake. + Thus, the environment must be set up using the + <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink> + script found in the + <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>. + You must also be sure of the state of your build's + configuration in the + <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>. + The following commands initialize the BitBake environment, + run the + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configme'><filename>do_kernel_configme</filename></ulink> + task, and launch <filename>menuconfig</filename>. + These commands assume the Source Directory's top-level folder + is <filename>~/poky</filename>: <literallayout class='monospaced'> - $ git status + $ cd poky + $ source oe-init-build-env + $ bitbake linux-yocto -c kernel_configme -f + $ bitbake linux-yocto -c menuconfig </literallayout> + Once <filename>menuconfig</filename> comes up, its standard + interface allows you to interactively examine and configure + all the kernel configuration parameters. + After making your changes, simply exit the tool and save your + changes to create an updated version of the + <filename>.config</filename> configuration file. + <note> + You can use the entire <filename>.config</filename> file + as the <filename>defconfig</filename> file. + For information on <filename>defconfig</filename> files, + see the + "<link linkend='changing-the-configuration'>Changing the Configuration</link>", + "<link linkend='using-an-in-tree-defconfig-file'>Using an In-Tree <filename>defconfig</filename> File</link>, + and + "<link linkend='creating-a-defconfig-file'>Creating a <filename>defconfig</filename> File</link>" + sections. + </note> </para> <para> - You can use the above Git command to report modified, - removed, or added files. - You should commit those changes to the tree regardless of - whether they will be saved, exported, or used. - Once you commit the changes, you need to rebuild the kernel. + Consider an example that configures the "CONFIG_SMP" setting + for the <filename>linux-yocto-4.12</filename> kernel. + <note> + The OpenEmbedded build system recognizes this kernel as + <filename>linux-yocto</filename> through Metadata (e.g. + <ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></ulink><filename>_linux-yocto ?= "12.4%"</filename>). + </note> + Once <filename>menuconfig</filename> launches, use the + interface to navigate through the selections to find the + configuration settings in which you are interested. + For this example, you deselect "CONFIG_SMP" by clearing the + "Symmetric Multi-Processing Support" option. + Using the interface, you can find the option under + "Processor Type and Features". + To deselect "CONFIG_SMP", use the arrow keys to + highlight "Symmetric Multi-Processing Support" and enter "N" + to clear the asterisk. + When you are finished, exit out and save the change. </para> <para> - To force a pickup and commit of all such pending changes, - enter the following: + Saving the selections updates the <filename>.config</filename> + configuration file. + This is the file that the OpenEmbedded build system uses to + configure the kernel during the build. + You can find and examine this file in the Build Directory in + <filename>tmp/work/</filename>. + The actual <filename>.config</filename> is located in the + area where the specific kernel is built. + For example, if you were building a Linux Yocto kernel based + on the <filename>linux-yocto-4.12</filename> kernel and you + were building a QEMU image targeted for + <filename>x86</filename> architecture, the + <filename>.config</filename> file would be: <literallayout class='monospaced'> - $ git add . - $ git commit -s -a -m "getting rid of -dirty" + poky/build/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+gitAUTOINC+eda4d18... + ...967-r0/linux-qemux86-standard-build/.config + </literallayout> + <note> + The previous example directory is artificially split and + many of the characters in the actual filename are omitted + in order to make it more readable. + Also, depending on the kernel you are using, the exact + pathname might differ. + </note> + </para> + + <para> + Within the <filename>.config</filename> file, you can see the + kernel settings. + For example, the following entry shows that symmetric + multi-processor support is not set: + <literallayout class='monospaced'> + # CONFIG_SMP is not set </literallayout> </para> <para> - Next, rebuild the kernel. + A good method to isolate changed configurations is to use a + combination of the <filename>menuconfig</filename> tool and + simple shell commands. + Before changing configurations with + <filename>menuconfig</filename>, copy the existing + <filename>.config</filename> and rename it to something else, + use <filename>menuconfig</filename> to make as many changes as + you want and save them, then compare the renamed configuration + file against the newly created file. + You can use the resulting differences as your base to create + configuration fragments to permanently save in your kernel + layer. + <note> + Be sure to make a copy of the <filename>.config</filename> + file and do not just rename it. + The build system needs an existing + <filename>.config</filename> file from which to work. + </note> + </para> + </section> + + <section id='creating-a-defconfig-file'> + <title>Creating a <filename>defconfig</filename> File</title> + + <para> + A <filename>defconfig</filename> file is simply a + <filename>.config</filename> renamed to "defconfig". + You can use a <filename>defconfig</filename> file + to retain a known set of kernel configurations from which the + OpenEmbedded build system can draw to create the final + <filename>.config</filename> file. + <note> + Out-of-the-box, the Yocto Project never ships a + <filename>defconfig</filename> or + <filename>.config</filename> file. + The OpenEmbedded build system creates the final + <filename>.config</filename> file used to configure the + kernel. + </note> + </para> + + <para> + To create a <filename>defconfig</filename>, start with a + complete, working Linux kernel <filename>.config</filename> + file. + Copy that file to the appropriate + <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename> + directory in your layer's + <filename>recipes-kernel/linux</filename> directory, and rename + the copied file to "defconfig" (e.g. + <filename>~/meta-mylayer/recipes-kernel/linux/linux-yocto/defconfig</filename>). + Then, add the following lines to the linux-yocto + <filename>.bbappend</filename> file in your layer: + <literallayout class='monospaced'> + FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + SRC_URI += "file://defconfig" + </literallayout> + The + <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> + tells the build system how to search for the file, while the + <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> + extends the + <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink> + variable (search directories) to include the + <filename>${PN}</filename> directory you created to hold the + configuration changes. + <note> + The build system applies the configurations from the + <filename>defconfig</filename> file before applying any + subsequent configuration fragments. + The final kernel configuration is a combination of the + configurations in the <filename>defconfig</filename> + file and any configuration fragments you provide. + You need to realize that if you have any configuration + fragments, the build system applies these on top of and + after applying the existing defconfig file configurations. + </note> + For more information on configuring the kernel, see the + "<link link='changing-the-configuration'>Changing the Configuration</link>" + section. </para> </section> - <section id='generating-configuration-files'> - <title>Generating Configuration Files</title> + <section id='creating-config-fragments'> + <title>Creating Configuration Fragments</title> + + <para> + Configuration fragments are simply kernel options that + appear in a file placed where the OpenEmbedded build system + can find and apply them. + The build system applies configuration fragments after + applying configurations from a <filename>defconfig</filename> + file. + Thus, the final kernel configuration is a combination of the + configurations in the <filename>defconfig</filename> + file and then any configuration fragments you provide. + The build system applies fragments on top of and + after applying the existing defconfig file configurations. + </para> + + <para> + Syntactically, the configuration statement is identical to + what would appear in the <filename>.config</filename> file, + which is in the + <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>. + <note> + For more information about where the + <filename>.config</filename> file is located, see the + example in the + "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" + section. + </note> + </para> <para> - You can manipulate the <filename>.config</filename> file - used to build a linux-yocto recipe with the - <filename>menuconfig</filename> command as follows: + It is simple to create a configuration fragment. + One method is to use shell commands. + For example, issuing the following from the shell creates a + configuration fragment file named + <filename>my_smp.cfg</filename> that enables multi-processor + support within the kernel: <literallayout class='monospaced'> - $ bitbake linux-yocto -c menuconfig + $ echo "CONFIG_SMP=y" >> my_smp.cfg </literallayout> - This command starts the Linux kernel configuration tool, - which allows you to prepare a new - <filename>.config</filename> file for the build. - When you exit the tool, be sure to save your changes - at the prompt. - </para> - - <para> - The resulting <filename>.config</filename> file is - located in the build directory, - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-B'><filename>B</filename></ulink><filename>}</filename>, - which expands to - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename><filename>/linux-</filename><filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGE_ARCH'><filename>PACKAGE_ARCH</filename></ulink><filename>}-${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink><filename>}-build</filename>. - You can use the entire <filename>.config</filename> file as the - <filename>defconfig</filename> file as described in the - "<link linkend='changing-the-configuration'>Changing the Configuration</link>" section. - For more information on the <filename>.config</filename> file, - see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#using-menuconfig'>Using <filename>menuconfig</filename></ulink>" - section in the Yocto Project Development Manual. <note> - You can determine what a variable expands to by looking - at the output of the <filename>bitbake -e</filename> - command: - <literallayout class='monospaced'> - $ bitbake -e virtual/kernel - </literallayout> - Search the output for the variable in which you are - interested to see exactly how it is expanded and used. + All configuration fragment files must use the + <filename>.cfg</filename> extension in order for the + OpenEmbedded build system to recognize them as a + configuration fragment. </note> </para> <para> - A better method is to create a configuration fragment using the + Another method is to create a configuration fragment using the differences between two configuration files: one previously created and saved, and one freshly created using the <filename>menuconfig</filename> tool. @@ -567,40 +1732,47 @@ To create a configuration fragment using this method, follow these steps: <orderedlist> - <listitem><para>Complete a build at least through the kernel + <listitem><para> + <emphasis>Complete a Build Through Kernel Configuration:</emphasis> + Complete a build at least through the kernel configuration task as follows: <literallayout class='monospaced'> $ bitbake linux-yocto -c kernel_configme -f </literallayout> - This step ensures that you will be creating a + This step ensures that you create a <filename>.config</filename> file from a known state. Because situations exist where your build state might - become unknown, it is best to run the previous - command prior to starting up - <filename>menuconfig</filename>. + become unknown, it is best to run this task prior + to starting <filename>menuconfig</filename>. </para></listitem> - <listitem><para>Run the <filename>menuconfig</filename> - command: + <listitem><para> + <emphasis>Launch <filename>menuconfig</filename>:</emphasis> + Run the <filename>menuconfig</filename> command: <literallayout class='monospaced'> $ bitbake linux-yocto -c menuconfig - </literallayout></para></listitem> - <listitem><para>Run the <filename>diffconfig</filename> + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Create the Configuration Fragment:</emphasis> + Run the <filename>diffconfig</filename> command to prepare a configuration fragment. The resulting file <filename>fragment.cfg</filename> - will be placed in the + is placed in the <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename> directory: <literallayout class='monospaced'> $ bitbake linux-yocto -c diffconfig - </literallayout></para></listitem> + </literallayout> + </para></listitem> </orderedlist> </para> <para> - The <filename>diffconfig</filename> command creates a file that is a - list of Linux kernel <filename>CONFIG_</filename> assignments. + The <filename>diffconfig</filename> command creates a file + that is a list of Linux kernel <filename>CONFIG_</filename> + assignments. See the "<link linkend='changing-the-configuration'>Changing the Configuration</link>" - section for information on how to use the output as a - configuration fragment. + section for additional information on how to use the output + as a configuration fragment. <note> You can also use this method to create configuration fragments for a BSP. @@ -610,34 +1782,126 @@ </para> <para> - The kernel tools also provide configuration validation. - You can use these tools to produce warnings for when a + Where do you put your configuration fragment files? + You can place these files in an area pointed to by + <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> + as directed by your <filename>bblayers.conf</filename> file, + which is located in your layer. + The OpenEmbedded build system picks up the configuration and + adds it to the kernel's configuration. + For example, suppose you had a set of configuration options + in a file called <filename>myconfig.cfg</filename>. + If you put that file inside a directory named + <filename>linux-yocto</filename> that resides in the same + directory as the kernel's append file within your layer + and then add the following statements to the kernel's append + file, those configuration options will be picked up and applied + when the kernel is built: + <literallayout class='monospaced'> + FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + SRC_URI += "file://myconfig.cfg" + </literallayout> + </para> + + <para> + As mentioned earlier, you can group related configurations + into multiple files and name them all in the + <filename>SRC_URI</filename> statement as well. + For example, you could group separate configurations + specifically for Ethernet and graphics into their own files + and add those by using a <filename>SRC_URI</filename> statement + like the following in your append file: + <literallayout class='monospaced'> + SRC_URI += "file://myconfig.cfg \ + file://eth.cfg \ + file://gfx.cfg" + </literallayout> + </para> + </section> + + <section id='validating-configuration'> + <title>Validating Configuration</title> + + <para> + You can use the + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configcheck'><filename>do_kernel_configcheck</filename></ulink> + task to provide configuration validation: + <literallayout class='monospaced'> + $ bitbake linux-yocto -c kernel_configcheck -f + </literallayout> + Running this task produces warnings for when a requested configuration does not appear in the final <filename>.config</filename> file or when you override a policy configuration in a hardware configuration fragment. - Here is an example with some sample output of the command - that runs these tools: + </para> + + <para> + In order to run this task, you must have an existing + <filename>.config</filename> file. + See the + "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" + section for information on how to create a configuration file. + </para> + + <para> + Following is sample output from the + <filename>do_kernel_configcheck</filename> task: <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configcheck -f + Loading cache: 100% |########################################################| Time: 0:00:00 + Loaded 1275 entries from dependency cache. + NOTE: Resolving any missing task queue dependencies - ... + Build Configuration: + . + . + . + + NOTE: Executing SetScene Tasks + NOTE: Executing RunQueue Tasks + WARNING: linux-yocto-4.12.12+gitAUTOINC+eda4d18ce4_16de014967-r0 do_kernel_configcheck: + [kernel config]: specified values did not make it into the kernel's final configuration: + + ---------- CONFIG_X86_TSC ----------------- + Config: CONFIG_X86_TSC + From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/bsp/common-pc/common-pc-cpu.cfg + Requested value: CONFIG_X86_TSC=y + Actual value: + + + ---------- CONFIG_X86_BIGSMP ----------------- + Config: CONFIG_X86_BIGSMP + From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg + /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig + Requested value: # CONFIG_X86_BIGSMP is not set + Actual value: - NOTE: validating kernel configuration - This BSP sets 3 invalid/obsolete kernel options. - These config options are not offered anywhere within this kernel. - The full list can be found in your kernel src dir at: - meta/cfg/standard/mybsp/invalid.cfg - - This BSP sets 21 kernel options that are possibly non-hardware related. - The full list can be found in your kernel src dir at: - meta/cfg/standard/mybsp/specified_non_hdw.cfg - - WARNING: There were 2 hardware options requested that do not - have a corresponding value present in the final ".config" file. - This probably means you are not getting the config you wanted. - The full list can be found in your kernel src dir at: - meta/cfg/standard/mybsp/mismatch.cfg + + ---------- CONFIG_NR_CPUS ----------------- + Config: CONFIG_NR_CPUS + From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg + /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/bsp/common-pc/common-pc.cfg + /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig + Requested value: CONFIG_NR_CPUS=8 + Actual value: CONFIG_NR_CPUS=1 + + + ---------- CONFIG_SCHED_SMT ----------------- + Config: CONFIG_SCHED_SMT + From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg + /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig + Requested value: CONFIG_SCHED_SMT=y + Actual value: + + + + NOTE: Tasks Summary: Attempted 288 tasks of which 285 didn't need to be rerun and all succeeded. + + Summary: There were 3 WARNING messages shown. </literallayout> + <note> + The previous output example has artificial line breaks + to make it more readable. + </note> </para> <para> @@ -646,113 +1910,210 @@ items. You can use the information in the logs to adjust your configuration files and then repeat the - <filename>kernel_configme</filename> and - <filename>kernel_configcheck</filename> commands until - they produce no warnings. + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configme'><filename>do_kernel_configme</filename></ulink> + and + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configcheck'><filename>do_kernel_configcheck</filename></ulink> + tasks until they produce no warnings. </para> <para> For more information on how to use the <filename>menuconfig</filename> tool, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#using-menuconfig'>Using <filename>menuconfig</filename></ulink>" - section in the Yocto Project Development Manual. + "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" + section. </para> </section> - <section id='modifying-source-code'> - <title>Modifying Source Code</title> + <section id='fine-tuning-the-kernel-configuration-file'> + <title>Fine-Tuning the Kernel Configuration File</title> <para> - You can experiment with source code changes and create a - simple patch without leaving the BitBake environment. - To get started, be sure to complete a build at - least through the kernel configuration task: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configme -f - </literallayout> - Taking this step ensures you have the sources prepared - and the configuration completed. - You can find the sources in the build directory within the - <filename>source/</filename> directory, which is a symlink - (i.e. <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-B'><filename>B</filename></ulink><filename>}/source</filename>). - The <filename>source/</filename> directory expands to - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename><filename>/linux-</filename><filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGE_ARCH'><filename>PACKAGE_ARCH</filename></ulink><filename>}-${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink><filename>}-build/source</filename>. - The directory pointed to by the - <filename>source/</filename> symlink is also known as - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink><filename>}</filename>. - </para> - - <para> - You can edit the sources as you would any other Linux source - tree. - However, keep in mind that you will lose changes if you - trigger the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink> - task for the recipe. - You can avoid triggering this task by not using BitBake to - run the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>cleanall</filename></ulink>, - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>cleansstate</filename></ulink>, - or forced - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>fetch</filename></ulink> - commands. - Also, do not modify the recipe itself while working - with temporary changes or BitBake might run the - <filename>fetch</filename> command depending on the - changes to the recipe. - </para> - - <para> - To test your temporary changes, instruct BitBake to run the - <filename>compile</filename> again. - The <filename>-f</filename> option forces the command to run - even though BitBake might think it has already done so: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c compile -f - </literallayout> - If the compile fails, you can update the sources and repeat - the <filename>compile</filename>. - Once compilation is successful, you can inspect and test - the resulting build (i.e. kernel, modules, and so forth) from - the following build directory: - <literallayout class='monospaced'> - ${WORKDIR}/linux-${PACKAGE_ARCH}-${LINUX_KERNEL_TYPE}-build - </literallayout> - Alternatively, you can run the <filename>deploy</filename> - command to place the kernel image in the - <filename>tmp/deploy/images</filename> directory: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c deploy - </literallayout> - And, of course, you can perform the remaining installation and - packaging steps by issuing: - <literallayout class='monospaced'> - $ bitbake linux-yocto - </literallayout> + You can make sure the <filename>.config</filename> file is as + lean or efficient as possible by reading the output of the + kernel configuration fragment audit, noting any issues, making + changes to correct the issues, and then repeating. </para> <para> - For rapid iterative development, the edit-compile-repeat loop - described in this section is preferable to rebuilding the - entire recipe because the installation and packaging tasks - are very time consuming. + As part of the kernel build process, the + <filename>do_kernel_configcheck</filename> task runs. + This task validates the kernel configuration by checking the + final <filename>.config</filename> file against the input + files. + During the check, the task produces warning messages for the + following issues: + <itemizedlist> + <listitem><para> + Requested options that did not make the final + <filename>.config</filename> file. + </para></listitem> + <listitem><para> + Configuration items that appear twice in the same + configuration fragment. + </para></listitem> + <listitem><para> + Configuration items tagged as "required" that were + overridden. + </para></listitem> + <listitem><para> + A board overrides a non-board specific option. + </para></listitem> + <listitem><para> + Listed options not valid for the kernel being + processed. + In other words, the option does not appear anywhere. + </para></listitem> + </itemizedlist> + <note> + The <filename>do_kernel_configcheck</filename> task can + also optionally report if an option is overridden during + processing. + </note> </para> <para> - Once you are satisfied with your source code modifications, - you can make them permanent by generating patches and - applying them to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statement as described in the - "<link linkend='applying-patches'>Applying Patches</link>" - section. - If you are not familiar with generating patches, refer to the - "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-the-patch'>Creating the Patch</ulink>" - section in the Yocto Project Development Manual. + For each output warning, a message points to the file + that contains a list of the options and a pointer to the + configuration fragment that defines them. + Collectively, the files are the key to streamlining the + configuration. + </para> + + <para> + To streamline the configuration, do the following: + <orderedlist> + <listitem><para> + <emphasis>Use a Working Configuration:</emphasis> + Start with a full configuration that you + know works. + Be sure the configuration builds and boots + successfully. + Use this configuration file as your baseline. + </para></listitem> + <listitem><para> + <emphasis>Run Configure and Check Tasks:</emphasis> + Separately run the + <filename>do_kernel_configme</filename> and + <filename>do_kernel_configcheck</filename> tasks: + <literallayout class='monospaced'> + $ bitbake linux-yocto -c kernel_configme -f + $ bitbake linux-yocto -c kernel_configcheck -f + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Process the Results:</emphasis> + Take the resulting list of files from the + <filename>do_kernel_configcheck</filename> task + warnings and do the following: + <itemizedlist> + <listitem><para> + Drop values that are redefined in the fragment + but do not change the final + <filename>.config</filename> file. + </para></listitem> + <listitem><para> + Analyze and potentially drop values from the + <filename>.config</filename> file that override + required configurations. + </para></listitem> + <listitem><para> + Analyze and potentially remove non-board + specific options. + </para></listitem> + <listitem><para> + Remove repeated and invalid options. + </para></listitem> + </itemizedlist> + </para></listitem> + <listitem><para> + <emphasis>Re-Run Configure and Check Tasks:</emphasis> + After you have worked through the output of the kernel + configuration audit, you can re-run the + <filename>do_kernel_configme</filename> and + <filename>do_kernel_configcheck</filename> tasks to + see the results of your changes. + If you have more issues, you can deal with them as + described in the previous step. + </para></listitem> + </orderedlist> + </para> + + <para> + Iteratively working through steps two through four eventually + yields a minimal, streamlined configuration file. + Once you have the best <filename>.config</filename>, you can + build the Linux Yocto kernel. </para> </section> </section> + <section id='expanding-variables'> + <title>Expanding Variables</title> + + <para> + Sometimes it is helpful to determine what a variable expands + to during a build. + You can do examine the values of variables by examining the + output of the <filename>bitbake -e</filename> command. + The output is long and is more easily managed in a text file, + which allows for easy searches: + <literallayout class='monospaced'> + $ bitbake -e virtual/kernel > <replaceable>some_text_file</replaceable> + </literallayout> + Within the text file, you can see exactly how each variable is + expanded and used by the OpenEmbedded build system. + </para> + </section> + + <section id='working-with-a-dirty-kernel-version-string'> + <title>Working with a "Dirty" Kernel Version String</title> + + <para> + If you build a kernel image and the version string has a + "+" or a "-dirty" at the end, uncommitted modifications exist + in the kernel's source directory. + Follow these steps to clean up the version string: + <orderedlist> + <listitem><para> + <emphasis>Discover the Uncommitted Changes:</emphasis> + Go to the kernel's locally cloned Git repository + (source directory) and use the following Git command + to list the files that have been changed, added, or + removed: + <literallayout class='monospaced'> + $ git status + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Commit the Changes:</emphasis> + You should commit those changes to the kernel source + tree regardless of whether or not you will save, + export, or use the changes: + <literallayout class='monospaced'> + $ git add + $ git commit -s -a -m "getting rid of -dirty" + </literallayout> + </para></listitem> + <listitem><para> + <emphasis>Rebuild the Kernel Image:</emphasis> + Once you commit the changes, rebuild the kernel.</para> + + <para>Depending on your particular kernel development + workflow, the commands you use to rebuild the + kernel might differ. + For information on building the kernel image when + using <filename>devtool</filename>, see the + "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" + section. + For information on building the kernel image when + using Bitbake, see the + "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" + section. + </para></listitem> + </orderedlist> + </para> + </section> + <section id='working-with-your-own-sources'> <title>Working With Your Own Sources</title> @@ -763,7 +2124,7 @@ working with your own sources. When you use your own sources, you will not be able to leverage the existing kernel - <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> and + <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink> and stabilization work of the linux-yocto sources. However, you will be able to manage your own Metadata in the same format as the linux-yocto sources. @@ -788,23 +2149,29 @@ </para> <para> - Here are some basic steps you can use to work with your own sources: + Here are some basic steps you can use to work with your own + sources: <orderedlist> - <listitem><para>Copy the <filename>linux-yocto-custom.bb</filename> + <listitem><para> + <emphasis>Create a Copy of the Kernel Recipe:</emphasis> + Copy the <filename>linux-yocto-custom.bb</filename> recipe to your layer and give it a meaningful name. - The name should include the version of the Linux kernel you - are using (e.g. - <filename>linux-yocto-myproject_3.19.bb</filename>, - where "3.19" is the base version of the Linux kernel - with which you would be working).</para></listitem> - <listitem><para>In the same directory inside your layer, - create a matching directory - to store your patches and configuration files (e.g. - <filename>linux-yocto-myproject</filename>). + The name should include the version of the Yocto Linux + kernel you are using (e.g. + <filename>linux-yocto-myproject_4.12.bb</filename>, + where "4.12" is the base version of the Linux kernel + with which you would be working). + </para></listitem> + <listitem><para> + <emphasis>Create a Directory for Your Patches:</emphasis> + In the same directory inside your layer, create a matching + directory to store your patches and configuration files + (e.g. <filename>linux-yocto-myproject</filename>). </para></listitem> - <listitem><para>Make sure you have either a - <filename>defconfig</filename> file or configuration - fragment files. + <listitem><para> + <emphasis>Ensure You Have Configurations:</emphasis> + Make sure you have either a <filename>defconfig</filename> + file or configuration fragment files in your layer. When you use the <filename>linux-yocto-custom.bb</filename> recipe, you must specify a configuration. If you do not have a <filename>defconfig</filename> file, @@ -813,27 +2180,32 @@ $ make defconfig </literallayout> After running the command, copy the resulting - <filename>.config</filename> to the - <filename>files</filename> directory as "defconfig" and - then add it to the + <filename>.config</filename> file to the + <filename>files</filename> directory in your layer + as "defconfig" and then add it to the <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> variable in the recipe.</para> + <para>Running the <filename>make defconfig</filename> command results in the default configuration for your architecture as defined by your kernel. However, no guarantee exists that this configuration is valid for your use case, or that your board will even boot. - This is particularly true for non-x86 architectures. - To use non-x86 <filename>defconfig</filename> files, you - need to be more specific and find one that matches your + This is particularly true for non-x86 architectures.</para> + + <para>To use non-x86 <filename>defconfig</filename> files, + you need to be more specific and find one that matches your board (i.e. for arm, you look in <filename>arch/arm/configs</filename> and use the one that is the best starting point for your board). </para></listitem> - <listitem><para>Edit the following variables in your recipe - as appropriate for your project: + <listitem><para> + <emphasis>Edit the Recipe:</emphasis> + Edit the following variables in your recipe as appropriate + for your project: <itemizedlist> - <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>: The <filename>SRC_URI</filename> should specify a Git repository that uses one of the supported Git fetcher protocols (i.e. <filename>file</filename>, @@ -845,24 +2217,32 @@ The skeleton recipe provides an example <filename>SRC_URI</filename> as a syntax reference. </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION'><filename>LINUX_VERSION</filename></ulink>: + <listitem><para> + <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION'><filename>LINUX_VERSION</filename></ulink>: The Linux kernel version you are using (e.g. - "3.19").</para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION_EXTENSION'><filename>LINUX_VERSION_EXTENSION</filename></ulink>: - The Linux kernel <filename>CONFIG_LOCALVERSION</filename> - that is compiled into the resulting kernel and visible + "4.12"). + </para></listitem> + <listitem><para> + <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION_EXTENSION'><filename>LINUX_VERSION_EXTENSION</filename></ulink>: + The Linux kernel + <filename>CONFIG_LOCALVERSION</filename> that is + compiled into the resulting kernel and visible through the <filename>uname</filename> command. </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink>: + <listitem><para> + <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink>: The commit ID from which you want to build. </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>: - Treat this variable the same as you would in any other - recipe. - Increment the variable to indicate to the OpenEmbedded - build system that the recipe has changed. + <listitem><para> + <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>: + Treat this variable the same as you would in any + other recipe. + Increment the variable to indicate to the + OpenEmbedded build system that the recipe has + changed. </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>: The default <filename>PV</filename> assignment is typically adequate. It combines the <filename>LINUX_VERSION</filename> @@ -870,16 +2250,17 @@ as derived from the <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCPV'><filename>SRCPV</filename></ulink> variable. - The combined results are a string with - the following form: + The combined results are a string with the + following form: <literallayout class='monospaced'> 3.19.11+git1+68a635bf8dfb64b02263c1ac80c948647cc76d5f_1+218bd8d2022b9852c60d32f0d770931e3cf343e2 </literallayout> - While lengthy, the extra verbosity in <filename>PV</filename> - helps ensure you are using the exact - sources from which you intend to build. + While lengthy, the extra verbosity in + <filename>PV</filename> helps ensure you are using + the exact sources from which you intend to build. </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>: + <listitem><para> + <ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>: A list of the machines supported by your new recipe. This variable in the example recipe is set by default to a regular expression that matches @@ -888,18 +2269,24 @@ failure. You must change it to match a list of the machines that your new recipe supports. - For example, to support the <filename>qemux86</filename> - and <filename>qemux86-64</filename> machines, use + For example, to support the + <filename>qemux86</filename> and + <filename>qemux86-64</filename> machines, use the following form: <literallayout class='monospaced'> COMPATIBLE_MACHINE = "qemux86|qemux86-64" - </literallayout></para></listitem> - </itemizedlist></para></listitem> - <listitem><para>Provide further customizations to your recipe + </literallayout> + </para></listitem> + </itemizedlist> + </para></listitem> + <listitem><para> + <emphasis>Customize Your Recipe as Needed:</emphasis> + Provide further customizations to your recipe as needed just as you would customize an existing linux-yocto recipe. - See the "<link linkend='modifying-an-existing-recipe'>Modifying - an Existing Recipe</link>" section for information. + See the + "<link linkend='modifying-an-existing-recipe'>Modifying an Existing Recipe</link>" + section for information. </para></listitem> </orderedlist> </para> @@ -1230,7 +2617,8 @@ The OpenEmbedded build system searches all forms of kernel Metadata on the <filename>SRC_URI</filename> statement regardless of whether the Metadata is in the "kernel-cache", system kernel - Metadata, or a recipe-space Metadata. + Metadata, or a recipe-space Metadata (i.e. part of the kernel + recipe). See the "<link linkend='kernel-metadata-location'>Kernel Metadata Location</link>" section for additional information. @@ -1253,6 +2641,7 @@ to the build. <orderedlist> <listitem><para> + <emphasis>Create the Feature File:</emphasis> Create a <filename>.scc</filename> file and locate it just as you would any other patch file, <filename>.cfg</filename> file, or fetcher item @@ -1295,6 +2684,7 @@ <filename>test.cfg</filename>. </para></listitem> <listitem><para> + <emphasis>Add the Feature File to <filename>SRC_URI</filename>:</emphasis> Add the <filename>.scc</filename> file to the recipe's <filename>SRC_URI</filename> statement: <literallayout class='monospaced'> @@ -1304,7 +2694,9 @@ path is appended to the existing path. </para></listitem> <listitem><para> - Specify the feature as a kernel feature: + <emphasis>Specify the Feature as a Kernel Feature:</emphasis> + Use the <filename>KERNEL_FEATURES</filename> statement + to specify the feature as a kernel feature: <literallayout class='monospaced'> KERNEL_FEATURES_append = " test.scc" </literallayout> |