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kernel-dev: Applied review feedback
Various edits for review feedback on the manual in general. (From yocto-docs rev: 218061535b5bed326331d00eee6f514c81299238) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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Scott Rifenbark
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Richard Purdie
Richard Purdie
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commit
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@@ -57,7 +57,7 @@
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</para>
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<section id='getting-ready-to-develop-using-devtool'>
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<title>Getting Ready to Develop using <filename>devtool</filename></title>
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<title>Getting Ready to Develop Using <filename>devtool</filename></title>
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<para>
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Follow these steps to prepare to update the kernel image using
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@@ -129,15 +129,18 @@
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Don't forget to add it to your BBLAYERS (for details see ../meta-mylayer/README).
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</literallayout>
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<note>
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For background information on working with layers,
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see the
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For background information on working with
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common and BSP layers, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
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section in the Yocto Project Development Manual.
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See the
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section in the Yocto Project Development Manual
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and the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
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section in the Yocto Project Board Support (BSP)
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Developer's Guide, respectively.
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For information on how to use the
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<filename>yocto-layer</filename> script, see the
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"<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>"
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section in the Yocto Project Development Manual for
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details on how to use the
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<filename>yocto-layer</filename> script.
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section in the Yocto Project Development Manual.
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</note>
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</para></listitem>
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<listitem><para>
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@@ -350,15 +353,18 @@
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Don't forget to add it to your BBLAYERS (for details see ../meta-mylayer/README).
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</literallayout>
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<note>
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For background information on working with layers,
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see the
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For background information on working with
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common and BSP layers, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
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section in the Yocto Project Development Manual.
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See the
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section in the Yocto Project Development Manual
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and the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
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section in the Yocto Project Board Support (BSP)
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Developer's Guide, respectively.
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For information on how to use the
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<filename>yocto-layer</filename> script, see the
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"<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>"
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section in the Yocto Project Development Manual for
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details on how to use the
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<filename>yocto-layer</filename> script.
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section in the Yocto Project Development Manual.
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</note>
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</para></listitem>
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<listitem><para>
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@@ -815,7 +821,7 @@
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<filename>devtool</filename>, see the
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"<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>"
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and
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"<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel'></link>"
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"<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>"
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sections.
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</para>
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</section>
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@@ -935,16 +941,17 @@
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<para>
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To specify an "in-tree" <filename>defconfig</filename> file,
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use the following
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KBUILD_DEFCONFIG'><filename>KBUILD_DEFCONFIG</filename></ulink>
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statement form in the append file for the kernel recipe:
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use the following statement form:
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<literallayout class='monospaced'>
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KBUILD_DEFCONFIG_<replaceable>KMACHINE</replaceable> ?= <replaceable>defconfig_file</replaceable>
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</literallayout>
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You need to append the variable with
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>
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and then supply the path to your "in-tree"
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<filename>defconfig</filename> file.
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Here is an example that appends the
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<filename>KBUILD_DEFCONFIG</filename> variable with
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"common-pc" and provides the path to the "in-tree"
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<filename>defconfig</filename> file:
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<literallayout class='monospaced'>
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KBUILD_DEFCONFIG_common-pc ?= "/home/scottrif/configfiles/my_defconfig_file"
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</literallayout>
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</para>
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<para>
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@@ -990,14 +997,6 @@
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to an existing kernel, changing or adding recipes to the kernel
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that are needed to support specific hardware features, or even
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altering the source code itself.
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<note>
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You can also use the <filename>yocto-kernel</filename> script
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found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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under <filename>scripts</filename> to manage kernel patches and configuration.
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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>"
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section in the Yocto Project Board Support Packages (BSP)
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Developer's Guide for more information.
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</note>
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</para>
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<para>
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@@ -1007,12 +1006,10 @@
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code file.
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Applying the patch and booting the modified image causes the added
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messages to appear on the emulator's console.
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<note>
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The example is a continuation of the setup procedure found in
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the
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"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop using <filename>devtool</filename></link>"
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Section.
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</note>
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The example is a continuation of the setup procedure found in
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the
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"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>"
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Section.
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<orderedlist>
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<listitem><para>
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<emphasis>Check Out the Kernel Source Files:</emphasis>
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@@ -1161,7 +1158,7 @@
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<filename>meta-mylayer</filename>.
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<note>
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See Step 3 of the
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"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop using devtool</link>"
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"<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using devtool</link>"
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section for information on setting up this layer.
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</note>
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<literallayout class='monospaced'>
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@@ -1212,31 +1209,31 @@
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to an existing kernel, changing or adding recipes to the kernel
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that are needed to support specific hardware features, or even
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altering the source code itself.
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<note>
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You can also use the <filename>yocto-kernel</filename> script
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found in the
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<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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under <filename>scripts</filename> to manage kernel patches
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and configuration.
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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>"
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section in the Yocto Project Board Support Packages (BSP)
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Developer's Guide for more information.
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</note>
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</para>
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<para>
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This example creates a simple patch by adding some QEMU emulator
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console output at boot time through <filename>printk</filename>
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statements in the kernel's <filename>calibrate.c</filename> source
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code file.
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The example in this section creates a simple patch by adding some
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QEMU emulator console output at boot time through
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<filename>printk</filename> statements in the kernel's
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<filename>calibrate.c</filename> source code file.
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Applying the patch and booting the modified image causes the added
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messages to appear on the emulator's console.
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<note>
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The example is a continuation of the setup procedure found in
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the
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"<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>"
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Section.
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</note>
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The example is a continuation of the setup procedure found in
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the
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"<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>"
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Section.
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</para>
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<para>
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Although this example uses Git and shell commands to generate the
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patch, you could use the <filename>yocto-kernel</filename> script
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found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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under <filename>scripts</filename> to add and manage kernel
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patches and configuration.
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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>"
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section in the Yocto Project Board Support Packages (BSP)
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Developer's Guide for more information on the
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<filename>yocto-kernel</filename> script.
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<orderedlist>
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<listitem><para>
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<emphasis>Edit the Source Files</emphasis>
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@@ -2115,114 +2112,6 @@
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</para>
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</section>
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<section id='iteratively-modifying-source-code'>
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<title>Iteratively Modifying Source Code</title>
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<para>
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If you do not have existing patches or configuration files and
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you are using traditional kernel development methods,
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you can iteratively generate them from within the BitBake build
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environment as described within this section.
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During an iterative workflow, running a previously completed BitBake
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task causes BitBake to invalidate the tasks that follow the
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completed task in the build sequence.
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Invalidated tasks rebuild the next time you run the build using
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BitBake.
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</para>
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<para>
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As you read this section, be sure to substitute the name
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of your Linux kernel recipe for the term
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"linux-yocto".
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</para>
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<para>
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You can experiment with source code changes and create a
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simple patch without leaving the BitBake environment.
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To get started, be sure to complete a build at
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least through the kernel configuration task:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto -c kernel_configme -f
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</literallayout>
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Taking this step ensures you have the sources prepared
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and the configuration completed.
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You can find the sources in the build directory within the
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<filename>source/</filename> directory, which is a symlink
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(i.e. <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-B'><filename>B</filename></ulink><filename>}/source</filename>).
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The <filename>source/</filename> directory expands to
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<filename>${</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>.
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The directory pointed to by the
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<filename>source/</filename> symlink is also known as
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<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink><filename>}</filename>.
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</para>
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<para>
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You can edit the sources as you would any other Linux source
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tree.
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However, keep in mind that you will lose changes if you
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trigger the
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<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink>
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task for the recipe.
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You can avoid triggering this task by not using BitBake to
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run the
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<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>cleanall</filename></ulink>,
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<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>cleansstate</filename></ulink>,
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or forced
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<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>fetch</filename></ulink>
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commands.
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Also, do not modify the recipe itself while working
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with temporary changes or BitBake might run the
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<filename>fetch</filename> command depending on the
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changes to the recipe.
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</para>
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<para>
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To test your temporary changes, instruct BitBake to run the
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<filename>compile</filename> again.
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The <filename>-f</filename> option forces the command to run
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even though BitBake might think it has already done so:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto -c compile -f
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</literallayout>
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If the compile fails, you can update the sources and repeat
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the <filename>compile</filename>.
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Once compilation is successful, you can inspect and test
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the resulting build (i.e. kernel, modules, and so forth) from
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the following build directory:
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<literallayout class='monospaced'>
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${WORKDIR}/linux-${PACKAGE_ARCH}-${LINUX_KERNEL_TYPE}-build
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</literallayout>
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Alternatively, you can run the <filename>deploy</filename>
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command to place the kernel image in the
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<filename>tmp/deploy/images</filename> directory:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto -c deploy
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</literallayout>
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And, of course, you can perform the remaining installation and
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packaging steps by issuing:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto
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</literallayout>
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</para>
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<para>
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For rapid iterative development, the edit-compile-repeat loop
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described in this section is preferable to rebuilding the
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entire recipe because the installation and packaging tasks
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are very time consuming.
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</para>
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<para>
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Once you are satisfied with your source code modifications,
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you can make them permanent by generating patches and
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applying them to the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
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statement as described in the
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"<link linkend='applying-patches'>Applying Patches</link>"
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section.
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</para>
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</section>
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<section id='working-with-your-own-sources'>
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<title>Working With Your Own Sources</title>
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@@ -129,10 +129,12 @@
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the LTSI kernel is <filename>linux-yocto-4.1</filename>.
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</para></listitem>
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<listitem><para>
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<filename>linux-yocto-4.1</filename>,
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<filename>linux-yocto-4.4</filename>, and
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<filename>linux-yocto-4.9</filename> are all LTS
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kernels.
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For Yocto Project release 2.4, the LTSI kernel is
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<filename>linux-yocto-4.9</filename>
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</para></listitem>
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<listitem><para>
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<filename>linux-yocto-4.4</filename> is an LTS
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kernel.
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</para></listitem>
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</itemizedlist>
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</note>
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Reference in New Issue
Block a user