diff --git a/documentation/dev-manual/dev-manual-cases.xml b/documentation/dev-manual/dev-manual-cases.xml deleted file mode 100644 index fc93b53744..0000000000 --- a/documentation/dev-manual/dev-manual-cases.xml +++ /dev/null @@ -1,446 +0,0 @@ - - - - -Development Cases - -
- Modifying a Kernel - - - Kernel modification involves changing or adding configurations to an existing kernel, or - adding recipes to the kernel that are needed to support specific hardware features. - The process is similar to creating a Board Support Package (BSP) except that it does not - involve a BSP layer. - - - - This section presents a brief overview of the kernel structure and then provides a simple - example that shows how to modify the kernel. - - -
- Yocto Project Kernel Overview - - - When one thinks of the source files for a kernel they usually think of a fixed structure - of files that contain kernel patches. - The Yocto Project, however, employs mechanisims that in a sense result in a kernel source - generator. - - - - The Yocto Project uses the source code management (SCM) tool Git to manage and track Yocto - Project files. - Git employs branching strategies that effectively produce a tree-like structure whose - branches represent diversions from more general code. - For example, suppose two kernels are basically identical with the exception of a couple - different features in each. - In the Yocto Project source repositories managed by Git a main branch can contain the - common or shared - parts of the kernel source and two branches that diverge from that common branch can - each contain the features specific to the respective kernel. - The result is a managed tree whose "leaves" represent the end of a specific path that yields - a set of kernel source files necessary for a specific piece of hardware and its features. - - - - A big advantage to this scheme is the sharing of common features by keeping them in - "larger" branches that are further up the tree. - This practice eliminates redundant storage of similar features shared among kernels. - - - - When you build the kernel on your development system all files needed for the build - are taken from the Yocto Project source repositories pointed to by the - SRC_URI variable and gathered in a temporary work area - where they are subsequently used to create the unique kernel. - Thus, in a sense, the process constructs a local source tree specific to your - kernel to generate the new kernel image - a source generator if you will. - - - - For a complete discussion of the Yocto Project kernel's architcture and its branching strategy, - see the - The Yocto Project Kernel Architecture and Use Manual. - - - - You can find a web interface to the Yocto Project source repository at - . - Within the interface you will see groups of related source code, each of which can - be cloned using Git to result in a working Git repository on your local system - (referred to as the "local Yocto Project files" in this manual). - The Yocto Project supports four types of kernels in its source repositories at - : - - linux-yocto-2.6.34 - The - stable Linux Yocto kernel that is based on the Linux 2.6.34 release. - linux-yocto-2.6.37 - The current - Linux Yocto kernel that is based on the Linux 2.6.37 release. - linux-yocto-dev - A development - kernel based on the Linux 2.6.39-rc1 release. - linux-2.6 - A kernel based on - minimal Linux mainline tracking. - [WRITER'S NOTE: I don't know which Git repository the user needs to clone to get this - repository on their development system.] - - -
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- Modifying a Kernel Example - - - This section presents a simple example that illustrates kernel modification - based on the linux-yocto-2.6.37 kernel. - The example uses the audio and mixer capabilities supported by the - Advanced Linux - Sound Architecture (ALSA) Project. - As the example progresses you will see how to do the following: - - Iteratively modify a base kernel locally. - Provide a recipe-based solution for your modified kernel. - - Proved an "in-tree" solution for your modified kernel - (i.e. make the modifcations part of the Yocto Project). - - - - - The example flows as follows: - - - - - Be sure your host development system is set up to support - development using the Yocto Project. - See - - The Linux Distributions section and - - The Packages section both - in the Yocto Project Quick Start for requirements. - You will also need a release of Yocto Project installed on the host. - Set up your environment for optimal local kernel development. - - Create a layer to isolate your kernel work. - Next item. - Next item. - Next item. - Next item. - - - -
- Setting Up Yocto Project - - - You need to have the Yocto Project files available on your host system. - The process is identical to that described in the - "Getting Setup" section earlier in this - manual. - Be sure to either set up a local Git repository for poky - or download and unpack the Yocto Project release tarball. - -
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- Create a Git Repository of <filename>poky-extras</filename> - - - Everytime you change a configuration or add a recipe to the kernel you need to - do a fetch from the Linux Yocto kernel source repositories. - This can get tedious and time consuming if you need to fetch the entire - Linux Yocto 2.6.37 Git repository down from the Internet everytime you make a change - to the kernel. - - - - You can get around this by setting up a meta-kernel-dev - area on your local system. - This area contains "append" files for every kernel recipe, which also include - a KSRC statement that points to the kernel source files. - You can set up the environment so that the KSRC points to the - meta-kernel-dev, thus pulling source from a local area. - This setup can speed up development time. - - - - To get set up you need to do two things: create a local Git repository - of the poky-extras repository, and create a bare clone of the - Linux Yocto 2.6.37 kernel Git repository. - - - - The following transcript shows how to clone the poky-extras - Git repository into the current working directory, which is poky - in this example. - The command creates the repository in a directory named poky-extras: - - $ git clone git://git.yoctoproject.org/poky-extras - Initialized empty Git repository in /home/scottrif/poky/poky-extras/.git/ - remote: Counting objects: 532, done. - remote: Compressing objects: 100% (472/472), done. - remote: Total 532 (delta 138), reused 307 (delta 39) - Receiving objects: 100% (532/532), 534.28 KiB | 362 KiB/s, done. - Resolving deltas: 100% (138/138), done. - - - - - This transcript shows how to clone a bare Git repository of the Linux Yocto - 2.6.37 kernel: - - $ git clone --bare git://git.yoctoproject.org/linux-yocto-2.6.37 - Initialized empty Git repository in /home/scottrif/linux-yocto-2.6.37.git/ - remote: Counting objects: 1886034, done. - remote: Compressing objects: 100% (314326/314326), done. - remote: Total 1886034 (delta 1570202), reused 1870335 (delta 1554798) - Receiving objects: 100% (1886034/1886034), 401.51 MiB | 714 KiB/s, done. - Resolving deltas: 100% (1570202/1570202), done. - - - - - The bare clone of the Linux Yocto 2.6.37 kernel on your local system mirrors - the upstream repository of the kernel. - You can effectively point to this local clone now during development to avoid - having to fetch the entire Linux Yocto 2.6.37 kernel every time you make a - kernel change. - -
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- Create a Layer for Your Kernel Work - - - It is always good to isolate your work using your own layer. - Doing so allows you to experiment and easily start over should things go wrong. - This example uses a layer named meta-amixer. - - - - When you set up a layer for kernel work you should follow the general layout - guidelines as described for BSP layers. - This layout is described in the - - Example Filesystem Layout section of the Board Support Package (BSP) Development - Guide. - In the standard layout you will notice a suggested structure for recipes and - configuration information. - [WRITER'S NOTE: The meta-elc example uses an - images directory. - Currently, images is not part of the standard BSP layout. - I need to find out from Darren if this directory is required for kernel work.] - - - - [WRITER'S NOTE: I need a paragraph here describing how to set up the layer. - I am not sure if you should copy an existing BSP layer and modify from there. - Or, if you should just look at a BSP layer and then create your own files. - Email to Darren on this but no answer yet.] - -
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- Making Changes to Your Kernel Layer - - - In the standard layer structure you have several areas that you need to examine or - modify. - For this example the layer contains four areas: - - conf - Contains the - layer.conf that identifies the location of the recipe files. - - images - Contains the - image recipe file. - This recipe includes the base image you will be using and specifies other - packages the image might need. - recipes-bsp - Contains - recipes specific to the hardware for which you are developing the kernel. - - recipes-kernel - Contains the - "append" files that add information to the main recipe kernel. - - - - - - Let's take a look at the layer.conf in the - conf directory first. - This configuration file enables the Yocto Project build system to locate and - use the information in your new layer. - - - - The variable BBPATH needs to include the path to your layer - as follows: - - BBPATH := "${BBPATH}:${LAYERDIR}" - - And, the variable BBFILES needs to be modified to include your - recipe and append files: - - BBFILES := "${BBFILES} ${LAYERDIR}/images/*.bb \ - ${LAYERDIR}/images/*.bbappend \ - ${LAYERDIR}/recipes-*/*/*.bb \ - ${LAYERDIR}/recipes-*/*/*.bbappend" - - Finally, you need to be sure to use your layer name in these variables at the - end of the file: - - BBFILE_COLLECTIONS += "elc" - BBFILE_PATTERN_elc := "^${LAYERDIR}/" - BBFILE_PRIORITY_elc = "9" - - - - - The images directory contains an append file that helps - further define the image. - In our example, the base image is core-image-minimal. - The image does, however, need some additional modules that we are using - for this example. - These modules support the amixer functionality. - Here is the append file: - - require recipes-core/images/poky-image-minimal.bb - - IMAGE_INSTALL += "dropbear alsa-utils-aplay alsa-utils-alsamixer" - IMAGE_INSTALL_append_qemux86 += " kernel-module-snd-ens1370 \ - kernel-module-snd-rawmidi kernel-module-loop kernel-module-nls-cp437 \ - kernel-module-nls-iso8859-1 qemux86-audio alsa-utils-amixer" - - LICENSE = "MIT" - - - - - While the focus of this example is not on the BSP, it is worth mentioning that the - recipes-bsp directory has the recipes and append files for - features that the hardware requires. - In this example, there is a script and a recipe to support the - amixer functionality in QEMU. - It is beyond the scope of this manual to go too deeply into the script. - Suffice it to say that the script tests for the presence of the mixer, sets up - default mixer values, enables the mixer, unmutes master and then - sets the volume to 100. - - - - The recipe qemu86-audio.bb installs and runs the - amixer when the system boots. - Here is the recipe: - - SUMMARY = "Provide a basic init script to enable audio" - DESCRIPTION = "Set the volume and unmute the Front mixer setting during boot." - SECTION = "base" - LICENSE = "MIT" - LIC_FILES_CHKSUM = "file://${POKYBASE}/LICENSE;md5=3f40d7994397109285ec7b81fdeb3b58" - - PR = "r4" - - inherit update-rc.d - - RDEPENDS = "alsa-utils-amixer" - - SRC_URI = "file://qemux86-audio" - - INITSCRIPT_NAME = "qemux86-audio" - INITSCRIPT_PARAMS = "defaults 90" - - do_install() { - install -d ${D}${sysconfdir} \ - ${D}${sysconfdir}/init.d - install -m 0755 ${WORKDIR}/qemux86-audio ${D}${sysconfdir}/init.d - cat ${WORKDIR}/${INITSCRIPT_NAME} | \ - sed -e 's,/etc,${sysconfdir},g' \ - -e 's,/usr/sbin,${sbindir},g' \ - -e 's,/var,${localstatedir},g' \ - -e 's,/usr/bin,${bindir},g' \ - -e 's,/usr,${prefix},g' > ${D}${sysconfdir}/init.d/${INITSCRIPT_NAME} - chmod 755 ${D}${sysconfdir}/init.d/${INITSCRIPT_NAME} - } - - - - - The last area to look at is recipes-kernel. - This area holds configuration fragments and kernel append files. - The append file must have the same name as the kernel recipe, which is - linux-yocto-2.6.37 in this example. - The file can SRC_URI statements to point to configuration - fragments you might have in the layer. - The file can also contain KERNEL_FEATURES statements that specify - included kernel configurations that ship with the Yocto Project. - -
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