From ed0d609c7c40ad638f634a5e1822ab3bcc4e6681 Mon Sep 17 00:00:00 2001 From: Scott Rifenbark Date: Mon, 27 Mar 2017 09:17:08 -0700 Subject: bsp-guide, kernel-dev: Updates to how kernel metadata is found Fixes [YOCTO #10946] There was insufficient information in the combination of the BSP Guide and the Kernel Development Manual on just how to locate and use kernel metadata. * bsp-guide - Removed the detailed append file example for the kernel recipe. This is moved now to the chapter in the kernel manual that describes append files. * kernel-dev - Placed the example from the BSP Guide into the section that describes kernel append files. Cleaned up some terminology issues throughout chapter 3. Added information about how BitBake picks up kernel metadata when the metadata is in a hierarchical directory and not just a simple *.scc file. (From yocto-docs rev: 1048acb7127e77ca9c1f524a208fe25344fcb57c) Signed-off-by: Scott Rifenbark Signed-off-by: Richard Purdie --- documentation/kernel-dev/kernel-dev-common.xml | 149 ++++++++++++++++++++++++- 1 file changed, 147 insertions(+), 2 deletions(-) (limited to 'documentation/kernel-dev/kernel-dev-common.xml') diff --git a/documentation/kernel-dev/kernel-dev-common.xml b/documentation/kernel-dev/kernel-dev-common.xml index a9aafd3c21..d49aa3ce17 100644 --- a/documentation/kernel-dev/kernel-dev-common.xml +++ b/documentation/kernel-dev/kernel-dev-common.xml @@ -84,11 +84,11 @@ You also name it accordingly based on the linux-yocto recipe you are using. For example, if you are modifying the - meta/recipes-kernel/linux/linux-yocto_3.19.bb + meta/recipes-kernel/linux/linux-yocto_4.4.bb recipe, the append file will typically be located as follows within your custom layer: - your-layer/recipes-kernel/linux/linux-yocto_3.19.bbappend + your-layer/recipes-kernel/linux/linux-yocto_4.4.bbappend The append file should initially extend the FILESPATH @@ -114,6 +114,151 @@ Yocto Project Board Support Package (BSP) Developer's Guide. + + + As an example, consider the following append file + used by the BSPs in meta-yocto-bsp: + + meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.4.bbappend + + The following listing shows the file. + Be aware that the actual commit ID strings in this + example listing might be different than the actual strings + in the file from the meta-yocto-bsp + layer upstream. + + KBRANCH_genericx86 = "standard/base" + KBRANCH_genericx86-64 = "standard/base" + + KMACHINE_genericx86 ?= "common-pc" + KMACHINE_genericx86-64 ?= "common-pc-64" + KBRANCH_edgerouter = "standard/edgerouter" + 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" + + COMPATIBLE_MACHINE_genericx86 = "genericx86" + COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64" + COMPATIBLE_MACHINE_edgerouter = "edgerouter" + 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" + + This append file contains statements used to support + several BSPs that ship with the Yocto Project. + The file defines machines using the + COMPATIBLE_MACHINE + variable and uses the + KMACHINE + variable to ensure the machine name used by the OpenEmbedded + build system maps to the machine name used by the Linux Yocto + kernel. + The file also uses the optional + KBRANCH + variable to ensure the build process uses the + appropriate kernel branch. + + + + Although this particular example does not use it, the + KERNEL_FEATURES + variable could be used to enable features specific to + the kernel. + The append file points to specific commits in the + Source Directory + Git repository and the meta Git repository + branches to identify the exact kernel needed to build the + BSP. + + + + One thing missing in this particular BSP, which you will + typically need when developing a BSP, is the kernel configuration + file (.config) 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. + You can accomplish this definition by putting the configurations + 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 + SRC_URI + statement in the append file. + + + + For example, suppose you had some configuration options + in a file called network_configs.cfg. + You can place that file inside a directory named + linux-yocto and then add + a SRC_URI statement such as the + following to the append file. + When the OpenEmbedded build system builds the kernel, the + configuration options are picked up and applied. + + SRC_URI += "file://network_configs.cfg" + + + + + To group related configurations into multiple files, you + perform a similar procedure. + Here is an example that groups separate configurations + specifically for Ethernet and graphics into their own + files and adds the configurations by using a + SRC_URI statement like the following + in your append file: + + SRC_URI += "file://myconfig.cfg \ + file://eth.cfg \ + file://gfx.cfg" + + + + + Another variable you can use in your kernel recipe append + file is the + FILESEXTRAPATHS + variable. + When you use this statement, you are extending the locations + used by the OpenEmbedded system to look for files and + patches as the recipe is processed. + + + + + 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 meta 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 + meta branch for your BSP. + The configuration options will likely end up in that location anyway if the BSP gets + added to the Yocto Project. + + + + In general, however, the Yocto Project maintainers take care of moving the + SRC_URI-specified + configuration options to the kernel's meta 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. + +
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