I hope somebody can shine me a light. I am using Yocto/Poky with linux kernel sources from a custom repository with an "in-tree" kernel configuration and device tree. (not using fragments or overlays)
When building the kernel stand alone using:
make myconfig_defconfig
make
All the device tree binaries for the configured architecture are built.
When building the same kernel+config within Yocto (Kirkstone), the kernel image is built, but no device tree files.
During Yocto build, a defconfig is generated in "/.kernel-meta/configs"
This config is what I expect and has the correct "CONFIG_ARCH_" set to match the devicetree Makefile.
Compared to the previous setup(s) another machine definition is used (meta-Xilinx), Poky-dunfell changed to Poky-Kirkstone and the kernel is a newer version. (but since this compiles the devicetree when used stand alone, it seems not the cause)
At this moment I have no idea what may cause not to compile the devicetree files.
Any suggestions are welcome.
Related
I've found various kernel configs in kernel/configs/q.
When I alter them, and run mm in kernel/msm-4.14 the kernel is not rebuilt.
Where do I edit the kernel config, such that a kernel rebuild is forced when mm is run?
The kernel is built separately from the Android platform first. Then the Android platform build system is pointed at where the kernel image is located, using the TARGET_PREBUILT_KERNEL environment variable.
Here is an outline of how I usually configure and build. I have done it this way for both Android 9 and 10, for various vendors. The scheme I use is mentioned in the docs here. Non-Google kernels usually don't come with version control (repo), I don't know what you're dealing with so I'll cover both.
Configuring the kernel
For repo-checkout kernels, you do the config in build/build.config. Basically, after defconfig was taken as basis, you use the ${KERNEL_DIR}/scripts/config tool to alter the config. This usually looks as follows:
POST_DEFCONFIG_CMDS="check_defconfig && update_config"
function update_config() {
${KERNEL_DIR}/scripts/config --file ${OUT_DIR}/.config \
-d CONFIG_SOMETHING_I_DISABLE \
-e CONFIG_SOMETHING_I_ENABLE \
--set-val CONFIG_FOO = 123
}
If you don't have a repo-checkout kernel, locations and details may differ but the basic idea is usually the same: Find/Create the script that kicks of the build, and add invocations of the config tool after making defconfig.
Run the config tool by its own to see full options and more info on its usage, but the above is usually all you need. Beware: If you make syntactically-correct invalid changes (e.g. enable symbols of which the dependencies are not met), the build system will NOT complain and ignore these changes silently. If you face this situation, e.g. use menuconfig to find out what's wrong, as it shows dependencies.
Building AOSP / Making boot.img
After you've built your kernel, you will have Image.lz4 in out/.../dist (or Image.gz in out/.../private/msm-google/arch/arm64/boot). You go to your Android source, and in addition to the usual things (source build/envsetup.sh, lunch) you point the build system at the image you built, e.g. export TARGET_PREBUILT_KERNEL=/path/to/Image.lz4. Then just start the build normally, e.g. make bootimage or m droid.
Note that for Android 10 at least in some cases, you'll have to copy over the kernel modules from out/.../dist too, since the new kernel can't load the old ones. With this part, I am having problems myself at the moment. I think they have to be copied to device/VENDOR/DEVICE (e.g. google/coral-kernel), you may also copy your kernel image there btw, since the original prebuilt one also is there by default. The problem is that at least in my case, the new kernel modules were not copied to device after all.
I have a Linux kernel for NXP i.MX6. There are some capture kernel modules in /driver/media/platform/mxc/capture.
One of the files called mxc_v4l2_capture.c. I had to change this file for using it with my own new kernel driver.
I created a repository with my driver and the sources for mxc_v4l2_capture. Then I made a new Yocto recipe in my layer recipies-kernel -> kernel-modules->my-kernel-module.bb
Yocto can build these two kernel modules (my-kernel-module.ko and mxc_v4l2_capture.ko).
Okay, now there is a problem because the kernel recipe already builds the mxc_v4l2_capture module. Therefore I want to manipulate the Makefile for the original kernel modules and exclude the make of mxc_v4l2_capture.
I have created the patch but I don't know how to use the patch with Yocto. Where to place it and how can I call it?
Normally I put a patch into a .bbappend file and finish but I don't know the name of the recipe that build the kernel modules.
It would be great if there is a way without manipulating this Makefile.
Is there a way to solve this with my kernel module recipe?
mxc_v4l2_capture.c is in-tree kernel driver. If you want to change the in-tree driver code and compile, it's highly recommended to patch the kernel and compile the kernel with usual recipe.
Having additional bitbake recipe for the in-tree kernel module is not necessary. To patch the kernel and compile, you can use .bbappend or .bb itself. For example,
if you have recipes-kernel/linux/linux-stable_4.19.75.bb in your Yocto BSP layer, you can add the patch to SRC_URI as below.
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}-${PV}:"
SRC_URI += "file://mxc_v4l2_capture.patch"
Now, you create recipes-kernel/linux/linux-stable-4.19.75/ and copy the mxc_v4l2_capture.patch file inside.
Or if you don't have permission or not possible to modify the Kernel recipe in BSP layer, you can create .bbappend in your custom layer. For the above example, you can create linux-stable_4.19.75.bbappend (specific version) or linux-stable_%.bbappend (any version). Then place the same content as mentioned above.
Yocto supports various patch formats, refer here for more details.
Look at this answer I wrote some days ago. The steps are basically the same. Using
devtool modify virtual/kernel
will create a working copy in build/workspace where you can do the work you want. Commiting those changes to the local branch and running
devtool finish linux-mainline <path-to-your-layer>
will create a .bbappend file with the patches already created and put to the correct location for you.
If you want to learn how to do it manually follow the advice #Parthiban gave.
Userspace package built for and along with root file system image of some embedded Linux-based system here (using Yocto project) apparently uses autotools - one can see Makefile.am's and configure.ac in package's sources. pkg-config or its successor seems to be used too (.pc.in is present), however out-of scope here.
Package in focus here does it this way (by involving autotools) as in the beginning of its development it was apparently the line of lowest resistance to copy and adopt build scripts from similar but already-existing package.
Actually autotools seem to be dispensable when building with Yocto, as Yocto build system meta data do specify target precisely enough for every target. For good reason standard build flow in Yocto is download, unpack, patch, configure, build,... with scan-and-detect-target-environment not included in this chain.
Now I wonder if it was good to streamline package's build process by removing autotools stage. I'm going to conduct it by proceeding in sequence of few steps starting with replacing .am file with real makefile. Question is if it will be sufficient enough to find env. variables defined and used in .am and .ac then transfer them to makefile? Remaining target-device specification should actually come from Yocto build system meta data. Possibly it will work this straightforward if to build package in scope of root file system image build. But how to ensure build environment provides complete target device specification when building only this package bitbake package-name?
Replacing autotools with a bare makefile isn't a trivial operation, as https://nibblestew.blogspot.co.uk/2017/12/a-simple-makefile-is-unicorn.html demonstrates nicely.
If you don't want to use autotools in your packages then alternatives such as Meson are generally faster.
Im playing around with buildroot together with linaro 2016.11 for arm.
Im actually building the latest Linux Kernel for the i.MX6 Processors.
So far so good.
I have setup the buildroot config with
$ make makeconfig
I have configured an external toolchain (the linaro one). I also configured the uboot to be built. In the uboot section, i had to choose the appropriate board name for the defconfig.
Now the problem:
I have done a full make which was successfull without any errors.
After that, i have changed the uboot board name to something which does not exist in the source. Just to make sure everything is working correct.
i have restartet the build process with
$ make uboot-rebuild
to my confusion, the build was sucessfull. After a deeper look to the shell commands, i saw, that the new config was just ignored. I have tried everything without success. It only rebuilds correctly after i do a
$make clean
$make
but this will build the whole thing again and it takes a lot of time.
I hope someone could help me with that and give me some hint.
Thanks.
make <pkg>-rebuild rebuilds the package without applying a new configuration, so what happens is correct.
After changing the U-Boot configuration you have to run make uboot-reconfigure. This command first applies the configuration, then it does the same actions as uboot-rebuild.
See also the Buildroot manual, section Understanding how to rebuild packages.
I need to build mmc_block.ko but with MMC_BLOCK_MINORS=16. I do not wish to build the entire kernel. I am using Ubuntu 15.10. How do I do this?
Dpending on how the Makefile has been written, a module can be compiled out of the kernel tree or in the kernel tree.
Concerning your specific example, I assume the module is the one shipped with the kernel and therefore the Makefile has been written for in-tree compilation. In this case, you can just type make modules to rebuild the module, provided that the kernel has been already compiled (which is a mandatory condition also for out-of-the-tree compilation).