Goal
Basically I've got a custom board (based on the tobi) for the overo and I want to create a custom build for it with a custom kernel.
bitbake custom-board-image
1000-foot overview
- Choose a kernel that compiles
- Use it as a base for your custom kernel
- Copy the source with all Overo patches built-in
- Make the changes
- Test
- Create the necessary bitbake patches and files
Copying the bitbake skeleton for the kernel
First test that the kernel you wish to use as your base bitbakes successfully
bitbake linux-omap-psp
Then copy that base
cd ~/overo-oe
mkdir -p user.collection/recipes/linux/
mkdir -p user.collection/recipes/linux/files/configs
touch user.collection/recipes/linux/files/configs/.empty
cp org.openembedded.dev/recipes/linux/linux.inc user.collection/recipes/linux/
cp org.openembedded.dev/recipes/linux/multi-kernel.inc user.collection/recipes/linux/
cp org.openembedded.dev/recipes/linux/linux-omap-psp_2.6.32 \
user.collection/recipes/linux/linux-my-custom_2.6.32.bb
cp -a org.openembedded.dev/recipes/linux/linux-omap-psp-2.6.32 \
user.collection/recipes/linux/linux-my-custom-2.6.32
That is everything necessary to start a custom kernel. Test that it will actually build
bitbake linux-my-custom
Using bitbake to get the source + patches
cd ~/overo-oe
bitbake linux-my-custom
cp -a ./tmp/work/overo-angstrom-linux-gnueabi/linux-my-custom-2.6.32-r81 ./linux-my-custom
sudo cp -a ./tmp/work/overo-angstrom-linux-gnueabi/linux-my-custom-2.6.32-r81/git/.pc ./linux-my-custom/
cd ./linux-my-custom/
git init
git add .
git commit -m "freshly patched kernel source from mainstream"
In the appendix I list a way which may work for manually getting the source + patches.
Making customizations
Let's say a handy-dandy friend has made some modifications to board-overo.c and created board-overo-camera.c.
I can grab his files from my e-mail and plop them into the mix.
I'll check to see that the changes are good and I understand them
diff -y --suppress-common-lines ~/Downloads/board-overo.c arch/arm/mach-omap2/board-overo.c
static struct platform_device my_custom_cam_device = { <
.name = "my_custom_cam", <
.id = -1, <
}; <
Then I copy it over
cp ~/Downloads/board-overo.c arch/arm/mach-omap2/board-overo.c
cp ~/Downloads/board-custom-camera.c arch/arm/mach-omap2/board-custom-camera.c
cp ~/Downloads/board-custom-camera.h arch/arm/mach-omap2/board-custom-camera.h
cp ~/Downloads/custom-cam.c drivers/media/video/custom-cam.c
cp ~/Downloads/config arch/arm/configs/overo_defconfig
cp ~/Downloads/Makefile arch/arm/mach-omap2/Makefile
I can also check the differences now
git diff
And then I commit my changes with a comment
git status
git add ./arch ./drivers
git commit -m "added custom_cam support for custom_board"
Testing
PATH=~/overo-oe/tmp/sysroots/i686-linux/usr/bin/:$PATH
#cp ~/overo-oe/tmp/sysroots/i686-linux/usr/bin/mkimage /usr/bin/
#sudo apt-get install uboot-mkimage
make ARCH=arm CROSS_COMPILE=~/overo-oe/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi- overo_defconfig
make ARCH=arm CROSS_COMPILE=~/overo-oe/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi- menuconfig
make ARCH=arm CROSS_COMPILE=~/overo-oe/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi- uImage modules
scp arch/arm/boot/uImage gumstix:/media/mmcblk0p1/
TODO: use my_custom_defconfig
Creating custom patches
Creating patches for the past two commits
git format-patch -2
TODO: to be continued
Resources
Appendix
Manually getting the source + patches
In linux-my-custom_2.6.32.bb I found the original kernel source and I'm going to clone that and add the patches I need.
cd ~/overo-oe
git clone git://arago-project.org/git/people/sriram/ti-psp-omap.git
mv ti-psp-omap linux-my-custom
cd linux-my-custom
mkdir patches
cp user.collection/recipes/linux/linux-my-custom-2.6.32/*.patch patches/
# You may also want additional board patches
cp -a user.collection/recipes/linux/linux-my-custom-2.6.32/overo/ patches/
Now we want to apply all of those patches - here's a miniscript for it
ls patches/*.patch | sort | while read PATCH
do
echo $PATCH
git apply --stat --apply --whitespace=fix $PATCH && rm $PATCH || break
done
In my case, a few patches didn't apply so I had to apply them by hand. No big deal - probably just a problem with whitespace and line numbers.
After all that, time to commit
rm -rf patches
git add .
git commit -m "brought kernel up to mainline"
Creating a raw capture driver
These are the files to start with
./drivers/media/video/Makefile
./drivers/media/video/Kconfig
./drivers/media/video/mt9t111_reg.h
./drivers/media/video/mt9t111.c
./include/media/mt9t111.h
./arch/arm/mach-omap2/board-omap3beagle-camera.c
./arch/arm/mach-omap2/board-overo-camera.c
./arch/arm/mach-omap2/board-overo.c
./arch/arm/mach-omap2/Makefile
./arch/arm/mach-omap2/board-omap3beagle.c
#./arch/arm/mach-omap2/board-overo-camera.h
./arch/arm/configs/overo_defconfig
./arch/arm/configs/omap3_beagle_cam_defconfig
./arch/arm/configs/omap3_beagle_defconfig