build aosp kernel with module - for starlte galaxy s9 - lineage

setup

gadget source: https://github.com/oandrew/ipod-gadget.git commmit: 731a4714248f1fc13bd1f1fd9b24c5ddaeb5a501
kernel source: https://github.com/LineageOS/android_kernel_samsung_exynos9810a commit: 6a9461f9460ca51d1217e5069a5d5556fcc79e63
on a debian 12 system with packages to build kernel + gcc-arm-linux-gnueabi installed
aosp source tree to build kernel
- nix build github:c2vi/nixos/fe411df12d5d4e2017e7fa99dea2a4c05b149b5e#robotnixConfigurations.s9.config.build.debugEnterEnv —option max-call-depth 100000000
- needs change to open file limit
- run ./result in an empty folder
- source build/envsetup && breakfast starlte && make bootimage # to build kernel

i didn’t get building it out of tree to work
- where you would use the original makefile with make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- KERNEL_PATH=/path/to/kernel/src
- rel: aosp - compile out of tree kernel module
copying the ipod-gadget into the kernel source inside aosp however worked
- mkdir $aosp-root/kernel/samsung/exynos9810/drivers/ipod-gadget/
- ipod-gadget/gadget/* → $aosp-root/kernel/samsung/exynos9810/drivers/ipod-gadget/
- then add to $kernel/drivers/Kconfig
```
source "drivers/ipod-gadget/Kconfig"
```
- add to $kernel/drivers/Makefile at the bottom
```
obj-$(CONFIG_IPOD_MOD) += ipod-gadget/
```
- add $kernel/drivers/ipod-gadget/Kconfig
```
config IPOD_MOD
    tristate "Ipod protocol gadget module"
    default m
    depends on MODULES
    help
      see: https://github.com/oandrew/ipod-gadget
```
- and change the Makefile $kernel/drivers/ipod-gadget/Makefile to
```
# call from kernel build system
ifneq ($(KERNELRELEASE),)

g_ipod-y := ipod.o
g_ipod_hid-y := ipod_hid.o
g_ipod_audio-y := ipod_audio.o
g_ipod_gadget-y := ipod_gadget.o

obj-m += g_ipod_hid.o g_ipod_audio.o g_ipod_gadget.o

endif
```
- then: source build/envsetup.sh && breakfast starlte && m bootimage
- you have a flashable boot.img in $aosp-root/out/target/product/starlte/boot.img