Customizing AOSP 12 for Raspberry Pi 4: Missing boot.img and Flashing Issues

Question

I am working on customizing AOSP 12 for Raspberry Pi 4. I successfully downloaded and built AOSP 12, and verified that it works properly using the emulator. However, after making customizations, I encountered an issue with the boot.img file and flashing the images to the SD card.

Here’s what I’ve done so far:

Downloaded and built AOSP 12.

Verified the build using the emulator (it works fine).

Made customizations and generated the following images:

system.img

userdata.img

ramdisk.img

Note: boot.img was not generated.

Manually created a boot.img file and attempted to flash it along with the other images to the SD card. However, the Raspberry Pi 4 did not boot successfully.

Tried two approaches to flash the images:

Combined all four images (system.img, userdata.img, ramdisk.img, and boot.img) into a single disk image and flashed it to the SD card using Balena Etcher.

Created separate partitions on the SD card and flashed each image to its respective partition.

Neither approach worked, and the Raspberry Pi 4 failed to boot.

Expected Outcome: I expected the Raspberry Pi 4 to boot successfully after flashing the custom AOSP 12 images. However, the device failed to boot, likely due to issues with the boot.img file or the flashing process.

Questions:

Why is boot.img not being generated during the build process? Are there specific steps or configurations I need to enable to generate it?

What could be the issue with the manually created boot.img? Are there specific requirements for the boot.img file for Raspberry Pi 4?

Are there any known issues or additional steps required when flashing AOSP 12 to a Raspberry Pi 4?