[aarch64, mainline RPI 3B+] No libbcm_host.so in alarm repo?

[adam900710]

Hi,

I got my RPI 3B+ working using mainline kernel and all raspberry related packages in alarm repo.
(prepared the rootfs using qemu-user-static chroot environment)
Even built python-picamera, with some modification to skip board model check.

However when I try to use picamera module to do some test, python3 complains about can't find libbcm_host.so.
I'm wonder where I can find the package containing libbcm_host.so?

Or is that closed-source prop not supported in aarch64?
And if that's the case, how could I utilize the CSI picamera?

Thanks.