root@mars:/lib/firmware/i915# update-initramfs -u update-initramfs: Generating /boot/initrd.img-5.16.0-1-amd64 W: Possible missing firmware /lib/firmware/i915/adlp_dmc_ver2_12.bin for module i915
I'm also seeing this warning on a lenovo x230 with: Intel Corporation 3rd Gen Core processor Graphics Controller
It can be found here: https://anduin.linuxfromscratch.org/sources/linux-firmware/i915/
From what I can see, upstream has merged the addition of version 2.12 of the firmware (and later also 2.14, 2.15 and 2.16)
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/?id=0268c1b8a06798f5167cbef8fb16241298b3eba9 so this package would have the firmware available on the next version bump.