RPI3: Instructions on how to compile kernel with functional wifi

[phinxy]

NetBSD-current does not have a working wifi driver for raspberrypi-3, it is unclear to me how Jun modified the kernel source tree to make the kernel set up a functional wifi device.
It seems that something compiled in to Jun's kernel makes it load the brcmfmac43430-sdio.bin while a unmodified GENERIC64 aarch64 NetBSD-current does not.

[phinxy]

Question 1: What does "bwfm* at sdmmc?" in kernel configuration accomplish?

Question 2: Should the brcmfmac43430-sdio.bin be copied in to this directory /usr/src/external/broadcom/bwfm/dist/ and then should the makefile in the directory above, plus distrib/sets/lists/base/mi be edited to accommodate the firmware?

Question 3: There are no *-sdio.bin in the source tree when there are *-pcie.bin's, how come?

[jdek]

It seems that something compiled in to Jun's kernel makes it load the brcmfmac43430-sdio.bin while a unmodified GENERIC64 aarch64 NetBSD-current does not.

I am also wondering about this for the RPI4 because the bwfm is not shown at all in dmesg. bwfm* at sdmmc? is already in GENERIC kernel so there should be no need to add it manually I think(?).

I'm using brcmfmac43455 for the RPI4 (which I think is the right firmware).

Edit:
I've been told in the netbsd IRC channel that it might be a .dtb issue.