reproduce (this is a W=1 build):
        # https://github.com/AsahiLinux/linux/commit/0c10263acfe5f842f214a45de3a4f667d9113013
        git remote add asahilinux https://github.com/AsahiLinux/linux
        git fetch --no-tags asahilinux bits/080-wifi
        git checkout 0c10263acfe5f842f214a45de3a4f667d9113013
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/net/wireless/broadcom/brcm80211/brcmfmac/