reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-47-g365b9520-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/commit/?id=1b53c116232e082db06ab5310c1be1d4bf75dfe1
        git remote add tiwai-sound https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
        git fetch --no-tags tiwai-sound topic/scarlett2
        git checkout 1b53c116232e082db06ab5310c1be1d4bf75dfe1
        # 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 sound/usb/