Ready NAS OS 6.4.2 sound modules (x86_64)

Hello

I'm trying to build the usb sound modules for my Ultra 2 running OS 6.4.2.

I'm using the following steps (sources downloaded from http://kb.netgear.com/app/answers/detail/a_id/2649/)

unzip ReadyNASOS_V6.4.2_WW_src.zip
cd linux-4.1.16-x86_64

cp ./arch/x86/configs/readynas_defconfig .config

make prepare
make scripts
make -j2
make menuconfig

Device driver 
> Sound card support
    > ALSA
        <M> OSS Mixer API
        <M> OSS PCM API
        [*] USB sound devices
            <M> USB Audio/MIDI driver
> USB support
    > Support for Host-side USB
        <M> USB/IP support
            <M> VHCI hcd
">" means keep as it is
"<M>" means I enabled module building
"[*]" means I enabled building but module is not supported

make modules

And this is where i'm stuck

syan@Roost:/data/linux/kernel/linux-4.1.16-x86_64$ make modules
scripts/kconfig/conf  --silentoldconfig Kconfig
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/bounds.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CC [M]  sound/core/hwdep.o
  LD [M]  sound/core/snd-hwdep.o
  CC [M]  sound/core/rawmidi.o
  LD [M]  sound/core/snd-rawmidi.o
  CC [M]  sound/core/oss/mixer_oss.o
  LD [M]  sound/core/oss/snd-mixer-oss.o
  CC [M]  sound/core/oss/pcm_oss.o
  CC [M]  sound/core/oss/pcm_plugin.o
  CC [M]  sound/core/oss/io.o
  CC [M]  sound/core/oss/copy.o
  CC [M]  sound/core/oss/linear.o
  CC [M]  sound/core/oss/mulaw.o
  CC [M]  sound/core/oss/route.o
  CC [M]  sound/core/oss/rate.o
  LD [M]  sound/core/oss/snd-pcm-oss.o
  CC [M]  sound/usb/card.o
  CC [M]  sound/usb/clock.o
  CC [M]  sound/usb/endpoint.o
  CC [M]  sound/usb/format.o
  CC [M]  sound/usb/helper.o
  CC [M]  sound/usb/mixer.o
  CC [M]  sound/usb/mixer_quirks.o
  CC [M]  sound/usb/mixer_scarlett.o
  CC [M]  sound/usb/pcm.o
  CC [M]  sound/usb/proc.o
  CC [M]  sound/usb/quirks.o
  CC [M]  sound/usb/stream.o
  LD [M]  sound/usb/snd-usb-audio.o
  CC [M]  sound/usb/midi.o
  LD [M]  sound/usb/snd-usbmidi-lib.o
  Building modules, stage 2.
  MODPOST 7 modules
ERROR: "snd_lookup_oss_minor_data" [sound/core/snd-rawmidi.ko] undefined!
ERROR: "snd_oss_info_register" [sound/core/snd-rawmidi.ko] undefined!
ERROR: "snd_register_oss_device" [sound/core/snd-rawmidi.ko] undefined!
ERROR: "snd_unregister_oss_device" [sound/core/snd-rawmidi.ko] undefined!
ERROR: "snd_lookup_oss_minor_data" [sound/core/snd-hwdep.ko] undefined!
ERROR: "snd_register_oss_device" [sound/core/snd-hwdep.ko] undefined!
ERROR: "snd_unregister_oss_device" [sound/core/snd-hwdep.ko] undefined!
ERROR: "snd_lookup_oss_minor_data" [sound/core/oss/snd-pcm-oss.ko] undefined!
ERROR: "snd_oss_info_register" [sound/core/oss/snd-pcm-oss.ko] undefined!
ERROR: "snd_register_oss_device" [sound/core/oss/snd-pcm-oss.ko] undefined!
ERROR: "snd_unregister_oss_device" [sound/core/oss/snd-pcm-oss.ko] undefined!
ERROR: "snd_lookup_oss_minor_data" [sound/core/oss/snd-mixer-oss.ko] undefined!
ERROR: "snd_oss_info_register" [sound/core/oss/snd-mixer-oss.ko] undefined!
ERROR: "snd_mixer_oss_notify_callback" [sound/core/oss/snd-mixer-oss.ko] undefined!
ERROR: "snd_register_oss_device" [sound/core/oss/snd-mixer-oss.ko] undefined!
ERROR: "snd_unregister_oss_device" [sound/core/oss/snd-mixer-oss.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

I'm beginning to think the Modules.symvers file generated isn't excactly right. I tried building ALSA too as a module but then those errors still fire and errors about symboles being exported twice (once in module and once in vmlinux) appear too.

I also tried building with the same exact version of GCC than the running kernel :

gcc version 4.7.2 (Debian 4.7.2-5)

But this didn't make a difference.

If anybody has any idea I would love to hear about it :)

Thanks a lot