Comment 2 for bug 1377653

I have the same N56VZ laptop running 14.04 as well, and can confirm this problem.

According to http://http.download.nvidia.com/XFree86/gpu-hdmi-audio-document/gpu-hdmi-audio.html#_verify_your_card_exists the nVidia card should show an audio device in lspci output if HDMI is connected and enabled. This doesn't happen on my laptop. I am using the proprietary 331 nvidia drivers and nvidia-prime *without* bumblebee. I can plugin an HDMI cable and the display automatically mirrors to the HDMI output, but no nVidia audio device is ever detected with lspci. NOTE: the snd_hda_codec_hdmi module doesn't load when I connect HDMI. Manually modprobing it loads the module but shows a 0 count for 'Used By' and no dmesg output.

# lspci output with HDMI connected and screen mirrored to TV:

00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1 (rev c4)
00:1c.1 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 2 (rev c4)
00:1c.3 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 4 (rev c4)
00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM76 Express Chipset LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller (rev 04)
01:00.0 VGA compatible controller: NVIDIA Corporation GK107M [GeForce GT 650M] (rev a1)
03:00.0 Network controller: Qualcomm Atheros AR9485 Wireless Network Adapter (rev 01)
04:00.0 Ethernet controller: Qualcomm Atheros AR8161 Gigabit Ethernet (rev 10)

# cat /proc/asound/cards output with HDMI connected:
 0 [PCH ]: HDA-Intel - HDA Intel PCH
                      HDA Intel PCH at 0xf7a00000 irq 44