amd64/148488: Headphone won't work on NVidia MCP78 High Definition Audio Controller

[Stéphane Thibaud]

>Number:         148488
>Category:       amd64
>Synopsis:       Headphone won't work on NVidia MCP78 High Definition Audio Controller
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jul 11 00:40:05 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Stéphane Thibaud
>Release:        FreeBSD 8.0-RELEASE-p2 (PCBSD really)
>Organization:
>Environment:
FreeBSD pcbsd-5973 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #10: Thu Jan  7 14:50:53 EST 2010     root at build8x64.pcbsd.org:/usr/obj/usr/pcbsd-build80/fbsd-source/8.0-src/sys/PCBSD  amd64
>Description:
The headphone output doesn't provide a signal nomatter what sliders I move in KMix.

My soundcard gets detected as follows:

hdac0: HDA Driver Revision: 20090624_0136
hdac0: [ITHREAD]
hdac0: HDA Codec #0: Conexant CX20561 (Hermosa)
hdac0: HDA Codec #3: NVidia MCP78 HDMI
pcm0: <HDA Conexant CX20561 (Hermosa) PCM #0 Analog> at cad 0 nid 1 on hdac0
pcm1: <HDA Conexant CX20561 (Hermosa) PCM #1 Analog> at cad 0 nid 1 on hdac0
pcm2: <HDA NVidia MCP78 HDMI PCM #0 Digital> at cad 3 nid 1 on hdac0

I have a stereo headphone output on this laptop and a microphone input. Please note that I do hear sound over the built-in speakers and plugging in a headphone doesn't change that (sound isn't muted either). Perhaps some kind of jack-sensing doesn't work
>How-To-Repeat:
Boot Kde4, play sound.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: