VIA8235 stuck in mono mode - using snd_via8233

[thematrixeatsyou]

This problem has plagued FreeBSD and Linux lists, but seeing as this chip isn't the most common around (I have a VIA motherboard), there's still no answer to this problem.

Problem: Sound only plays out of the left speaker. I am almost certain that the chipset is stuck in mono mode, as the "left speaker" part of the plug is at the very end, while the "ground" part of the plug is at the far back - the "right" part is in the middle.

Gory details:
--------------------
 dmesg tells me:
 pcm0: <VIA VT8235> port 0xe800-0xe8ff irq 22 at device 17.5 on pci0
 pcm0: [ITHREAD]
 pcm0: <Avance Logic ALC655 AC97 Codec>
 pcm0: <VIA DXS Enabled: DXS 4 / SGD 1 / REC 1>
 
 /dev/sndstat tells me:
 pcm0: <VIA VT8235> at io 0xe800 irq 22 kld snd_via8233 [MPSAFE] (5p:1v/1r:1v channels duplex default)
 
 pciconf -lv tells me:
 isab0 at pci0:0:17:0:      class=0x060100 card=0x31771106 chip=0x31771106 rev=0x00 hdr=0x00
     vendor     = 'VIA Technologies Inc'
     device     = 'VT8235 PCI to ISA Bridge'
     class      = bridge
     subclass   = PCI-ISA
 pcm0 at pci0:0:17:5:       class=0x040100 card=0x73401462 chip=0x30591106 rev=0x50 hdr=0x00
     vendor     = 'VIA Technologies Inc'
     device     = 'VT8237 AC97 Enhanced Audio Controller - the 8251 controller is different'
     class      = multimedia
     subclass   = audio
 --------------------

Apparently, the snd_via8233 driver is designed for AC'97 v2.2, whereas this chip (a 5.1 chip) follows the v2.3 specs.

I've had a look at the datasheet for the ALC655 chipset which this follows (google "alc655 datasheet"), and it appears that there's a MONO-OUT output. I suggest that you have a look into this - there's a suggestion of 4 possible "modes" (MX20/bit 9 AFAIK is just for feeding the mic into mono-out, not a mono channel disable or something like that). I haven't found anything about the modes yet, sadly :/

One more thing: DO NOT tell me that it's a cable/plug/hardware problem. I have already considered this.


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