ALC887-VD line-in not visible

[Arthur Marsh <arthur.marsh@internode.on.net>]

Earlier this year I could use line-in on an Asus PRIME B350M-A motherboard,
with dmesg reporting:

 snd_hda_codec_realtek hdaudioC0D0: autoconfig for ALC887-VD: line_outs=1 (0x14/
0x0/0x0/0x0/0x0) type:line
 snd_hda_codec_realtek hdaudioC0D0:    speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
 snd_hda_codec_realtek hdaudioC0D0:    hp_outs=1 (0x1b/0x0/0x0/0x0/0x0)
 snd_hda_codec_realtek hdaudioC0D0:    mono: mono_out=0x0
 snd_hda_codec_realtek hdaudioC0D0:    dig-out=0x11/0x0
 snd_hda_codec_realtek hdaudioC0D0:    inputs:
 snd_hda_codec_realtek hdaudioC0D0:      Rear Mic=0x18
 snd_hda_codec_realtek hdaudioC0D0:      Front Mic=0x19
 snd_hda_codec_realtek hdaudioC0D0:      Line=0x1a
 input: HD-Audio Generic Rear Mic as /devices/pci0000:00/0000:00:08.1/0000:08:00
.6/sound/card0/input6
 input: HD-Audio Generic Front Mic as /devices/pci0000:00/0000:00:08.1/0000:08:0
0.6/sound/card0/input7
 input: HD-Audio Generic Line as /devices/pci0000:00/0000:00:08.1/0000:08:00.6/s
ound/card0/input8
 input: HD-Audio Generic Line Out as /devices/pci0000:00/0000:00:08.1/0000:08:00
.6/sound/card0/input9
 input: HD-Audio Generic Front Headphone as /devices/pci0000:00/0000:00:08.1/000
0:08:00.6/sound/card0/input10

After the post-6.16 updates, I now get:

 snd_hda_codec_generic hdaudioC0D0: autoconfig for Generic: line_o
uts=1 (0x14/0x0/0x0/0x0/0x0) type:line
 snd_hda_codec_generic hdaudioC0D0:    speaker_outs=0 (0x0/0x0/0x0
/0x0/0x0)
 snd_hda_codec_generic hdaudioC0D0:    hp_outs=1 (0x1b/0x0/0x0/0x0
/0x0)
 snd_hda_codec_generic hdaudioC0D0:    mono: mono_out=0x0
 snd_hda_codec_generic hdaudioC0D0:    dig-out=0x11/0x0
 snd_hda_codec_generic hdaudioC0D0:    inputs:
 snd_hda_codec_generic hdaudioC0D0:      Rear Mic=0x18
 snd_hda_codec_generic hdaudioC0D0:      Front Mic=0x19
 snd_hda_codec_generic hdaudioC0D0:      Line=0x1a
 input: HD-Audio Generic Rear Mic as /devices/pci0000:00/0000:00:0
8.1/0000:08:00.6/sound/card0/input6
 input: HD-Audio Generic Front Mic as /devices/pci0000:00/0000:00:
08.1/0000:08:00.6/sound/card0/input7
 input: HD-Audio Generic Line as /devices/pci0000:00/0000:00:08.1/
0000:08:00.6/sound/card0/input8
 input: HD-Audio Generic Line Out as /devices/pci0000:00/0000:00:0
8.1/0000:08:00.6/sound/card0/input9
 input: HD-Audio Generic Front Headphone as /devices/pci0000:00/00
00:00:08.1/0000:08:00.6/sound/card0/input10

lspci reports:

  lspci -v -s 0000:08:00.1
08:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Renoir Radeon High Definition Audio Controller
        Subsystem: ASUSTeK Computer Inc. Device 8809
        Flags: bus master, fast devsel, latency 0, IRQ 87, IOMMU group 11
        Memory at fca88000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [64] Express Legacy Endpoint, IntMsgNum 0
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Capabilities: [2a0] Access Control Services
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_hda_intel


When using alsamixer, in the former case, I would get a "loopback" device, 
which when un-muted would enable line-in to work.

With the current git head kernel, I get no such loopback device and have been
unable to get audio via line input.

Any suggestions welcome.