[alsa-devel] Should we get rid of {surround21/surround41/surround50}.conf from alsa-lib?

[Tom Yan]

What I mean is, should we really by default set up PCMs that provide a
SUBSET of POSSIBLE channel configurations that IS BUILT and RELYS ON
ttable?

[tom at localhost ~]$ grep ttable /usr/share/alsa/pcm/surround*
/usr/share/alsa/pcm/surround21.conf:    ttable.0.FL 1
/usr/share/alsa/pcm/surround21.conf:    ttable.1.FR 1
/usr/share/alsa/pcm/surround21.conf:    ttable.2.LFE 1
/usr/share/alsa/pcm/surround41.conf:    ttable.0.FL 1
/usr/share/alsa/pcm/surround41.conf:    ttable.1.FR 1
/usr/share/alsa/pcm/surround41.conf:    ttable.2.RL 1
/usr/share/alsa/pcm/surround41.conf:    ttable.3.RR 1
/usr/share/alsa/pcm/surround41.conf:    ttable.4.LFE 1
/usr/share/alsa/pcm/surround50.conf:    ttable.0.FL 1
/usr/share/alsa/pcm/surround50.conf:    ttable.1.FR 1
/usr/share/alsa/pcm/surround50.conf:    ttable.2.RL 1
/usr/share/alsa/pcm/surround50.conf:    ttable.3.RR 1
/usr/share/alsa/pcm/surround50.conf:    ttable.4.FC 1

If we are really gonna provide them, why only these 3? What about:
surround30 (surround51 - RL - RR - LFE)
surround31 (surround51 - RL - RR)
surround60 (surround71 - FC - LFE, corresponds to surround40)
surround61 (surround71 - FC, corresponds to surround41)
surround70 (surround71 - LFE, corresponds to surround 50)

surround30 more or less corresponds to surround50 as well, and
surround31 doesn't even have the weirdness of using only either one
channel in the C/Sub port like the others.