[pulseaudio-discuss] [RFC PATCH 0/3] alsa: Support for only-multichannel devices

[David Henningsson]

This should allow us to automatically probe devices using the recent
firewire drivers, as well as some USB devices people have been asking
about lately.

Sorry that it has taken some time since I said I would work on this patch
set, and I've rewritten and rethought it as well a few times. Anyway, here's
a proposal.

 * Exact-channels can be set to false to allow devices to be opened with
   any channel count instead of just the one specified in the channel map.
   PA will make a standard ALSA channel map for the additional channels.

 * Fallback profiles will only be considered if all other profiles fail.

 * Then we add a "generic" fallback profile without the exact-channel restriction.
   We don't want this "generic" profile to show up for normal devices, hence
   the fallback logic.

It's the fallback stuff I'm most unsure about, e g if things can be fallback
in one direction but not the other, this algorithm is not perfect.
This probably needs another patch revision, but I'm sending this out for your
additional comments, thoughts and (hopefully) testing.

I'm also unsure of what ports (if any) to add for the generic mapping, and if it 
should be called "multichannel" instead of "generic", or something else.

David Henningsson (3):
  alsa: Add "exact-channels" mapping configurability
  alsa: Allow "fallback" configuration for mappings and profiles
  alsa: Add a generic fallback mapping

 src/modules/alsa/alsa-mixer.c                    | 79 +++++++++++++++++++++++-
 src/modules/alsa/alsa-mixer.h                    |  3 +
 src/modules/alsa/mixer/profile-sets/default.conf | 15 ++++-
 3 files changed, 92 insertions(+), 5 deletions(-)

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1.9.1