[alsa-devel] Channel mapping

Clemens Ladisch cladisch at fastmail.net
Wed Nov 21 16:17:41 CET 2007

Takashi Iwai wrote:
> Yes, querying channel mapping is another missing piece with popular
> demand.
> The implementation would be easy, I guess.  But we have to define the
> way to inform this from kernel to user space: whether create a new
> ioctl or extend the existing ones (if possible)...

It's just metadata that describes a PCM device, so I think we should use
TLV for this.

The existing struct snd_ctl_tlv uses a single integer to identify
control elements.  We could restrict control numid's to 31 bits and
use the upper bit to signal that this value includes device type and
device number in the lower bits, if we want to reuse the same TLV


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