[alsa-devel] Best representation for TDM devices

[Maxime Ripard]

Hi,

I'm currently working on a device that has two Analog's ADAU7002
connected to an I2S/TDM Controller (sound/soc/sunxi/sun4i-i2s.c, with
some modifications), over the slots 1/2 and 3/4.

The capture itself is working fine, however I'm not quite sure about
the way to expose those streams to the userspace.

Since I have two codecs, I have two links (described through
simple-card) and thus two subdevices. However, the microphones
connected are really separate streams, so ideally (I guess?) we should
have 1 subdevice per microphone.

An alternative would be that we capture the whole 4 channels and use
dsnoop to demux them, but trying to use the device directly (using
arecord -D hw:0) results in the ioctl to change the number of channels
being rejected, I'm assuming because each codec only has 2 channels?

So I'm a bit lost at this point about how I should go and expose
this. I couldn't really find any similar setup either in the
kernel. Any preferred way of doing this?

Thanks!
Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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