[megous]

Proper codec driver would be heavily abstracted though. I2C hidden behind regmap. Regmap mostly hidden behind ALSA kcontrol API. A lot of codec drivers consist mostly of tables of mappings between abstract controls and register locations/values. Not very exciting stuff. Finding an acquirable SoC that doesn't have DAI driver implemented may also be a challenge.

But why not I guess. :)

Camera sensor drivers are a bit less abstracted and many sensors don't have upstream drivers. But there's also a lack of quality documentation for HW in this area, oftentimes... v4l2 API is a bit more approachable than alsa PCM API, IMO. And on advanced SoCs you can pass around video buffers bewteen various v4l2 mem2mem devices to transform/process the data in HW. Drivers for HW acceleration of image or video data processing are seldom exercised in all their features, so there are many bugs there waiting to be squashed, and features to be implemented. It's a deep rabbit hole.

[cushychicken]

Anywhere is a good place to start.

Let the fella learn.