On Fri, 24 May 2019 01:39:45 +0200, Pierre-Louis Bossart wrote:
This is the second take on same problem of detecting when the HDaudio legacy driver can be used and when the SST or SOF drivers are required.
The previous attempt based on a the PCI Class information was a resounding failure and broke audio on Linus' laptop, so we need additional information to avoid enabling a DSP-based driver without a good reason to do so.
This patchset suggests the use of the NHLT information which *in theory* exposes DMIC endpoints. The legacy HDaudio driver cannot handle DMICs and will not provide any capture capabilities. Since it's typically the first one to probe due to the Makefile order, aborting the probe will let the PCI subsystem look for the next driver which hopefully will support this capability.
I tested this patch on 5 devices (SKL, KBL, APL, GLK, WHL), three without DMICs and two with, and the detection seems to work as planned. I would appreciate it if HDaudio integrators and folks at Google/Canonical/Endless can give this a try. As usual I expect that we will have to use quirks and work-arounds, but it'd be a better idea than a build-time mutual exclusion. We could also make this optional (Kconfig and/or module parameters) if people prefer to muck with blacklists.
Feedback and comments welcome!
The general idea and suggested implementation look almost good to me. Of course we have to provide a way to override the default behavior in case of buggy BIOS (I bet a drink for the existence of such :)
thanks,
Takashi