Hi Amadeusz,
On the product I am working on, a hostless PCM device is defined for purpose of activating CODEC driver to setup the path inside CODEC. So, CPU DAI and PCM Platform are defined to use dummy dai & DMA supplied by sound/soc/soc-utils.c.
After upgrading to newer kernel, hostless PCM device failed to open. After doing a bit of digging, the root cause is that dummy_dma_hardware is not set in dummy_dma_open() due to new conditional check logic introduced in this commit - 6c504663ba2ee2abeaf5622e27082819326c1bd4.
In order to fix problem I am encountering properly without regressing your scenario, I would like to get a better understanding of problem you were addressing. My understanding, from looking through other drivers under sound/soc, is that pcm hardware info is usually set by PCM platform/DMA drivers. For your scenario, do you have other component e.g CPU/CODEC DAI, set PCM hardware definition? I am not sure conditional check logic from 6c504663ba2ee2abeaf5622e27082819326c1bd4 guarantees that other component would be setting pcm hardware info. Appreciate if you can provide more insight to your scenario?
Thanks Patrick