Hi > I am trying to find the cause of a rather unusual regression between kernel v5.4 and v5.5, > for an out-of-tree driver on the raspberrypi. I think out-of-tree code needs update. We merged snd_pcm_ops into component between v5.4 - v5.5 e2cb4a14541dba3587bb78e0f62da27a0e1ad399 ("ASoC: soc-core: merge snd_pcm_ops member to component driver") And all drivers which used it was updated. For example, 1fddf424b3c49a475ca7c23662f515b53f884172 ("ASoC: mediatek: remove snd_pcm_ops") And snd_pcm_ops is no longer used on ALSA SoC e9067bb502787869dabe385727baff233024097b ("ASoC: soc-component: remove snd_pcm_ops from component driver") If your out-of-tree is using it, and not yet updated, some issue can be happen, I think. Thank you for your help !! Best regards --- Kuninori Morimoto