As explained in this previous series [0], on Amlogic, we are using codec to codec links to deal with the glue which is between the i2s backends and the synopsys hdmi controller.
This worked well until I tried to .get_eld() support in the dw-hdmi-i2s driver. Doing so adds channel mapping controls to the codec. This shown several problem
1) .pcm_new() is not called on codec to codec links. struct snd_soc_pcm_runtime do not even have a valid .pcm 2) struct snd_pcm_substream and struct snd_pcm_runtime are ephemeral This is a problem if a control needs to access them
The goal of this patchset is to resolve the above issues and improve the codec to codec link support enough to correctly handle the hdmi-codec
The support of these codec to codec links could probably be improved in the future to behave like any other link and use soc_pcm_open(), soc_pcm_hw_params(), etc...
The challenge lies in the dapm mutex. The soc_pcm call dapm function locking this mutex but the dapm mutex is already held in snd_soc_dai_link_event()
[0]: https://lkml.kernel.org/r/20190515131858.32130-1-jbrunet@baylibre.com
Jerome Brunet (6): ASoC: codec2codec: run callbacks in order ASoC: codec2codec: name link using stream direction ASoC: codec2codec: deal with params when necessary ASoC: create pcm for codec2codec links as well ASoC: codec2codec: remove ephemeral variables ASoC: codec2codec: fill some of the runtime stream parameters
sound/soc/soc-core.c | 42 +++------- sound/soc/soc-dapm.c | 186 +++++++++++++++++++++++++++---------------- sound/soc/soc-pcm.c | 35 +++++++- 3 files changed, 162 insertions(+), 101 deletions(-)