[alsa-devel] [PATCH 0/6] ASoC: improve codec to codec link support

[Jerome Brunet]

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(-)

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2.21.0