[PATCH v2 0/6] ASoC: improve codec to codec link support

From: Jerome Brunet
Date: Thu Jul 25 2019 - 14:08:38 EST

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()

Changes since v1 [1]:
* Fix rebase on Murimoto-san's patches
* Allocate params dynamically again and refactor the pre_pmu code to
simplify the error handling and rollback a bit

[0]: https://lkml.kernel.org/r/20190515131858.32130-1-jbrunet@xxxxxxxxxxxx
[1]: https://lkml.kernel.org/r/20190724162405.6574-1-jbrunet@xxxxxxxxxxxx

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 | 220 +++++++++++++++++++++++++++----------------
sound/soc/soc-pcm.c | 35 ++++++-
3 files changed, 182 insertions(+), 115 deletions(-)