On Nov 6 2016 22:43, Arnaud Pouliquen wrote:
Well, as a glance of ALSA SoC core, we have a call of 'struct
snd_soc_card.late_probe()' just before 'snd_card_register()'. We can
probably add ad-hoc control element sets for each PCM character devices.
snd_soc_register_card()
->snd_soc_instantiate_card()
->soc_bind_dai_link()
->soc_probe_link_dais()
->snd_soc_add_card_controls()
->struct snd_soc_card.late_probe()
->snd_card_register()
But it seems to be a bit cumbersome. I think it better to add a smart
framework for the PCM-related controls. In this point, I agree with your
direction.
Another point is that, at least in theory, a DAI driver can add a
control after card creation. In this case PCM control should also be
associated to PCM device. Late probe could not handle it.
I don't think so. But in your case, 'snd-soc-simple-card' is used to
maintain own sound card instance, and this module has no handlers for
the callback. So we don't utilize the callback for this aim unless
integrating the module.
If we are aligned on direction, what is your suggestion to continue
discussion?
Do you want to continue discussion based on [RFC 1/4] ASoC: core: allow
PCM control binding to PCM device?
Other?
If you focused on ALSA SoC part only, I'd not continue this discussion
more. I'm not a developer for the part, and join in this discussion just
for ALSA control interface.
I have not upstreamed my card conf file but an example is available at
end of my mail.
Value of the device field must be aligned with ASoC driver device values:
HDMI: STI-B2120.pcm.hdmi.0.hooks.0.device=0
SPDIF: STI-B2120.pcm.iec958.0.hooks.0.device=3
If these controls were associated to the PCM device, I should not have
to fix the value but I should be able to retrieve it.
As long as I know, 'pcm/iec958.conf' and 'pcm/hdmi.conf' use different
strategy to handle PCM-related control element set for IEC958 type. Your
configuration does not work well for pcm.iec958 plugin.
Please could you detail?
HDMI supports more configurations than SPDIF (e.g HBRA). Furthermore
application can retrieve HDMI sinks capability with EDID. So full agree
that strategy can be different. That's why Two IEC controls are needed.
But focusing on 'pcm/iec958.conf' and 'pcm/hdmi.conf', they are almost
identical...
I prefer discuss after deciding your approach on kernel side. But in
previous message I misunderstood that S/PDIF interface of your STI SoC
in system side can handle IEC 60958 sub-frame. Actually, it seems not to
be. In this case, usage of pcm hook for 'ctl_elems' type might be
appropriate. I'm sorry to have confused you.
Regards
Takashi Sakamoto
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