Re: [alsa-devel] [PATCH] ASoC: core: add support to card re-bind/unbind using component framework

[Mark Brown <broonie@kernel.org>]

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On Thu, Jul 12, 2018 at 05:42:30PM +0200, Takashi Iwai wrote:
> Pierre-Louis Bossart wrote:
> > On 7/11/18 3:43 AM, Srinivas Kandagatla wrote:

> > > This patch aims at add achieving dynamic behaviour of audio card when
> > > the dependent components disappear and reappear.

> > Humm, no real comment on this patch proper but rather on how userspace
> > would deal with this dynamic behavior?
> > We had similar opens when we worked on the BYT/CHT HDMI stuff and
> > ended-up with quite a few issues in userspace (PulseAudio mainly)
> > related to dynamic behavior at the kernel level as a result of
> > plug/unplug. Also not sure how an Android HAL would deal with a card
> > disappearing temporarily if DSP resources become unavailable or
> > unresponsive. Any thoughts or guidance you might think of?

> Was the card-level register / unregister really problematic with PA?
> It's basically similar as the hotplug like USB, so I thought it would
> work as is.

Yeah, I'd expect normal desktop stuff to be able to cope with this due
to physically hotpluggable hardware.  The main use case for doing things
like this with module unload is in a development context where hopefully
people can also arrange to use a userspace that can cope or to do
whatever to reset it, any limitations in some userspace shouldn't prevent
people from having the facility available.

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