[alsa-devel] Question about struct snd_soc_dai() :: cpu_dai->codec

[Takashi Iwai]

On Thu, 28 Jul 2016 22:33:31 +0200,
Lars-Peter Clausen wrote:
> 
> On 07/28/2016 05:46 AM, Vinod Koul wrote:
> > On Wed, Jul 27, 2016 at 10:22:41PM +0200, Takashi Iwai wrote:
> >> On Wed, 27 Jul 2016 20:22:33 +0200,
> >> Mark Brown wrote:
> >>>
> >>> On Wed, Jul 27, 2016 at 08:11:49PM +0200, Takashi Iwai wrote:
> >>>
> >>>> I'm wondering whether it's a better option to block the unbind
> >>>> behavior, either in driver base (allowing to return an error) or in
> >>>> the sound side (waiting in remove() until the sane point). 
> >>>
> >>> That's certainly going to be a lot easier and part of the reason it's
> >>> never been looked at much is that (unlike USB) there's very little
> >>> reason why an ASoC sound card would ever be hotplugged - even in
> >>> development these days the normal development flow involves rebooting.
> > 
> > I agree, it makese no sense for devices to be hotplugged. And for
> > developement flows people can do rmmond and insmod. That works fine!
> 
> I don't agree. In my opinion hot-plug is an essential feature of a
> modern device driver framework and if ASoC wants to claim to fall in
> this category we ought to support it. Hotplug is something that always
> pops up sooner or later. E.g. if someone puts a ASoC supported CODEC on
> a hot-pluggable device (maybe USB) we don't want to duplicate the code,
> but be able to reuse.
> 
> One area that e.g. requires hot-plug/-unplug and were ASoC supported
> devices are used is embedded development boards that support shields and
> devicetree overlays. Like e.g. RPI and similar.
> 
> The reason why we don't support hot-unplug in ASoC at the moment is
> because it is not trivial to implement and nobody has cared enough yet.
> 
> But if somebody wants to and has the resources to implement this we
> should not discourage this.
> 
> I'd very much prefer to have proper hot-plug support instead of
> prohibiting unbinding even on systems that do not require hot-plug
> support normally. It's a much cleaner solution.

Well, but hot-unplugging only a component like codec would be needed
in a real scenario?  It's a different story from the hotplug in the
card level.


Takashi