[alsa-devel] [PATCH v2] ASoC: max98090: save and restore SHDN when changing sensitive registers

[Mark Brown]

On Fri, Dec 13, 2019 at 02:05:32AM +0800, Tzung-Bi Shih wrote:

> I have no enough resources to test and trace the code temporarily.
> But is it possible:
> - snd_card_new( ) succeed in snd_soc_bind_card( ), so that userspace
> can see the control

This feels like snd_card_new() is being overly enthusiastic here, I'd
expect that we might have other problems elsewhere with that.  I'd not
expect userspace to see things until snd_card_register() since between
_new() and that we're in the process of building the card up.  Given
this we *will* need to handle partially constructed cards after all,
unless we change the ALSA core.  Takashi?

> - code in later snd_soc_bind_card( ) decided to defer the probe
> - soc_cleanup_card_resources( ) may forget to clean the control?  (not
> sure about this)

There's going to be a race condition where userspace can see the control
on the partially built card regardless of if it gets cleaned up or not.
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