[RFC PATCH] ASoC: mediatek: mt8192-mt6359: fix device_node leak

[Tzung-Bi Shih]

On Tue, Dec 14, 2021 at 12:00 PM Tzung-Bi Shih <tzungbi at google.com> wrote:
> Option 1. Machine driver makes sure the object is valid until registered
>
> This patch adopts the option.  It needs snd_soc_register_card() to call
> of_node_get() somewhere to hold the reference count of of_node.  However,
> I failed to find similar logic in soc-core.c.
>
> Option 2. Machine driver borrows the reference count
>
> This is what [1] adopts.  Decreasing the reference count in device's
> remove() to make sure the object is valid for whole sound card's lifecycle.
>
> [1]: https://elixir.bootlin.com/linux/v5.16-rc5/source/sound/soc/mediatek/mt8195/mt8195-mt6359-rt1019-rt5682.c#L1065

I guess I have found the answer to my original questions.  The of_node
in snd_soc_dai_link_component in snd_soc_dai_link is mainly for
matching the component[4].  snd_soc_component itself should hold the
reference count.

[4]: https://elixir.bootlin.com/linux/v5.16-rc6/source/sound/soc/soc-core.c#L749

In summary:
- ASoC doesn't need to hold the device_node reference counts.
- Device nodes can be released after components have bound.