[alsa-devel] [PATCH 1/2] ASoC: max98090: fix incorrect helper in max98090_dapm_put_enum_double()

[Tzung-Bi Shih]

On Wed, Jan 8, 2020 at 7:50 PM Marek Szyprowski
<m.szyprowski at samsung.com> wrote:
> Fixes: 62d5ae4cafb7 ("ASoC: max98090: save and restore SHDN when changing sensitive registers")
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
Reviewed-by: Tzung-Bi Shih <tzungbi at google.com>

Thanks for finding and fixing the bug.

The fix also reminded me: there are two possible "context" to call
max98090_dapm_put_enum_double( ): DAPM and userspace mixer control.
- max98090_shdn_save( ) is designed for mixer control because it
acquires dapm_mutex.
- max98090_shdn_save_locked( ) is designed for DAPM without acquiring lock.

Current code:
> +static int max98090_dapm_put_enum_double(struct snd_kcontrol *kcontrol,
[snip]
> + max98090_shdn_save(max98090);
> + ret = snd_soc_dapm_put_enum_double(kcontrol, ucontrol);
> + max98090_shdn_restore(max98090);

Should it cause a deadlock if DAPM calls the
max98090_dapm_put_enum_double( )?  I didn't see a deadlock last time I
tested the series.  Will do further analysis on this.