linux-kernel - Re: [PATCH] ASoC: atmel: mchp-pdmc: Skip ALSA restoration if substream runtime is uninitialized

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Message-ID: <20240924112542.78321-1-andrei.simion@microchip.com>
Date: Tue, 24 Sep 2024 14:25:44 +0300
From: Andrei Simion <andrei.simion@...rochip.com>
To: <broonie@...nel.org>
CC: <alexandre.belloni@...tlin.com>, <alsa-devel@...a-project.org>,
	<andrei.simion@...rochip.com>, <claudiu.beznea@...on.dev>,
	<lgirdwood@...il.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-sound@...r.kernel.org>,
	<nicolas.ferre@...rochip.com>, <perex@...ex.cz>, <tiwai@...e.com>
Subject: Re: [PATCH] ASoC: atmel: mchp-pdmc: Skip ALSA restoration if substream runtime is uninitialized

On 24.09.2024 11:59, Mark Brown wrote:
> 
> 
> On Tue, Sep 24, 2024 at 11:12:38AM +0300, Andrei Simion wrote:
> 
>> Update the driver to prevent alsa-restore.service from failing when
>> reading data from /var/lib/alsa/asound.state at boot. Ensure that the
>> restoration of ALSA mixer configurations is skipped if substream->runtime
>> is NULL.
>> +++ b/sound/soc/atmel/mchp-pdmc.c
>> @@ -302,6 +302,9 @@ static int mchp_pdmc_chmap_ctl_put(struct snd_kcontrol *kcontrol,
>>	if (!substream)
>>		return -ENODEV;
>>
>> +	if (!substream->runtime)
>> +		return 0; /* just for avoiding error from alsactl restore */
>> +
> This then means that control writes are just discarded which presumably
> is going to upset things if they actually saved a value here.  Why is
> that a good choice, rather than either fixing the race so the card
> doesn't come up too early or removing the need for the runtime?

Ok. I understand. My first intention was to follow the
https://github.com/torvalds/linux/blob/master/sound/hda/hdmi_chmap.c#L794
but after your point of view, I intend to return -EAGAIN in V2
to specify the substream->runtime is not ready.

I retested: configured pdmc, then reboot the board and the configuration:
as a result the configuration kept.

alsa-restore.service status success.

Do you think this solution is enough?

Thank you and best regards,
Andrei Simion