Re: [RFC PATCH] ALSA: pci: add PreSonus Quantum PCI driver

[Markus Elfring]

…
> +++ b/sound/pci/quantum/quantum_dma.c
> @@ -0,0 +1,853 @@
…
> +static ssize_t cpu_latency_us_store(struct device *dev,
> +				    struct device_attribute *attr,
> +				    const char *buf, size_t count)
> +{
…
> +	mutex_lock(&chip->dma_mutex);
> +	chip->cpu_latency_us = value;
> +	if (READ_ONCE(chip->stream_active))
> +		quantum_cpu_latency_qos_apply(chip);
> +	mutex_unlock(&chip->dma_mutex);
> +
> +	return count;
> +}
…

Under which circumstances would you become interested to apply a statement
like “guard(mutex)(&chip->dma_mutex);”?
https://elixir.bootlin.com/linux/v7.2/source/include/linux/mutex.h#L253

Regards,
Markus