Re: [RFC PATCH 0/3] ASoC: tegra: ASRC control fixes and ratio caching

[Thierry Reding]

On Mon, Sep 21, 2026 at 08:57:01AM +0000, Sheetal wrote:
> This RFC series updates the Tegra186 ASRC driver control handling.
> 
> The main RFC point is the userspace-visible ALSA mixer control ABI
> change in patch 2. The existing per-stream controls expose the software
> ratio as separate integer and fractional mixer controls. This series
> replaces each pair with one two-value mixer control so userspace updates
> the integer and fractional parts together. That avoids programming a
> transient mixed ratio to hardware, but it does require userspace that
> sets ASRC software ratios to switch to the new paired controls.

Given the ABI change, do we have a good understanding of who might be
using these features? My understanding is that these are used for the
setup of hardware pipelines involving sample rate conversions. So these
are likely not your regular users that just want to change the volume
for headphones and such. This is for highly specific use-cases. Do we
know if people use extra userspace software on top of ALSA to set these
up, or are they typically dealing with fixed configuration files for
specifying these values?

So essentially to be able to better understand how to proceed it'd be
good to know what the upgrade path is for this. How easy or difficult
will it be for people to transition to this? Can we transition them
automatically by keeping write-only backwards-compatibility controls
that mirror the old ABI and maybe provide a hint that people should be
upgrading to the new controls?

Since we expect this to also fix the occasional glitch caused by
mismatched ratios, I think we really want this, but we need to make sure
users aren't left in the dark about such changes and have a reasonable
upgrade path.

Mark, Liam, do you have any guidelines on how to handle such ABI
changes?

Thierry

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