linux-kernel - Re: [PATCH 05/11] ALSA: hda/cs35l56: Create sysfs files for factory calibration

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Message-ID: <14617d69-7312-418f-abd9-3c65a84f8421@opensource.cirrus.com>
Date: Thu, 16 Oct 2025 12:58:15 +0100
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.de>
Cc: tiwai@...e.com, linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH 05/11] ALSA: hda/cs35l56: Create sysfs files for factory
 calibration

On 16/10/2025 12:27 pm, Mark Brown wrote:
> On Thu, Oct 16, 2025 at 01:01:41PM +0200, Takashi Iwai wrote:
>> Richard Fitzgerald wrote:
> 
>>> Create sysfs files that can be used to perform factory calibration.
> 
>> What kind of data format should be written to calibrate sysfs entry?
>> Since those are no trivial files, we may need to document the
>> formats.
> 
> This feels like it might be a better fit for debugfs or possibly
> configfs?  It's not really within the sysfs rules, and especially
> debugfs is a lot more relaxed about everything.
> 

debugfs is an easy change in the driver but more complex for the
tooling. Unlike sysfs there's no standard layout or naming convention
for the ASoC debugfs tree, so it's more troublesome to locate the amp
entries.

ASoC creates a debugfs root by default if DEBUGFS is enabled. But HDA
doesn't have its own debugfs. There is an ALSA debugfs enabled by
CONFIG_SND_DEBUG, which is normally disabled. But enabling
CONFIG_SND_DEBUG has other side-effects, it enables more than debugfs.

Or we could create a new debugfs node specifically for Cirrus Logic
directly in /sys/kernel/debug.

I'll have a look at configfs. Although it works backwards (userside
must create the directory in which attributes will appear) it might
have some benefits.