linux-kernel - Question about Tegra UCMs

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Date:   Wed, 19 May 2021 01:31:28 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Takashi Iwai <tiwai@...e.com>, Ion Agorria <ion@...rria.com>,
        Svyatoslav Ryhel <clamor95@...il.com>,
        Frank Rowand <frowand.list@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-tegra@...r.kernel.org, devicetree@...r.kernel.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh@...nel.org>
Subject: Question about Tegra UCMs

Mark, could you please help me to understand the UCM naming scheme that ALSA uses..

About a year ago I tried to complain to Jaroslav Kysela in a comment to the UCM change [1] that it should be breaking the naming scheme of Tegra UCMs, but haven't got a meaningful reply and moved on to other things.

[1] https://github.com/alsa-project/alsa-ucm-conf/commit/8ff2d50745efbb6959324f672460e413f0b618b8

Today I noticed that the naming scheme changed again and I still don't understand what to do about it.

I have two devices:

 1. Acer Picasso tablet that uses "Acer Iconia Tab A500 WM8903" for the card model name.

 2. Google Nexus 7 that uses "ASUS Google Nexus 7 ALC5642".

Previously UCMs were picked up by pulseaudio from these paths:

 1. /usr/share/alsa/ucm2/Acer Iconia Tab A500 WM8903/
 2. /usr/share/alsa/ucm2/ASUS Google Nexus 7 ALC5642/

Now the lookup paths are changed to:

 1. /usr/share/alsa/ucm2/Acer_Iconia_Tab/
 2. /usr/share/alsa/ucm2/ASUS_Google_Nex/

Strace shows that pulseaudio searches UCMs only at these paths.

The output of /proc/asound/cards:

 0 [WM8903         ]: Acer_Iconia_Tab - Acer Iconia Tab A500 WM8903
                      Acer Iconia Tab A500 WM8903

 0 [ALC5642        ]: ASUS_Google_Nex - ASUS Google Nexus 7 ALC5642
                      ASUS Google Nexus 7 ALC5642

IIUC, the "ucm2/Tegra/codec_name" scheme [2] that the current ALSA UCM uses simply doesn't work at all. Is there anything on the kernel side that I could change to get a working naming scheme? If yes, I may try to do something about it in the v2, thanks in advance.

[2] https://github.com/alsa-project/alsa-ucm-conf/tree/master/ucm2/Tegra