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Subject: Question about Tegra UCMs
To:     Mark Brown <broonie@kernel.org>, Jaroslav Kysela <perex@perex.cz>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Takashi Iwai <tiwai@suse.com>, Ion Agorria <ion@agorria.com>,
        Svyatoslav Ryhel <clamor95@gmail.com>,
        Frank Rowand <frowand.list@gmail.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        linux-tegra@vger.kernel.org, devicetree@vger.kernel.org,
        alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        Rob Herring <robh@kernel.org>
References: <20210518001356.19227-1-digetx@gmail.com>
 <20210518001356.19227-3-digetx@gmail.com>
 <20210518180949.GA949047@robh.at.kernel.org>
 <20210518183455.GE4358@sirena.org.uk>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <92cef674-c454-e08c-b44d-d8c08b1e8ccf@gmail.com>
Date:   Wed, 19 May 2021 01:31:28 +0300
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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