Common ALSA module parameters look a little bit confusing because of the description lacking, and it took me a while to understand the purpose of their existence. To figure it out I asked the question about them to the "alsa-devel" mailing list, and Takashi Iwai answered me with the text I appended to the ALSA documentation in this patch.

These common module parameters aren't used a lot nowadays, but as I understand they are important for providing compatibility with some existing user-space apps. So in my opinion it is a good idea to document why we need them.

Signed-off-by: Ivan Orlov ivan.orlov0322@gmail.com --- Documentation/sound/alsa-configuration.rst | 13 +++++++++++++ 1 file changed, 13 insertions(+)

diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst index af71c68f1e4e..829c672d9fe6 100644 --- a/Documentation/sound/alsa-configuration.rst +++ b/Documentation/sound/alsa-configuration.rst @@ -133,6 +133,19 @@ enable enable card; Default: enabled, for PCI and ISA PnP cards

+These options are used for either specifying the order of instances or +controlling enabling and disabling of each one of the devices if there +are multiple devices bound with the same driver. For example, there are +many machines which have two HD-audio controllers (one for HDMI/DP +audio and another for onboard analog). In most cases, the second one is +in primary usage, and people would like to assign it as the first +appearing card. They can do it by specifying "index=1,0" module +parameter, which will swap the assignment slots. + +Today, with the sound backend like PulseAudio and PipeWire which +supports dynamic configuration, it's of little use, but that was a +help for static configuration in the past. + Module snd-adlib ----------------