On Fri, Jan 19, 2024 at 12:24:18PM +0100, Johan Hovold wrote:
The UCM configuration for the Lenovo ThinkPad X13s has up until now been setting the speaker PA volume to the minimum -3 dB when enabling the speakers, but this does not prevent the user from increasing the volume further.
Limit the digital gain and PA volumes to a combined -3 dB in the machine driver to reduce the risk of speaker damage until we have active speaker protection in place (or higher safe levels have been established).
Note that the PA volume limit cannot be set lower than 0 dB or PulseAudio gets confused when the first 16 levels all map to -3 dB.
I tracked the down the root cause for this, which appears to be a bug (feature) in pulseaudio that causes it to reject the dB range if the maximum is negative:
https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/447
This happened to work with v3 which limited the PA volume to the single lowest setting, but would similarly break if anyone wants to set a -1.5 dB limit.
Johan