set_hardware_volume attached the mixer to the stream's raw PCM id
(iec958:/hdmi:/front:/DEV-qualified hw:) — snd_mixer_attach needs the
per-card ctl device, so hardware volume silently no-oped on plugin-alias
devices (HiFiBerry Digi as iec958:CARD=sndrpihifiberry,DEV=0). Derive
hw:CARD=<name> / hw:<n> first. With this, qbzd's 'Hardware volume'
toggle reaches the DAC's mixer control (e.g. 'Digital') as intended;
with the toggle off, ALSA Direct stays fixed-volume by design
(bit-perfect, no software gain).
km
vicrodh
def93528bc