AC97(4) BSD Kernel Interfaces Manual AC97(4)
ac97 -- generic AC'97 codec driver
AC'97 codecs contain the analog to digital (A/D), digital to analog
(D/A), and mixing circuitry of many modern sound cards. AC'97 codecs,
for the most part, do not talk to host buses like the PCI bus directly.
Instead, they communicate through an interface chip, called the host con-
troller. The Ensoniq AudioPCI 97 (see eap(4)) is an example of such a
Unlike many drivers, the ac97 driver does not appear in the configuration
file. Instead, the driver is automatically attached by the drivers that
auacer(4), auich(4), auixp(4), autri(4), auvia(4), clcs(4), clct(4),
eap(4), emu(4), esa(4), fms(4), maestro(4), neo(4), yds(4)
The ac97 driver does not keep track of the current user settings and
instead relies on the hardware to do this.
The ac97 driver could do more to detect mixer channels that don't work
and cull them from the list.
BSD March 24, 2017 BSD