FreeBSD manual
download PDF document: snd_uaudio.4.pdf
SND_UAUDIO(4) FreeBSD Kernel Interfaces Manual SND_UAUDIO(4)
NAME
snd_uaudio - USB audio and MIDI device driver
SYNOPSIS
To compile this driver into the kernel, place the following lines in your
kernel configuration file:
device sound
device usb
device snd_uaudio
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
snd_uaudio_load="YES"
DESCRIPTION
The snd_uaudio driver provides support for USB audio class devices and
USB MIDI class devices.
A USB audio device consists of a number of components: input terminals
(e.g. USB digital input), output terminals (e.g. speakers), and a number
of units in between (e.g. volume control).
Refer to the `USB Audio Class Specification' for more information.
SEE ALSO
sound(4), usb(4)
USB Audio Class Specifications,
http://www.usb.org/developers/docs/devclass_docs/.
HISTORY
The snd_uaudio driver first appeared in FreeBSD 4.7.
AUTHORS
This manual page was adopted from NetBSD 1.6 and modified for FreeBSD by
Hiten Pandya <hmp@FreeBSD.org>.
BUGS
The PCM framework in FreeBSD only supports synchronous device detach.
That means all mixer and DSP character devices belonging to a given USB
audio device must be closed when receiving an error on a DSP read, a DSP
write or a DSP IOCTL request. Else the USB audio driver will wait for
this to happen, preventing enumeration of new devices on the parenting
USB controller.
Some USB audio devices might refuse to work properly unless the sample
rate is configured the same for both recording and playback, even if only
simplex is used. See the dev.pcm.%d.[play|rec].vchanrate sysctls.
The PCM framework in FreeBSD currently doesn't support the full set of
USB audio mixer controls. Some mixer controls are only available as
dev.pcm.%d.mixer sysctls.
FreeBSD 14.0-RELEASE-p11 November 12, 2016 FreeBSD 14.0-RELEASE-p11