SND_UAUDIO(4) MidnightBSD Kernel Interfaces Manual SND_UAUDIO(4)


snd_uaudio — USB audio device driver


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):



The snd_uaudio driver provides support for USB audio 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.


sound(4), usb(4)

USB Audio Class Specifications

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The snd_uaudio driver first appeared in FreeBSD 4.7.


This manual page was adopted from NetBSD 1.6 and modified for FreeBSD by Hiten Pandya 〈〉.


The PCM framework in FreeBSD, as of this writing, does not handle device un-registrations in a properly abstracted manner, i.e., a detach request is refused by the PCM framework if the device is in use. For USB and supposedly other detach-able busses, it is necessary to allow the device un-registration to complete successfully, otherwise the driver leaves wild pointers to invalid data structures and thus leading to a panic.

MidnightBSD 0.3 December 15, 2005 MidnightBSD 0.3