1.\"- 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2024 The FreeBSD Foundation 5.\" 6.\" Portions of this software were developed by Christos Margiolis 7.\" <christos@FreeBSD.org> under sponsorship from the FreeBSD Foundation. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd October 22, 2025 31.Dt SND_DUMMY 4 32.Os 33.Sh NAME 34.Nm snd_dummy 35.Nd Dummy audio driver 36.Sh SYNOPSIS 37To load the driver at boot time, place the following line in 38.Xr loader.conf 5 : 39.Bd -literal -offset indent 40snd_dummy_load="YES" 41.Ed 42.Sh DESCRIPTION 43The 44.Nm 45driver implements a virtual testing device, meaning it does not correspond to a 46physical sound card. 47It is intended for testing, so that test programs do not need to rely on 48hardware being present in the machine in order to run. 49.Pp 50The driver attaches as a regular 51.Xr sound 4 52device, with two channels (one playback and one recording), as well as a mixer. 53.Pp 54Playback works by discarding all input, and recording by returning silence 55(zeros). 56.Sh FILES 57.Bl -tag -width "/dev/dsp.dummy" -compact 58.It Pa /dev/dsp.dummy 59Alias to the device's 60.Pa /dev/dsp%d 61file created by 62.Xr sound 4 . 63This makes it easy for tests to open the dummy devic when there are more 64devices present in the system. 65.El 66.Sh SEE ALSO 67.Xr sound 4 , 68.Xr loader.conf 5 , 69.Xr loader 8 70.Sh AUTHORS 71The 72.Nm 73driver was implemented by 74.An Christos Margiolis Aq Mt christos@FreeBSD.org 75under sponsorship from the 76.Fx 77Foundation. 78.Sh CAVEATS 79Because the driver automatically attaches once the module is loaded, it can 80only be attached once. 81