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snd_hda — Intel High Definition Audio bridge device driver
To compile this driver into the kernel, place the following lines in your
kernel configuration file:
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
The High Definition (HD) Audio specification was developed by Intel as
the logical successor of the old AC'97 specification and has several
advantages, such as higher bandwidth which allows more channels and more
detailed formats, support for several logical audio devices, and general
purpose DMA channels.
The snd_hda driver is a HDA bus controller driver and HDA codecs audio
functions bridge driver that allows the generic audio driver, sound(4),
to be used with this hardware. Only audio functions are supported by
snd_hda. Modem and other possible functions are not implemented.
The snd_hda driver supports hardware that conforms with revision 1.0 of
the Intel High Definition Audio specification and tries to behave much
like the Microsoft Universal Audio Architecture (UAA) draft (revision
0.7b) for handling audio devices.
According to HDA and UAA specifications, depending on the number of HDA
buses and codecs present in system, their audio capabilities and BIOS
provided configuration, the snd_hda driver often provides several PCM
audio devices. For example, one device for main rear 7.1 output and
inputs, one device for independent headset connectors at front and one
device for SPDIF or HDMI audio input/output. The assignment of audio
inputs and outputs may be tuned with device.hints(5). The driver's
verbose boot messages provide a lot of information about the operation of
the driver and present audio setup.
The default audio device may be tuned by setting the hw.snd.default_unit
sysctl, as described in sound(4), or explicitly specified in application
The following variables are available at boot-time through the
hint.hdac.%d.config Configures a range of possible options.
Possible values are: “dmapos”, “eapdinv”,
“gpio0”, “gpio1”, “gpio2”, “gpio3”, “gpio4”,
“gpio5”, “gpio6”, “gpio7”, “gpioflush”,
“ivref”, “ivref50”, “ivref80”, “ivref100”,
“fixedrate”, “forcestereo”, “ovref”,
“ovref50”, “ovref80”, “ovref100”, “senseinv”,
“softpcmvol”, and “vref”. An option prefixed
with “no”, such as “nofixedrate”, will do the
opposite and takes precedence. Options can be
separated by whitespace and commas.
“GPIOs” are a codec's General Purpose I/O pins
which system integrators sometimes use to
control external muters, amplifiers and so on.
If you have no sound, or sound volume is not
adequate, you may have to experiment a bit
with the GPIO setup to find the optimal setup
for your system.
The “ivrefX” and “ovrefX” options control the
voltage used to power external microphones.
hint.hdac.%d.msi Controls MSI (Message Signaled Interrupts)
Overrides codec pin configuration set by BIOS.
May be specified as a 32-bit hexadecimal value
with a leading “0x”, or as a set of space-
separated “option=value” pairs.
Pin configuration is the UAA driver's main source of information about
codec usage. This information is usually provided by the codec
manufacturer and tuned by system integrators for specific system
requirements. The snd_hda driver allows users to override it to fix
integrator mistakes or to use the available codec in alternative ways
(for example to get stereo output and 2 inputs instead of a single 5.1
The following options are supported:
as Association number. Associations are used to group
individual pins to form a complex multi-pin device. For
example, to group 4 connectors for 7.1 output, or to treat
several input connectors as sources for the same input
device. Association numbers can be specified as numeric
values from 0 to 15. A value of 0 means disabled pin. A
value of 15 is a set of independent unassociated pins.
Each association includes only pins of the same direction
(in/out) and is detected atomically (all pins or none). A
separate PCM audio device is created for every pair of
input and output associations.
seq Sequence number. A unique, per-association number used to
order pins inside the particular association. Sequence
numbers can be specified as numeric values from 0 to 15.
For output assotiations sequence numbers encode speaker
pairs positions: 0 - Front, 1 - Center/LFE, 2 - Back, 3 -
Front Wide Center, 4 - Side. Standard combinations are:
(0) - Stereo; (0, 2), (0, 4) - Quadro; (0, 1, 2), (0, 1,
4) - 5.1; (0, 1, 2, 4) - 7.1.
The sequence number 15 has a special meaning for output
associations. Output pins with this number and device
type “Headphones” will duplicate (with automatic mute if
jack detection is supported) the first pin in that
device Device type. Can be specified as a number from 0 to 15 or
as a name: “Line-out”, “Speaker”, “Headphones,” “CD”,
“SPDIF-out”, “Digital-out”, “Modem-line”, “Modem-handset”,
“Line-in”, “AUX”, “Mic”, “Telephony”, “SPDIF-in”,
“Digital-in”, “Res.E”, or “Other”. The device type also
describes the pin direction (in/out). For example, “CD”
always means an input pin, while “Headphones” always means
conn Connection type. Can be specified as a number from 0 to
3. The connection type can also be specified as one of
the special names “Jack”, “None”, “Fixed”, or “Both”.
Pins with a connection type of “None” are disabled.
ctype Connector physical type. Can be specified as a number
from 0 to 15. This is a reference only value. It is
ignored by the snd_hda driver.
color Connector color. Can be specified as a number from 0 to
15 or as one of the names “Unknown”, “Black”, “Grey”,
“Blue”, “Green”, “Red”, “Orange”, “Yellow”, “Purple”,
“Pink”, “Res.A”, “Res.B”, “Res.C”, “Res.D”, “White”, or
“Other”. This is a reference only value. It is ignored
by the snd_hda driver.
loc Connector physical location. Can be specified as a number
from 0 to 63. This is a reference only value. It is
ignored by the snd_hda driver.
misc Misc bits. Can be specified as a number from 0 to 15.
Bit 0 has a special meaning. When set it means that jack
detection is not implemented in hardware.
The following sysctl(8) variables are available in addition to those
available to all sound(4) devices:
dev.hdac.%d.polling Enables polling mode. In this mode the driver
operates by querying the device state on timer
ticks using callout(9) instead of interrupts.
Polling is disabled by default. Do not enable
it unless you are facing weird interrupt
problems or if the device cannot generate
interrupts at all.
Controller/Jack Sense polling interval (1-1000
dev.hdac.%d.pindump Setting this to a non-zero value dumps the
current pin configuration, main capabilities
and jack sense status to console and syslog.
Taking HP Compaq DX2300 with Realtek ALC888 HDA codec for example. This
system has two audio connectors on a front side, three audio connectors
on a rear side and one internal speaker. According to verbose driver
output and the codec datasheet, this codec has five stereo DACs and two
stereo ADCs, all of them are routable to any codec pin (external
connector). All codec pins are reversible (could be configured either as
input or output).
So high codec uniformity and flexibility allow driver to configure it in
many different ways, depending on requested pins usage decribed by pins
configuration. The driver reports such default pin configuration when
verbose messages enabled:
hdac0: nid 20 0x01014020 as 2 seq 0 Line-out Jack jack 1 loc 1 color Green misc 0
hdac0: nid 21 0x99130110 as 1 seq 0 Speaker Fixed jack 3 loc 25 color Unknown misc 1
hdac0: nid 22 0x411111f0 as 15 seq 0 Speaker None jack 1 loc 1 color Black misc 1
hdac0: nid 23 0x411111f0 as 15 seq 0 Speaker None jack 1 loc 1 color Black misc 1
hdac0: nid 24 0x01a19830 as 3 seq 0 Mic Jack jack 1 loc 1 color Pink misc 8
hdac0: nid 25 0x02a1983f as 3 seq 15 Mic Jack jack 1 loc 2 color Pink misc 8
hdac0: nid 26 0x01813031 as 3 seq 1 Line-in Jack jack 1 loc 1 color Blue misc 0
hdac0: nid 27 0x0221401f as 1 seq 15 Headphones Jack jack 1 loc 2 color Green misc 0
hdac0: nid 28 0x411111f0 as 15 seq 0 Speaker None jack 1 loc 1 color Black misc 1
hdac0: nid 30 0x411111f0 as 15 seq 0 Speaker None jack 1 loc 1 color Black misc 1
hdac0: nid 31 0x411111f0 as 15 seq 0 Speaker None jack 1 loc 1 color Black misc 1
Here we can see, that the nodes with ID (nid) 25 and 27 are front panel
connectors (Jack, loc 2), nids 20, 24 and 26 are rear panel connectors
(Jack, loc 1) and nid 21 is a built-in speaker (Fixed, loc 25). Pins
with nids 22, 23, 28, 30 and 31 will be disabled by driver due to "None"
connectivity. So the pin count and description matches to connectors that
Using association (as) and sequence (seq) fields values pins are grouped
into 3 associations:
hdac0: Association 0 (1) out:
hdac0: Pin nid=21 seq=0
hdac0: Pin nid=27 seq=15
hdac0: Association 1 (2) out:
hdac0: Pin nid=20 seq=0
hdac0: Association 2 (3) in:
hdac0: Pin nid=24 seq=0
hdac0: Pin nid=26 seq=1
hdac0: Pin nid=25 seq=15
Each pcm(4) device uses two associations: one for playback and one for
recording. Associations processed and assigned to pcm(4) devices in
increasing numerical order. In this case association #0 (1) will become
pcm0 device playback, using the internal speakers and Headphones jack
with speaker automute on the headphones jack connection. Association #1
(2) will become pcm1 playback, using the Line-out jack. Association #2
(3) will become pcm0 recording, using the external microphones and the
The snd_hda driver provides extensive verbose messages to diagnose its
operation logic and describe its current codec configuration.
Using device.hints(5) it is possible to modify the configuration of the
existing pins, allowing a broad range of different audio setups. Here
are a few examples of some setups possible for this particular hardware:
Setting the device.hints(5) options
will swap line-out and speaker functions. So the pcm0 device will play
to the line-out and headphones jacks. Line-out will be muted on the
headphones jack connection. Recording on pcm0 will go from two external
microphones and line-in jacks. pcm1 playback will go to the internal
Setting the device.hints(5) options
hint.hdac.0.cad0.nid20.config="as=1 seq=15 device=Headphones"
will split the headphones and one of the microphones to a separate
device. The pcm0 device will play to the internal speaker and to the
line-out jack, with speaker automute on the line-out jack connection.
Recording on pcm0 will use input from one external microphone and the
line-in jacks. The pcm1 device will be completely dedicated to a headset
(headphones and mic) connected to the front connectors.
Setting the device.hints(5) options
hint.hdac.0.cad0.nid24.config="as=5 seq=0 device=Line-out"
will give 4 independent devices: pcm0 (line-out and line-in), pcm1
(headphones and mic), pcm2 (additional line-out via retasked rear mic
jack), and pcm3 (internal speaker).
Setting the device.hints(5) options
hint.hdac.0.cad0.nid24.config="as=1 seq=1 device=Line-out"
hint.hdac.0.cad0.nid26.config="as=1 seq=2 device=Line-out"
will give 2 devices: pcm0 for 5.1 playback via 3 rear connectors (line-
out and retasked mic and line-in) and headset (headphones and mic) at
front connectors. pcm1 for internal speaker playback. On headphones
connection rear connectors will be muted.
Depending on codec configuration, these controls and signal sources could
be reported to sound(4):
vol overall output level (volume)
rec overall recording level
igain input-to-output monitoring loopback level
ogain external amplifier control
pcm PCM playback
mix input mix
mic first external or second internal microphone input
monitor first internal or second external microphone input
line, line1, line2, line3
analog (line) inputs
dig1, dig2, dig3
digital (S/PDIF, HDMI or DisplayPort) inputs
cd CD input
speaker PC speaker input
phin, phout, radio. video
other random inputs
Controls have different precision. Some could be just an on/off triggers.
Most of controls use logarithmic scale.
The snd_hda driver supports many Intel HDA compatible audio chipsets
including the following:
· ATI SB450
· ATI SB600
· Intel 631x/632xESB
· Intel 82801F (ICH6)
· Intel 82801G (ICH7)
· Intel 82801H (ICH8)
· Intel 82801I (ICH9)
· Intel 82801J (ICH10)
· Intel US15W (SCH)
· nVidia MCP51
· nVidia MCP55
· nVidia MCP61A
· nVidia MCP61B
· nVidia MCP63
· nVidia MCP65A
· nVidia MCP65B
· nVidia MCP67A
· nVidia MCP67B
· nVidia MCP68
· nVidia MCP69
· nVidia MCP73
· nVidia MCP78
· nVidia MCP79
· nVidia MCP89
· SiS 966
· VIA VT8251/8237A
The following and many other codecs have been verified to work:
· Analog Devices AD1981HD
· Analog Devices AD1983
· Analog Devices AD1984
· Analog Devices AD1986A
· Analog Devices AD1988
· Analog Devices AD1988B
· CMedia CMI9880
· Conexant CX20549 (Venice)
· Conexant CX20551 (Waikiki)
· Conexant CX20561 (Hermosa)
· Realtek ALC260
· Realtek ALC262
· Realtek ALC268
· Realtek ALC660
· Realtek ALC861
· Realtek ALC861VD
· Realtek ALC880
· Realtek ALC882
· Realtek ALC883
· Realtek ALC885
· Realtek ALC888
· Realtek ALC889
· Sigmatel STAC9205
· Sigmatel STAC9220
· Sigmatel STAC9220D / 9223D
· Sigmatel STAC9221
· Sigmatel STAC9221D
· Sigmatel STAC9227D
· Sigmatel STAC9227X
· Sigmatel STAC9228D
· Sigmatel STAC9228X
· Sigmatel STAC9229D
· Sigmatel STAC9229X
· Sigmatel STAC9230D
· Sigmatel STAC9230X
· Sigmatel STAC9271D
· Sigmatel STAC9872AK
· VIA VT1708
· VIA VT1708B
· VIA VT1709
sound(4), snd_ich(4), device.hints(5), loader.conf(5), sysctl(8)
The snd_hda device driver first appeared in FreeBSD 6.3.
The snd_hda driver was written by Stephane E. Potvin
⟨firstname.lastname@example.org⟩, Ariff Abdullah ⟨ariff@FreeBSD.org⟩ and Alexander
Motin ⟨mav@FreeBSD.org⟩. This manual page was written by Joel Dahl
⟨joel@FreeBSD.org⟩, Alexander Motin ⟨mav@FreeBSD.org⟩ and Giorgos
A few Hardware/OEM vendors tend to screw up BIOS settings, thus rendering
the snd_hda driver useless, which usually results in a state where the
snd_hda driver seems to attach and work, but without any sound. Some of
that cases can be solved by tuning loader.conf variables. But before
trying to fix problem that way, make sure that problem is really exists
and the PCM audio device you are using really corresponds to expected
Some vendors use non-standardized General Purpose I/O (GPIO) pins of
codec to control external amplifiers. In some cases setting proper
combination of GPIO bits may be needed to make sound work on specific
HDMI and DisplayPort audio may also require support from video driver.