Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
SND_HDA(4)             FreeBSD Kernel Interfaces Manual             SND_HDA(4)

     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:

           device sound
           device snd_hda

     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 includes HDA bus controller driver (hdac), HDA codec
     driver (hdacc) and HDA codecs audio functions bridge driver (hdaa) 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) or sysctl(8).  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

   Boot-time Configuration
     The following variables are available at boot-time through the
     device.hints(5) file:

           hint.hdac.%d.config      Configures a range of possible controller
                                    options.  Possible values are: ``64bit'',
                                    ``dmapos'', ``msi''.  An option prefixed
                                    with ``no'', such as ``nomsi'', will do
                                    the opposite and takes precedence.
                                    Options can be separated by whitespace and

           hint.hdac.%d.msi         Controls MSI (Message Signaled Interrupts)

                                    Same as hint.hdaa.%d.nid%d.config

           hint.hdaa.%d.config      Configures a range of possible audio
                                    function options.  Possible values are:
                                    ``eapdinv'', ``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.

                                    The ``eapdinv'' option inverts External
                                    Amplifier Power Down signal.  The
                                    ``fixedrate'' denies all sampling rates
                                    except 48KHz.  The ``forcestereo'' denies
                                    mono playback/recording.  The ``senseinv''
                                    option inverts jack sensing logic.  The
                                    ``ivrefX'' and ``ovrefX'' options control
                                    the voltage used to power external

                                    Overrides audio function GPIO pins
                                    configuration set by BIOS.  May be
                                    specified as a set of space-separated
                                    ``num=value'' pairs, where num is GPIO
                                    line number, and value is one of:
                                    ``keep'', ``set'', ``clear'', ``disable''
                                    and ``input''.

                                    ``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.

                                    Overrides audio function 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.

           hint.pcm.%d.rec.autosrc  Controls automatic recording source
                                    0   disabled,
                                    1   once on attach,
                                    2   enabled.
                                    When enabled, driver will automatically
                                    set recording source of the mixer to
                                    connected input using jack presence
                                    detection statuses.

     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
                        input/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.

                        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 association.

                        The sequence numbers 14 and 15 has a special meaning
                        for input associations.  Their presence in association
                        defines it as multiplexed or mixed respectively.  If
                        none of them are present and there are more than one
                        pin in association, the association will provide
                        multichannel input.

                        For multichannel input/output associations sequence
                        numbers encode channel 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.

           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 an output.

           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.

   Runtime Configuration
     The following sysctl(8) variables are available in addition to those
     available to all sound(4) devices:

           dev.hdac.%d.pindump             Setting this to a non-zero value
                                           dumps the current pin
                                           configuration, main capabilities
                                           and jack sense status of all audio
                                           functions on the controller to
                                           console and syslog.

           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.

           dev.hdaa.%d.config              Run-time equivalent of the
                                           hint.hdaa.%d.config tunable.

           dev.hdaa.%d.gpi_state           Current state of GPI lines.

           dev.hdaa.%d.gpio_state          Current state of GPIO lines.

           dev.hdaa.%d.gpio_config         Run-time equivalent of the
                                           hint.hdaa.%d.gpio.config tunable.

           dev.hdaa.%d.gpo_state           Current state of GPO lines.

           dev.hdaa.%d.nid%d_config        Run-time equivalent of the
                                           hint.hdaa.%d.nid%d.config tunable.

           dev.hdaa.%d.nid%d_original      Original pin configuration written
                                           by BIOS.

           dev.hdaa.%d.reconfig            Setting this to a non-zero value
                                           makes driver to destroy existing
                                           pcm devices and process new pins
                                           configuration set via

 , dev.pcm.%d.rec.32bit
                                           HDA controller uses 32bit
                                           representation for all samples of
                                           more then 16 bits.  These variables
                                           allow to specify how many bits of
                                           these 32 should be used by CODEC.
                                           Depending on codec capabilities,
                                           possible values are 20, 24 and 32
                                           bit.  The default value is 24.

           dev.pcm.%d.rec.autosrc          Run-time equivalent of the
                                           hint.pcm.%d.rec.autosrc tunable.

     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 described by pins
     configuration.  The driver reports such default pin configuration when
     verbose messages enabled:

     hdaa0: nid   0x    as seq device       conn  jack    loc        color   misc
     hdaa0: 20 01014020 2  0  Line-out      Jack  1/8     Rear       Green   0
     hdaa0: 21 99130110 1  0  Speaker       Fixed ATAPI   Onboard    Unknown 1
     hdaa0: 22 411111f0 15 0  Speaker       None  1/8     Rear       Black   1 DISA
     hdaa0: 23 411111f0 15 0  Speaker       None  1/8     Rear       Black   1 DISA
     hdaa0: 24 01a19830 3  0  Mic           Jack  1/8     Rear       Pink    8
     hdaa0: 25 02a1983f 3  15 Mic           Jack  1/8     Front      Pink    8
     hdaa0: 26 01813031 3  1  Line-in       Jack  1/8     Rear       Blue    0
     hdaa0: 27 0221401f 1  15 Headphones    Jack  1/8     Front      Green   0
     hdaa0: 28 411111f0 15 0  Speaker       None  1/8     Rear       Black   1 DISA
     hdaa0: 30 411111f0 15 0  Speaker       None  1/8     Rear       Black   1 DISA
     hdaa0: 31 411111f0 15 0  Speaker       None  1/8     Rear       Black   1 DISA

     Here we can see, that the nodes with ID (nid) 25 and 27 are front panel
     connectors (Jack, Front), nids 20, 24 and 26 are rear panel connectors
     (Jack, Rear) and nid 21 is a built-in speaker (Fixed, Onboard).  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
     we have.

     Using association (as) and sequence (seq) fields values pins are grouped
     into 3 associations:

     hdaa0: Association 0 (1) out:
     hdaa0:   Pin nid=21 seq=0
     hdaa0:   Pin nid=27 seq=15
     hdaa0: Association 1 (2) out:
     hdaa0:   Pin nid=20 seq=0
     hdaa0: Association 2 (3) in:
     hdaa0:   Pin nid=24 seq=0
     hdaa0:   Pin nid=26 seq=1
     hdaa0:   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
     Line-in jack.

     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:

   Example 1
     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

   Example 2
     Setting the device.hints(5) options

     hint.hdac.0.cad0.nid20.config="as=1 seq=15 device=Headphones"
     hint.hdac.0.cad0.nid27.config="as=2 seq=0"
     hint.hdac.0.cad0.nid25.config="as=4 seq=0"

     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.

   Example 3
     Setting the device.hints(5) options

     hint.hdac.0.cad0.nid20.config="as=1 seq=0"
     hint.hdac.0.cad0.nid26.config="as=2 seq=0"
     hint.hdac.0.cad0.nid27.config="as=3 seq=0"
     hint.hdac.0.cad0.nid25.config="as=4 seq=0"
     hint.hdac.0.cad0.nid24.config="as=5 seq=0 device=Line-out"
     hint.hdac.0.cad0.nid21.config="as=6 seq=0"

     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).

   Example 4
     Setting the device.hints(5) options

     hint.hdac.0.cad0.nid20.config="as=1 seq=0"
     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"
     hint.hdac.0.cad0.nid21.config="as=2 seq=0"

     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 controllers having PCI class 4 (multimedia)
     and subclass 3 (HDA), compatible with Intel HDA specification.

     The snd_hda driver supports more than two hundred different controllers
     and CODECs.  There is no sense to list all of them here, as in most cases
     specific CODEC configuration and wiring are more important then type of
     the CODEC itself.

     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
     <>, Ariff Abdullah <> and Alexander
     Motin <>.  This manual page was written by Joel Dahl
     <>, Alexander Motin <> and Giorgos
     Keramidas <>.

     Some Hardware/OEM vendors tend to screw up BIOS settings or use custom
     unusual CODEC wiring that create problems to the driver.  This may result
     in missing pcm devices, or a state where the snd_hda driver seems to
     attach and work, but no sound is played.  Some cases can be solved by
     tuning loader.conf variables.  But before trying to fix problem that way,
     make sure that there really is a problem and that the PCM audio device in
     use really corresponds to the expected audio connector.

     Some vendors use non-standardized General Purpose I/O (GPIO) pins of the
     codec to control external amplifiers.  In some cases setting a
     combination of GPIO bits may be needed to make sound work on a specific

     HDMI and DisplayPort audio may also require support from video driver.

FreeBSD 11.0-PRERELEASE        January 25, 2012        FreeBSD 11.0-PRERELEASE


Want to link to this manual page? Use this URL:

home | help