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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:

           device sound
           device snd_hda

     Alternatively, to load the driver as a module at boot time, place the following line in



     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 settings.

   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 commas.

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

                                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

                                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 microphones.

                                Zero out the pin widget config setup by the system.  Some systems
                                seem to have unuseable audio devices if the pin widgit
                                configuration is cleared.  Set this value to 0 to accept the
                                default configuration values setup by the BIOS.

                                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.

                                Controls automatic recording source feature:
                                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

     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 output).

     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

           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

                    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

   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

           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

           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

           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

           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.hdaa.%d.nid%d_config.

 , 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


     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

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

     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 speaker.

   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

           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.


     snd_ich(4), sound(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 device.

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