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NAME

snd_hda — Intel High Definition Audio bridge device driver

SYNOPSIS

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):

snd_hda_load="YES"

DESCRIPTION

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.

EXAMPLES

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:

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

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"

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"

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"

MIXER CONTROLS

Depending on codec configuration, these controls and signal sources could be reported to sound(4):

Controls have different precision. Some could be just an on/off triggers. Most of controls use logarithmic scale.

HARDWARE

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.

SEE ALSO

snd_ich(4), sound(4), device.hints(5), loader.conf(5), sysctl(8)

HISTORY

The snd_hda device driver first appeared in FreeBSD 6.3.

AUTHORS

The snd_hda driver was written by Stephane E. Potvin <sepotvin@videotron.ca>, 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 Keramidas <keramida@FreeBSD.org>.

BUGS

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.