code:
===================
Tracepoints in ALSA
===================

2017/07/02
Takasahi Sakamoto

Tracepoints in ALSA PCM core
============================

ALSA PCM core registers ``snd_pcm`` subsystem to kernel tracepoint system.
This subsystem includes two categories of tracepoints; for state of PCM buffer
and for processing of PCM hardware parameters. These tracepoints are available
when corresponding kernel configurations are enabled. When ``CONFIG_SND_DEBUG``
is enabled, the latter tracepoints are available. When additional
``SND_PCM_XRUN_DEBUG`` is enabled too, the former trace points are enabled.

Tracepoints for state of PCM buffer
------------------------------------

This category includes four tracepoints; ``hwptr``, ``applptr``, ``xrun`` and
``hw_ptr_error``.

Tracepoints for processing of PCM hardware parameters
-----------------------------------------------------

This category includes two tracepoints; ``hw_mask_param`` and
``hw_interval_param``.

In a design of ALSA PCM core, data transmission is abstracted as PCM substream.
Applications manage PCM substream to maintain data transmission for PCM frames.
Before starting the data transmission, applications need to configure PCM
substream. In this procedure, PCM hardware parameters are decided by
interaction between applications and ALSA PCM core. Once decided, runtime of
the PCM substream keeps the parameters.

The parameters are described in struct snd_pcm_hw_params. This
structure includes several types of parameters. Applications set preferable
value to these parameters, then execute ioctl(2) with SNDRV_PCM_IOCTL_HW_REFINE
or SNDRV_PCM_IOCTL_HW_PARAMS. The former is used just for refining available
set of parameters. The latter is used for an actual decision of the parameters.

The struct snd_pcm_hw_params structure has below members:

``flags``
        Configurable. ALSA PCM core and some drivers handle this flag to select
        convenient parameters or change their behaviour.
``masks``
        Configurable. This type of parameter is described in
        struct snd_mask and represent mask values. As of PCM protocol
        v2.0.13, three types are defined.

        - SNDRV_PCM_HW_PARAM_ACCESS
        - SNDRV_PCM_HW_PARAM_FORMAT
        - SNDRV_PCM_HW_PARAM_SUBFORMAT
``intervals``
        Configurable. This type of parameter is described in
        struct snd_interval and represent values with a range. As of
        PCM protocol v2.0.13, twelve types are defined.

        - SNDRV_PCM_HW_PARAM_SAMPLE_BITS
        - SNDRV_PCM_HW_PARAM_FRAME_BITS
        - SNDRV_PCM_HW_PARAM_CHANNELS
        - SNDRV_PCM_HW_PARAM_RATE
        - SNDRV_PCM_HW_PARAM_PERIOD_TIME
        - SNDRV_PCM_HW_PARAM_PERIOD_SIZE
        - SNDRV_PCM_HW_PARAM_PERIOD_BYTES
        - SNDRV_PCM_HW_PARAM_PERIODS
        - SNDRV_PCM_HW_PARAM_BUFFER_TIME
        - SNDRV_PCM_HW_PARAM_BUFFER_SIZE
        - SNDRV_PCM_HW_PARAM_BUFFER_BYTES
        - SNDRV_PCM_HW_PARAM_TICK_TIME
``rmask``
        Configurable. This is evaluated at ioctl(2) with
        SNDRV_PCM_IOCTL_HW_REFINE only. Applications can select which
        mask/interval parameter can be changed by ALSA PCM core. For
        SNDRV_PCM_IOCTL_HW_PARAMS, this mask is ignored and all of parameters
        are going to be changed.
``cmask``
        Read-only. After returning from ioctl(2), buffer in user space for
        struct snd_pcm_hw_params includes result of each operation.
        This mask represents which mask/interval parameter is actually changed.
``info``
        Read-only. This represents hardware/driver capabilities as bit flags
        with SNDRV_PCM_INFO_XXX. Typically, applications execute ioctl(2) with
        SNDRV_PCM_IOCTL_HW_REFINE to retrieve this flag, then decide candidates
        of parameters and execute ioctl(2) with SNDRV_PCM_IOCTL_HW_PARAMS to
        configure PCM substream.
``msbits``
        Read-only. This value represents available bit width in MSB side of
        a PCM sample. When a parameter of SNDRV_PCM_HW_PARAM_SAMPLE_BITS was
        decided as a fixed number, this value is also calculated according to
        it. Else, zero. But this behaviour depends on implementations in driver
        side.
``rate_num``
        Read-only. This value represents numerator of sampling rate in fraction
        notation. Basically, when a parameter of SNDRV_PCM_HW_PARAM_RATE was
        decided as a single value, this value is also calculated according to
        it. Else, zero. But this behaviour depends on implementations in driver
        side.
``rate_den``
        Read-only. This value represents denominator of sampling rate in
        fraction notation. Basically, when a parameter of
        SNDRV_PCM_HW_PARAM_RATE was decided as a single value, this value is
        also calculated according to it. Else, zero. But this behaviour depends
        on implementations in driver side.
``fifo_size``
        Read-only. This value represents the size of FIFO in serial sound
        interface of hardware. Basically, each driver can assigns a proper
        value to this parameter but some drivers intentionally set zero with
        a care of hardware design or data transmission protocol.

ALSA PCM core handles buffer of struct snd_pcm_hw_params when
applications execute ioctl(2) with SNDRV_PCM_HW_REFINE or SNDRV_PCM_HW_PARAMS.
Parameters in the buffer are changed according to
struct snd_pcm_hardware and rules of constraints in the runtime. The
structure describes capabilities of handled hardware. The rules describes
dependencies on which a parameter is decided according to several parameters.
A rule has a callback function, and drivers can register arbitrary functions
to compute the target parameter. ALSA PCM core registers some rules to the
runtime as a default.

Each driver can join in the interaction as long as it prepared for two stuffs
in a callback of struct snd_pcm_ops.open.

1. In the callback, drivers are expected to change a member of
   struct snd_pcm_hardware type in the runtime, according to
   capacities of corresponding hardware.
2. In the same callback, drivers are also expected to register additional rules
   of constraints into the runtime when several parameters have dependencies
   due to hardware design.

The driver can refers to result of the interaction in a callback of
struct snd_pcm_ops.hw_params, however it should not change the
content.

Tracepoints in this category are designed to trace changes of the
mask/interval parameters. When ALSA PCM core changes them, ``hw_mask_param`` or
``hw_interval_param`` event is probed according to type of the changed parameter.

ALSA PCM core also has a pretty print format for each of the tracepoints. Below
is an example for ``hw_mask_param``.

::

    hw_mask_param: pcmC0D0p 001/023 FORMAT 00000000000000000000001000000044 00000000000000000000001000000044

Below is an example for ``hw_interval_param``.

::

    hw_interval_param: pcmC0D0p 000/023 BUFFER_SIZE 0 0 [0 4294967295] 0 1 [0 4294967295]

The first three fields are common. They represent name of ALSA PCM character
device, rules of constraint and name of the changed parameter, in order. The
field for rules of constraint consists of two sub-fields; index of applied rule
and total number of rules added to the runtime. As an exception, the index 000
means that the parameter is changed by ALSA PCM core, regardless of the rules.

The rest of field represent state of the parameter before/after changing. These
fields are different according to type of the parameter. For parameters of mask
type, the fields represent hexadecimal dump of content of the parameter. For
parameters of interval type, the fields represent values of each member of
``empty``, ``integer``, ``openmin``, ``min``, ``max``, ``openmax`` in
struct snd_interval in this order.

Tracepoints in drivers
======================

Some drivers have tracepoints for developers' convenience. For them, please
refer to each documentation or implementation.


code:
======================================
HD-Audio Codec-Specific Mixer Controls
======================================

This file explains the codec-specific mixer controls.

Realtek codecs
--------------

Channel Mode
  This is an enum control to change the surround-channel setup,
  appears only when the surround channels are available.
  It gives the number of channels to be used, "2ch", "4ch", "6ch",
  and "8ch".  According to the configuration, this also controls the
  jack-retasking of multi-I/O jacks.

Auto-Mute Mode
  This is an enum control to change the auto-mute behavior of the
  headphone and line-out jacks.  If built-in speakers and headphone
  and/or line-out jacks are available on a machine, this controls
  appears.
  When there are only either headphones or line-out jacks, it gives
  "Disabled" and "Enabled" state.  When enabled, the speaker is muted
  automatically when a jack is plugged.

  When both headphone and line-out jacks are present, it gives
  "Disabled", "Speaker Only" and "Line-Out+Speaker".  When
  speaker-only is chosen, plugging into a headphone or a line-out jack
  mutes the speakers, but not line-outs.  When line-out+speaker is
  selected, plugging to a headphone jack mutes both speakers and
  line-outs.

IDT/Sigmatel codecs
-------------------

Analog Loopback
  This control enables/disables the analog-loopback circuit.  This
  appears only when "loopback" is set to true in a codec hint
  (see HD-Audio.txt).  Note that on some codecs the analog-loopback
  and the normal PCM playback are exclusive, i.e. when this is on, you
  won't hear any PCM stream.

Swap Center/LFE
  Swaps the center and LFE channel order.  Normally, the left
  corresponds to the center and the right to the LFE.  When this is
  ON, the left to the LFE and the right to the center.

Headphone as Line Out
  When this control is ON, treat the headphone jacks as line-out
  jacks.  That is, the headphone won't auto-mute the other line-outs,
  and no HP-amp is set to the pins.

Mic Jack Mode, Line Jack Mode, etc
  These enum controls the direction and the bias of the input jack
  pins.  Depending on the jack type, it can set as "Mic In" and "Line
  In", for determining the input bias, or it can be set to "Line Out"
  when the pin is a multi-I/O jack for surround channels.

VIA codecs
----------

Smart 5.1
  An enum control to re-task the multi-I/O jacks for surround outputs.
  When it's ON, the corresponding input jacks (usually a line-in and a
  mic-in) are switched as the surround and the CLFE output jacks.

Independent HP
  When this enum control is enabled, the headphone output is routed
  from an individual stream (the third PCM such as hw:0,2) instead of
  the primary stream.  In the case the headphone DAC is shared with a
  side or a CLFE-channel DAC, the DAC is switched to the headphone
  automatically.

Loopback Mixing
  An enum control to determine whether the analog-loopback route is
  enabled or not.  When it's enabled, the analog-loopback is mixed to
  the front-channel.  Also, the same route is used for the headphone
  and speaker outputs.  As a side-effect, when this mode is set, the
  individual volume controls will be no longer available for
  headphones and speakers because there is only one DAC connected to a
  mixer widget.

Dynamic Power-Control
  This control determines whether the dynamic power-control per jack
  detection is enabled or not.  When enabled, the widgets power state
  (D0/D3) are changed dynamically depending on the jack plugging
  state for saving power consumptions.  However, if your system
  doesn't provide a proper jack-detection, this won't work; in such a
  case, turn this control OFF.

Jack Detect
  This control is provided only for VT1708 codec which gives no proper
  unsolicited event per jack plug.  When this is on, the driver polls
  the jack detection so that the headphone auto-mute can work, while
  turning this off would reduce the power consumption.

Conexant codecs
---------------

Auto-Mute Mode
  See Realtek codecs.

Analog codecs
--------------

Channel Mode
  This is an enum control to change the surround-channel setup,
  appears only when the surround channels are available.
  It gives the number of channels to be used, "2ch", "4ch" and "6ch".
  According to the configuration, this also controls the
  jack-retasking of multi-I/O jacks.

Independent HP
  When this enum control is enabled, the headphone output is routed
  from an individual stream (the third PCM such as hw:0,2) instead of
  the primary stream.

repo_name: angery/linux


code:
=======================
HD-Audio DP-MST Support
=======================

To support DP MST audio, HD Audio hdmi codec driver introduces virtual pin
and dynamic pcm assignment.

Virtual pin is an extension of per_pin. The most difference of DP MST
from legacy is that DP MST introduces device entry. Each pin can contain
several device entries. Each device entry behaves as a pin.

As each pin may contain several device entries and each codec may contain
several pins, if we use one pcm per per_pin, there will be many PCMs.
The new solution is to create a few PCMs and to dynamically bind pcm to
per_pin. Driver uses spec->dyn_pcm_assign flag to indicate whether to use
the new solution.

PCM
===
To be added

Pin Initialization
==================
Each pin may have several device entries (virtual pins). On Intel platform,
the device entries number is dynamically changed. If DP MST hub is connected,
it is in DP MST mode, and the device entries number is 3. Otherwise, the
device entries number is 1.

To simplify the implementation, all the device entries will be initialized
when bootup no matter whether it is in DP MST mode or not.

Connection list
===============
DP MST reuses connection list code. The code can be reused because
device entries on the same pin have the same connection list.

This means DP MST gets the device entry connection list without the
device entry setting.

Jack
====

Presume:
 - MST must be dyn_pcm_assign, and it is acomp (for Intel scenario);
 - NON-MST may or may not be dyn_pcm_assign, it can be acomp or !acomp;

So there are the following scenarios:
 a. MST (&& dyn_pcm_assign && acomp)
 b. NON-MST && dyn_pcm_assign && acomp
 c. NON-MST && !dyn_pcm_assign && !acomp

Below discussion will ignore MST and NON-MST difference as it doesn't
impact on jack handling too much.

Driver uses struct hdmi_pcm pcm[] array in hdmi_spec and snd_jack is
a member of hdmi_pcm. Each pin has one struct hdmi_pcm * pcm pointer.

For !dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] statically.

For dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n]
when monitor is hotplugged.

Build Jack
----------

- dyn_pcm_assign

  Will not use hda_jack but use snd_jack in spec->pcm_rec[pcm_idx].jack directly.

- !dyn_pcm_assign

  Use hda_jack and assign spec->pcm_rec[pcm_idx].jack = jack->jack statically.

Unsolicited Event Enabling
--------------------------
Enable unsolicited event if !acomp.

Monitor Hotplug Event Handling
------------------------------
- acomp

  pin_eld_notify() -> check_presence_and_report() -> hdmi_present_sense() ->
  sync_eld_via_acomp().

  Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for
  both dyn_pcm_assign and !dyn_pcm_assign

- !acomp

  hdmi_unsol_event() -> hdmi_intrinsic_event() -> check_presence_and_report() ->
  hdmi_present_sense() -> hdmi_prepsent_sense_via_verbs()

  Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for dyn_pcm_assign.
  Use hda_jack mechanism to handle jack events.

Others to be added later
========================


code:
HD-Audio
========

.. toctree::
   :maxdepth: 2

   notes
   models
   controls
   dp-mst
   realtek-pc-beep


code:
==============================
HD-Audio Codec-Specific Models
==============================

ALC880
======
3stack
    3-jack in back and a headphone out
3stack-digout
    3-jack in back, a HP out and a SPDIF out
5stack
    5-jack in back, 2-jack in front
5stack-digout
    5-jack in back, 2-jack in front, a SPDIF out
6stack
    6-jack in back, 2-jack in front
6stack-digout
    6-jack with a SPDIF out
6stack-automute
    6-jack with headphone jack detection

ALC260
======
gpio1
    Enable GPIO1
coef
    Enable EAPD via COEF table
fujitsu
    Quirk for FSC S7020
fujitsu-jwse
    Quirk for FSC S7020 with jack modes and HP mic support

ALC262
======
inv-dmic
    Inverted internal mic workaround
fsc-h270
    Fixups for Fujitsu-Siemens Celsius H270
fsc-s7110
    Fixups for Fujitsu-Siemens Lifebook S7110
hp-z200
    Fixups for HP Z200
tyan
    Fixups for Tyan Thunder n6650W
lenovo-3000
    Fixups for Lenovo 3000
benq
    Fixups for Benq ED8
benq-t31
    Fixups for Benq T31
bayleybay
    Fixups for Intel BayleyBay

ALC267/268
==========
inv-dmic
    Inverted internal mic workaround
hp-eapd
    Disable HP EAPD on NID 0x15
spdif
    Enable SPDIF output on NID 0x1e

ALC22x/23x/25x/269/27x/28x/29x (and vendor-specific ALC3xxx models)
===================================================================
laptop-amic
    Laptops with analog-mic input
laptop-dmic
    Laptops with digital-mic input
alc269-dmic
    Enable ALC269(VA) digital mic workaround
alc271-dmic
    Enable ALC271X digital mic workaround
inv-dmic
    Inverted internal mic workaround
headset-mic
    Indicates a combined headset (headphone+mic) jack
headset-mode
    More comprehensive headset support for ALC269 & co
headset-mode-no-hp-mic
    Headset mode support without headphone mic
lenovo-dock
    Enables docking station I/O for some Lenovos
hp-gpio-led
    GPIO LED support on HP laptops
hp-dock-gpio-mic1-led
    HP dock with mic LED support
dell-headset-multi
    Headset jack, which can also be used as mic-in
dell-headset-dock
    Headset jack (without mic-in), and also dock I/O
dell-headset3
    Headset jack (without mic-in), and also dock I/O, variant 3
dell-headset4
    Headset jack (without mic-in), and also dock I/O, variant 4
alc283-dac-wcaps
    Fixups for Chromebook with ALC283
alc283-sense-combo
    Combo jack sensing on ALC283
tpt440-dock
    Pin configs for Lenovo Thinkpad Dock support
tpt440
    Lenovo Thinkpad T440s setup
tpt460
    Lenovo Thinkpad T460/560 setup
tpt470-dock
    Lenovo Thinkpad T470 dock setup
dual-codecs
    Lenovo laptops with dual codecs
alc700-ref
    Intel reference board with ALC700 codec
vaio
    Pin fixups for Sony VAIO laptops
dell-m101z
    COEF setup for Dell M101z
asus-g73jw
    Subwoofer pin fixup for ASUS G73JW
lenovo-eapd
    Inversed EAPD setup for Lenovo laptops
sony-hweq
    H/W EQ COEF setup for Sony laptops
pcm44k
    Fixed PCM 44kHz constraints (for buggy devices)
lifebook
    Dock pin fixups for Fujitsu Lifebook
lifebook-extmic
    Headset mic fixup for Fujitsu Lifebook
lifebook-hp-pin
    Headphone pin fixup for Fujitsu Lifebook
lifebook-u7x7
    Lifebook U7x7 fixups
alc269vb-amic
    ALC269VB analog mic pin fixups
alc269vb-dmic
    ALC269VB digital mic pin fixups
hp-mute-led-mic1
    Mute LED via Mic1 pin on HP
hp-mute-led-mic2
    Mute LED via Mic2 pin on HP
hp-mute-led-mic3
    Mute LED via Mic3 pin on HP
hp-gpio-mic1
    GPIO + Mic1 pin LED on HP
hp-line1-mic1
    Mute LED via Line1 + Mic1 pins on HP
noshutup
    Skip shutup callback
sony-nomic
    Headset mic fixup for Sony laptops
aspire-headset-mic
    Headset pin fixup for Acer Aspire
asus-x101
    ASUS X101 fixups
acer-ao7xx
    Acer AO7xx fixups
acer-aspire-e1
    Acer Aspire E1 fixups
acer-ac700
    Acer AC700 fixups
limit-mic-boost
    Limit internal mic boost on Lenovo machines
asus-zenbook
    ASUS Zenbook fixups
asus-zenbook-ux31a
    ASUS Zenbook UX31A fixups
ordissimo
    Ordissimo EVE2 (or Malata PC-B1303) fixups
asus-tx300
    ASUS TX300 fixups
alc283-int-mic
    ALC283 COEF setup for Lenovo machines
mono-speakers
    Subwoofer and headset fixupes for Dell Inspiron
alc290-subwoofer
    Subwoofer fixups for Dell Vostro
thinkpad
    Binding with thinkpad_acpi driver for Lenovo machines
dmic-thinkpad
    thinkpad_acpi binding + digital mic support
alc255-acer
    ALC255 fixups on Acer machines
alc255-asus
    ALC255 fixups on ASUS machines
alc255-dell1
    ALC255 fixups on Dell machines
alc255-dell2
    ALC255 fixups on Dell machines, variant 2
alc293-dell1
    ALC293 fixups on Dell machines
alc283-headset
    Headset pin fixups on ALC283
aspire-v5
    Acer Aspire V5 fixups
hp-gpio4
    GPIO and Mic1 pin mute LED fixups for HP
hp-gpio-led
    GPIO mute LEDs on HP
hp-gpio2-hotkey
    GPIO mute LED with hot key handling on HP
hp-dock-pins
    GPIO mute LEDs and dock support on HP
hp-dock-gpio-mic
    GPIO, Mic mute LED and dock support on HP
hp-9480m
    HP 9480m fixups
alc288-dell1
    ALC288 fixups on Dell machines
alc288-dell-xps13
    ALC288 fixups on Dell XPS13
dell-e7x
    Dell E7x fixups
alc293-dell
    ALC293 fixups on Dell machines
alc298-dell1
    ALC298 fixups on Dell machines
alc298-dell-aio
    ALC298 fixups on Dell AIO machines
alc275-dell-xps
    ALC275 fixups on Dell XPS models
lenovo-spk-noise
    Workaround for speaker noise on Lenovo machines
lenovo-hotkey
    Hot-key support via Mic2 pin on Lenovo machines
dell-spk-noise
    Workaround for speaker noise on Dell machines
alc255-dell1
    ALC255 fixups on Dell machines
alc295-disable-dac3
    Disable DAC3 routing on ALC295
alc280-hp-headset
    HP Elitebook fixups
alc221-hp-mic
    Front mic pin fixup on HP machines
alc298-spk-volume
    Speaker pin routing workaround on ALC298
dell-inspiron-7559
    Dell Inspiron 7559 fixups
ativ-book
    Samsung Ativ book 8 fixups
alc221-hp-mic
    ALC221 headset fixups on HP machines
alc256-asus-mic
    ALC256 fixups on ASUS machines
alc256-asus-aio
    ALC256 fixups on ASUS AIO machines
alc233-eapd
    ALC233 fixups on ASUS machines
alc294-lenovo-mic
    ALC294 Mic pin fixup for Lenovo AIO machines
alc225-wyse
    Dell Wyse fixups
alc274-dell-aio
    ALC274 fixups on Dell AIO machines
alc255-dummy-lineout
    Dell Precision 3930 fixups
alc255-dell-headset
    Dell Precision 3630 fixups
alc295-hp-x360
    HP Spectre X360 fixups
alc-sense-combo
    Headset button support for Chrome platform
huawei-mbx-stereo
    Enable initialization verbs for Huawei MBX stereo speakers;
    might be risky, try this at your own risk
alc298-samsung-headphone
    Samsung laptops with ALC298
alc256-samsung-headphone
    Samsung laptops with ALC256

ALC66x/67x/892
==============
aspire
    Subwoofer pin fixup for Aspire laptops
ideapad
    Subwoofer pin fixup for Ideapad laptops
mario
    Chromebook mario model fixup
hp-rp5800
    Headphone pin fixup for HP RP5800
asus-mode1
    ASUS
asus-mode2
    ASUS
asus-mode3
    ASUS
asus-mode4
    ASUS
asus-mode5
    ASUS
asus-mode6
    ASUS
asus-mode7
    ASUS
asus-mode8
    ASUS
zotac-z68
    Front HP fixup for Zotac Z68
inv-dmic
    Inverted internal mic workaround
alc662-headset-multi
    Dell headset jack, which can also be used as mic-in (ALC662)
dell-headset-multi
    Headset jack, which can also be used as mic-in
alc662-headset
    Headset mode support on ALC662
alc668-headset
    Headset mode support on ALC668
bass16
    Bass speaker fixup on pin 0x16
bass1a
    Bass speaker fixup on pin 0x1a
automute
    Auto-mute fixups for ALC668
dell-xps13
    Dell XPS13 fixups
asus-nx50
    ASUS Nx50 fixups
asus-nx51
    ASUS Nx51 fixups
asus-g751
    ASUS G751 fixups
alc891-headset
    Headset mode support on ALC891
alc891-headset-multi
    Dell headset jack, which can also be used as mic-in (ALC891)
acer-veriton
    Acer Veriton speaker pin fixup
asrock-mobo
    Fix invalid 0x15 / 0x16 pins
usi-headset
    Headset support on USI machines
dual-codecs
    Lenovo laptops with dual codecs
alc285-hp-amp-init
    HP laptops which require speaker amplifier initialization (ALC285)

ALC680
======
N/A

ALC88x/898/1150/1220
====================
abit-aw9d
    Pin fixups for Abit AW9D-MAX
lenovo-y530
    Pin fixups for Lenovo Y530
acer-aspire-7736
    Fixup for Acer Aspire 7736
asus-w90v
    Pin fixup for ASUS W90V
cd
    Enable audio CD pin NID 0x1c
no-front-hp
    Disable front HP pin NID 0x1b
vaio-tt
    Pin fixup for VAIO TT
eee1601
    COEF setups for ASUS Eee 1601
alc882-eapd
    Change EAPD COEF mode on ALC882
alc883-eapd
    Change EAPD COEF mode on ALC883
gpio1
    Enable GPIO1
gpio2
    Enable GPIO2
gpio3
    Enable GPIO3
alc889-coef
    Setup ALC889 COEF
asus-w2jc
    Fixups for ASUS W2JC
acer-aspire-4930g
    Acer Aspire 4930G/5930G/6530G/6930G/7730G
acer-aspire-8930g
    Acer Aspire 8330G/6935G
acer-aspire
    Acer Aspire others
macpro-gpio
    GPIO setup for Mac Pro
dac-route
    Workaround for DAC routing on Acer Aspire
mbp-vref
    Vref setup for Macbook Pro
imac91-vref
    Vref setup for iMac 9,1
mba11-vref
    Vref setup for MacBook Air 1,1
mba21-vref
    Vref setup for MacBook Air 2,1
mp11-vref
    Vref setup for Mac Pro 1,1
mp41-vref
    Vref setup for Mac Pro 4,1
inv-dmic
    Inverted internal mic workaround
no-primary-hp
    VAIO Z/VGC-LN51JGB workaround (for fixed speaker DAC)
asus-bass
    Bass speaker setup for ASUS ET2700
dual-codecs
    ALC1220 dual codecs for Gaming mobos
clevo-p950
    Fixups for Clevo P950

ALC861/660
==========
N/A

ALC861VD/660VD
==============
N/A

CMI9880
=======
minimal
    3-jack in back
min_fp
    3-jack in back, 2-jack in front
full
    6-jack in back, 2-jack in front
full_dig
    6-jack in back, 2-jack in front, SPDIF I/O
allout
    5-jack in back, 2-jack in front, SPDIF out
auto
    auto-config reading BIOS (default)

AD1882 / AD1882A
================
3stack
    3-stack mode
3stack-automute
    3-stack with automute front HP (default)
6stack
    6-stack mode

AD1884A / AD1883 / AD1984A / AD1984B
====================================
desktop	3-stack desktop (default)
laptop	laptop with HP jack sensing
mobile	mobile devices with HP jack sensing
thinkpad	Lenovo Thinkpad X300
touchsmart	HP Touchsmart

AD1884
======
N/A

AD1981
======
basic		3-jack (default)
hp		HP nx6320
thinkpad	Lenovo Thinkpad T60/X60/Z60
toshiba	Toshiba U205

AD1983
======
N/A

AD1984
======
basic		default configuration
thinkpad	Lenovo Thinkpad T61/X61
dell_desktop	Dell T3400

AD1986A
=======
3stack
    3-stack, shared surrounds
laptop
    2-channel only (FSC V2060, Samsung M50)
laptop-imic
    2-channel with built-in mic
eapd
    Turn on EAPD constantly

AD1988/AD1988B/AD1989A/AD1989B
==============================
6stack
    6-jack
6stack-dig
    ditto with SPDIF
3stack
    3-jack
3stack-dig
    ditto with SPDIF
laptop
    3-jack with hp-jack automute
laptop-dig
    ditto with SPDIF
auto
    auto-config reading BIOS (default)

Conexant 5045
=============
cap-mix-amp
    Fix max input level on mixer widget
toshiba-p105
    Toshiba P105 quirk
hp-530
    HP 530 quirk

Conexant 5047
=============
cap-mix-amp
    Fix max input level on mixer widget

Conexant 5051
=============
lenovo-x200
    Lenovo X200 quirk

Conexant 5066
=============
stereo-dmic
    Workaround for inverted stereo digital mic
gpio1
    Enable GPIO1 pin
headphone-mic-pin
    Enable headphone mic NID 0x18 without detection
tp410
    Thinkpad T400 & co quirks
thinkpad
    Thinkpad mute/mic LED quirk
lemote-a1004
    Lemote A1004 quirk
lemote-a1205
    Lemote A1205 quirk
olpc-xo
    OLPC XO quirk
mute-led-eapd
    Mute LED control via EAPD
hp-dock
    HP dock support
mute-led-gpio
    Mute LED control via GPIO
hp-mic-fix
    Fix for headset mic pin on HP boxes

STAC9200
========
ref
    Reference board
oqo
    OQO Model 2
dell-d21
    Dell (unknown)
dell-d22
    Dell (unknown)
dell-d23
    Dell (unknown)
dell-m21
    Dell Inspiron 630m, Dell Inspiron 640m
dell-m22
    Dell Latitude D620, Dell Latitude D820
dell-m23
    Dell XPS M1710, Dell Precision M90
dell-m24
    Dell Latitude 120L
dell-m25
    Dell Inspiron E1505n
dell-m26
    Dell Inspiron 1501
dell-m27
    Dell Inspiron E1705/9400
gateway-m4
    Gateway laptops with EAPD control
gateway-m4-2
    Gateway laptops with EAPD control
panasonic
    Panasonic CF-74
auto
    BIOS setup (default)

STAC9205/9254
=============
ref
    Reference board
dell-m42
    Dell (unknown)
dell-m43
    Dell Precision
dell-m44
    Dell Inspiron
eapd
    Keep EAPD on (e.g. Gateway T1616)
auto
    BIOS setup (default)

STAC9220/9221
=============
ref
    Reference board
3stack
    D945 3stack
5stack
    D945 5stack + SPDIF
intel-mac-v1
    Intel Mac Type 1
intel-mac-v2
    Intel Mac Type 2
intel-mac-v3
    Intel Mac Type 3
intel-mac-v4
    Intel Mac Type 4
intel-mac-v5
    Intel Mac Type 5
intel-mac-auto
    Intel Mac (detect type according to subsystem id)
macmini
    Intel Mac Mini (equivalent with type 3)
macbook
    Intel Mac Book (eq. type 5)
macbook-pro-v1
    Intel Mac Book Pro 1st generation (eq. type 3)
macbook-pro
    Intel Mac Book Pro 2nd generation (eq. type 3)
imac-intel
    Intel iMac (eq. type 2)
imac-intel-20
    Intel iMac (newer version) (eq. type 3)
ecs202
    ECS/PC chips
dell-d81
    Dell (unknown)
dell-d82
    Dell (unknown)
dell-m81
    Dell (unknown)
dell-m82
    Dell XPS M1210
auto
    BIOS setup (default)

STAC9202/9250/9251
==================
ref
    Reference board, base config
m1
    Some Gateway MX series laptops (NX560XL)
m1-2
    Some Gateway MX series laptops (MX6453)
m2
    Some Gateway MX series laptops (M255)
m2-2
    Some Gateway MX series laptops
m3
    Some Gateway MX series laptops
m5
    Some Gateway MX series laptops (MP6954)
m6
    Some Gateway NX series laptops
auto
    BIOS setup (default)

STAC9227/9228/9229/927x
=======================
ref
    Reference board
ref-no-jd
    Reference board without HP/Mic jack detection
3stack
    D965 3stack
5stack
    D965 5stack + SPDIF
5stack-no-fp
    D965 5stack without front panel
dell-3stack
    Dell Dimension E520
dell-bios
    Fixes with Dell BIOS setup
dell-bios-amic
    Fixes with Dell BIOS setup including analog mic
volknob
    Fixes with volume-knob widget 0x24
auto
    BIOS setup (default)

STAC92HD71B*
============
ref
    Reference board
dell-m4-1
    Dell desktops
dell-m4-2
    Dell desktops
dell-m4-3
    Dell desktops
hp-m4
    HP mini 1000
hp-dv5
    HP dv series
hp-hdx
    HP HDX series
hp-dv4-1222nr
    HP dv4-1222nr (with LED support)
auto
    BIOS setup (default)

STAC92HD73*
===========
ref
    Reference board
no-jd
    BIOS setup but without jack-detection
intel
    Intel DG45* mobos
dell-m6-amic
    Dell desktops/laptops with analog mics
dell-m6-dmic
    Dell desktops/laptops with digital mics
dell-m6
    Dell desktops/laptops with both type of mics
dell-eq
    Dell desktops/laptops
alienware
    Alienware M17x
asus-mobo
    Pin configs for ASUS mobo with 5.1/SPDIF out
auto
    BIOS setup (default)

STAC92HD83*
===========
ref
    Reference board
mic-ref
    Reference board with power management for ports
dell-s14
    Dell laptop
dell-vostro-3500
    Dell Vostro 3500 laptop
hp-dv7-4000
    HP dv-7 4000
hp_cNB11_intquad
    HP CNB models with 4 speakers
hp-zephyr
    HP Zephyr
hp-led
    HP with broken BIOS for mute LED
hp-inv-led
    HP with broken BIOS for inverted mute LED
hp-mic-led
    HP with mic-mute LED
headset-jack
    Dell Latitude with a 4-pin headset jack
hp-envy-bass
    Pin fixup for HP Envy bass speaker (NID 0x0f)
hp-envy-ts-bass
    Pin fixup for HP Envy TS bass speaker (NID 0x10)
hp-bnb13-eq
    Hardware equalizer setup for HP laptops
hp-envy-ts-bass
    HP Envy TS bass support
auto
    BIOS setup (default)

STAC92HD95
==========
hp-led
    LED support for HP laptops
hp-bass
    Bass HPF setup for HP Spectre 13

STAC9872
========
vaio
    VAIO laptop without SPDIF
auto
    BIOS setup (default)

Cirrus Logic CS4206/4207
========================
mbp53
    MacBook Pro 5,3
mbp55
    MacBook Pro 5,5
imac27
    IMac 27 Inch
imac27_122
    iMac 12,2
apple
    Generic Apple quirk
mbp101
    MacBookPro 10,1
mbp81
    MacBookPro 8,1
mba42
    MacBookAir 4,2
auto
    BIOS setup (default)

Cirrus Logic CS4208
===================
mba6
    MacBook Air 6,1 and 6,2
gpio0
    Enable GPIO 0 amp
mbp11
    MacBookPro 11,2
macmini
    MacMini 7,1
auto
    BIOS setup (default)

VIA VT17xx/VT18xx/VT20xx
========================
auto
    BIOS setup (default)


code:
=============================
More Notes on HD-Audio Driver
=============================

Takashi Iwai <tiwai@suse.de>

General
=======

HD-audio is the new standard on-board audio component on modern PCs
after AC97.  Although Linux has been supporting HD-audio since long
time ago, there are often problems with new machines.  A part of the
problem is broken BIOS, and the rest is the driver implementation.
This document explains the brief trouble-shooting and debugging
methods for the	HD-audio hardware.

The HD-audio component consists of two parts: the controller chip and
the codec chips on the HD-audio bus.  Linux provides a single driver
for all controllers, snd-hda-intel.  Although the driver name contains
a word of a well-known hardware vendor, it's not specific to it but for
all controller chips by other companies.  Since the HD-audio
controllers are supposed to be compatible, the single snd-hda-driver
should work in most cases.  But, not surprisingly, there are known
bugs and issues specific to each controller type.  The snd-hda-intel
driver has a bunch of workarounds for these as described below.

A controller may have multiple codecs.  Usually you have one audio
codec and optionally one modem codec.  In theory, there might be
multiple audio codecs, e.g. for analog and digital outputs, and the
driver might not work properly because of conflict of mixer elements.
This should be fixed in future if such hardware really exists.

The snd-hda-intel driver has several different codec parsers depending
on the codec.  It has a generic parser as a fallback, but this
functionality is fairly limited until now.  Instead of the generic
parser, usually the codec-specific parser (coded in patch_*.c) is used
for the codec-specific implementations.  The details about the
codec-specific problems are explained in the later sections.

If you are interested in the deep debugging of HD-audio, read the
HD-audio specification at first.  The specification is found on
Intel's web page, for example:

* https://www.intel.com/standards/hdaudio/

HD-Audio Controller
===================

DMA-Position Problem
--------------------
The most common problem of the controller is the inaccurate DMA
pointer reporting.  The DMA pointer for playback and capture can be
read in two ways, either via a LPIB register or via a position-buffer
map.  As default the driver tries to read from the io-mapped
position-buffer, and falls back to LPIB if the position-buffer appears
dead.  However, this detection isn't perfect on some devices.  In such
a case, you can change the default method via ``position_fix`` option.

``position_fix=1`` means to use LPIB method explicitly.
``position_fix=2`` means to use the position-buffer.
``position_fix=3`` means to use a combination of both methods, needed
for some VIA controllers.  The capture stream position is corrected
by comparing both LPIB and position-buffer values.
``position_fix=4`` is another combination available for all controllers,
and uses LPIB for the playback and the position-buffer for the capture
streams.
``position_fix=5`` is specific to Intel platforms, so far, for Skylake
and onward.  It applies the delay calculation for the precise position
reporting.
``position_fix=6`` is to correct the position with the fixed FIFO
size, mainly targeted for the recent AMD controllers.
0 is the default value for all other
controllers, the automatic check and fallback to LPIB as described in
the above.  If you get a problem of repeated sounds, this option might
help.

In addition to that, every controller is known to be broken regarding
the wake-up timing.  It wakes up a few samples before actually
processing the data on the buffer.  This caused a lot of problems, for
example, with ALSA dmix or JACK.  Since 2.6.27 kernel, the driver puts
an artificial delay to the wake up timing.  This delay is controlled
via ``bdl_pos_adj`` option.

When ``bdl_pos_adj`` is a negative value (as default), it's assigned to
an appropriate value depending on the controller chip.  For Intel
chips, it'd be 1 while it'd be 32 for others.  Usually this works.
Only in case it doesn't work and you get warning messages, you should
change this parameter to other values.

Codec-Probing Problem
---------------------
A less often but a more severe problem is the codec probing.  When
BIOS reports the available codec slots wrongly, the driver gets
confused and tries to access the non-existing codec slot.  This often
results in the total screw-up, and destructs the further communication
with the codec chips.  The symptom appears usually as error messages
like:
::

    hda_intel: azx_get_response timeout, switching to polling mode:
          last cmd=0x12345678
    hda_intel: azx_get_response timeout, switching to single_cmd mode:
          last cmd=0x12345678

The first line is a warning, and this is usually relatively harmless.
It means that the codec response isn't notified via an IRQ.  The
driver uses explicit polling method to read the response.  It gives
very slight CPU overhead, but you'd unlikely notice it.

The second line is, however, a fatal error.  If this happens, usually
it means that something is really wrong.  Most likely you are
accessing a non-existing codec slot.

Thus, if the second error message appears, try to narrow the probed
codec slots via ``probe_mask`` option.  It's a bitmask, and each bit
corresponds to the codec slot.  For example, to probe only the first
slot, pass ``probe_mask=1``.  For the first and the third slots, pass
``probe_mask=5`` (where 5 = 1 | 4), and so on.

Since 2.6.29 kernel, the driver has a more robust probing method, so
this error might happen rarely, though.

On a machine with a broken BIOS, sometimes you need to force the
driver to probe the codec slots the hardware doesn't report for use.
In such a case, turn the bit 8 (0x100) of ``probe_mask`` option on.
Then the rest 8 bits are passed as the codec slots to probe
unconditionally.  For example, ``probe_mask=0x103`` will force to probe
the codec slots 0 and 1 no matter what the hardware reports.

Interrupt Handling
------------------
HD-audio driver uses MSI as default (if available) since 2.6.33
kernel as MSI works better on some machines, and in general, it's
better for performance.  However, Nvidia controllers showed bad
regressions with MSI (especially in a combination with AMD chipset),
thus we disabled MSI for them.

There seem also still other devices that don't work with MSI.  If you
see a regression wrt the sound quality (stuttering, etc) or a lock-up
in the recent kernel, try to pass ``enable_msi=0`` option to disable
MSI.  If it works, you can add the known bad device to the blacklist
defined in hda_intel.c.  In such a case, please report and give the
patch back to the upstream developer.

HD-Audio Codec
==============

Model Option
------------
The most common problem regarding the HD-audio driver is the
unsupported codec features or the mismatched device configuration.
Most of codec-specific code has several preset models, either to
override the BIOS setup or to provide more comprehensive features.

The driver checks PCI SSID and looks through the static configuration
table until any matching entry is found.  If you have a new machine,
you may see a message like below:
::

    hda_codec: ALC880: BIOS auto-probing.

Meanwhile, in the earlier versions, you would see a message like:
::

    hda_codec: Unknown model for ALC880, trying auto-probe from BIOS...

Even if you see such a message, DON'T PANIC.  Take a deep breath and
keep your towel.  First of all, it's an informational message, no
warning, no error.  This means that the PCI SSID of your device isn't
listed in the known preset model (white-)list.  But, this doesn't mean
that the driver is broken.  Many codec-drivers provide the automatic
configuration mechanism based on the BIOS setup.

The HD-audio codec has usually "pin" widgets, and BIOS sets the default
configuration of each pin, which indicates the location, the
connection type, the jack color, etc.  The HD-audio driver can guess
the right connection judging from these default configuration values.
However -- some codec-support codes, such as patch_analog.c, don't
support the automatic probing (yet as of 2.6.28).  And, BIOS is often,
yes, pretty often broken.  It sets up wrong values and screws up the
driver.

The preset model (or recently called as "fix-up") is provided
basically to overcome such a situation.  When the matching preset
model is found in the white-list, the driver assumes the static
configuration of that preset with the correct pin setup, etc.
Thus, if you have a newer machine with a slightly different PCI SSID
(or codec SSID) from the existing one, you may have a good chance to
re-use the same model.  You can pass the ``model`` option to specify the
preset model instead of PCI (and codec-) SSID look-up.

What ``model`` option values are available depends on the codec chip.
Check your codec chip from the codec proc file (see "Codec Proc-File"
section below).  It will show the vendor/product name of your codec
chip.  Then, see Documentation/sound/hd-audio/models.rst file,
the section of HD-audio driver.  You can find a list of codecs
and ``model`` options belonging to each codec.  For example, for Realtek
ALC262 codec chip, pass ``model=ultra`` for devices that are compatible
with Samsung Q1 Ultra.

Thus, the first thing you can do for any brand-new, unsupported and
non-working HD-audio hardware is to check HD-audio codec and several
different ``model`` option values.  If you have any luck, some of them
might suit with your device well.

There are a few special model option values:

* when 'nofixup' is passed, the device-specific fixups in the codec
  parser are skipped.
* when ``generic`` is passed, the codec-specific parser is skipped and
  only the generic parser is used.

A new style for the model option that was introduced since 5.15 kernel
is to pass the PCI or codec SSID in the form of ``model=XXXX:YYYY``
where XXXX and YYYY are the sub-vendor and sub-device IDs in hex
numbers, respectively.  This is a kind of aliasing to another device;
when this form is given, the driver will refer to that SSID as a
reference to the quirk table.  It'd be useful especially when the
target quirk isn't listed in the model table.  For example, passing
model=103c:8862 will apply the quirk for HP ProBook 445 G8 (which
isn't found in the model table as of writing) as long as the device is
handled equivalently by the same driver.

Speaker and Headphone Output
----------------------------
One of the most frequent (and obvious) bugs with HD-audio is the
silent output from either or both of a built-in speaker and a
headphone jack.  In general, you should try a headphone output at
first.  A speaker output often requires more additional controls like
the external amplifier bits.  Thus a headphone output has a slightly
better chance.

Before making a bug report, double-check whether the mixer is set up
correctly.  The recent version of snd-hda-intel driver provides mostly
"Master" volume control as well as "Front" volume (where Front
indicates the front-channels).  In addition, there can be individual
"Headphone" and "Speaker" controls.

Ditto for the speaker output.  There can be "External Amplifier"
switch on some codecs.  Turn on this if present.

Another related problem is the automatic mute of speaker output by
headphone plugging.  This feature is implemented in most cases, but
not on every preset model or codec-support code.

In anyway, try a different model option if you have such a problem.
Some other models may match better and give you more matching
functionality.  If none of the available models works, send a bug
report.  See the bug report section for details.

If you are masochistic enough to debug the driver problem, note the
following:

* The speaker (and the headphone, too) output often requires the
  external amplifier.  This can be set usually via EAPD verb or a
  certain GPIO.  If the codec pin supports EAPD, you have a better
  chance via SET_EAPD_BTL verb (0x70c).  On others, GPIO pin (mostly
  it's either GPIO0 or GPIO1) may turn on/off EAPD.
* Some Realtek codecs require special vendor-specific coefficients to
  turn on the amplifier.  See patch_realtek.c.
* IDT codecs may have extra power-enable/disable controls on each
  analog pin.  See patch_sigmatel.c.
* Very rare but some devices don't accept the pin-detection verb until
  triggered.  Issuing GET_PIN_SENSE verb (0xf09) may result in the
  codec-communication stall.  Some examples are found in
  patch_realtek.c.

Capture Problems
----------------
The capture problems are often because of missing setups of mixers.
Thus, before submitting a bug report, make sure that you set up the
mixer correctly.  For example, both "Capture Volume" and "Capture
Switch" have to be set properly in addition to the right "Capture
Source" or "Input Source" selection.  Some devices have "Mic Boost"
volume or switch.

When the PCM device is opened via "default" PCM (without pulse-audio
plugin), you'll likely have "Digital Capture Volume" control as well.
This is provided for the extra gain/attenuation of the signal in
software, especially for the inputs without the hardware volume
control such as digital microphones.  Unless really needed, this
should be set to exactly 50%, corresponding to 0dB -- neither extra
gain nor attenuation.  When you use "hw" PCM, i.e., a raw access PCM,
this control will have no influence, though.

It's known that some codecs / devices have fairly bad analog circuits,
and the recorded sound contains a certain DC-offset.  This is no bug
of the driver.

Most of modern laptops have no analog CD-input connection.  Thus, the
recording from CD input won't work in many cases although the driver
provides it as the capture source.  Use CDDA instead.

The automatic switching of the built-in and external mic per plugging
is implemented on some codec models but not on every model.  Partly
because of my laziness but mostly lack of testers.  Feel free to
submit the improvement patch to the author.

Direct Debugging
----------------
If no model option gives you a better result, and you are a tough guy
to fight against evil, try debugging via hitting the raw HD-audio
codec verbs to the device.  Some tools are available: hda-emu and
hda-analyzer.  The detailed description is found in the sections
below.  You'd need to enable hwdep for using these tools.  See "Kernel
Configuration" section.

Other Issues
============

Kernel Configuration
--------------------
In general, I recommend you to enable the sound debug option,
``CONFIG_SND_DEBUG=y``, no matter whether you are debugging or not.
This enables snd_printd() macro and others, and you'll get additional
kernel messages at probing.

In addition, you can enable ``CONFIG_SND_DEBUG_VERBOSE=y``.  But this
will give you far more messages.  Thus turn this on only when you are
sure to want it.

Don't forget to turn on the appropriate ``CONFIG_SND_HDA_CODEC_*``
options.  Note that each of them corresponds to the codec chip, not
the controller chip.  Thus, even if lspci shows the Nvidia controller,
you may need to choose the option for other vendors.  If you are
unsure, just select all yes.

``CONFIG_SND_HDA_HWDEP`` is a useful option for debugging the driver.
When this is enabled, the driver creates hardware-dependent devices
(one per each codec), and you have a raw access to the device via
these device files.  For example, ``hwC0D2`` will be created for the
codec slot #2 of the first card (#0).  For debug-tools such as
hda-verb and hda-analyzer, the hwdep device has to be enabled.
Thus, it'd be better to turn this on always.

``CONFIG_SND_HDA_RECONFIG`` is a new option, and this depends on the
hwdep option above.  When enabled, you'll have some sysfs files under
the corresponding hwdep directory.  See "HD-audio reconfiguration"
section below.

``CONFIG_SND_HDA_POWER_SAVE`` option enables the power-saving feature.
See "Power-saving" section below.

Codec Proc-File
---------------
The codec proc-file is a treasure-chest for debugging HD-audio.
It shows most of useful information of each codec widget.

The proc file is located in /proc/asound/card*/codec#*, one file per
each codec slot.  You can know the codec vendor, product id and
names, the type of each widget, capabilities and so on.
This file, however, doesn't show the jack sensing state, so far.  This
is because the jack-sensing might be depending on the trigger state.

This file will be picked up by the debug tools, and also it can be fed
to the emulator as the primary codec information.  See the debug tools
section below.

This proc file can be also used to check whether the generic parser is
used.  When the generic parser is used, the vendor/product ID name
will appear as "Realtek ID 0262", instead of "Realtek ALC262".

HD-Audio Reconfiguration
------------------------
This is an experimental feature to allow you re-configure the HD-audio
codec dynamically without reloading the driver.  The following sysfs
files are available under each codec-hwdep device directory (e.g.
/sys/class/sound/hwC0D0):

vendor_id
    Shows the 32bit codec vendor-id hex number.  You can change the
    vendor-id value by writing to this file.
subsystem_id
    Shows the 32bit codec subsystem-id hex number.  You can change the
    subsystem-id value by writing to this file.
revision_id
    Shows the 32bit codec revision-id hex number.  You can change the
    revision-id value by writing to this file.
afg
    Shows the AFG ID.  This is read-only.
mfg
    Shows the MFG ID.  This is read-only.
name
    Shows the codec name string.  Can be changed by writing to this
    file.
modelname
    Shows the currently set ``model`` option.  Can be changed by writing
    to this file.
init_verbs
    The extra verbs to execute at initialization.  You can add a verb by
    writing to this file.  Pass three numbers: nid, verb and parameter
    (separated with a space).
hints
    Shows / stores hint strings for codec parsers for any use.
    Its format is ``key = value``.  For example, passing ``jack_detect = no``
    will disable the jack detection of the machine completely.
init_pin_configs
    Shows the initial pin default config values set by BIOS.
driver_pin_configs
    Shows the pin default values set by the codec parser explicitly.
    This doesn't show all pin values but only the changed values by
    the parser.  That is, if the parser doesn't change the pin default
    config values by itself, this will contain nothing.
user_pin_configs
    Shows the pin default config values to override the BIOS setup.
    Writing this (with two numbers, NID and value) appends the new
    value.  The given will be used instead of the initial BIOS value at
    the next reconfiguration time.  Note that this config will override
    even the driver pin configs, too.
reconfig
    Triggers the codec re-configuration.  When any value is written to
    this file, the driver re-initialize and parses the codec tree
    again.  All the changes done by the sysfs entries above are taken
    into account.
clear
    Resets the codec, removes the mixer elements and PCM stuff of the
    specified codec, and clear all init verbs and hints.

For example, when you want to change the pin default configuration
value of the pin widget 0x14 to 0x9993013f, and let the driver
re-configure based on that state, run like below:
::

    # echo 0x14 0x9993013f > /sys/class/sound/hwC0D0/user_pin_configs
    # echo 1 > /sys/class/sound/hwC0D0/reconfig

Hint Strings
------------
The codec parser have several switches and adjustment knobs for
matching better with the actual codec or device behavior.  Many of
them can be adjusted dynamically via "hints" strings as mentioned in
the section above.  For example, by passing ``jack_detect = no`` string
via sysfs or a patch file, you can disable the jack detection, thus
the codec parser will skip the features like auto-mute or mic
auto-switch.  As a boolean value, either ``yes``, ``no``, ``true``, ``false``,
``1`` or ``0`` can be passed.

The generic parser supports the following hints:

jack_detect (bool)
    specify whether the jack detection is available at all on this
    machine; default true
inv_jack_detect (bool)
    indicates that the jack detection logic is inverted
trigger_sense (bool)
    indicates that the jack detection needs the explicit call of
    AC_VERB_SET_PIN_SENSE verb
inv_eapd (bool)
    indicates that the EAPD is implemented in the inverted logic
pcm_format_first (bool)
    sets the PCM format before the stream tag and channel ID
sticky_stream (bool)
    keep the PCM format, stream tag and ID as long as possible;
    default true
spdif_status_reset (bool)
    reset the SPDIF status bits at each time the SPDIF stream is set
    up
pin_amp_workaround (bool)
    the output pin may have multiple amp values
single_adc_amp (bool)
    ADCs can have only single input amps
auto_mute (bool)
    enable/disable the headphone auto-mute feature; default true
auto_mic (bool)
    enable/disable the mic auto-switch feature; default true
line_in_auto_switch (bool)
    enable/disable the line-in auto-switch feature; default false
need_dac_fix (bool)
    limits the DACs depending on the channel count
primary_hp (bool)
    probe headphone jacks as the primary outputs; default true
multi_io (bool)
    try probing multi-I/O config (e.g. shared line-in/surround,
    mic/clfe jacks)
multi_cap_vol (bool)
    provide multiple capture volumes
inv_dmic_split (bool)
    provide split internal mic volume/switch for phase-inverted
    digital mics
indep_hp (bool)
    provide the independent headphone PCM stream and the corresponding
    mixer control, if available
add_stereo_mix_input (bool)
    add the stereo mix (analog-loopback mix) to the input mux if
    available
add_jack_modes (bool)
    add "xxx Jack Mode" enum controls to each I/O jack for allowing to
    change the headphone amp and mic bias VREF capabilities
power_save_node (bool)
    advanced power management for each widget, controlling the power
    sate (D0/D3) of each widget node depending on the actual pin and
    stream states
power_down_unused (bool)
    power down the unused widgets, a subset of power_save_node, and
    will be dropped in future
add_hp_mic (bool)
    add the headphone to capture source if possible
hp_mic_detect (bool)
    enable/disable the hp/mic shared input for a single built-in mic
    case; default true
vmaster (bool)
    enable/disable the virtual Master control; default true
mixer_nid (int)
    specifies the widget NID of the analog-loopback mixer

Early Patching
--------------
When ``CONFIG_SND_HDA_PATCH_LOADER=y`` is set, you can pass a "patch"
as a firmware file for modifying the HD-audio setup before
initializing the codec.  This can work basically like the
reconfiguration via sysfs in the above, but it does it before the
first codec configuration.

A patch file is a plain text file which looks like below:

::

    [codec]
    0x12345678 0xabcd1234 2

    [model]
    auto

    [pincfg]
    0x12 0x411111f0

    [verb]
    0x20 0x500 0x03
    0x20 0x400 0xff

    [hint]
    jack_detect = no

The file needs to have a line ``[codec]``.  The next line should contain
three numbers indicating the codec vendor-id (0x12345678 in the
example), the codec subsystem-id (0xabcd1234) and the address (2) of
the codec.  The rest patch entries are applied to this specified codec
until another codec entry is given.  Passing 0 or a negative number to
the first or the second value will make the check of the corresponding
field be skipped.  It'll be useful for really broken devices that don't
initialize SSID properly.

The ``[model]`` line allows to change the model name of the each codec.
In the example above, it will be changed to model=auto.
Note that this overrides the module option.

After the ``[pincfg]`` line, the contents are parsed as the initial
default pin-configurations just like ``user_pin_configs`` sysfs above.
The values can be shown in user_pin_configs sysfs file, too.

Similarly, the lines after ``[verb]`` are parsed as ``init_verbs``
sysfs entries, and the lines after ``[hint]`` are parsed as ``hints``
sysfs entries, respectively.

Another example to override the codec vendor id from 0x12345678 to
0xdeadbeef is like below:
::

    [codec]
    0x12345678 0xabcd1234 2

    [vendor_id]
    0xdeadbeef

In the similar way, you can override the codec subsystem_id via
``[subsystem_id]``, the revision id via ``[revision_id]`` line.
Also, the codec chip name can be rewritten via ``[chip_name]`` line.
::

    [codec]
    0x12345678 0xabcd1234 2

    [subsystem_id]
    0xffff1111

    [revision_id]
    0x10

    [chip_name]
    My-own NEWS-0002

The hd-audio driver reads the file via request_firmware().  Thus,
a patch file has to be located on the appropriate firmware path,
typically, /lib/firmware.  For example, when you pass the option
``patch=hda-init.fw``, the file /lib/firmware/hda-init.fw must be
present.

The patch module option is specific to each card instance, and you
need to give one file name for each instance, separated by commas.
For example, if you have two cards, one for an on-board analog and one
for an HDMI video board, you may pass patch option like below:
::

    options snd-hda-intel patch=on-board-patch,hdmi-patch

Power-Saving
------------
The power-saving is a kind of auto-suspend of the device.  When the
device is inactive for a certain time, the device is automatically
turned off to save the power.  The time to go down is specified via
``power_save`` module option, and this option can be changed dynamically
via sysfs.

The power-saving won't work when the analog loopback is enabled on
some codecs.  Make sure that you mute all unneeded signal routes when
you want the power-saving.

The power-saving feature might cause audible click noises at each
power-down/up depending on the device.  Some of them might be
solvable, but some are hard, I'm afraid.  Some distros such as
openSUSE enables the power-saving feature automatically when the power
cable is unplugged.  Thus, if you hear noises, suspect first the
power-saving.  See /sys/module/snd_hda_intel/parameters/power_save to
check the current value.  If it's non-zero, the feature is turned on.

The recent kernel supports the runtime PM for the HD-audio controller
chip, too.  It means that the HD-audio controller is also powered up /
down dynamically.  The feature is enabled only for certain controller
chips like Intel LynxPoint.  You can enable/disable this feature
forcibly by setting ``power_save_controller`` option, which is also
available at /sys/module/snd_hda_intel/parameters directory.

Tracepoints
-----------
The hd-audio driver gives a few basic tracepoints.
``hda:hda_send_cmd`` traces each CORB write while ``hda:hda_get_response``
traces the response from RIRB (only when read from the codec driver).
``hda:hda_bus_reset`` traces the bus-reset due to fatal error, etc,
``hda:hda_unsol_event`` traces the unsolicited events, and
``hda:hda_power_down`` and ``hda:hda_power_up`` trace the power down/up
via power-saving behavior.

Enabling all tracepoints can be done like
::

    # echo 1 > /sys/kernel/debug/tracing/events/hda/enable

then after some commands, you can traces from
/sys/kernel/debug/tracing/trace file.  For example, when you want to
trace what codec command is sent, enable the tracepoint like:
::

    # cat /sys/kernel/debug/tracing/trace
    # tracer: nop
    #
    #       TASK-PID    CPU#    TIMESTAMP  FUNCTION
    #          | |       |          |         |
	   <...>-7807  [002] 105147.774889: hda_send_cmd: [0:0] val=e3a019
	   <...>-7807  [002] 105147.774893: hda_send_cmd: [0:0] val=e39019
	   <...>-7807  [002] 105147.999542: hda_send_cmd: [0:0] val=e3a01a
	   <...>-7807  [002] 105147.999543: hda_send_cmd: [0:0] val=e3901a
	   <...>-26764 [001] 349222.837143: hda_send_cmd: [0:0] val=e3a019
	   <...>-26764 [001] 349222.837148: hda_send_cmd: [0:0] val=e39019
	   <...>-26764 [001] 349223.058539: hda_send_cmd: [0:0] val=e3a01a
	   <...>-26764 [001] 349223.058541: hda_send_cmd: [0:0] val=e3901a

Here ``[0:0]`` indicates the card number and the codec address, and
``val`` shows the value sent to the codec, respectively.  The value is
a packed value, and you can decode it via hda-decode-verb program
included in hda-emu package below.  For example, the value e3a019 is
to set the left output-amp value to 25.
::

    % hda-decode-verb 0xe3a019
    raw value = 0x00e3a019
    cid = 0, nid = 0x0e, verb = 0x3a0, parm = 0x19
    raw value: verb = 0x3a0, parm = 0x19
    verbname = set_amp_gain_mute
    amp raw val = 0xa019
    output, left, idx=0, mute=0, val=25

Development Tree
----------------
The latest development codes for HD-audio are found on sound git tree:

* git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git

The master branch or for-next branches can be used as the main
development branches in general while the development for the current
and next kernels are found in for-linus and for-next branches,
respectively.

Sending a Bug Report
--------------------
If any model or module options don't work for your device, it's time
to send a bug report to the developers.  Give the following in your
bug report:

* Hardware vendor, product and model names
* Kernel version (and ALSA-driver version if you built externally)
* ``alsa-info.sh`` output; run with ``--no-upload`` option.  See the
  section below about alsa-info

If it's a regression, at best, send alsa-info outputs of both working
and non-working kernels.  This is really helpful because we can
compare the codec registers directly.

Send a bug report either the following:

kernel-bugzilla
    https://bugzilla.kernel.org/
alsa-devel ML
    alsa-devel@alsa-project.org

Debug Tools
===========

This section describes some tools available for debugging HD-audio
problems.

alsa-info
---------
The script ``alsa-info.sh`` is a very useful tool to gather the audio
device information.  It's included in alsa-utils package.  The latest
version can be found on git repository:

* git://git.alsa-project.org/alsa-utils.git

The script can be fetched directly from the following URL, too:

* https://www.alsa-project.org/alsa-info.sh

Run this script as root, and it will gather the important information
such as the module lists, module parameters, proc file contents
including the codec proc files, mixer outputs and the control
elements.  As default, it will store the information onto a web server
on alsa-project.org.  But, if you send a bug report, it'd be better to
run with ``--no-upload`` option, and attach the generated file.

There are some other useful options.  See ``--help`` option output for
details.

When a probe error occurs or when the driver obviously assigns a
mismatched model, it'd be helpful to load the driver with
``probe_only=1`` option (at best after the cold reboot) and run
alsa-info at this state.  With this option, the driver won't configure
the mixer and PCM but just tries to probe the codec slot.  After
probing, the proc file is available, so you can get the raw codec
information before modified by the driver.  Of course, the driver
isn't usable with ``probe_only=1``.  But you can continue the
configuration via hwdep sysfs file if hda-reconfig option is enabled.
Using ``probe_only`` mask 2 skips the reset of HDA codecs (use
``probe_only=3`` as module option). The hwdep interface can be used
to determine the BIOS codec initialization.

hda-verb
--------
hda-verb is a tiny program that allows you to access the HD-audio
codec directly.  You can execute a raw HD-audio codec verb with this.
This program accesses the hwdep device, thus you need to enable the
kernel config ``CONFIG_SND_HDA_HWDEP=y`` beforehand.

The hda-verb program takes four arguments: the hwdep device file, the
widget NID, the verb and the parameter.  When you access to the codec
on the slot 2 of the card 0, pass /dev/snd/hwC0D2 to the first
argument, typically.  (However, the real path name depends on the
system.)

The second parameter is the widget number-id to access.  The third
parameter can be either a hex/digit number or a string corresponding
to a verb.  Similarly, the last parameter is the value to write, or
can be a string for the parameter type.

::

    % hda-verb /dev/snd/hwC0D0 0x12 0x701 2
    nid = 0x12, verb = 0x701, param = 0x2
    value = 0x0

    % hda-verb /dev/snd/hwC0D0 0x0 PARAMETERS VENDOR_ID
    nid = 0x0, verb = 0xf00, param = 0x0
    value = 0x10ec0262

    % hda-verb /dev/snd/hwC0D0 2 set_a 0xb080
    nid = 0x2, verb = 0x300, param = 0xb080
    value = 0x0

Although you can issue any verbs with this program, the driver state
won't be always updated.  For example, the volume values are usually
cached in the driver, and thus changing the widget amp value directly
via hda-verb won't change the mixer value.

The hda-verb program is included now in alsa-tools:

* git://git.alsa-project.org/alsa-tools.git

Also, the old stand-alone package is found in the ftp directory:

* ftp://ftp.suse.com/pub/people/tiwai/misc/

Also a git repository is available:

* git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-verb.git

See README file in the tarball for more details about hda-verb
program.

hda-analyzer
------------
hda-analyzer provides a graphical interface to access the raw HD-audio
control, based on pyGTK2 binding.  It's a more powerful version of
hda-verb.  The program gives you an easy-to-use GUI stuff for showing
the widget information and adjusting the amp values, as well as the
proc-compatible output.

The hda-analyzer:

* https://git.alsa-project.org/?p=alsa.git;a=tree;f=hda-analyzer

is a part of alsa.git repository in alsa-project.org:

* git://git.alsa-project.org/alsa.git

Codecgraph
----------
Codecgraph is a utility program to generate a graph and visualizes the
codec-node connection of a codec chip.  It's especially useful when
you analyze or debug a codec without a proper datasheet.  The program
parses the given codec proc file and converts to SVG via graphiz
program.

The tarball and GIT trees are found in the web page at:

* http://helllabs.org/codecgraph/

hda-emu
-------
hda-emu is an HD-audio emulator.  The main purpose of this program is
to debug an HD-audio codec without the real hardware.  Thus, it
doesn't emulate the behavior with the real audio I/O, but it just
dumps the codec register changes and the ALSA-driver internal changes
at probing and operating the HD-audio driver.

The program requires a codec proc-file to simulate.  Get a proc file
for the target codec beforehand, or pick up an example codec from the
codec proc collections in the tarball.  Then, run the program with the
proc file, and the hda-emu program will start parsing the codec file
and simulates the HD-audio driver:

::

    % hda-emu codecs/stac9200-dell-d820-laptop
    # Parsing..
    hda_codec: Unknown model for STAC9200, using BIOS defaults
    hda_codec: pin nid 08 bios pin config 40c003fa
    ....

The program gives you only a very dumb command-line interface.  You
can get a proc-file dump at the current state, get a list of control
(mixer) elements, set/get the control element value, simulate the PCM
operation, the jack plugging simulation, etc.

The program is found in the git repository below:

* git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-emu.git

See README file in the repository for more details about hda-emu
program.

hda-jack-retask
---------------
hda-jack-retask is a user-friendly GUI program to manipulate the
HD-audio pin control for jack retasking.  If you have a problem about
the jack assignment, try this program and check whether you can get
useful results.  Once when you figure out the proper pin assignment,
it can be fixed either in the driver code statically or via passing a
firmware patch file (see "Early Patching" section).

The program is included in alsa-tools now:

* git://git.alsa-project.org/alsa-tools.git


code:
===============================
Realtek PC Beep Hidden Register
===============================

This file documents the "PC Beep Hidden Register", which is present in certain
Realtek HDA codecs and controls a muxer and pair of passthrough mixers that can
route audio between pins but aren't themselves exposed as HDA widgets. As far
as I can tell, these hidden routes are designed to allow flexible PC Beep output
for codecs that don't have mixer widgets in their output paths. Why it's easier
to hide a mixer behind an undocumented vendor register than to just expose it
as a widget, I have no idea.

Register Description
====================

The register is accessed via processing coefficient 0x36 on NID 20h. Bits not
identified below have no discernible effect on my machine, a Dell XPS 13 9350::

  MSB                           LSB
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | |h|S|L|         | B |R|       | Known bits
  +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
  |0|0|1|1|  0x7  |0|0x0|1|  0x7  | Reset value
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

1Ah input select (B): 2 bits
  When zero, expose the PC Beep line (from the internal beep generator, when
  enabled with the Set Beep Generation verb on NID 01h, or else from the
  external PCBEEP pin) on the 1Ah pin node. When nonzero, expose the headphone
  jack (or possibly Line In on some machines) input instead. If PC Beep is
  selected, the 1Ah boost control has no effect.

Amplify 1Ah loopback, left (L): 1 bit
  Amplify the left channel of 1Ah before mixing it into outputs as specified
  by h and S bits. Does not affect the level of 1Ah exposed to other widgets.

Amplify 1Ah loopback, right (R): 1 bit
  Amplify the right channel of 1Ah before mixing it into outputs as specified
  by h and S bits. Does not affect the level of 1Ah exposed to other widgets.

Loopback 1Ah to 21h [active low] (h): 1 bit
  When zero, mix 1Ah (possibly with amplification, depending on L and R bits)
  into 21h (headphone jack on my machine). Mixed signal respects the mute
  setting on 21h.

Loopback 1Ah to 14h (S): 1 bit
  When one, mix 1Ah (possibly with amplification, depending on L and R bits)
  into 14h (internal speaker on my machine). Mixed signal **ignores** the mute
  setting on 14h and is present whenever 14h is configured as an output.

Path diagrams
=============

1Ah input selection (DIV is the PC Beep divider set on NID 01h)::

  <Beep generator>   <PCBEEP pin>    <Headphone jack>
          |                |                |
          +--DIV--+--!DIV--+       {1Ah boost control}
                  |                         |
                  +--(b == 0)--+--(b != 0)--+
                               |
               >1Ah (Beep/Headphone Mic/Line In)<

Loopback of 1Ah to 21h/14h::

               <1Ah (Beep/Headphone Mic/Line In)>
                               |
                        {amplify if L/R}
                               |
                  +-----!h-----+-----S-----+
                  |                        |
          {21h mute control}               |
                  |                        |
          >21h (Headphone)<     >14h (Internal Speaker)<

Background
==========

All Realtek HDA codecs have a vendor-defined widget with node ID 20h which
provides access to a bank of registers that control various codec functions.
Registers are read and written via the standard HDA processing coefficient
verbs (Set/Get Coefficient Index, Set/Get Processing Coefficient). The node is
named "Realtek Vendor Registers" in public datasheets' verb listings and,
apart from that, is entirely undocumented.

This particular register, exposed at coefficient 0x36 and named in commits from
Realtek, is of note: unlike most registers, which seem to control detailed
amplifier parameters not in scope of the HDA specification, it controls audio
routing which could just as easily have been defined using standard HDA mixer
and selector widgets.

Specifically, it selects between two sources for the input pin widget with Node
ID (NID) 1Ah: the widget's signal can come either from an audio jack (on my
laptop, a Dell XPS 13 9350, it's the headphone jack, but comments in Realtek
commits indicate that it might be a Line In on some machines) or from the PC
Beep line (which is itself multiplexed between the codec's internal beep
generator and external PCBEEP pin, depending on if the beep generator is
enabled via verbs on NID 01h). Additionally, it can mix (with optional
amplification) that signal onto the 21h and/or 14h output pins.

The register's reset value is 0x3717, corresponding to PC Beep on 1Ah that is
then amplified and mixed into both the headphones and the speakers. Not only
does this violate the HDA specification, which says that "[a vendor defined
beep input pin] connection may be maintained *only* while the Link reset
(**RST#**) is asserted", it means that we cannot ignore the register if we care
about the input that 1Ah would otherwise expose or if the PCBEEP trace is
poorly shielded and picks up chassis noise (both of which are the case on my
machine).

Unfortunately, there are lots of ways to get this register configuration wrong.
Linux, it seems, has gone through most of them. For one, the register resets
after S3 suspend: judging by existing code, this isn't the case for all vendor
registers, and it's led to some fixes that improve behavior on cold boot but
don't last after suspend. Other fixes have successfully switched the 1Ah input
away from PC Beep but have failed to disable both loopback paths. On my
machine, this means that the headphone input is amplified and looped back to
the headphone output, which uses the exact same pins! As you might expect, this
causes terrible headphone noise, the character of which is controlled by the
1Ah boost control. (If you've seen instructions online to fix XPS 13 headphone
noise by changing "Headphone Mic Boost" in ALSA, now you know why.)

The information here has been obtained through black-box reverse engineering of
the ALC256 codec's behavior and is not guaranteed to be correct. It likely
also applies for the ALC255, ALC257, ALC235, and ALC236, since those codecs
seem to be close relatives of the ALC256. (They all share one initialization
function.) Additionally, other codecs like the ALC225 and ALC285 also have this
register, judging by existing fixups in ``patch_realtek.c``, but specific
data (e.g. node IDs, bit positions, pin mappings) for those codecs may differ
from what I've described here.


code:
===================================
Linux Sound Subsystem Documentation
===================================

.. toctree::
   :maxdepth: 2

   kernel-api/index
   designs/index
   soc/index
   alsa-configuration
   hd-audio/index
   cards/index

.. only::  subproject and html

   Indices
   =======

   * :ref:`genindex`


code:
===================
The ALSA Driver API
===================

Management of Cards and Devices
===============================

Card Management
---------------
.. kernel-doc:: sound/core/init.c

Device Components
-----------------
.. kernel-doc:: sound/core/device.c

Module requests and Device File Entries
---------------------------------------
.. kernel-doc:: sound/core/sound.c

Memory Management Helpers
-------------------------
.. kernel-doc:: sound/core/memory.c
.. kernel-doc:: sound/core/memalloc.c

PCM API
=======

PCM Core
--------
.. kernel-doc:: sound/core/pcm.c
.. kernel-doc:: sound/core/pcm_lib.c
.. kernel-doc:: sound/core/pcm_native.c
.. kernel-doc:: include/sound/pcm.h

PCM Format Helpers
------------------
.. kernel-doc:: sound/core/pcm_misc.c

PCM Memory Management
---------------------
.. kernel-doc:: sound/core/pcm_memory.c

PCM DMA Engine API
------------------
.. kernel-doc:: sound/core/pcm_dmaengine.c
.. kernel-doc:: include/sound/dmaengine_pcm.h

Control/Mixer API
=================

General Control Interface
-------------------------
.. kernel-doc:: sound/core/control.c

AC97 Codec API
--------------
.. kernel-doc:: sound/pci/ac97/ac97_codec.c
.. kernel-doc:: sound/pci/ac97/ac97_pcm.c

Virtual Master Control API
--------------------------
.. kernel-doc:: sound/core/vmaster.c
.. kernel-doc:: include/sound/control.h

MIDI API
========

Raw MIDI API
------------
.. kernel-doc:: sound/core/rawmidi.c

MPU401-UART API
---------------
.. kernel-doc:: sound/drivers/mpu401/mpu401_uart.c

Proc Info API
=============

Proc Info Interface
-------------------
.. kernel-doc:: sound/core/info.c

Compress Offload
================

Compress Offload API
--------------------
.. kernel-doc:: sound/core/compress_offload.c
.. kernel-doc:: include/uapi/sound/compress_offload.h
.. kernel-doc:: include/uapi/sound/compress_params.h
.. kernel-doc:: include/sound/compress_driver.h

ASoC
====

ASoC Core API
-------------
.. kernel-doc:: include/sound/soc.h
.. kernel-doc:: sound/soc/soc-core.c
.. kernel-doc:: sound/soc/soc-devres.c
.. kernel-doc:: sound/soc/soc-component.c
.. kernel-doc:: sound/soc/soc-pcm.c
.. kernel-doc:: sound/soc/soc-ops.c
.. kernel-doc:: sound/soc/soc-compress.c

ASoC DAPM API
-------------
.. kernel-doc:: sound/soc/soc-dapm.c

ASoC DMA Engine API
-------------------
.. kernel-doc:: sound/soc/soc-generic-dmaengine-pcm.c

Miscellaneous Functions
=======================

Hardware-Dependent Devices API
------------------------------
.. kernel-doc:: sound/core/hwdep.c

Jack Abstraction Layer API
--------------------------
.. kernel-doc:: include/sound/jack.h
.. kernel-doc:: sound/core/jack.c
.. kernel-doc:: sound/soc/soc-jack.c

ISA DMA Helpers
---------------
.. kernel-doc:: sound/core/isadma.c

Other Helper Macros
-------------------
.. kernel-doc:: include/sound/core.h
.. kernel-doc:: sound/sound_core.c


code:
ALSA Kernel API Documentation
=============================

.. toctree::
   :maxdepth: 2

   alsa-driver-api
   writing-an-alsa-driver