linux/Documentation/sound/designs/jack-injection.rst
Hui Wang 2d670ea2bd ALSA: jack: implement software jack injection via debugfs
This change adds audio jack injection feature through debugfs, with
this feature, we could validate alsa userspace changes by injecting
plugin or plugout events to the non-phantom audio jacks.

With this change, the sound core will build the folders
$debugfs_mount_dir/sound/cardN if SND_DEBUG and DEBUG_FS are enabled.
And if users also enable the SND_JACK_INJECTION_DEBUG, the jack
injection nodes will be built in the folder cardN like below:

$tree $debugfs_mount_dir/sound
$debugfs_mount_dir/sound
├── card0
│   ├── HDMI_DP_pcm_10_Jack
│   │   ├── jackin_inject
│   │   ├── kctl_id
│   │   ├── mask_bits
│   │   ├── status
│   │   ├── sw_inject_enable
│   │   └── type
...
│   └── HDMI_DP_pcm_9_Jack
│       ├── jackin_inject
│       ├── kctl_id
│       ├── mask_bits
│       ├── status
│       ├── sw_inject_enable
│       └── type
└── card1
    ├── HDMI_DP_pcm_5_Jack
    │   ├── jackin_inject
    │   ├── kctl_id
    │   ├── mask_bits
    │   ├── status
    │   ├── sw_inject_enable
    │   └── type
    ...
    ├── Headphone_Jack
    │   ├── jackin_inject
    │   ├── kctl_id
    │   ├── mask_bits
    │   ├── status
    │   ├── sw_inject_enable
    │   └── type
    └── Headset_Mic_Jack
        ├── jackin_inject
        ├── kctl_id
        ├── mask_bits
        ├── status
        ├── sw_inject_enable
        └── type

The nodes kctl_id, mask_bits, status and type are read-only, users
could check jack or jack_kctl's information through them.

The nodes sw_inject_enable and jackin_inject are directly used for
injection. The sw_inject_enable is read-write, users could check if
software injection is enabled or not on this jack, and users could
echo 1 or 0 to enable or disable software injection on this jack. Once
the injection is enabled, the jack will not change by hardware events
anymore, once the injection is disabled, the jack will restore the
last reported hardware events to the jack. The jackin_inject is
write-only, if the injection is enabled, users could echo 1 or 0 to
this node to inject plugin or plugout events to this jack.

For the detailed usage information on these nodes, please refer to
Documentation/sound/designs/jack-injection.rst.

Reviewed-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Link: https://lore.kernel.org/r/20210127085639.74954-2-hui.wang@canonical.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2021-02-02 10:37:07 +01:00

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============================
ALSA Jack Software Injection
============================
Simple Introduction On Jack Injection
=====================================
Here jack injection means users could inject plugin or plugout events
to the audio jacks through debugfs interface, it is helpful to
validate ALSA userspace changes. For example, we change the audio
profile switching code in the pulseaudio, and we want to verify if the
change works as expected and if the change introduce the regression,
in this case, we could inject plugin or plugout events to an audio
jack or to some audio jacks, we don't need to physically access the
machine and plug/unplug physical devices to the audio jack.
In this design, an audio jack doesn't equal to a physical audio jack.
Sometimes a physical audio jack contains multi functions, and the
ALSA driver creates multi ``jack_kctl`` for a ``snd_jack``, here the
``snd_jack`` represents a physical audio jack and the ``jack_kctl``
represents a function, for example a physical jack has two functions:
headphone and mic_in, the ALSA ASoC driver will build 2 ``jack_kctl``
for this jack. The jack injection is implemented based on the
``jack_kctl`` instead of ``snd_jack``.
To inject events to audio jacks, we need to enable the jack injection
via ``sw_inject_enable`` first, once it is enabled, this jack will not
change the state by hardware events anymore, we could inject plugin or
plugout events via ``jackin_inject`` and check the jack state via
``status``, after we finish our test, we need to disable the jack
injection via ``sw_inject_enable`` too, once it is disabled, the jack
state will be restored according to the last reported hardware events
and will change by future hardware events.
The Layout of Jack Injection Interface
======================================
If users enable the SND_JACK_INJECTION_DEBUG in the kernel, the audio
jack injection interface will be created as below:
::
$debugfs_mount_dir/sound
|-- card0
|-- |-- HDMI_DP_pcm_10_Jack
|-- |-- |-- jackin_inject
|-- |-- |-- kctl_id
|-- |-- |-- mask_bits
|-- |-- |-- status
|-- |-- |-- sw_inject_enable
|-- |-- |-- type
...
|-- |-- HDMI_DP_pcm_9_Jack
|-- |-- jackin_inject
|-- |-- kctl_id
|-- |-- mask_bits
|-- |-- status
|-- |-- sw_inject_enable
|-- |-- type
|-- card1
|-- HDMI_DP_pcm_5_Jack
|-- |-- jackin_inject
|-- |-- kctl_id
|-- |-- mask_bits
|-- |-- status
|-- |-- sw_inject_enable
|-- |-- type
...
|-- Headphone_Jack
|-- |-- jackin_inject
|-- |-- kctl_id
|-- |-- mask_bits
|-- |-- status
|-- |-- sw_inject_enable
|-- |-- type
|-- Headset_Mic_Jack
|-- jackin_inject
|-- kctl_id
|-- mask_bits
|-- status
|-- sw_inject_enable
|-- type
The Explanation Of The Nodes
======================================
kctl_id
read-only, get jack_kctl->kctl's id
::
sound/card1/Headphone_Jack# cat kctl_id
Headphone Jack
mask_bits
read-only, get jack_kctl's supported events mask_bits
::
sound/card1/Headphone_Jack# cat mask_bits
0x0001 HEADPHONE(0x0001)
status
read-only, get jack_kctl's current status
- headphone unplugged:
::
sound/card1/Headphone_Jack# cat status
Unplugged
- headphone plugged:
::
sound/card1/Headphone_Jack# cat status
Plugged
type
read-only, get snd_jack's supported events from type (all supported events on the physical audio jack)
::
sound/card1/Headphone_Jack# cat type
0x7803 HEADPHONE(0x0001) MICROPHONE(0x0002) BTN_3(0x0800) BTN_2(0x1000) BTN_1(0x2000) BTN_0(0x4000)
sw_inject_enable
read-write, enable or disable injection
- injection disabled:
::
sound/card1/Headphone_Jack# cat sw_inject_enable
Jack: Headphone Jack Inject Enabled: 0
- injection enabled:
::
sound/card1/Headphone_Jack# cat sw_inject_enable
Jack: Headphone Jack Inject Enabled: 1
- to enable jack injection:
::
sound/card1/Headphone_Jack# echo 1 > sw_inject_enable
- to disable jack injection:
::
sound/card1/Headphone_Jack# echo 0 > sw_inject_enable
jackin_inject
write-only, inject plugin or plugout
- to inject plugin:
::
sound/card1/Headphone_Jack# echo 1 > jackin_inject
- to inject plugout:
::
sound/card1/Headphone_Jack# echo 0 > jackin_inject