jack-injection.rst (4479B)
1============================ 2ALSA Jack Software Injection 3============================ 4 5Simple Introduction On Jack Injection 6===================================== 7 8Here jack injection means users could inject plugin or plugout events 9to the audio jacks through debugfs interface, it is helpful to 10validate ALSA userspace changes. For example, we change the audio 11profile switching code in the pulseaudio, and we want to verify if the 12change works as expected and if the change introduce the regression, 13in this case, we could inject plugin or plugout events to an audio 14jack or to some audio jacks, we don't need to physically access the 15machine and plug/unplug physical devices to the audio jack. 16 17In this design, an audio jack doesn't equal to a physical audio jack. 18Sometimes a physical audio jack contains multi functions, and the 19ALSA driver creates multi ``jack_kctl`` for a ``snd_jack``, here the 20``snd_jack`` represents a physical audio jack and the ``jack_kctl`` 21represents a function, for example a physical jack has two functions: 22headphone and mic_in, the ALSA ASoC driver will build 2 ``jack_kctl`` 23for this jack. The jack injection is implemented based on the 24``jack_kctl`` instead of ``snd_jack``. 25 26To inject events to audio jacks, we need to enable the jack injection 27via ``sw_inject_enable`` first, once it is enabled, this jack will not 28change the state by hardware events anymore, we could inject plugin or 29plugout events via ``jackin_inject`` and check the jack state via 30``status``, after we finish our test, we need to disable the jack 31injection via ``sw_inject_enable`` too, once it is disabled, the jack 32state will be restored according to the last reported hardware events 33and will change by future hardware events. 34 35The Layout of Jack Injection Interface 36====================================== 37 38If users enable the SND_JACK_INJECTION_DEBUG in the kernel, the audio 39jack injection interface will be created as below: 40:: 41 42 $debugfs_mount_dir/sound 43 |-- card0 44 |-- |-- HDMI_DP_pcm_10_Jack 45 |-- |-- |-- jackin_inject 46 |-- |-- |-- kctl_id 47 |-- |-- |-- mask_bits 48 |-- |-- |-- status 49 |-- |-- |-- sw_inject_enable 50 |-- |-- |-- type 51 ... 52 |-- |-- HDMI_DP_pcm_9_Jack 53 |-- |-- jackin_inject 54 |-- |-- kctl_id 55 |-- |-- mask_bits 56 |-- |-- status 57 |-- |-- sw_inject_enable 58 |-- |-- type 59 |-- card1 60 |-- HDMI_DP_pcm_5_Jack 61 |-- |-- jackin_inject 62 |-- |-- kctl_id 63 |-- |-- mask_bits 64 |-- |-- status 65 |-- |-- sw_inject_enable 66 |-- |-- type 67 ... 68 |-- Headphone_Jack 69 |-- |-- jackin_inject 70 |-- |-- kctl_id 71 |-- |-- mask_bits 72 |-- |-- status 73 |-- |-- sw_inject_enable 74 |-- |-- type 75 |-- Headset_Mic_Jack 76 |-- jackin_inject 77 |-- kctl_id 78 |-- mask_bits 79 |-- status 80 |-- sw_inject_enable 81 |-- type 82 83The Explanation Of The Nodes 84====================================== 85 86kctl_id 87 read-only, get jack_kctl->kctl's id 88 :: 89 90 sound/card1/Headphone_Jack# cat kctl_id 91 Headphone Jack 92 93mask_bits 94 read-only, get jack_kctl's supported events mask_bits 95 :: 96 97 sound/card1/Headphone_Jack# cat mask_bits 98 0x0001 HEADPHONE(0x0001) 99 100status 101 read-only, get jack_kctl's current status 102 103- headphone unplugged: 104 105 :: 106 107 sound/card1/Headphone_Jack# cat status 108 Unplugged 109 110- headphone plugged: 111 112 :: 113 114 sound/card1/Headphone_Jack# cat status 115 Plugged 116 117type 118 read-only, get snd_jack's supported events from type (all supported events on the physical audio jack) 119 :: 120 121 sound/card1/Headphone_Jack# cat type 122 0x7803 HEADPHONE(0x0001) MICROPHONE(0x0002) BTN_3(0x0800) BTN_2(0x1000) BTN_1(0x2000) BTN_0(0x4000) 123 124sw_inject_enable 125 read-write, enable or disable injection 126 127- injection disabled: 128 129 :: 130 131 sound/card1/Headphone_Jack# cat sw_inject_enable 132 Jack: Headphone Jack Inject Enabled: 0 133 134- injection enabled: 135 136 :: 137 138 sound/card1/Headphone_Jack# cat sw_inject_enable 139 Jack: Headphone Jack Inject Enabled: 1 140 141- to enable jack injection: 142 143 :: 144 145 sound/card1/Headphone_Jack# echo 1 > sw_inject_enable 146 147- to disable jack injection: 148 149 :: 150 151 sound/card1/Headphone_Jack# echo 0 > sw_inject_enable 152 153jackin_inject 154 write-only, inject plugin or plugout 155 156- to inject plugin: 157 158 :: 159 160 sound/card1/Headphone_Jack# echo 1 > jackin_inject 161 162- to inject plugout: 163 164 :: 165 166 sound/card1/Headphone_Jack# echo 0 > jackin_inject