Re: [PATCH 1/2] ALSA: usb-audio: Support jack detection on Dell dock

On Mon, 27 Jun 2022 19:18:54 +0200, Jan Schär wrote:

The Dell WD15 dock has a headset and a line out port. Add support for detecting if a jack is inserted into one of these ports. For the headset jack, additionally determine if a mic is present.

The WD15 contains an ALC4020 USB audio controller and ALC3263 audio codec from Realtek. It is a UAC 1 device, and UAC 1 does not support jack detection. Instead, jack detection works by sending HD Audio commands over vendor-type USB messages.

I found out how it works by looking at USB captures on Windows. The audio codec is very similar to the one supported by sound/soc/codecs/rt298.c / rt298.h, some constant names and the mic detection are adapted from there. The realtek_add_jack function is adapted from build_connector_control in sound/usb/mixer.c.

I tested this on a WD15 dock with the latest firmware.

Signed-off-by: Jan Schär jan@jschaer.ch

For testing this patch, you need to change the content of the file /usr/share/alsa/ucm2/USB-Audio/Dell-WD15-Dock-HiFi.conf to the following:

SectionDevice."Headphones" {
   Comment "Headphones"

   Value {
   	PlaybackPriority 100
   	PlaybackPCM "hw:${CardId}"
   	JackControl "Headphone Jack"

   	If.Headphone_ctl {
   		Condition {
   			Type ControlExists
   			Control "name='Headphone Playback Switch'"
   		}
   		True {
   			PlaybackMixerElem "Headphone"
   			PlaybackVolume "Headphone Playback Volume"
   			PlaybackSwitch "Headphone Playback Switch"
   		}
   	}
   }
}

SectionDevice."Line" {
   Comment "Line Out"

   Value {
   	PlaybackPriority 200
   	PlaybackPCM "hw:${CardId},1"
   	JackControl "Line Out Jack"

   	If.Line_ctl {
   		Condition {
   			Type ControlExists
   			Control "name='Line Playback Switch'"
   		}
   		True {
   			PlaybackMixerElem "Line"
   			PlaybackVolume "Line Playback Volume"
   			PlaybackSwitch "Line Playback Switch"
   		}
   	}
   }
}

SectionDevice."Headset" {
   Comment "Headset Microphone"

   Value {
   	CapturePriority 100
   	CapturePCM "hw:${CardId}"
   	JackControl "Headset Mic Jack"

   	If.Mic_ctl {
   		Condition {
   			Type ControlExists
   			Control "name='Mic Capture Switch'"
   		}
   		True {
   			CaptureMixerElem "Mic"
   			CaptureVolume "Mic Capture Volume"
   			CaptureSwitch "Mic Capture Switch"
   		}
   	}
   }
}

This is an interesting finding. Applied both patches to for-next branch now.

Thanks!

Takashi