Hi Bastien, On 12/10/16 12:58, Bastien Nocera wrote: > On Wed, 2016-10-12 at 19:36 +0900, Takashi Sakamoto wrote: >> On Oct 12 2016 14:10, Bastien Nocera wrote: >>> My questions are: >>> - does the USB audio driver support jack sensing? >>> - is this something standard that's just not implemented yet? In >>> which >>> case, I'd be up for at least trying, given specs. >>> - or is it something that depends on the device, and in which case, >>> how >>> would I find out? >> >> >> In ALSA usb-related codes, there's no functions calls for >> snd_jack_*(), >> thus none of ALSA drivers for USB support Jack sense feature of ALSA >> control interface. >> >> The requirement of Jack sense feature is whether hardwares support >> it. >> For example, some hardware codecs such as HDA codecs generates >> signals >> when plugs are insert to jacks connected to the codecs. Corresponding >> ALSA drivers catch the signals, then tell it to user land. >> >> If your hardware performs like it, you have a probability to add >> support >> for jack sense feature to ALSA drivers for USB. But I don't know >> exactly >> that USB related specifications such as USB Audio Device Class >> 1.0/2.0/3.0 supports the feature. > > Looks like whether or not jack sensing works depends on the device > itself, but there is a mechanism to propagate the change in setup in > the USB Audio 2.0 spec, in the "Interrupts" section: > " > A change of state in the audio function is most often caused by a > certain event that takes place. An event can either be user-initiated > or device-initiated. User-initiated jack insertion or removal is a > typical example of a user-initiated event. > " snd_usb_audio doesn't support control interrupts yet. It's a nice feature to work on. -- Felipe
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