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. " I guess I should probably test in another operating system to check whether the hardware I have supports this to start with, and go from there. Cheers _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
