On 01/18/2012 06:35 PM, Tanu Kaskinen wrote: > On Wed, 2012-01-11 at 17:03 +0100, David Henningsson wrote: >> With 3.3 merge window opened, and the new jack detection interface >> scheduled to go in, maybe it's time to talk about the implementation as >> well. >> >> My draft patch is here: >> http://kernel.ubuntu.com/git?p=diwic/pulseaudio.git;a=commit;h=1f239a9966fe7e43d3c9cb37fedabf31ff7d706e >> >> Fetching the jack state is done through the alsa-lib hctl interface, >> whereas the existing mixer stuff uses the alsa-lib smixer interface, >> which layers on top of the hctl interface. Right now I've tried to reuse >> the existing mixer code, which leads to stuff such as: >> >> if (fdl->hctl) >> err = snd_hctl_poll_descriptors_revents(fdl->hctl, >> fdl->work_fds, fdl->num_fds,&revents); >> else >> err = snd_mixer_poll_descriptors_revents(fdl->mixer, >> fdl->work_fds, fdl->num_fds,&revents); >> >> Looks a bit copy-pasted, but I think it is the easiest solution at the >> moment. It's just five or so places anyway. >> The other option would be to try to port the entire mixer stuff to use >> the hctl interface instead of the smixer interface, but I'm not sure I >> can foresee how much trouble that actually would be, and if we would run >> in to any regressions. >> >> Thoughts? > > The current approach of using hctl and smixer side by side looks ok to > me. A couple of questions: > > Supposedly the simple mixer interface is significantly simpler in some > way. If we moved to hctl entirely, do you know roughly how much there > would be extra complexity? A lot, a little or are the two interfaces > about the same? Do you know in what ways the simple interface is > simpler? If there's no explosion of unnecessary code resulting from > moving to hctl, I'd file a wishlist bug. Otherwise we can just forget > about it. I'm not completely sure but after a short look I think we should remain at using smixer for the mixers. They got stuff like reading tlv and turning it into dB information; and by doing that manually, we would have to adapt if ALSA ever wanted to change that stuff. I'll see if I can clean up my patch a bit, to make it ready for merging upstream. > Have the alsa developers said anything about adding the jack stuff to > the smixer interface? No, this stuff is quite new and nobody's been requesting it anyway. But I'd say probably not - the jacks are not mixers. @Colin, I just had a quick look at libsalsa at seems to implement the hctl interface. So that should be okay. -- David Henningsson, Canonical Ltd. http://launchpad.net/~diwic
