Hi Takashi, On Thu, Oct 1, 2015 at 12:46 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > On Thu, 01 Oct 2015 13:35:48 +0200, > Felipe Tonello wrote: >> >> Hi Clemens, >> >> On Thu, Oct 1, 2015 at 12:27 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: >> > Felipe Tonello wrote: >> >> I am planning to start the support of MIDI BLE profile[1]. >> >> >> >> I suggest two main goals: >> >> * To be transparent to applications, i.e., use rawmidi and sequencer >> >> ALSA interfaces to interact. >> >> * To support peripheral and central BLE roles. >> >> >> >> My question is: what is the best way possible of doing it? >> > >> > Just write a (user-space) sequencer client. >> >> But this will limit to seq interface only. It will not be available >> via rawmidi interface, right? Unless I load snd-virtmidi, correct? > > Right. > >> That was what I was suggesting at first, but I don't really like the >> idea of loading snd-virtmidi for that. > > Well, many audio/music apps may talk directly sequencer API, too, so > it's not too bad. Whether loading snd-virmidi is a system setup > question, and it'd be more or less static configuration like snd-seq > core module. > >> >> [...] >> >> They all have the problem of context switching between bluez plugin >> >> and alsa midi driver. >> > >> > Why would context switches be a problem? >> >> It is just too much travelling around. GATT messages are parsed in >> userspace by BlueZ, so it sounds unnecessary to copy buffers to the >> kernel and copy back to user space to the application (ALSA). > > Of course it'd be optimal if we can avoid context switching, but > usually its latency isn't too critical for MIDI, even on a much slower > machine in 20 years ago. > > So, IMO, we should go for a simpler implementation at first. Fair enough. So, initially the best way to go would be to write a seq back-end using D-Bus GATT API from BlueZ. An important thing to notice is that this implementation doesn't support BLE peripheral role. Felipe -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
