В Чт, 02/07/2020 в 13:28 +0200, Pavel Hofman пишет: > Dne 29. 06. 20 v 17:08 Pavel Hofman napsal(a): > > Dne 29. 06. 20 v 13:28 Pavel Hofman napsal(a): > > > Audio analyzer RTX6001 (XMOS-based) is using implicit feedback, > > > yet the > > > feedback is not used by the latest kernel 5.8 rc3 (i.e. already > > > with the > > > latest implicit-feedback patches). > > > > > > Two analyzers on two different PCs are getting clicks in duplex- > > > mode > > > loobpack, one every 10 secs, the other one every 50 secs. > > > > > I am very sure the problem is identical to that for MOTU M2/4, Solid > State Logic SSL2+, Fractal Audio Axe-Fx III etc. > https://github.com/torvalds/linux/commit/e7585db1b0b5b4e4eb1967bb1472df308f7ffcbf > . I will try the simple quirk, IMO it will work OK. BTW if I > understand > correctly all these devices use the XMOS. > > However, I would like to ask, why a quirk for these devices is > required. > The comment explanation in this interesting patch > https://lore.kernel.org/patchwork/patch/1174179/ talks about the same > EP > numbers, but in the different direction. 0x01 EP OUT + 0x81 EP IN > implicit feedback data. All the devices mentioned above have this > numbering, just the EP IN is in a different interface than the EP > OUT. > But please are there actually any duplex implicit feedback devices > having EP OUT and implicit-feedback EP IN in the same interface? The > explicit feedback EP IN is clear, they are in the same interface. E- > MU > 0404 USB has EP OUT + EP IN explicit feedback in interface 1, > together, > EP IN implicit feedback data in interface 2. My other soundcards, > adaptive OUT and async IN again each in a different interface (though > there is no feedback to solve). > > Please is the requirement that EP OUT + EP IN implicit feedback data > must be in the same interface really necessary? If such a requirement > was dropped, IMO many devices could be removed from the existing > set_sync_ep_implicit_fb_quirk and many devices would work out of the > box, as they require no other quirk (unlike the MOTUs, but that's a > different issue). USB Audio Class specs are pretty clear about it: only one isochronous endpoint is allowed per interface. And it can be accompanied by the *explicit* feedback endpoint. I have patches that implement autodetection of implicit feedback, but I need to clean them up and be careful not to break Scarlett 18i8/18i20 3rd Gen (these devices have 3 altsettings per interface and probably require some additional sample rates filtering, so that each sample rate uniquely match one single altsetting).
