> OK, annoying. I am traveling for conferences this/next week so I cannot verify here, but presumably you are correct. Do you perhaps have a more complete capture you can share? Sure. First, get MSOS feature descriptor: SETUP packet requesting header: C0 A1 00 00 04 00 10 00 Data IN response: 28 00 00 00 00 01 04 00 01 00 00 00 00 00 00 00 SETUP packet requesting full descriptor: C0 A1 00 00 04 00 28 00 DATA IN response: 28 00 00 00 00 01 04 00 01 00 00 00 00 00 00 00 02 01 57 49 4E 55 53 42 ..WINUSB 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 This is wIndex 4 and device request. There is no problem as interface/wValue is 0. Now the property: SETUP packet requesting header: C1 A1 02 00 05 00 0A 00 DATA IN response: 8E 00 00 00 00 01 05 00 01 00 SETUP packet requesting full descriptor: C1 A1 02 00 05 00 8E 00 DATA IN response (3 packets): 00 00 28 00 44 00 65 00 ..(.D.e. 76 00 69 00 63 00 65 00 v.i.c.e. 49 00 6E 00 74 00 65 00 I.n.t.e. 72 00 66 00 61 00 63 00 r.f.a.c. 65 00 47 00 55 00 49 00 e.G.U.I. 44 00 00 00 4E 00 00 00 D...N... 7B 00 43 00 46 00 34 00 39 00 33 00 45 00 31 00 41 00 2D 00 41 00 32 00 37 00 32 00 2D 00 34 00 32 00 32 00 42 00 2D 00 41 00 33 00 36 00 34 00 2D 00 39 00 36 00 37 00 42 00 34 00 39 00 42 00 32 00 36 00 42 00 35 00 37 00 7D 00 00 00 I omitted ACSII value for our interface GUID as it is not important here. The important part is wIndex 5 (request number), device request (0xC1) and our interface number 2 at offset 2 which is LOW byte of wValue. There is the problem. Captured at Win10 23H2 but it behaves the same way at least 2 years, probably always. > It's been a while, but I believe Windows 10. In the end I ended up shuffling the interfaces around so the one with the MSOS descriptors was interface 0 for better compatibility, so it is possible that something went wrong with my interface != 0 tests. It would be interesting if you can reproduce it but I presume it was a different problem. I tested it at my old Win7 machine and it behaves the same way as at Win10/11 i.e. interface number is in the low byte. Also, Linux implementation had it correctly for a long time and maybe somebody did it for a reason even when MS documentation claims opposite. > If so, then I am fine with reverting, but we should probably add a comment explaining that the documentation is wrong. Yes. Note the documentation is from 2007 which is before Win7 release where it was used for the first time. Michal
