On Thu, 01 Dec 2016 08:41:17 +0100, Clemens Ladisch wrote: > > Jiada Wang wrote: > > since commit 57e6dae1087bbaa6b33d3dd8a8e90b63888939a3 the expected packetsize is always limited to > > nominal + 25%. It was discovered, that some devices > > Which devices? > > > have a much higher jitter in used packetsizes than 25% > > How high? (Please note that the USB specification restricts the jitter > to at most one frame in consecutive packets.) > > > which would result in BABBLE condition and dropping of packets. > > A better solution is so assume the jitter to be the nominal packetsize > > This solution is better for this one particular device, but how does it > affect normal devices, or the Scarlett 2i4 on EHCI affected? Actually, which value does this affected device in ep->maxpacksize? In the commit mentioned above, we changed the logic to take +25% frequency as the basis, and it my *reduce* if ep->maxpacksize is lower than that. OTOH, if ep->maxpacksize is sane, we can rely on it rather than the implicit +25% frequency. That said, maybe we can check ep->maxpacksize whether it fits within the expected range, then adapt it, or take +25% freq as fallback? thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
