Re: [RFT PATCHv3 1/3] xhci: fix frame id calculation and checks for isoc URBs

On Fri, Aug 7, 2026 at 5:29 PM Michal Pecio wrote:
>    Complicated by the fact that new URBs may be submitted after the
>    underrun occurs but before our IRQ handler learns about it. Those
>    are doomed to execute with some lag (unless unlinked). We could
>    mark them -EXDEV or some such so that drivers don't trust them.

IMO, it would be fine for the URBs that are submitted after the
underrun but before the IRQ handler learns about it to have their
transfers happen discontinuously, as long as they are marked -EXDEV or
similar upon completion. This only applies to URBs submitted from
their own endpoint's completion handler, right?

Any driver establishing a stream must submit more than one URB at
startup. I've often seen discontinuities with the class audio driver
happening with these initial URBs. These would not be detectable from
the completion status because they are not submitted from completion
context. However, perhaps once the non-CFC implementation starts
streams without SIA, a class driver could instead use start_frame
continuity across completions to detect these cases.