On Wed, 1 Apr 2015, Peter Chen wrote: > > This is bad. All the endpoints have maxpacket = 1023, and that's much > > too big for this test. We need a maxpacket size of 64 (maybe a little > > bigger but not much). > > > > Back to this issue, 1024 bytes is only ~70% for frame, why it reports > "iso sched full" when I only wants to use one endpoint for playback > or capture?
The low/full-speed periodic scheduler in ehci-hcd is pretty bad. It doesn't follow the recommendations of the USB spec and it is sub-optimal in several respects. One consequence of these problems is that it is not able to schedule any isochronous transfer with a maximum packet size larger than about 990 bytes. Your case is even worse, because with a full-speed hub plugged in, part of the periodic schedule is already committed for the hub's status URB. As a result, no isochronous transfer with maxpacket larger than about 830 bytes can be scheduled. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
