Sancho Dauskardt wrote:
Hi,
I'm getting -ENOSPC when opening /dev/ttyUSB0 with following setup:
PL2303 --> USB 2.0 TT hub (Cypress CY7C65640) --> ehci PCI Card (NEC)
No other devices.
Try forcing it to use a period other than 1 usec.
You'll probably notice that the periodic schedule dump
in /sys/class/usb_host/$EHCI/periodic just shows the hub's
interrupt qh, period 256 usec.
The problem is that the EHCI interrupt scheduling code takes
a shortcut right now (the first FIXME you quoted), and only
recently has enough sw infrastructure been there to fix it.
(Or hw users reporting they'd like it fixed ...)
I have a patch that should fix this, but it needs debugging
cycles that I don't have lately. It relies on TT scheduler
infrastructure added a few months back. EHCI basically just
needs a schedule tree like OHCI has -- but it's a lot more
complicated, in oopsy parts of the code.
Do the two 256ms interrupt endpoints of the hub have something to do
with the check failing on frame 255 ?
Only one should be live at a given time; the altsetting has
the tt-per-port mode. That's less demanding of TT schedules,
eventually allowing for webcam-per-port.
- Dave
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