What is wrong with FreeBSD and USB Support

Markus Rechberger mrechberger at gmail.com
Mon Mar 6 10:53:31 UTC 2017

On Mon, Mar 6, 2017 at 11:49 AM, Markus Rechberger
<mrechberger at gmail.com> wrote:
> On Mon, Mar 6, 2017 at 11:34 AM, Hans Petter Selasky <hps at selasky.org> wrote:
>> On 03/06/17 11:00, Markus Rechberger wrote:
>>> even though it's going up and down DVB-T is okay due to the lower
>>> bandwidth so something's obviously wrong with the freebsd USB Support.
>> Hi,
>> Can you provide a usbdump trace and send it to me off-list?
>> usbdump -i usbusX -f Y -s65536 -w usb_capture.pcap
>> X and Y are number after ugenX.Y
>> If you are using ISOCHRONOUS high-speed transfers with an XHCI USB
>> controller, the XHCI is much less forgiving about the USB PIDs of the
>> multi-data payloads coming from the USB device than the EHCI. I have seen at
>> least one DVB-T USB adapter which is totally broken with XHCI and works just
>> fine with EHCI. This has been verified with a USB wire analyzer.
> I'm using EHCI only.
> Attached you can find the pcap file.
> Please note that DVB-T is okay due to the low bandwidth, only high
> bandwidth kicks in immediately with stalled transfers

We have 2 issues so far
1. slow usb control messages - did you already noticed that?
2. high latency bulk requests (I have seen this issue with Linux and
MacOSX too if we don't request enough urbs at once) Seems like that
double buffering strategy with FreeBSD is a real problem now - of
course you cannot have all the hardware out there so that issue might
be new for you.

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