Re: pwc-webcam attached to usb-ohci card blocks on read() indefinitely.

Mark Cooke
2002-03-09T07:18:58Z

Just as a FYI, I had similar trouble using usb-uhci (440BX chipset) to
a 680K using pwc/pwcx. I had to add a bunch of error recovery (close
/ open device, ignore open() failing and retry, etc).

I get a group of EMC messages logged , then the reset seems to take
quite a while.

(2.4.19-pre2-ac2, but have seem this will many recent 2.4.x kernels)

Mark

On Fri, 8 Mar 2002, Thomas Winischhofer wrote:

> > The camera attached to the UHCI-controller running usb-uhci works just
> > fine,out the three attached to the OHCI-controllers running usb-ohci don't.
> > After a random amount of frames being read from a camera the read()-call
> > blocks indefinitely until the device is closed. Next time the v4l-device is
> > opened the program can again read frames from the camera but read() always
> > blocks after some time.
>
> I can't help, but I have the exact same problem here. Closing the
> application (eg. camstream) and re-opening it makes it work again for a
> while.
>
> As Carl-Johan said, this happens with or without the pwcx module, so
> that's not the problem.
>
> I think it's an ohci problem.
>
> Furthermore, the usb driver(s) behave strangely on
> connecting/disconnecting the camera. Sometimes this works flawlessly,
> sometimes I get a lot of USB timeout ("usb_control/bulk_msg: timeout")
> and/or "USBDEVFS_CONTROL failed dev x rqt 128 rq 6 len 490 ret -110"
> messages in the syslog. (Kernel is 2.4.16 and 2.4.18 - no difference)
> After a couple of times disconnecting and reconnecting the camera it's
> being detected. Since 2.4.18, the camera's LED sometimes is on,
> sometimes off - seems quite random.
>
> Even closing the cam application (xawtv, camstream) after the camera
> stopped working never results in any error messages in the log, I only
> read "pwc: Closing video device: xxx frames received, dumped 0 frames, 0
> frames with errors"
>
> Thomas
>
>

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Mark Cooke The views expressed above are mine and are not
Systems Programmer necessarily representative of university policy
University Of Birmingham URL: http://www.sr.bham.ac.uk/~mpc/
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