On Sat, 14 Nov 2009, Kevin wrote:
Theodore Kilgore wrote:
On Sat, 14 Nov 2009, Oliver Neukum wrote:
Am Samstag, 14. November 2009 04:35:55 schrieb Theodore Kilgore:
At this point, I have put identical copies of the camera driver, along
with identical copies of the rest of the gspca development tree, on six
different machines. Three of them use OHCI, and three of them use UHCI.
On
the three machines which use OHCI, everything works perfectly. On the
three machines which run UHCI, there are serious problems, to the extent
that some of the cameras I have intended to support will not function
while others do continue to work.
This sounds very much like a problem I had when developing the stv680 camera
driver. I had ohci hardware and the camera worked well, but I kept getting
reports that others where having problems- the video output (as seen in an
application, e.g., xawtv) would be very jumpy and even freeze up. It wasn't
until I got a computer with uhci hardware that I started having the same
problem. One of the camera users sent me a patch for the (then) uhci code.
This was back in the 2.4 or early 2.6 kernel days. The patch was simply to
change a parameter in the uhci code. With this patch, the camera worked as
well as with ohci. I believe that at the time there were several uhci
drivers, or usb core, or something, and when they were consolidated, the
patch was lost. Currently (I am now using 2.6.29.7), when connected to uhci
hardware the camera has problems as before, but still works as expected with
ohci. I will have to dig through my hard copies of the stv680 driver
development to find out what version of uhci had this problem and exactly
what the fix was, but the code has changed so much since then that the
information may not be useful.
Kevin
If one is having a strange problem, it is good to know that one is
not alone. Thanks.
Theodore Kilgore
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