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
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