[Linux-uvc-devel] Patch for USB problem with Logitech webcams?
MOMOR at tdc.dk
Mon Aug 13 10:43:38 CEST 2007
Yes, I am pretty certain, that I used the same kernel for both tests. My
Fedora 7 system did have its kernel upgraded at some point some weeks
back from... a 2.6.19 to a 2.6.21, I belive out from memory. But this
kernel-upgrade was weeks before I changed UVC drivers, I think.
Yes, I will try to find out which SVN revision made a difference. I can
try it out within a day or two, I expect.
But right now, I can tell you for certain, that when the UVC driver
worked "for periods of multiple minuttes at a time", I wrote to mr.
Xhaard asking about the luvcview output with cc to this list about this
very problem. This was Friday 20. July - I see from my earlier posting,
that my kernel was the current "2.6.21-1.3228.fc7". So no kernel changes
was made in between. An instance of the UVC driver working "for periods
of a few seconds only" is the one which I checked out from the
Subversion repository last night about 12 hours ago. From my point of
view, something has changed in between. I have not reconfigured the
physical USB setup or anything like that, but I have been playing around
with other (USB) drivers (I say this because you mention, that the
problem is somehow related to timing; maybe something else than changes
in the UVC source code triggered something).
I will *try* to narrow this down relative to SVN revisions.
Morten Sabroe Mortensen
Fra: Laurent Pinchart [mailto:laurent.pinchart at skynet.be]
Sendt: 13. august 2007 10:04
Til: linux-uvc-devel at lists.berlios.de
Cc: Morten Mortensen
Emne: Re: [Linux-uvc-devel] Patch for USB problem with Logitech webcams?
On Monday 13 August 2007 08:25, Morten Mortensen wrote:
> - I own a couple of these "fine" Logitech webcams. Something *is*
> in the UVC-driver, because the driver I had until yesterday - a couple
> weeks old - could run the Ultra Vision and the Fusion for a period of
> a minute and up to three, four or even five minuttes.
> The latest UVC-driver runs for one to three seconds, so something has
> changed, which influences this by an order of magnitude. These
> are absolutely identical for my instances of the Ultra Vision and the
Have you used the same kernel for both tests ? Could you please try to
out which SVN revision introduced the problem ?
> One wonders how Logitech circumvents the problem in their Windows
They don't. The Windows USB stack seems to be slower than the Linux one,
it just doesn't trigger the problem. It's a matter of timings, and
never noticed the problem. From the limited amount of knowledge I have
this bug, it seems there is a hardware problem which has been
by a firmware hack in recent webcams. Both the hardware and the firmware
provided by the IC vendor, so Logitech isn't the only one to blame.
> One wonders *when* manufacturers implement reflashability of their
> monitors, webcams, etc.
The two issues here are support and cost. They don't want to support
reflashing, as that would mean replacing dead webcams. And flash costs
> Please keep up the good work.
Thanks. I'll do my best :-)
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