On 08.07.2012 07:37, Eric Ding wrote:
On 07/08/2012 09:52 AM, Alan Stern wrote:
On Sat, 7 Jul 2012, Rafael J. Wysocki wrote:
Well, the quirk does make sense. What doesn't make sense is why moving
the runtime PM operation pointers from usb_bus_type to usb_device_type
should cause any change in the autosuspend behavior. That's what we
would like to know.
I think the reason was the way rpm_suspend() worked at the time of that
commit (it works a bit differently now, but not as much as to avoid the
problem).
Namely, before commit e1620d591a75a10b15cf61dbf8243a0b7e6731a2 the device
had a device type without runtime PM callbacks. So, rpm_suspend() saw
that dev->type was set and dev->type->pm was set, so it assigned NULL to
callback. As a result, nothing happened when rpm_callback(callback, dev)
was run.
I don't follow. If that were the reason then no USB device would have
been runtime-suspended before the e1620d commit.
Are you saying this actually was true for some period of time (such as
between the commit that added the "callback" variable and the e1620d
commit)?
I think this is, in fact, what happened. See rpm_suspend() before and
after commit 9659cc0; I suspect that between commit 9659cc0 and commit
e1620d5, no USB device was being runtime-suspended. Since this was
after v2.6.38 and before v2.6.39-rc1, though, it wouldn't have been
widely seen or tested, right?
However, that doesn't fully explain why the webcam wouldn't have been
autosuspended in v2.6.38 -- perhaps you all can guess at this more
quickly than I can? Was enough changed in the runtime PM architecture
from v2.6.38 to e1620d to explain this difference?
Eric
Hi, can you please do one more test.
Try to reproduce it with MJPEG stream. Use this command:
luvcview -f jpg -C
it will force jpeg (i think your cam support it) and store each frame
separately. If you can reproduce it, please send me one of this frames.
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