I recently purchased a usb webcam and found that polling /proc/apm
causes the webcam in xawtv to skip. I can do this either by doing 'cat
/proc/apm' or using the gnome battstat-applet. Syslog says:
Sep 23 10:14:17 sirius kernel: usb-uhci.c: iso_find_start: gap in
seamless isochronous scheduling
Sep 23 10:14:18 sirius kernel: quickcam: too little data by 48260
Sep 23 10:14:18 sirius kernel: quickcam: failed qc_imag_convert()=-90
Disabling the battstat-applet and not touching /proc/apm lets xawtv work
fine without the above errors. Polling /proc/apm also causes clock
drift.
I have a Dell Inspiron 8200 laptop (1.6Ghz Pentium 4). Using kernel
2.4.18-686 from debian. I read that this happened to people in the 2.2
series. Is this a kernel apm bug or BIOS problem? Do I just have to
live with it?
Thanks,
Jamie Strandboge
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Email: [email protected]
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James D Strandboge <[email protected]> wrote:
> polling /proc/apm causes the webcam in xawtv to skip.
> [...]
> Is this a kernel apm bug or BIOS problem?
The apm driver calls the APM BIOS with interrupts disabled
each time /proc/apm is read. This appears to be taking
too much time away from video processing.
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On Tue, 2002-09-24 at 12:22, Philipp Matthias Hahn wrote:
> Hi James!
>
> On Tue, Sep 24, 2002 at 09:12:00AM -0400, James D Strandboge wrote:
> > Disabling the battstat-applet and not touching /proc/apm lets xawtv work
> > fine without the above errors. Polling /proc/apm also causes clock
> > drift.
> >
> > I have a Dell Inspiron 8200 laptop (1.6Ghz Pentium 4). Using kernel
> > 2.4.18-686 from debian. I read that this happened to people in the 2.2
> > series. Is this a kernel apm bug or BIOS problem? Do I just have to
> > live with it?
>
> This is a known BIOS limitation. Interrupts are disabled during
> APM-BIOS calls and they may take a long time, during which the kernel
> might miss some clock interrupts.
> You can try to enable CONFIG_APM_ALLOW_INTS=y during kernel compile, but
> your BIOS might not like it.
>
Thanks. Yes I have this disabled because it has caused problems with
others using the inspiron 8200. I will play with it though. This most
definitely is a BIOS bug then, and I have to live with it. Is ACPI any
better?
Jamie Strandboge
--
Email: [email protected]
GPG/PGP ID: 26384A3A
Fingerprint: D9FF DF4A 2D46 A353 A289 E8F5 AA75 DCBE 2638 4A3A