Cuse4BSD + Webcamd + FE_GET_EVENT ioctl

Joerg Pulz Joerg.Pulz at
Tue Mar 2 09:59:42 UTC 2010

Hash: SHA1

Dear Hans,

first i want to thank you again for your hard work and your continuing 
fast support.

I think i discoverd a problem with my siano based DVB-T stick together 
with Cuse4BSD and Webcamd while using VDR (
VDR is using a thread for tuning to new frequencies on channel change when 
neccessary. This thread makes use of the FE_GET_EVENT ioctl on the 
frontend device to continuously empty the frontend event queue. It makes 
no further use of the received events it just emties the queue. As i had 
a problem to switch to channels with a frequency different than the one 
the first channel at VDR startup is on i digged deeper to find the cause.
For now, i'm at the point where i can say that the thread simply hangs at 
the second or third FE_GET_EVENT ioctl and never returns from there.
If i just comment out the FE_GET_EVENT ioctl line in VDR it works normal 
but i'm not sure what happens to the device when the frontend event queue 
reaches the maximum number of events (8 events if i got it right) and 

Maybe you can have a look at dvb_frontend_get_event() in
to see if there is anything that blocks the ioctl forever.
Or you can give me a hint how i can debug this part by myself.

Thanks and kind regards

- -- 
The beginning is the most important part of the work.
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