[linux-dvb] How to use a DVB FRONTEND in read only?

Claudio Luck cluck at ethz.ch
Sat Jun 14 14:13:01 CEST 2008

Andrea wrote:
> I would like to open the dvb in readonly and take whatever frequency is currently tuned:
> 1) I open the frontend in read only
> 2) query the current frequency to check is there is a lock
> 3) I open the demux, set some filters and read from the demux.
> There is a *big* issue here:
> The card streams packets *only* and *as long* as the frontend is opened in read/write (by some other 
> application) and tuned.
> If my application opens the frontend in readonly and there is no other application running, the 
> ioctl FE_GET_INFO still returns FE_HAS_LOCK but no data goes through the demux.
> As soon as the frontend is tuned, the data arrives.
> Am I correct? How can I detect if the dvb is running or not?

Check for open filehandles on demux device:

root at iptv:~# ls -l /proc/*/fd/* | grep demux
lrwx------ 1 vlc  vlc  64 2008-06-14 14:02 /proc/19876/fd/6 ->
lrwx------ 1 vlc  vlc  64 2008-06-14 14:02 /proc/19892/fd/6 ->

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