[linux-dvb] dvb_frontend_recover not working

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

I was looking into why the driver doesn't recover after a loss
of signal (like when pulling the antenna cable for a few seconds)
and found that apparently (at least with DVB-S) it starts a
dvb_frontend_recover() sequence, but aquires a lock at a completely
different frequency, which is some 16MHz off the original transponder.

This is not surprising, because the fe->lnb_drift takes on values
of up to +/-15462 or so, which lets it run into the next transponder
at the same polarization as the current one. So no wonder there is no
more picture then, because the PIDs may be totally different on different
transponders.

I therefore limited the range of fe->lnb_drift in dvb_frontend_recover()
to some 8MHz, but then it didn't lock on to any transponder any more.
This is what puzzles me, because the original transponder was perfectly
locked on with fe->lnb_drift==0, and that value is the first one that
gets tried in dvb_frontend_recover(). And since there can (due to the
limitation to 8MHz) be no more other transponder it might lock on to
by mistake, I don't understand why it doesn't lock on to the original
transponder any more. It just loops through the original frequency
+/-8MHz in 32 steps over and over again.

Note that I did all these tests with the most recent CVS version of the
DVB driver, but dvb_frontend.c appears to be quite the same (with respect
to the dvb_frontend_recover() mechanism) as in the dvb-kernel driver.

Does anybody have an idea why this doesn't work as expected?
We should really get this to work in order to make an application
automatically "come back" after the signal was lost, for instance
due to bad weather.

Klaus


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