[linux-dvb] Re: frequency bending on DVB-T cards

[Andrew de Quincey <adq_dvb@lidskialf.net>]

> I've just noticed a behavioural difference between "DVB/driver" and "dvb-kernel" 
> (I have temporarily removed my grundig mods in case it was that)
> 
> If I do "dvbtune -f .....", and then "dvbtune -m", in DVB/driver, this works fine, 
> but in dvb-kernel, it "loses" the the tuning after about 4 seconds.
> 
> Similarily, dvbscan (from dvbsak) has problems with dvb-kernel. 
> 
> Could this be something to do with not keeping the frontend device open?

Spotted the problem. in "DVB/linux", if "fe->dvbdev->users" is non-zero,
it keeps the fe-thread running.

However, in "dvb-kernel", it uses "fe->dvbdev->writers"... "dvbtune -m"
and dvbscan are opening the frontend in readonly mode, so it just
decides to shut down the frontend.

Is this the correct behaviour though? I can see the wish to have
multiple readers for the FE information.. but the problem with the
grundig 401 tuner is that it is put into sleep mode when it is shut
down... so the tuning dies.

This isn't a problem with the grundig 491 (DVB-S) tuner, because it
doesn't support being put to sleep.... so it just happily continues.

The solution to me would seem to be to stop putting the grundig 401 
tuner to sleep when shutting down... perhaps this should only be done if
the user explicitly calls the FE_SLEEP ioctl. Just patching the
applications to always open in read/write mode isn't good enough.

What do people think? I'll put a patch together based on feedback if you
want.


-- 
Andrew de Quincey <adq_dvb@lidskialf.net>



-- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.