[linux-dvb] Re: Couple of frontend questions

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

> > > (b) the LNB is broken (high LNB drift)
> >
> > Well, I'm not an experienced LNB guy, but IMHO what you call "broken"
> > is just normal behaviour. Low price -> high drift. And it also
> > depends on how large the temperature variations are.
>
> For me, 'broken' is a drift which is larger than the AFC range. ;-)
> I remember we already had this discussion some time ago. At that time I had
> a phone call with Kathrein technical support. They stated that LNB drift
> can be corrected by AFC.
>
> My personal experience is that it is safe to disable zig-zag scan.
> So I would prefer a module parameter to disable this feature.
>
> Using [*] this could be easily implemented as a module parameter of the
> frontend driver. So zig-zag scan could be disabled or adjusted for each
> frontend type. What do you think?

I only have access to a few sat dishes, all of which are professional quality 
with quad LNBs. I haven't ever actually experienced LNB drift. Currently the 
only use I have for the zigzagging code is to finetune during the initial 
lock. Ideally, that would be done in a userspace library.

_However_, from what Johannes and Holger were saying, removing zigzag from the 
dirver has been tried before, but had to be re-added because it just didn't 
work right without it.

I suggest we implement my IOCTL suggestion, _as well as_ equivalent module 
parameters, which by default will be set on, so as not to break people who do 
need the current beheviour. The module parameters can then be used to 
override everything else by those who know for sure that they don't need any 
of the fancier stuff.


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