[linux-dvb] [PATCH] Fix the min/max frequencies of some DVB-C frontends

Oliver Endriss o.endriss at gmx.de
Wed Aug 8 03:44:39 CEST 2007


Manu Abraham wrote:
> On 8/6/07, Michael Krufky <mkrufky at linuxtv.org> wrote:
> >
> > Now I'm beginning to have doubts about Oliver's original patch:
> >
> > dvb_frontend: Range check of frequency and symbol rate
> > http://linuxtv.org/hg/v4l-dvb/rev/8186a34dd0a6
> >
> > Should we be checking fe->ops.tuner_ops.info.frequency_min|max , instead of
> > fe->ops.info.frequency_min|max ???
> 
> 
> Ideally, what's provided by the demod and not the tuner max/min. The
> tuners max/min should be checked by the demod on setting params.
> 
> The upper/lower limits in the demodulator drivers, came from the
> concept of a frontend as a whole. Independant bounds do not make sense
> (except internally -- It is the demod driver that which sets
> parameters for the tuner. The external world doesn't need to know
> what's the limit of the tuner, but only of the frontend as a whole).
> 
> Ideally, the demodulator should just demodulate only. There are some
> cases, there are some cases which are not.

Ok, I'm trying to put all pieces together:
There might be cases where demod and tuner have different limits.

So FE_GET_INFO and dvb_frontend_check_parameters() should use the
'smallest common bandwidth':

freq_min = max(fe->ops.info.frequency_min, fe->ops.tuner_ops.info.frequency_min);

if (fe->ops.info.frequency_max == 0)
	freq_max = fe->ops.tuner_ops.info.frequency_max;
else if (fe->ops.tuner_ops.info.frequency_max == 0)
	freq_max = fe->ops.info.frequency_max;
else
	freq_max = min(fe->ops.info.frequency_max, fe->ops.tuner_ops.info.frequency_max);

if (freq_min == 0 || freq_max == 0)
	printk(KERN_WARNING "frequency limits undefined - please fix the driver\n");

Conclusions:
- A tuner-only driver must set fe->ops.tuner_ops.info.
- Monolithic drivers must set fe->ops.tuner_ops.info or fe->ops.info
  (or both).

Ok?

CU
Oliver


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