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

Oliver Endriss o.endriss at gmx.de
Mon Aug 6 21:29:49 CEST 2007


Michael Krufky wrote:
> Oliver Endriss wrote:
> > Michael Krufky wrote:
> >   
> >> e9hack wrote:
> >>     
> >>> Hi,
> >>>
> >>> the min frequencies of the DVB-C frontends are wrong. In Europe, the center frequency of the lowest
> >>> channel is 50.5MHz and not 51MHz. All known cards with the stv0297/tda0002x/ves1820 frontend are
> >>> able to tune to this frequency. I've changed the range to the lowest channel - 1/2 bandwidth and the
> >>> highest channel + 1/2 bandwidth. For the design of the dvb driver, the frequency ranges must be part
> >>> of the tuner and not of the frontend itself. The same frontend may be used for different tuners. The
> >>> attached patch does only fix the ranges and not the design.
> >>>       
> >> 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 ???
> >>     
> >
> > Hm, I was not aware that there is another info.frequency_min|max
> > in tuner_ops. :-(
> >
> > Do we need both of them?
> I think it's most appropriate to keep tuner_ops.info.frequency_min|max ,
> since it is the tuner that we're talking about.  If the demodulator
> itself does not have such limitations, then we should not have such a
> field in the demod ops.info section.
> 
> I believe that this is leftover from before Andrew's original dvb tuner
> refactoring.

It is an API issue: FE_GET_INFO returns fe->ops.info, so we cannot
easily drop this field.

What about modifying dvb_pll_attach to override fe->ops.info.frequency?

CU
Oliver

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