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

Michael Krufky mkrufky at linuxtv.org
Mon Aug 6 22:03:54 CEST 2007


Trent Piepho wrote:
> On Mon, 6 Aug 2007, e9hack wrote:
>> Michael Krufky schrieb:
>>> 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 ???
>>>
>> I didn't see the ranges from the tuner, because the dvb-c drivers don't use the pll framework. They
>> have very simple tuning functions only. We should use both values. One part may be more restrictive
>> than the other one.
> 
> Most demodulators don't have frequency ranges.  They just take whatever the
> tuner gives them at a fixed intermediate frequency.  It's really the tuner
> that has the frequency range.
> 
> I think it would make more sense for the demodulator drivers to fill
> fe->ops.info.frequency_min|max using fe->ops.tuner_ops.info.frequency_min|max.
> A frontend driver that doesn't use a separate tuner driver (like DST) would
> set the fe->ops.info.frequency_min|max directly.

The way I see it, the demod driver that doesn't have a separate tuner driver
should just go ahead and fill ops.tuner_ops.info.frequency_min|max , because
otherwise those fields will be there anyway, just remaining empty.  Those
structures are not pointers, and we should always be able to rely on their presence.

There is no need for BOTH ops.info.frequency_min|max AND
ops.tuner_ops.info.frequency_min|max

-- 
Michael Krufky




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