[linux-dvb] DVB-S2 / Multiproto and future modulation support

hermann pitton hermann-pitton at arcor.de
Thu Sep 11 03:17:02 CEST 2008


Hi,

Am Mittwoch, den 10.09.2008, 21:00 -0400 schrieb Steven Toth:
> Christophe Thommeret wrote:
> > Le Thursday 11 September 2008 00:59:31 Andreas Oberritter, vous avez écrit :
> >> Hans Werner wrote:
> >>>> So applications could know that these 2 frontends are exclusive.
> >>>> That would not require any API change, but would have to be a rule
> >>>> followed by
> >>>> all drivers.
> >>> Yes, if we keep to that rule then only frontends which can operate truly
> >>> simultaneously should have a different adapter number.
> >> An adapter refers to a self-contained piece of hardware, whose parts can
> >> not be used by a second adapter (e.g. adapter0/demux0 can not access the
> >> data from adapter1/frontend1). In a commonly used setup it means that
> >> adapter0 is the first initialized PCI card and adapter1 is the second.
> >>
> >> Now, if you want a device with two tuners that can be accessed
> >> simultaneously to create a second adapter, then you would have to
> >> artificially divide its components so that it looks like two independant
> >> PCI cards. This might become very complicated and limits the functions
> >> of the hardware.
> >>
> >> However, on a setup with multiple accessible tuners you can expect at
> >> least the same amount of accessible demux devices on the same adapter
> >> (and also dvr devices for that matter). There is an ioctl to connect a
> >> frontend to a specific demux (DMX_SET_SOURCE).
> >>
> >> So, if there are demux0, frontend0 and frontend1, then the application
> >> knows that it can't use both frontends simultaneously. Otherwise, if 
> >> there are demux0, demux1, frontend0 and frontend1, then it can use both
> >> of them (by using both demux devices and connecting them to the
> >> frontends via the ioctl mentioned above).
> > 
> > Sounds logical. And that's why Kaffeine search for frontend/demux/dvr > 0 and 
> > uses demux1 with frontend1. (That was just a guess since i've never seen 
> > neither any such devices nor comments/recommendations/rules about such case).
> > 
> > However, all dual tuners devices drivers i know expose the 2 frontends as 
> > frontend0 in separate adapters. But all these devices seems to be USB.
> > 
> > The fact that Kaffeine works with the experimental hvr4000 driver indicates 
> > that this driver populates frontend1/demux1/dvr1 and then doesn't follow the 
> > way you describe (since the tuners can't be used at once).
> > I would like to hear from Steve on this point.
> > 
> > 
> 
> Correct, frontend1, demux1, dvr1 etc. All on the same adapter. The 
> driver and multi-frontend patches manage exclusive access to the single 
> internal resource.
> 

then please explain what is about the analog usage, which can always be
first and don't tell it has to stay back, since you always sit on that
bridge and else come nowhere ...

Cheers,
Hermann









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