[linux-dvb] Re: Proposal for new frontend architecture

[Holger Waechtler <holger@qanu.de>]

Andrew de Quincey wrote:

> On Wednesday 22 Sep 2004 16:06, Andrew de Quincey wrote:
>  
> > On Wednesday 22 Sep 2004 15:41, Gerd Knorr wrote:
> >    
> > > > This is similar to the proposal that Holger and I suggested
> > > >        
> > > Yep, is somewhat simliar.
> > >
> > >      
> > > > - we just took it
> > > > a step further and removed the frontend dependencies on kernel i2c
> > > > altogether.
> > > >        
> > > No way, I'd like to veto that.
> > >      
why? please elaborate.

The background of the read/write_demod_reg() function pointers in the 
card_spec struct is that for almost all demods and tuner ICs the chip 
adresses are configurable by strapping some config pins high or low.


> > > > The advantages of removing kernel i2c from the frontends
> > > > altogether  weree
> > > >
> > > > * It makes it easier for people to reuse the frontends in places where
> > > > kernel i2c is not usable
> > > >        
> > > ... and makes it harder for people which use kernel i2c anyway for other
> > > reasons.
> > >
> > >      
> > > > - does this actually occur though?
> > > >        
> > > Good question.  Before trying to solve a problem you should better
> > > verify there actually is one ;)
> > >
> > >      
> > > > * It also removes any trace of autoprobing problems since they're not
> > > > kernel i2c_drivers.
> > > >        
> > > .class will do that just fine as well.  If the dvb subsystem stops doing
> > > autoprobing itself and .class prevents any non-dvb i2c modules playing
> > > with the i2c bus on dvb cards everything is fine.
> > >      
> > OK, this plan sounds good to me.
> >    
> Oh - I take it this doesn't preclude having the PLL code in the adapters - I 
> did like that. You'd just pass two function calls init_pll() and set_pll() as 
> part of the initialisation structure.
>  
it's useful for other cards, too: usually the PLL/Synthesizer bandswitch 
and Chargepump settings are completely board-dependent and by no mean 
portable. Keeping them in the generic frontend code makes not much sense.

Holger