[linux-dvb] Re: CX88 i2c issue w/ DVB tuners

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Sunday 12 Sep 2004 18:56, Johannes Stezenbach wrote:
> Andrew de Quincey wrote:
> > On Sunday 12 Sep 2004 17:43, Johannes Stezenbach wrote:
> > > I've seen the source of [name deleted]'s STB software, which has
> > > absolutely nothing to do with Linux. And guess what? They do
> > > device probing, too. Because in real life one piece of software
> > > has to run on a multitude of hardware revisions.
> > >
> > > I can't wait until [name deleted] tells you that the new
> > > XY frontend is cheaper that Samsung's, and could you not add
> > > device probing to your USB thingy firmware.
> > >
> > > The only thing that is "broken" about kernel I2C autoprobing is
> > > that it is too simple. But hey, it worked for all those years ;-)
> > >
> > > Now, for those cases where the simple autoprobing indeed cannot
> > > be made to work, the addition of a NOPROBE flag and doing more
> > > sophisticated probing seems like a straight forward thing to me.
> >
> > Oh aye, we'll always have to do probing. However, the problems we're
> > having come from the i2c core probing for every single random i2c device
> > that happens to have a registered driver loaded. I bet [name deleted]'s
> > STB software only probes for i2c devices that they know their device
> > might see. No problems with *that* - it can fix any clashes itself, as it
> > knows what it expects.
>
> Oh, I thought we were already beyond that point, that it was agreed that
> we need the I2C device class field to keep non-DVB stuff away from DVB-I2C
> buses. (Really, I thought that issue had been sorted out months ago by
> patches posted by Michael Hunold to lkml.)
> http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=1Ajn2-5WU-1%40gated
>-at.bofh.it
>
> I was under the impression that only tda9987 vs. cx22702 was
> actually a more difficult to solve problem, currently. And my
> thinking was (I could easily be wrong, though), that the probe
> functions for those modules need to do something more than just
> ping for some device at an address.

yeah - the cx22702 isn't a problem - theres an ID register you can read to 
determine if its there or not (assuming some other device doesn't return the 
same value!). The tda9987 is though - its a really dumb tuner chip - I 
couldn't see any obvious way to reliably detect it. I don't have one though - 
maybe someone with one can find a way?

> > As for the changes Holger suggests w.r.t frontend libraries, they're
> > aimed at cleaning up the frontend code and making it more flexible.
> > Something which I've wanted to look into for some time.
>
> Sure, I trust you to do the right thing to improve the frontend code.

Its looking good - we'll post a sample patch for the tda1004x to the list over 
the next couple of days.