[linux-dvb] Re: [RFC] multi std silicon tuners and analog tuners

Mauro Carvalho Chehab mchehab at infradead.org
Thu Apr 5 22:23:48 CEST 2007


Em Qui, 2007-04-05 às 23:41 +0400, Manu Abraham escreveu:

> > DVB callback approach for dvb_frontends seems to be an interesting
> > approach. It doesn't cover, however, all needs for V4L. For example,
> > some devices have also FM radio support, where stereo carrier detect and
> > analog signal strengh are important measures. So, it is needed to add
> > newer callbacks and maybe some extra data field for this struct to be
> > used also by v4l.
> 
> 
> With what i thought, with some slight changes at both ends (very
> minimal) it should be able to work.

Yes. It doesn't seem to be hard to do a few changes on both sides in a
way that the same tuner driver can be used by both subsystem cores.

> > One interesting target is to have a common tuner/frontend code that can
> > be used by radio, analog and digital tuners, in a way that it can be
> > attached to dvb_frontend and/or to tuner_core.
> > 
> 
> 
> Even without a common tuner, things can be achieved quite well, which
> require lesser maintenance.
> With the case of DVB, things are moving, ie not stagnant due to the
> arrival/addition of new stuff, so that is also an important aspect in
> deciding how to go about. A high maintenance path is not a viable option.
> 
> Having a common tuner is not a nice aspect. Subsystems should be
> separated  out, while still being interoperable.

I'm thinking on having a common tuner/frontend struct that can be
attached on both subsystem cores.

For now, I agree that it is better to have the cores separate, since
there are some internal interfaces that would be difficult to merge.
Basically, on DVB, i2c support is used at the lowest possible API,
while, on V4L, we use the higher level I2C support.

I2C guys are working on providing some newer ways to attach devices at
the high level API. After those changes, maybe it would valuable to have
dvb and v4l using the same i2c api. Then, we may have one common tuner
core. 

> > If just one module is handling both analog and digital tuning, it would
> > be easier to have locks protecting the concurrence troubles you've
> > pointed above. 
> > 
> 
> 
> Already have a driver now. It requires some trimming of the V4L parts
> (someone probably might need to retouch/complete the V4L area), will
> post after a few reviews.

Ok. Markus also did another approach on his RFC. We really should
address this issue as soon as possible, to allow better support for
hybrid devices.

-- 
Cheers,
Mauro




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