[linux-dvb] Re: Hybrid tuner proposal (V4L/DVB)

Markus Rechberger mrechberger at gmail.com
Mon Apr 9 19:55:50 CEST 2007


On 4/9/07, Markus Rechberger <mrechberger at gmail.com> wrote:
> On 4/8/07, Johannes Stezenbach <js at linuxtv.org> wrote:
> > On Thu, Apr 05, 2007, Markus Rechberger wrote:
> > > I sent this proposal to several individual developers already around
> > > 1-2 weeks ago, and received several comments, maybe I should give it a
> > > try to push a very last discussion about it.
> > >
> > > Video4Linux/DVB Hybrid Tuner Support
> > > ====================================
> > ...
> > > >Mauro wrote that requesting the tuner module first and afterwards call an
> > > >init function within the driver
> > > >which requested that module, this might be a solution for using
> > > >initialization functions similar to
> > > >usb_register/usb_deregister.
> > > >on the other side this would break the dvb_attach approach and it might
> > > >require much bigger changes in the
> > > >dvb framework (?)
> > > >This approach is currently partly implemented in v4l-dvb-kernel on
> > > >mcentral (http://mcentral.de/hg/~mrec/v4l-dvb-kernel)
> > >
> > > a current implementation which uses the unified module approach and a
> > > similar approach like dvb_attach can be found
> > > at:
> > > http://mcentral.de/hg/~mrec/v4l-dvb-experimental
> > > (see tuner-core.c, v4l_dvb_tuner.h)
> >
> > In the discussions one month ago I had the impression that serveral
> > people agreed on this or at least wanted to help to do the
> > necessary work to get this merged.
> >
>
> writing != doing..
>
> > All private comments to Markus are fine, but if there's
> > any interest in getting this stuff merged, you need to show
> > it publicly.
> >

forgot to mention that the hybrid tuner code itself is in xc3028-tuner.c

>
> the work is available in v4l-dvb-experimental, I'm fully done with it
> and people on the em28xx mailinglist are posting about current
> implementation problems (there's an issue with request_firmware
> actually at the moment)
>
> > Any comments on the code are good. Not saying anything is bad.
> >
> >
> > FWIW, I very briefly looked at
> > http://mcentral.de/hg/~mrec/v4l-dvb-experimental/file/d1e8753a491b/linux/include/media/v4l_dvb_tuner.h
> > and I think the V4L_OPS macro is invalid because it yields a pointer
> > to a variable on the stack which just went out of scope.
> > This might work by accident, but IMHO gcc is allowed to
> > reuse the stack space for something else immediately after
> > the closing brace.
> >
> >
>
> it just gets converted into another format for that functioncall, this
> is one point I'd like to discuss and improve actually it works the way
> it is but it might be done in a better way.
>
> Someone might have a better idea how to integrate this, maybe moving
> that structure to SET_FRONTEND etc.
>
> Another issue is using symbol_request there's definitelly no bug in
> the code and the usecount only jumps up to 1 even if it's used 2
> times, that problem is solved for the em2880-dvb/em28xx in that
> repository but it's not intended to work that way I'd say.
>
> thanks for looking at it,
>
> Markus
>


-- 
Markus Rechberger



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