Re: Re: [RFC/PATCHES] xc3028 hybrid tuner, em28xx/em2880-dvb, saa7134, cx88

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On 5/17/07, Michael Krufky <mkrufky@xxxxxxxxxxx> wrote:
Mauro Carvalho Chehab wrote:
>
>> I do frown upon code duplication, however, in this case it is a safer
>> alternative to the one currently on the table.  Earlier versions of
>> the xc3028 tuner driver were bound to the video4linux tuner.ko
>> module, for the sake of tuning analog television stations.  There was
>> a wrapper present inside the em2880-dvb driver that allowed the dvb
>> subsystem to access the xc3028 via tuner.ko.  I am not a big fan of
>> this solution, however, it does not touch any core subsystem code.
>> DVB-only devices can use a separate module in order to access the
>> xc3028 without imposing dependencies on the v4l core.
>
> Duplicating a driver is not a solution, just a terrible hack. We
> should focus on a way to use the same tuner driver for both Analog and
> Digital TV.
>
Mauro,

Don't get me wrong -- I am not suggesting that we duplicate this code
and leave it in that state forever.  What I am suggesting is that we go
about this change in small steps.

The proposed changes are simply too large and span too many source files
to achieve a proper review by enough developers, especially in their
"spare time," not to mention all the regression testing that needs to be
done.


In that case I'm willing to fork the linuxtv project if I did too much
to review.
I just spent too much time on it to throw it away without a serious discussion.

The tuner refactoring code has around 600-700 lines of code I think,
the rest are the additional drivers and other things.


As much as we try to come to an agreement about this right now, I fear
that it will be very difficult -- this debate has gone on for over a
year and reaching an agreement will not be easy.

I think that the only way to move forward while keeping everybody happy
would be to proceed in the following order:

1) merge xc3028 support into tuner.ko for analog support*

2) break apart tuner.ko into modularized sub-modules*

3) add xc3028-fe.ko module for dvb-only support**

4) merge in updates to the em28xx driver***

5) add xc3028 support to other card drivers***

6) restart discussions about hybrid / tuner inter-subsystem API

7) apply changes agreed upon in step 6, to migrate the tuner modules to
the new tuner internal api, while removing the duplicated xc3028 module.


*(1) and (2) may be reversed

** http://linuxtv.org/~mkrufky/xc-bluebird.patch

*** analog functionality should use tuner.ko only
*** digital functionality should use xc3028-fe.ko only

---

Please take note, that if we proceed in the order above, this will allow
us to merge the majority of Markus' changes, leaving only the api
changes behind.  At this point, the remainder of the changesets will be
MUCH smaller, and much easier to review.

Under the conditions that we'll be under after step 5, it will be much
more conducive to a productive developer discussion on the issue.

At this point, there has been so much noise about this topic, that I
feel confident that many developers will be able to participate in this
review.  I, for one, would love to have this taken care of, and put this
issue behind us.

After step 5, with the majority of the changesets already being merged,
the pressure on the author and reviewers will be lessened, and
discussions should be able to take place with clear heads.

What I am asking for here is very sensible --  This should not be
difficult for everybody to agree to.  It allows us to merge in changes
one step at a time, while adding support for all devices gradually.
Through this means, we will ultimately achieve the goal of being able to
discuss the actual requirements and reasons for why Markus is making
this proposal to change the tuner api.

I repeat:  huge changes will never blow over well.  The only way to do
this in small steps is to do it in such a way that I've described in
this email.

If you simply shoot me down for the idea of temporarily having a
separate dvb module for the dvb subsystem to interface with the xc3028
tuner,  then you are not seeing the big picture.

Regards,

Mike Krufky





--
Markus Rechberger

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