[pvrusb2] pvrusb2 driver going into v4l...

[xavier.gnata at free.fr]

A very short answer IMHO :
IMHO, drop backwards compatibility :).
Why?
Ok,  pvrusb2 is going to be a driver merged into kernel. Which kernel.
Most probably 2.6.16. At this point, there is nostly no point to work to get it
backwards compatible because there is no rela point to say "it is in mainline"
and at the same time "here is the patch (or the hack) to keep it compatible
with 2.6.1X".
It is great to be in mainline and, IMHO, a driver in the mainline should only
care about the current kernel API (and not the old ones which are dead :))

Xavier.


> I might have mentioned here a while back that I have been invited to
> submit the pvrusb2 driver for inclusion into the v4l core and then
> subsequent inclusion into the main kernel.  This has been an open
> invitation for a while and last weekend I (finally) started real work to
> accomplish this goal.  The ivtv driver by the way is also going into V4L.
>
> During that effort to massage the sources into a V4L-acceptable form, I
> uncovered a number of complicating issues.  I won't bore you with the
> details here.  But it does lead to a key question that I'd like to get
> some feedback on:
>
> The effort to ready the driver would be significantly easier if I
> discarded any pretense towards supporting earlier versions of the kernel
> and any version of ivtv.  What do you all think about that?  I know it
> sounds radical, so let me fill in some details here...
>
> The ivtv driver is also being pulled into V4L, and I'm led to believe that
> this effort is going quite well.  A lot of the various "problem-child"
> modules that pvrusb2 leverages from ivtv will finally only exist in one
> version, that being V4L.  This means that *going forward*, there will no
> longer (in theory) be any traps / pitfalls towards getting the pvrusb2
> driver to play nicely with ivtv.  However, *going backwards*, this would
> also means that newer versions of the driver (either in v4l or separately
> released) would NOT be able to work with older versions of ivtv.  I've
> tried to maintain complete forwards / backwards compatibility with ivtv,
> but trying to do that while simultaneously arranging things for a seamless
> fit directly into V4L really really complicates things.  Just to make the
> point really clear: I want to forgo maintaining compatibility with older
> ivtv releases.  Breaking with backwards compatibility with ivtv would NOT
> means that we can't work with ivtv anymore; it would mean that we would no
> longer have any chance of working with *older* versions of ivtv.  With
> ivtv being pulled into V4L as well, it should actually be easier to
> coexist with ivtv.  Any thoughts on this anyone?
>
> As for earlier kernel versions, the pvrusb2 driver right now should work
> with all kernel versions from roughly 2.6.10 (w/ relevant V4L patches) up
> to the current kernel.  However there are things I do in the driver to
> maintain that backwards compatibility.  But putting that sort of stuff
> into a driver destined for ultimate inclusion in, say the official 2.6.15
> kernel tree, would seem kind of silly.  I expect right now that even after
> the driver goes into the kernel that I may want to still maintain an
> out-of-tree snapshot for rapid development of new code, and obviously I'd
> want that snapshot to stay as close as possible to the in-tree version in
> the kernel.  That would mean discarding anything needed for the older
> kernel versions.  Thoughts, comments?
>
> There is a chance this driver might get into 2.6.15, though right now I
> think the odds are low (it's almost too late for inclusion and I'm really
> short on time for the next few days).  However even if not 2.6.15 then
> certainly 2.6.16 may be possible.  I've never planned on permanently
> hosting this driver, and this seems like a chance to give the driver a
> place where it can live beyond any one person's attention span.  So I
> think it important to do the effort now to get it included, but the effort
> will be a lot easier if I can drop backwards compatibility with older
> kernels and older versions of ivtv.  So what do you all think?
>
> BTW, before anyone gets worried, no I am *NOT* looking to orphan this
> driver.  It's been a lot of fun working on this and I've actually quite
> enjoyed helping people out.  I plan to continue supporting and expanding
> the driver, even after inclusion.  For the first time, I'm really able to
> give back to the Open Source community.  In fact, I kind of hope I can
> find other interesting stuff I can contribute in the future (in V4L or
> whatever else looks interesting).  But certainly I don't expect to be
> hosting this driver forever.  The obvious endgame is kernel inclusion; the
> opportunity exists now, so let's do this...
>
> What do you all think?
>
>    -Mike
>
>
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