On Saturday, November 26, 2011 06:55:52 Oliver Endriss wrote:
> On Friday 25 November 2011 23:06:34 Andreas Oberritter wrote:
> > On 25.11.2011 17:51, Manu Abraham wrote:
> > > On Fri, Nov 25, 2011 at 9:56 PM, Mauro Carvalho Chehab
> > > <mche...@redhat.com> wrote:
> > >> Em 25-11-2011 14:03, Andreas Oberritter escreveu:
> > >>> On 25.11.2011 16:38, Mauro Carvalho Chehab wrote:
> > >>>> Em 25-11-2011 12:41, Andreas Oberritter escreveu:
> > >>>>> On 25.11.2011 14:48, Mauro Carvalho Chehab wrote:
> > >>>>>> If your complain is about the removal of audio.h, video.h
> > >>>>>
> > >>>>> We're back on topic, thank you!
> > >>>>>
> > >>>>>> and osd.h, then my proposal is
> > >>>>>> to keep it there, writing a text that they are part of a deprecated
> > >>>>>> API,
> > >>>>>
> > >>>>> That's exactly what I proposed. Well, you shouldn't write
> > >>>>> "deprecated",
> > >>>>> because it's not. Just explain - inside this text - when V4L2 should
> > >>>>> be
> > >>>>> preferred over DVB.
> > >>>>
> > >>>> It is deprecated, as the API is not growing to fulfill today's needs,
> > >>>> and
> > >>>> no patches adding new stuff to it to it will be accepted anymore.
> > >>>
> > >>> Haha, nice one. "It doesn't grow because I don't allow it to." Great!
> > >>
> > >> No. It didn't grow because nobody cared with it for years:
> > >>
> > >> Since 2.6.12-rc2 (start of git history), no changes ever happened at
> > >> osd.h.
> > >>
> > >> Excluding Hans changes for using it on a pure V4L device, and other
> > >> trivial
> > >> patches not related to API changes, the last API change on audio.h and
> > >> video.h
> > >> was this patch:
> > >> commit f05cce863fa399dd79c5aa3896d608b8b86d8030
> > >> Author: Andreas Oberritter <o...@linuxtv.org>
> > >> Date: Mon Feb 27 00:09:00 2006 -0300
> > >>
> > >> V4L/DVB (3375): Add AUDIO_GET_PTS and VIDEO_GET_PTS ioctls
> > >>
> > >> (yet not used on any upstream driver)
> > >>
> > >> An then:
> > >> commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
> > >> Author: Linus Torvalds <torva...@ppc970.osdl.org>
> > >> Date: Sat Apr 16 15:20:36 2005 -0700
> > >>
> > >> Linux-2.6.12-rc2
> > >>
> > >> No changes adding support for any in-kernel driver were ever added there.
> > >>
> > >> So, it didn't grow over the last 5 or 6 years because nobody submitted
> > >> driver patches requiring new things or _even_ using it.
> > >>
> > >>>
> > >>>>>> but keeping
> > >>>>>> the rest of the patches
> > >>>>>
> > >>>>> Which ones?
> > >>>>
> > >>>> V4L2, ivtv and DocBook patches.
> > >>>
> > >>> Fine.
> > >>>
> > >>>>>> and not accepting anymore any submission using them
> > >>>>>
> > >>>>> Why? First you complain about missing users and then don't want to
> > >>>>> allow
> > >>>>> any new ones.
> > >>>>
> > >>>> I didn't complain about missing users. What I've said is that, between
> > >>>> a
> > >>>> one-user API and broad used APIs like ALSA and V4L2, the choice is to
> > >>>> freeze
> > >>>> the one-user API and mark it as deprecated.
> > >>>
> > >>> Your assumtion about only one user still isn't true.
> > >>>
> > >>>> Also, today's needs are properly already covered by V4L/ALSA/MC/subdev.
> > >>>> It is easier to add what's missing there for DVB than to work the other
> > >>>> way around, and deprecate V4L2/ALSA/MC/subdev.
> > >>>
> > >>> Yes. Please! Add it! But leave the DVB API alone!
> > >>>
> > >>>>>> , removing
> > >>>>>> the ioctl's that aren't used by av7110 from them.
> > >>>>>
> > >>>>> That's just stupid. I can easily provide a list of used and valuable
> > >>>>> ioctls, which need to remain present in order to not break userspace
> > >>>>> applications.
> > >>>>
> > >>>> Those ioctl's aren't used by any Kernel driver, and not even
> > >>>> documented.
> > >>>> So, why to keep/maintain them?
> > >>>
> > >>> If you already deprecated it, why bother deleting random stuff from it
> > >>> that people are using?
> > >>>
> > >>> There's a difference in keeping and maintaining something. You don't
> > >>> need to maintain ioctls that haven't changed in years. Deleting
> > >>> something is more work than letting it there to be used by those who
> > >>> want to.
> > >>
> > >> Ok. Let's just keep the headers as is, just adding a comment that it is
> > >> now
> > >> considered superseded.
> >
> > Thank you! This is a step into the right direction.
> >
> > > http://dictionary.reference.com/browse/superseded
> > >
> > > to set aside or cause to be set aside as void, useless, or obsolete,
> > > usually
> > > in favor of something mentioned; make obsolete: They superseded the
> > > old statute with a new one.
> > >
> > > No, that's not acceptable. New DVB devices as they come will make use
> > > of the API and API changes might be applied.
> >
> > Honestly, I think we all should accept this proposal and just hope that
> > the comment is going to be written objectively.
>
> 'Hoping' is not enough for me anymore. I am deeply disappointed.
> Mauro and Hans have severely damaged my trust, that v4ldvb APIs are
> stable in Linux, and how things are handled in this project.
>
> So I request a public statement from the subsystem maintainer that
> 1. The DVB Decoder API will not be removed.
> 2. It can be updated if required (e.g. adding a missing function).
> 3. New drivers are allowed to use this architecture.
> 4. These driver will be accepted, if they follow the kernel standards.
>
> The reason is simple: I need to know, whether this project is still
> worth investing some time, or it is better to do something else.
1) There are two APIs that do the same thing: the DVB decoder API and the
V4L2 API.
2) That's bad because it confuses driver developers and application developers
who have to support *two* APIs to do the same thing.
3) The DVB decoder API is used in only one DVB driver (av7110), and in one
V4L2 driver (ivtv). The latter is easily converted to V4L2 which leaves only
one driver, av7110.
4) A decoder API has nothing to do with DVB as a standard, it simply takes
the output of the DVB part of the hardware and decodes it to the output.
That's basic V4L2 functionality.
5) Video output is present in quite a few V4L2 drivers (10 at a quick count)
and that already includes support for decoders (just not decoder operations
like PLAY/STOP/PAUSE/RESUME etc., that's where the V4L2 additions come in).
Note that most of the video output drivers these days are from SoCs. That's
where all the activity is these days. Ensuring that SoC vendors know what to
do and that they have the right APIs and frameworks is an important part of
our work these days.
6) So with 10 V4L2 video output drivers and 1 DVB output driver it is not
hard to see that the easiest solution is to make the DVB decoder API an
av7110-specific API and prohibit its use for new drivers.
What should be done with the existing audio.h, video.h and osd.h headers is
a separate issue. I believe that keeping them indefinitely is a bad move in
the long term if we decide to remove the DVB decoder API but that's just
my experience with similar situations (the removal of V4L1 springs to mind).
But I'll just follow what Mauro decides.
Yes, there are out-of-tree drivers that use the DVB decoder API. You know
the rules: if you are out-of-tree you do not count. That's true for everyone
maintaining an out-of-tree driver. I've maintained the out-of-tree ivtv
driver at the time and I know the pain. And that's also why SoC vendors are
now trying to get their video hardware supported in the kernel, because once
it is in much of that pain disappears.
Finally I want to mention again that the DVB subsystem isn't an ivory tower.
It doesn't exist in isolation. Particularly with the ever increasing
integration of video capabilities (include DVB) on SoCs cooperation between
subsystems is ever more important and will only increase in the future.
Regards,
Hans
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