Date:	Thu, 11 Oct 2012 14:11:34 +0530
From:	Manu Abraham <abraham.manu@...il.com>
To:	Oliver Endriss <o.endriss@....de>
Cc:	Mauro Carvalho Chehab <mchehab@...radead.org>,
	David Howells <dhowells@...hat.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Hans Verkuil <hverkuil@...all.nl>
Subject: Re: Re: [GIT PULL] Disintegrate UAPI for media

On Thu, Oct 11, 2012 at 1:53 PM, Oliver Endriss <o.endriss@....de> wrote:
> Mauro Carvalho Chehab <mchehab@...radead.org> wrote:
>> Em Tue, 09 Oct 2012 14:30:24 +0100
>> David Howells <dhowells@...hat.com> escreveu:
>>
>> > Can you merge the following branch into the media tree please.
>> >
>> > This is to complete part of the Userspace API (UAPI) disintegration for which
>> > the preparatory patches were pulled recently.  After these patches, userspace
>> > headers will be segregated into:
>> >
>> >     include/uapi/linux/.../foo.h
>> >
>> > for the userspace interface stuff, and:
>> >
>> >     include/linux/.../foo.h
>> >
>> > for the strictly kernel internal stuff.
>> >
>> > ---
>> > The following changes since commit 9e2d8656f5e8aa214e66b462680cf86b210b74a8:
>> >
>> >   Merge branch 'akpm' (Andrew's patch-bomb) (2012-10-09 16:23:15 +0900)
>> >
>> > are available in the git repository at:
>> >
>> >
>> >   git://git.infradead.org/users/dhowells/linux-headers.git tags/disintegrate-media-20121009
>> >
>> > for you to fetch changes up to 1c436decd49665be131887b08d172a7989cdceee:
>> >
>> >   UAPI: (Scripted) Disintegrate include/linux/dvb (2012-10-09 09:48:42 +0100)
>> >
>> > ----------------------------------------------------------------
>> > UAPI Disintegration 2012-10-09
>> >
>> > ----------------------------------------------------------------
>> > David Howells (1):
>> >       UAPI: (Scripted) Disintegrate include/linux/dvb
>> >
>> >  include/linux/dvb/Kbuild                |   8 -
>> >  include/linux/dvb/dmx.h                 | 130 +--------------
>> >  include/linux/dvb/video.h               | 249 +----------------------------
>> >  include/uapi/linux/dvb/Kbuild           |   8 +
>> >  include/{ => uapi}/linux/dvb/audio.h    |   0
>> >  include/{ => uapi}/linux/dvb/ca.h       |   0
>> >  include/uapi/linux/dvb/dmx.h            | 155 ++++++++++++++++++
>> >  include/{ => uapi}/linux/dvb/frontend.h |   0
>> >  include/{ => uapi}/linux/dvb/net.h      |   0
>> >  include/{ => uapi}/linux/dvb/osd.h      |   0
>> >  include/{ => uapi}/linux/dvb/version.h  |   0
>> >  include/uapi/linux/dvb/video.h          | 274 ++++++++++++++++++++++++++++++++
>> >  12 files changed, 439 insertions(+), 385 deletions(-)
>> >  rename include/{ => uapi}/linux/dvb/audio.h (100%)
>> >  rename include/{ => uapi}/linux/dvb/ca.h (100%)
>> >  create mode 100644 include/uapi/linux/dvb/dmx.h
>> >  rename include/{ => uapi}/linux/dvb/frontend.h (100%)
>> >  rename include/{ => uapi}/linux/dvb/net.h (100%)
>> >  rename include/{ => uapi}/linux/dvb/osd.h (100%)
>> >  rename include/{ => uapi}/linux/dvb/version.h (100%)
>> >  create mode 100644 include/uapi/linux/dvb/video.h
>>
>> Hmm... last year, it was decided that we would be putting the DVB av7110-only
>> API files on a separate place, as the API there conflicts with V4L/alsa APIs
>
> Wrong! Hans Verkuil and you tried to do it, without caring that it would
> break userspace, and it was NAKed.
>
> Btw, if there is an API conflict, you guys created it.
>
> Anyone, who is interested in the _true_ history, should have a look at
> the GIT changelog:
> - dvb/{video.h,audio.h,osd.h} was the original decoder API.
> - Then Hans extended this API, still using the same files.
> - Later the v4l guys decided to create a new API.
> - Now they want to (re)move the old one, breaking userspace.
>
> I explicitly NAK any attempt to break userspace applications and tools!
> There is no reason to do it!
>
>> and are used only by one upstream driver (there were two drivers using them,
>> at that time). As you might notice, av7110 hardware is really old, not
>> manufactured anymore since maybe 10 years ago, and it is an unmaintained
>> driver.
>
> The driver works fine, and it will continue to do so, unless someone
> tampers with it. It does not require maintenance.
> The hardware is old, but it is still in use, as it is easy to create a
> pc-based settopbox with it.


As of writing; the av7110 is the only driver in-kernel, but there is more to it:
Such drivers are hard to bring up and takes an awful amount of time. There
is already one driver which is nearing completion based on the same interface.


>
>> Some developers complained, arguing that moving it to a separate file would
>> be breaking the compilation on existing tools (they're basically concerned with
>> it due to out-of-tree drivers - mostly propietary ones, that use this API).
>
> It you move the API somewhere else, you will break userspace applications
> like VDR. This is not acceptable.
>
>> Now that we're moving everything, it does make sense to do that, moving
>> dvb/(audio|osd|video).h to someplace else (maybe linux/dvb/av7110.h or
>> linux/dvb/legacy/*.h).
>
> As far as I understand the original patchset, it will not break
> userspace, as it will simply move all files somewhere else, preserving
> file names and the position of the files in the tree.
>
> Mauro is trying to the move the old decoder API somewhere else, possibly
> into a different file, which will definitely break userspace.
> NAK for this!


I completely agree with Oliver on this and NAK the suggestion put forward
by Mauro (and Hans)


Regards,
Manu
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