RFC: drop support for kernels < 2.6.22

RFC: drop support for kernels < 2.6.22

[Hans Verkuil]

Hi all,

It been my opinion for quite some time now that we are too generous in 
the number of kernel versions we support. I think that the benefits no 
longer outweight the effort we have to put in.

This is true in particular for the i2c support since that changed a lot 
over time. Kernel 2.6.22 is a major milestone for that since it 
introduced the new-style i2c API.

In order to keep the #ifdefs to a minimum I introduced the 
v4l2-i2c-drv.h and v4l2-i2c-drv-legacy.h headers. These make sense when 
used in the v4l-dvb tree context, but when they are stripped and used 
in the actual kernel source they look very weird.

My proposal is to stop supporting kernels < 2.6.22 so that we no longer 
have to put a lot of effort in supporting the old-style i2c API.

In addition, I would suggest that for every new kernel release we also 
drop support for the oldest kernel. The only exception being that once 
2.6.27 is the oldest supported kernel we stick with that one since that 
is the new long-term maintained kernel. Unless we end up again with 
major compatibility issues.

Comments?

Regards,

	Hans

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Re: RFC: drop support for kernels < 2.6.22

[Mauro Carvalho Chehab]

On Thu, 27 Nov 2008 08:32:22 +0100
Hans Verkuil <hverkuil@xs4all.nl> wrote:

> Hi all,
> 
> It been my opinion for quite some time now that we are too generous in 
> the number of kernel versions we support. I think that the benefits no 
> longer outweight the effort we have to put in.
> 
> This is true in particular for the i2c support since that changed a lot 
> over time. Kernel 2.6.22 is a major milestone for that since it 
> introduced the new-style i2c API.

I prefer to keep backward compat with older kernels. Enterprise distros like
RHEL is shipped with older kernels (for example RHEL5 uses kernel 2.6.18). We
should support those kernels.

> In order to keep the #ifdefs to a minimum I introduced the 
> v4l2-i2c-drv.h and v4l2-i2c-drv-legacy.h headers. These make sense when 
> used in the v4l-dvb tree context, but when they are stripped and used 
> in the actual kernel source they look very weird.

We may use a different approach for the above files. For example, we may
include the headers just for older kernels, like we did in the past with i2c
backward compat with kernel 2.4. gentree can easily remove a #include line from
the upstream patch.

Cheers,
Mauro

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Re: RFC: drop support for kernels < 2.6.22

[Hans Verkuil]

> On Thu, 27 Nov 2008 08:32:22 +0100
> Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
>> Hi all,
>>
>> It been my opinion for quite some time now that we are too generous in
>> the number of kernel versions we support. I think that the benefits no
>> longer outweight the effort we have to put in.
>>
>> This is true in particular for the i2c support since that changed a lot
>> over time. Kernel 2.6.22 is a major milestone for that since it
>> introduced the new-style i2c API.
>
> I prefer to keep backward compat with older kernels. Enterprise distros
> like
> RHEL is shipped with older kernels (for example RHEL5 uses kernel 2.6.18).
> We
> should support those kernels.

Is RHEL (or anyone else for that matter) actually using our tree? I never
see any postings about problems or requests for these old kernels on the
v4l list.

Do you know if and how other subsystems handle this?

>
>> In order to keep the #ifdefs to a minimum I introduced the
>> v4l2-i2c-drv.h and v4l2-i2c-drv-legacy.h headers. These make sense when
>> used in the v4l-dvb tree context, but when they are stripped and used
>> in the actual kernel source they look very weird.
>
> We may use a different approach for the above files. For example, we may
> include the headers just for older kernels, like we did in the past with
> i2c
> backward compat with kernel 2.4. gentree can easily remove a #include line
> from
> the upstream patch.

You either using these headers, or you start using lots of #ifdefs in each
i2c driver. There is unfortunately no easy solution to this (I really
tried at the time). Dropping pre-2.6.22 support will make it feasible to
drop these headers. There would still be a few #ifdefs, but it will be
acceptable.

If you know of a distro or big customer that is actually using v4l-dvb on
old kernels, then I think we should keep it, but otherwise it is my
opinion that it is not worth the (substantial) hassle. I also have my
doubts about people using enterprise distros together with v4l. Doesn't
seem very likely to me.

Regards,

       Hans

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Re: RFC: drop support for kernels < 2.6.22

[Andy Walls]

On Thu, 2008-11-27 at 11:23 +0100, Hans Verkuil wrote:
> > On Thu, 27 Nov 2008 08:32:22 +0100
> > Hans Verkuil <hverkuil@xs4all.nl> wrote:
> >
> >> Hi all,
> >>
> >> It been my opinion for quite some time now that we are too generous in
> >> the number of kernel versions we support. I think that the benefits no
> >> longer outweight the effort we have to put in.
> >>
> >> This is true in particular for the i2c support since that changed a lot
> >> over time. Kernel 2.6.22 is a major milestone for that since it
> >> introduced the new-style i2c API.
> >
> > I prefer to keep backward compat with older kernels. Enterprise distros
> > like
> > RHEL is shipped with older kernels (for example RHEL5 uses kernel 2.6.18).
> > We
> > should support those kernels.
> 
> Is RHEL (or anyone else for that matter) actually using our tree? I never
> see any postings about problems or requests for these old kernels on the
> v4l list.

And from those working on or using surveillance/security systems, I
suspect you might never hear anything.


> Do you know if and how other subsystems handle this?
> 
> >
> >> In order to keep the #ifdefs to a minimum I introduced the
> >> v4l2-i2c-drv.h and v4l2-i2c-drv-legacy.h headers. These make sense when
> >> used in the v4l-dvb tree context, but when they are stripped and used
> >> in the actual kernel source they look very weird.


"Looks very weird" in newer kernels is likely not a weighty criteria for
elimination of support of older kernels, if I were to put myself in the
place of someone using an older kernel that still needed v4l-dvb.

The question is how large is that subset of users?


> > We may use a different approach for the above files. For example, we may
> > include the headers just for older kernels, like we did in the past with
> > i2c
> > backward compat with kernel 2.4. gentree can easily remove a #include line
> > from
> > the upstream patch.
> 
> You either using these headers, or you start using lots of #ifdefs in each
> i2c driver. There is unfortunately no easy solution to this (I really
> tried at the time). Dropping pre-2.6.22 support will make it feasible to
> drop these headers. There would still be a few #ifdefs, but it will be
> acceptable.
> 
> If you know of a distro or big customer that is actually using v4l-dvb on
> old kernels, then I think we should keep it, but otherwise it is my
> opinion that it is not worth the (substantial) hassle. I also have my
> doubts about people using enterprise distros together with v4l. Doesn't
> seem very likely to me.

Does the following pass the plausibility test?

1. Large businesses or organizations, or their commercial suppliers, use
enterprise distributions to gain paid support and an OS that can get
through security accreditation processes.

2. Once a system has gone through an accreditation process, it is costly
to repeat the entire process - which a wholesale OS distribution upgrade
may force.  Accreditation of smaller changes may be less costly.

3. Large businesses and organizations are often interested in
surveillance applications, especially for security systems which require
some sort of accreditation.

4. Suppliers and users of security and surveillance systems won't likely
broadcast to large audiences what configurations their systems use.  

Regards,
Andy


> Regards,
> 
>        Hans


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Re: RFC: drop support for kernels < 2.6.22

[Mauro Carvalho Chehab]

On Thu, 27 Nov 2008 11:23:12 +0100 (CET)
"Hans Verkuil" <hverkuil@xs4all.nl> wrote:

> > On Thu, 27 Nov 2008 08:32:22 +0100
> > Hans Verkuil <hverkuil@xs4all.nl> wrote:
> >
> >> Hi all,
> >>
> >> It been my opinion for quite some time now that we are too generous in
> >> the number of kernel versions we support. I think that the benefits no
> >> longer outweight the effort we have to put in.
> >>
> >> This is true in particular for the i2c support since that changed a lot
> >> over time. Kernel 2.6.22 is a major milestone for that since it
> >> introduced the new-style i2c API.
> >
> > I prefer to keep backward compat with older kernels. Enterprise distros
> > like
> > RHEL is shipped with older kernels (for example RHEL5 uses kernel 2.6.18).
> > We
> > should support those kernels.
> 
> Is RHEL (or anyone else for that matter) actually using our tree? I never
> see any postings about problems or requests for these old kernels on the
> v4l list.

RHEL bugs come to redhat bugzilla. Generated patches there should be tested
against the latest version and applied upstream.

> If you know of a distro or big customer that is actually using v4l-dvb on
> old kernels, then I think we should keep it, but otherwise it is my
> opinion that it is not worth the (substantial) hassle. I also have my
> doubts about people using enterprise distros together with v4l. Doesn't
> seem very likely to me.

Yes, there are customers with enterprise distros using V4L drivers.

Also, I am using V4L/DVB tree with a 2.6.18 kernel on some machines. Removing
support for 2.6.18 will be a pain for me. 

I suspect that Laurent is also using RHEL (or some uvc users), since he sent
some patches fixing compilation with RHEL.

Cheers,
Mauro

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Re: RFC: drop support for kernels < 2.6.22

[Hans Verkuil]

> On Thu, 27 Nov 2008 11:23:12 +0100 (CET)
> "Hans Verkuil" <hverkuil@xs4all.nl> wrote:
>
>> > On Thu, 27 Nov 2008 08:32:22 +0100
>> > Hans Verkuil <hverkuil@xs4all.nl> wrote:
>> >
>> >> Hi all,
>> >>
>> >> It been my opinion for quite some time now that we are too generous
>> in
>> >> the number of kernel versions we support. I think that the benefits
>> no
>> >> longer outweight the effort we have to put in.
>> >>
>> >> This is true in particular for the i2c support since that changed a
>> lot
>> >> over time. Kernel 2.6.22 is a major milestone for that since it
>> >> introduced the new-style i2c API.
>> >
>> > I prefer to keep backward compat with older kernels. Enterprise
>> distros
>> > like
>> > RHEL is shipped with older kernels (for example RHEL5 uses kernel
>> 2.6.18).
>> > We
>> > should support those kernels.
>>
>> Is RHEL (or anyone else for that matter) actually using our tree? I
>> never
>> see any postings about problems or requests for these old kernels on the
>> v4l list.
>
> RHEL bugs come to redhat bugzilla. Generated patches there should be
> tested
> against the latest version and applied upstream.
>
>> If you know of a distro or big customer that is actually using v4l-dvb
>> on
>> old kernels, then I think we should keep it, but otherwise it is my
>> opinion that it is not worth the (substantial) hassle. I also have my
>> doubts about people using enterprise distros together with v4l. Doesn't
>> seem very likely to me.
>
> Yes, there are customers with enterprise distros using V4L drivers.
>
> Also, I am using V4L/DVB tree with a 2.6.18 kernel on some machines.
> Removing
> support for 2.6.18 will be a pain for me.
>
> I suspect that Laurent is also using RHEL (or some uvc users), since he
> sent
> some patches fixing compilation with RHEL.

Darn. Oh well, so be it...

Regards,

        Hans

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Re: RFC: drop support for kernels < 2.6.22

[Laurent Pinchart]

On Thursday 27 November 2008, Mauro Carvalho Chehab wrote:
> On Thu, 27 Nov 2008 11:23:12 +0100 (CET)
> "Hans Verkuil" <hverkuil@xs4all.nl> wrote:
> > > On Thu, 27 Nov 2008 08:32:22 +0100
> > > Hans Verkuil <hverkuil@xs4all.nl> wrote:
> > >> Hi all,
> > >>
> > >> It been my opinion for quite some time now that we are too generous in
> > >> the number of kernel versions we support. I think that the benefits no
> > >> longer outweight the effort we have to put in.
> > >>
> > >> This is true in particular for the i2c support since that changed a
> > >> lot over time. Kernel 2.6.22 is a major milestone for that since it
> > >> introduced the new-style i2c API.
> > >
> > > I prefer to keep backward compat with older kernels. Enterprise distros
> > > like RHEL is shipped with older kernels (for example RHEL5 uses kernel
> > > 2.6.18). We should support those kernels.
> >
> > Is RHEL (or anyone else for that matter) actually using our tree? I never
> > see any postings about problems or requests for these old kernels on the
> > v4l list.
>
> RHEL bugs come to redhat bugzilla. Generated patches there should be tested
> against the latest version and applied upstream.
>
> > If you know of a distro or big customer that is actually using v4l-dvb on
> > old kernels, then I think we should keep it, but otherwise it is my
> > opinion that it is not worth the (substantial) hassle. I also have my
> > doubts about people using enterprise distros together with v4l. Doesn't
> > seem very likely to me.
>
> Yes, there are customers with enterprise distros using V4L drivers.
>
> Also, I am using V4L/DVB tree with a 2.6.18 kernel on some machines.
> Removing support for 2.6.18 will be a pain for me.
>
> I suspect that Laurent is also using RHEL (or some uvc users), since he
> sent some patches fixing compilation with RHEL.

Before moving to linuxtv.org the UVC driver was backward compatible with all 
kernels starting at 2.6.15 out of the box. With a minor patch applied this 
even extended to 2.6.10. While I have no statistics regarding kernel versions 
on which the UVC driver is used, the driver seems to be popular with embedded 
users who usually run "old" vendor-supplied kernels on their systems.

As such, at least for the UVC driver, I'd hate to see compatibility with 
2.6.16-2.6.21 going away anytime soon.

Best regards,

Laurent Pinchart

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Re: RFC: drop support for kernels < 2.6.22

[Douglas Schilling Landgraf]

Hello,

On Thu, 27 Nov 2008 07:41:39 -0200
Mauro Carvalho Chehab <mchehab@infradead.org> wrote:

> On Thu, 27 Nov 2008 08:32:22 +0100
> Hans Verkuil <hverkuil@xs4all.nl> wrote:
> 
> > Hi all,
> > 
> > It been my opinion for quite some time now that we are too generous
> > in the number of kernel versions we support. I think that the
> > benefits no longer outweight the effort we have to put in.
> > 
> > This is true in particular for the i2c support since that changed a
> > lot over time. Kernel 2.6.22 is a major milestone for that since it 
> > introduced the new-style i2c API.
> 
> I prefer to keep backward compat with older kernels. Enterprise
> distros like RHEL is shipped with older kernels (for example RHEL5
> uses kernel 2.6.18). We should support those kernels.

Agreed. I'm using 2.6.18 kernel on some of my machines.
 
Cheers,
Douglas

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Re: RFC: drop support for kernels < 2.6.22

[Jackson Yee]

On Thu, Nov 27, 2008 at 8:52 AM, Andy Walls <awalls@radix.net> wrote:
> And from those working on or using surveillance/security systems, I
> suspect you might never hear anything.

I've been working in the surveillance industry for about three years
now. About 95% of the working machines out there are all Windows
machines or dedicated embedded machines running specialized firmware.
There are a few Linux compatible cards out there, but most of them use
the bttv driver to provide video, and other ones provided their own
driver against a particular kernel version and distribution (usually
Red Hat). I believe that the future probably lies in MPEG4/H264 IP
cameras, but until their costs decrease significantly, most people
will probably stick with the cheap bttv cards.

Linux surveillance projects are few and far in between - mostly
Zoneminder users and Kenneth Lavrsen's motion. That's one of the
reasons why I've been working on my project to provide a high level
language interface to the V4L2 API to allow rapid development of
projects for others.

My personal opinion is that backwards compatibility is definitely
helpful, but for most drivers out there, it's probably not necessary
since most users will update their kernel along with their
distributions, and that kernel will include the newer drivers while
older users can simply keep using their same kernels - especially with
an enterprise system. I have no problems if Hans wishes to devote his
time to the newer kernels.

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The Possum Company
540-818-4079
me@gotpossum.com

P.S. Happy Thanksgiving to those of us who are in the U.S.! My
family's having duck and crab legs instead of the traditional turkey
this year, but it's nice to have a day off once in a while instead of
our normal hectic schedules!

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Re: RFC: drop support for kernels < 2.6.22

[Darren Longhorn]

Laurent Pinchart wrote:

> Before moving to linuxtv.org the UVC driver was backward compatible with all 
> kernels starting at 2.6.15 out of the box. With a minor patch applied this 
> even extended to 2.6.10. While I have no statistics regarding kernel versions 
> on which the UVC driver is used, the driver seems to be popular with embedded 
> users who usually run "old" vendor-supplied kernels on their systems.
> 
> As such, at least for the UVC driver, I'd hate to see compatibility with 
> 2.6.16-2.6.21 going away anytime soon.

As one of those embedded developers, I second this view.

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