On Thursday 05 March 2009 21:57:16 Trent Piepho wrote:
> On Thu, 5 Mar 2009, Guennadi Liakhovetski wrote:
> > On Thu, 5 Mar 2009, Trent Piepho wrote:
> > > On Thu, 5 Mar 2009, Guennadi Liakhovetski wrote:
> > > > On Wed, 4 Mar 2009, Mauro Carvalho Chehab wrote:
> > > > > Beside the fact that we don't need to strip support for legacy
> > > > > kernels, the advantage of using this method is that we can
> > > > > evolute to a new development model. As several developers already
> > > > > required, we should really use the standard -git tree as
> > > > > everybody's else. This will simplify a lot the way we work, and
> > > > > give us more agility to send patches upstream.
> > > > >
> > > > > With this backport script, plus the current v4l-dvb building
> > > > > systems, and after having all backport rules properly mapped, we
> > > > > can generate a "test tree" based on -git drivers/media, for the
> > > > > users to test the drivers against their kernels, and still use a
> > > > > clean tree for development.
> > > >
> > > > Sorry, switching to git is great, but just to make sure I
> > > > understood you right: by "-git drivers/media" you don't mean it is
> > > > going to be a git tree of only drivers/media, but it is going to be
> > > > a normal complete Linux kernel tree, right?
> > >
> > > So there will be no way we can test a driver without switching to a
> > > new kernel hourly? And there is no way we can test someone else's
> > > tree without compiling an entirely new kernel and rebooting? And
> > > every tree we want to work on requires a complete copy of the entire
> > > kernel source?
> >
> > AFAIR, Mauro wanted to provide snapshots for those who absolutely
> > prefer to work with partial trees. Although, to be honest, I don't
> > understand what makes video drivers so special. Think about audio
> > drivers, or network, including WLAN. I never heard about those
> > subsystems working with or providing subtree snapshots. If only before
> > specific drivers or subsystems are included in the mainline, but not
> > long after that.
>
> ALSA used a partial tree, but their system was much worse than v4l-dvb's.
> I think the reason more systems don't do it is that setting up the build
> system we have with v4l-dvb was a lot of work. They don't have that.
>
> Lots of subsystems are more tightly connected to the kernel and compiling
> the subsystem out of tree against any kernel just wouldn't work. Some
> subsystems (like say gpio or led) mostly provide a framework to the rest
> of the kernel so working on them without the rest of the tree doesn't
> make sense either. Or they don't get many patches and don't have many
> active maintainers so they don't really have any development SCM at all.
> Just some patches through email that get applied by one maintainer.
Our model of just the subsystem is fine when all you are dealing with are
PCI and USB devices, but especially with embedded devices you get a lot of
links to the platform code. For that you need to have a full kernel.
I expect that the embedded drivers will be a very active area for the next
several years so we have to make sure we can handle that.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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