On 18 Oct 2001, Gerd Knorr wrote:
> volodya@xxxxxxxxxxxxxx wrote:
> >
> > On 18 Oct 2001, Gerd Knorr wrote:
> >
> > > including v4l2 is planned for 2.5.x.
> >
> > And 2.6.x is still a ways off. What do you think about having "extended
> > v4l" ?
>
> Bad idea. v4l2 _is_ extended (and bugfixed) v4l, and I want people
> switch over to v4l2 instead of hacking v4l. Maybe we can put it into
> 2.4.x too later on, but I want give it some testing in 2.5.x first ...
>
The reason I am suggesting it is because, IMO, a little change to existing
v4l has a much bigger chance of making it in current kernel now. I am very
reluctant to port the driver to v4l2 because:
* it is not in current kernel. instead of telling people: download
kernel 2.4.x, download km-XXX.tar.gz, compile and install them. We'll be
requiring to install v4l2. This would be a major source of errors and
mistakes. People would be installing in wrong places. People will be
forgetting to install headers. Something else will come up.
* as someone pointed out if v4l2 was fully ready it would have been in
2.4.x now. I am not saying it is bad, I am saying that it is likely it
will change. Which means that driver developers will have to keep up with
changes in v4l2 (and users too) - I would really like to avoid that.
Now, these concerns might sound strange to you, but, unfortunately, I
have lots of experience with them. Our XFree86 driver is depending upon
XFree86 with it's many subparts. I got a ton of bug reports from people
because they had a slightly different version of dri of libXv.a or forgot
to install patches before our changes made it into the tree.
> > Specifically, I was thinking of adding an extra offset field to
> > mmap ioctls
>
> Adding more fields to structs breaks binary compatibility, this is no
> option.
>
How about an extra ioctl ? All we'll have to change in the kernel is
provide an extra struct and extra #define. This will not change any
existing code, but will enable new drivers to provide extra functionality.
Vladimir Dergachev
> Gerd
>
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