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List:       linux-video
Subject:    V4L2 and kernel 2.3
From:       Bill Dirks < dirks () rendition ! com>
Date:       1999-05-19 3:24:09

Hi, folks.

The 2.3 kernel branch is started, so I want to discuss again merging in
V4L2. Commercial application vendors are beginning V4L2 projects or are
considering it, and they don't want to require a kernel patch with the

The compatibility layer is in there now. I have tested it with a simple
test app I wrote based on the xcaptest program on the V4L2 page. I have
also tested it with xawtv and streamer by "sabotaging" grab-v4l2.c to
fail the V4L2 device open and thereby force it to use the v4l API on the
driver. (And I discovered a bug where I confused RGB and BGR but it's
fixed in the latest videodev on the V4L2 site.) Are there any other
applications anybody would like me to try?

I suppose the next issue is having a Bt848 driver for it. Omega, are you
reading this, can you comment on your Bt848 driver? Or perhaps it would
be better port the current driver shipping with the kernel?

If V4L2 goes into kernel 2.3, I'll continue to maintain the 2.2 patch as
a separate entity.

I had wanted to have a user-mode library for V4L2, but the 'libv4l2' guy
has had some serious writer's block, and has not finished an initial
release. The library does exist, though. A source RPM of the most recent
version I have is on the V4L2 web server. There is no link to it, but
you can reach it at
and get libv4l2-0.18.2-1.src.rpm
I hope Michael does not object to me showing it, but at this point I
think we will need some help to finish it. It actually does quite a bit
already. It wraps all the API calls, so an application using does not
have to make any calls at all to ioctl(), mmap(), etc. It has dozens of
built-in image conversion routines, which was the main impetus for
creating it, so image conversions do not have to be in kernel drivers.
It lacks device enumeration functions, and a way to plug-in external
image conversion modules.
I have a sample capture app that uses libv4l2, but it doesn't happen to
be on the server at the moment.

What else?


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