BSD video capture emulation question

John-Mark Gurney gurney_j at
Fri Jul 11 13:06:12 PDT 2003

Julian Elischer wrote this message on Fri, Jul 11, 2003 at 12:58 -0700:
> I'm hoping htere is a good compatibility with v4l since mot of the apps
> will be written to that spec.
> if not an exact match, at least something that can be 'logically'
> similar and thus portable with a simple shim.

I'm sorry, but that is probably not going to happen.  This is because
the v4l is a kernel interface.  It means that we'd have to write a
kernel module to back call a userland process to emulate it.  Very
bad.  This is another reason I am shoving more of the work outside
the kernel is that it makes it easier to emulate by others, and we could
see different implmentations.

the v4l is a userland to kernel interface, and so it expects to have
fd's to do ioctl's on.  It could be possible to do something wierd
with a pipe, and something that copies the ioctl data between kernel
and userland, but then you'd have a few extra context switches.

So, no, this won't be compatible because of how v4l was designed.

  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."

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