Date: Fri, 11 Jul 2003 13:05:33 -0700 From: John-Mark Gurney <gurney_j@efn.org> To: Julian Elischer <julian@elischer.org> Cc: multimedia@freebsd.org Subject: Re: BSD video capture emulation question Message-ID: <20030711200533.GJ35337@funkthat.com> In-Reply-To: <Pine.BSF.4.21.0307111256590.40558-100000@InterJet.elischer.org> References: <752678.1057948500755.JavaMail.nobody@kermit.psp.pas.earthlink.net> <Pine.BSF.4.21.0307111256590.40558-100000@InterJet.elischer.org>
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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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