From owner-freebsd-multimedia@FreeBSD.ORG Fri Jul 11 13:06:12 2003 Return-Path: Delivered-To: freebsd-multimedia@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5C0DA37B401 for ; Fri, 11 Jul 2003 13:06:12 -0700 (PDT) Received: from mail.cyberonic.com (mail.cyberonic.com [4.17.179.4]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6706243F75 for ; Fri, 11 Jul 2003 13:06:11 -0700 (PDT) (envelope-from jmg@hydrogen.funkthat.com) Received: from hydrogen.funkthat.com (node-40244c0a.sfo.onnet.us.uu.net [64.36.76.10]) by mail.cyberonic.com (8.12.8/8.12.5) with ESMTP id h6BKVhcU009992; Fri, 11 Jul 2003 16:31:44 -0400 Received: (from jmg@localhost) by hydrogen.funkthat.com (8.12.9/8.11.6) id h6BK5XXE056866; Fri, 11 Jul 2003 13:05:33 -0700 (PDT) (envelope-from jmg) Date: Fri, 11 Jul 2003 13:05:33 -0700 From: John-Mark Gurney To: Julian Elischer Message-ID: <20030711200533.GJ35337@funkthat.com> Mail-Followup-To: Julian Elischer , Sean_Welch@alum.wofford.org, multimedia@freebsd.org References: <752678.1057948500755.JavaMail.nobody@kermit.psp.pas.earthlink.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i X-Operating-System: FreeBSD 4.2-RELEASE i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html cc: Sean_Welch@alum.wofford.org cc: multimedia@freebsd.org Subject: Re: BSD video capture emulation question X-BeenThere: freebsd-multimedia@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: John-Mark Gurney List-Id: Multimedia discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Jul 2003 20:06:12 -0000 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."