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Date:      Thu, 29 Jun 2006 12:49:10 -0400
From:      Alexander Kabaev <kan@kan.dnsalias.net>
To:        Oleksandr Tymoshenko <gonzo@pbxpress.com>
Cc:        freebsd-hackers@freebsd.org, Christian Zander <czander@nvidia.com>
Subject:   Re: NVIDIA FreeBSD kernel feature requests
Message-ID:  <20060629164910.GA4242@kan.dnsalias.net>
In-Reply-To: <b1fa29170606290932m419e1dc0tf69a447daef5dde9@mail.gmail.com>
References:  <20060629111231.GA692@wolf.nvidia.com> <44A3FD87.8000006@pbxpress.com> <b1fa29170606290932m419e1dc0tf69a447daef5dde9@mail.gmail.com>

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On Thu, Jun 29, 2006 at 09:32:42AM -0700, Kip Macy wrote:
> IIRC lack of per instance cdevs also limits Freebsd to one vmware instanc=
e.
>=20
>            -Kip
>=20
> On 6/29/06, Oleksandr Tymoshenko <gonzo@pbxpress.com> wrote:
> >Christian Zander wrote:
> >> Hi all,
> >>  # Task:        implement mechanism to allow character drivers to
> >>                 maintain per-open instance data (e.g. like the Linux
> >>                 kernel's 'struct file *').
> >>    Motivation:  allows per thread NVIDIA notification delivery; also
> >>                 reduces CPU overhead for notification delivery
> >>                 from the NVIDIA kernel module to the X driver and to
> >>                 OpenGL.
> >>    Priority:    should translate to improved X/OpenGL performance.
> >>    Status:      has not been started.
> >	I've stumbled across this issue a while ago. Actually it can
> >be partially solved using EVENTHANDLER_REGISTER of dev_clone event with
> >keeping state structure in si_drv1 or si_drv2 fields. I'm not sure it's
> >the best solution but it works for me though it smells like hack, and
> >looks like hack :) Anyway, having legitimate per-open instance data
> >structures of cdevs is a great assistance in porting linux drivers to
> >FreeBSD. Just my $0.02.
> >

WHY it smells like a hack? It was designed precisely to do that. I am
using cloned devices in our  product with great success. Every client
opening 'magic' device gets its own exclusive cloned device instance
and everything works like a charm. I am yet to hear any single coherent
description of what Linux's approach has over device cloning in FreeBSD.
I wouldn't mind being educated on this.

--=20
Alexander Kabaev

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