Date: Wed, 08 Nov 2000 13:16:00 -0800 From: Julian Elischer <julian@elischer.org> To: Terry Lambert <tlambert@primenet.com> Cc: Mike Smith <msmith@FreeBSD.ORG>, bruno schwander <bschwand@dvart.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: close call in a device ? Message-ID: <3A09C290.DC5F0E3A@elischer.org> References: <200011082035.NAA25463@usr08.primenet.com>
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Terry Lambert wrote:
>
> > If I understand you correctly, you have multiple processes all of which
> > are going to try to open /dev/foo, and you want them to behave as though
> > they have each opened a unique device?
> >
> > You can't do this with FreeBSD, or with many other Unixes.
>
> Any SVR4 system can support this. So can AIX.
>
> > Arguably, this is a defect with the device model. If you are trying to
> > fake up concurrent access to a device, and the client processes are only
> > going to read and write (no ioctls) to this device, then you can use a
> > fifo and a multiplexor process.
> >
> > Alternatively, and this would be recommended; fix the client program.
>
> Or fix the device model. You can't have multiple VMWARE sessions
> in FreeBSD today because of this defect in the device model.
I believe that this is not the reason..
it's another resource that we only have globally.. (i.e. once) but I
forget what it is..
the problem here can be solved by using Poul's 'cloning device'
interface in the driver.
I don't think he has it quite completed but it is partly there.. maybe
enough..
only in -current at the moment and you need to have devfs turned on.
each time you open it, you actually get a different device and vnode..
>
> Terry Lambert
> terry@lambert.org
> ---
> Any opinions in this posting are my own and not those of my present
> or previous employers.
>
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