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Date: Thu, 20 Aug 2009 09:44:29 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] Re: virtio-serial: An interface for  host-guest
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To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Amit Shah <amit.shah@redhat.com>, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, qemu-devel@nongnu.org

On 08/20/09 09:31, Rusty Russell wrote:
> On Sat, 15 Aug 2009 01:55:32 am Anthony Liguori wrote:
>> Gerd Hoffmann wrote:
>>> Also I still think passing a 'protocol' string for each port is a good
>>> idea, so you can stick that into a sysfs file for guests use.
>> Or drops ports altogether and just use protocol strings...
>
> Both is silly, yes.
>
> I guess strings + HAL magic can make the /dev names sane.  I don't want to
> see userspace trolling through sysfs to figure out what device to open.

udev can create sane /dev names (or symlinks) by checking sysfs 
attributes, apps just open the /dev/whatever then.

> Which is why I prefer assigned numbers, which get mapped to minors.

ports map trivially to minors.  When using protocol strings minors can 
simply be dynamically auto-allocated by the guest and we don't need the 
port numbers in the host<->guest protocol any more.

I think strings are better as numbers for identifying protocols as you 
can work without a central registry for the numbers then.

cheers,
   Gerd