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Re: [Qemu-devel] Re: virtio-serial: An interface for host-guest communic

From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: virtio-serial: An interface for host-guest communication
Date: Mon, 10 Aug 2009 19:16:48 -0500
User-agent: Thunderbird (X11/20090320)

Rusty Russell wrote:
On Mon, 10 Aug 2009 07:17:54 pm Gerd Hoffmann wrote:
On 08/10/09 08:55, Amit Shah wrote:
Bad example.  Quite a lot of modern devices drivers are using dynamic
major/minor numbers because they have proven to be such a pain in the
butt.  That's why we have more sophisticated mechanisms like udev for
userspace to make use of.
Let me explain how we came to this numbering: we first had support for
'naming' ports and the names were obtained by userspace programs by an
ioctl. Rusty suggested to use some numbering scheme where some ports
could exist at predefined locations so that we wouldn't need the naming
and the ioctls around it.
I think the naming is very important.

I disagree.  If you can hand out names, you can hand out numbers.

The problem with handing out names is that there has to be someone to "hand" things out. And even if you have a good hander-outer, development is difficult in a distributed environment because you may have folks using your code before you've gotten an official hand-out.

A better discovery mechanism is based on something that piggy backs on another authority. For instance, reverse fully qualified domains work well. uuid's tend to work pretty well too although it's not perfect.

In general, even just open strings can work out okay given that people are responsible in how they name things.


Anthony Liguori

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