Re: [PATCH] virtio_console: Add support for multiple ports for generic guest and host communication

[Rusty Russell <rusty@rustcorp.com.au>]

On Sat, 12 Sep 2009 01:30:10 am Alan Cox wrote:
> > The interface presented to guest userspace is of a simple char
> > device, so it can be used like this:
> > 
> >     fd = open("/dev/vcon2", O_RDWR);
> >     ret = read(fd, buf, 100);
> >     ret = write(fd, string, strlen(string));
> > 
> > Each port is to be assigned a unique function, for example, the
> > first 4 ports may be reserved for libvirt usage, the next 4 for
> > generic streaming data and so on. This port-function mapping
> > isn't finalised yet.
> 
> Unless I am missing something this looks completely bonkers
> 
> Every time we have a table of numbers for functionality it ends in
> tears. We have to keep tables up to date and managed, we have to
> administer the magical number to name space.

The number comes from the ABI; we need some identifier for the different
ports.  Amit started using names, and I said "just use numbers"; they have
to be documented and agreed by all clients anyway.

ie. the host says "here's a port id 7", which might be the cut & paste
port or whatever.

Cheers,
Rusty.