Re: [Qemu-devel] [PATCH 3/6] virtio-console: Add a virtio-console bus, support for multiple ports

[Amit Shah]

On (Thu) Oct 01 2009 [14:15:53], Gerd Hoffmann wrote:
>   Hi,
>
>> So we will have to spawn a console port at id 0 when the bus is
>> initialised.
>>
>> There are a couple of problems though:
>> - How to identify which chardev to associate the port#0 with?
>
> I'd suggest to give the serial-bus a chardev attribute, which is then  
> simply passed through, i.e.
>
>   -device virtio-serial-bus,chardev=<name>
>
> automatically creates a virtioconsole with port=0 and chardev=<name> on  
> the newly created bus.

Hm, this looks weird. Because on one hand we're talking about decoupling
the char driver from the core (virtio-serial-bus) and here we're
actually attaching a char driver to the bus.

>> I guess for both these cases, some special command line tweaks will be
>> needed? Or keep the old '-virtioconsole' parameter and put that up as
>> port0?
>
> See above.
>
> Keeping -virtioconsole for backward compatibility is easy, it would  
> basically create a chardev with a virtio<nr> label as it does today,  
> then create virtio-serial-bus with chardev=virtio<nr>.

I prefer to remove the -virtioconsole argument because we won't be able
to specify the bus that's to be attached to.

Also, we can't say if a virtio-serial-bus is also specified. If one
is, we'd want the console to attach to that bus. If one isn't, we'd want
to spawn a new one in that case. But as per above, a virtio-serial-bus
should always spawn a virtio-console port.

I fear we'll end up in a mess of tricky if-else conditions.

And I can't think of a nice solution to the problem above right now.

                Amit