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Date: Wed, 7 Oct 2009 17:12:57 +0530
From: Amit Shah <amit.shah@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 3/6] virtio-console: Add a virtio-console
	bus, support for multiple ports
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: qemu-devel@nongnu.org

On (Wed) Oct 07 2009 [13:33:57], Gerd Hoffmann wrote:
> On 10/07/09 12:06, Amit Shah wrote:
>>> Oh, I thought it would create a new virtio-serial-bus (plus auto-created
>>> port0 console) unconditionally.  Just do enougth to keep existing users
>>> of the switch working.
>>>
>>> If you want new features (i.e. two consoles ports attached to one
>>> virtio-serial-bus device) you must use the new syntax.
>>
>> So it's better overall to drop the old syntax altogether, right? It
>> could get easily confusing otherwise.
>>
>> We can easily end up having:
>>
>> -virtioconsole<chardev>
>> <auto-creates a bus and attaches a console port to it>
>>
>> -device virtio-serial-pci,id=blah
>> <a second bus>
>>
>> -device virtport,bus=blah.0
>>
>> <and no way to connect a device to the bus that got created by
>> virtioconsole>
>
> It isn't that bad.
>
> First, the busses get names based on the bus type by default, i.e. when  
> creating a scsi adapter without specifying id=seomthing the bus is  
> simply named "scsi.0".  Likewise the -virtioconsole created bus would be  
> "port.0" or simliar (depends on the name in BusInfo).
>
> Second, the bus= argument is optional.  If not specified, qdev will pick  
> the first bus of a matching type it finds.  So as long you have a single  
> port/scsi/usb/... bus only you don't need bus= at all.  You can do:

The problem with this is that the management solution needs to know then
what is the default bus name (which could change if the code gets
updated).

And also there's the other problem of a console port spawning a bus
(which could end up spawning another console port at #0...)

So IMO it's better to leave that command line param out.

		Amit