Re: [Qemu-devel] KVM call minutes for Feb 8

[Anthony Liguori]

On 02/14/2011 03:25 PM, Blue Swirl wrote:
> I'd still like to have the inline wrapper over the factory interface,
> probably with similar signature to isa_serial_new. Then there would be
> two functions, one going through qdev and the other bypassing it. I
> don't see how that would be useful.
>
> The callers of the direct interface would force linkage between them
> and so it would be impossible to build QEMU with that device. We don't
> need that flexibility for every device though, but I don't see any
> advantages for using the direct interface either.
>
> Why shouldn't we want all devices to be exposed to the user? For
> example, there are still devices which don't show up in 'info qtree',
> which is a shame.
>    

Showing up in info qtree is goodness, but I'm talking about allowing a 
user to directly instantiate a device.

Any device we expose to the user through -device needs to maintain a 
compatible interface forever.  For our own sanity, I think we should try 
to expose as little as possible.

A good example of a device that we should model through qdev but not 
expose via -device is actually SerialState.

Today, we have ISASerialState which embeds SerialState.  We can also 
create a MMIO version of SerialState although there's no direct 
structure that wraps that.

Ideally, SerialState would be a proper qdev device that is embedded in 
both ISASerialState and MMIOSerialState (or pick a better name).  info 
qtree should show a has-a relationship for these devices.

Regards,

Anthony Liguori