[Qemu-devel] Re: Immutable qdev properties

[Markus Armbruster]

Gerd Hoffmann <address@hidden> writes:

> On 08/24/09 11:05, Markus Armbruster wrote:
>
>> iobase[] will start as whatever the user specifies in -device,
>> defaulting to { -1, -1 }, then revert to { 0x441, 0x443 } when the
>> device is initialized.  Not sure whether this is a problem.
>
> The ioport properties should reflect the values actually used, even in
> case they can not be configured.  So in case a ISA device finds '-1'
> aka 'not specified by the user', it should fill in (and use) the
> default value.  See also below ...

Works for me.

>> Taking a step back, the general problem is "immutable" qdev properties,
>> i.e. properties that aren't configurable.  I think it would be good to
>> agree on a common method there, and document it.
>
> On a even broader view: how to handle invalid property values?

Good point.

> Having a device support one fixed I/O port is just a special case of
> that.  Other ISA devices usually can be configured to a few possible
> I/O bases using dip switches (sound cards for example).  But the
> possible values are usually fairly limited.
>
> In case the user specifies a impossible iobase we can
>
>   (1) ignore it and use defaults instead.
>   (2) fix it (pick nearest possible value or so).
>   (3) fail.
>
> #3 is probably the most sane,

Agree.

>                               but that depends on the
> init()-callback-can-fail patches ...

Yes.