Re: [Qemu-devel] [PATCH] sysbus: add no_user for devices using mmio or IRQ or GPIO

[Peter Maydell]

On 5 March 2013 04:16, Paolo Bonzini <address@hidden> wrote:
> Il 04/03/2013 18:58, Peter Maydell ha scritto:
>>> > Mass-mark these devices as no_user.
>> "There is no such thing as a 'no-user' device" -- Anthony
>> (http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg00896.html)
>>
>> We should figure out what we might be trying to use 'no-user'
>> for, and consistently use it that way. Or alternatively we
>> should remove it (perhaps replacing it with other flags).
>> Mass-marking all the sysbus devices when we don't have a
>> consistent sane defined semantics for the flag seems like
>> a bad idea.
>
> $ x86_64-softmmu/qemu-system-x86_64 -device xlnx,,ps7-usb
> (qemu) info qtree
> bus: main-system-bus
>   type System
>   dev: xlnx,ps7-usb, id ""
>     maxframes = 128
>     irq 1
>     mmio ffffffffffffffff/0000000000001000
>     bus: usb-bus.0
>       type usb-bus
>
> I have no idea what this means, but I'm pretty sure that no matter how I
> configure it, it will never work.

I agree. Exhibiting something that's a suboptimal user
experience doesn't count as defining consistent semantics
for no_user, though :-)  [and I don't think "this device
can be added via the monitor but not the command line"
counts as consistent or coherent...]

> Yes, the right thing to do would be to QOMify memory regions and
> introduce pins, but that's a bit more than the amount of time I have now
> for this.

...plus it means that when we do have these things we
have to go round and identify the cases where no_user
was set only because we didn't have the features before.

My attitude here really is "yes, it's not great but it's
been like this forever and we don't seem to have had a
huge flood of user complaints, so better not to mess
with it unless what you're doing is going to amount to
some kind of cleanup".

-- PMM