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

[Markus Armbruster <armbru@redhat.com>]

Anthony Liguori <aliguori@us.ibm.com> writes:

> Markus Armbruster <armbru@redhat.com> writes:
>
>> Peter Maydell <peter.maydell@linaro.org> writes:
>>>>>                          [and I don't think "this device
>>>>> can be added via the monitor but not the command line"
>>>>> counts as consistent or coherent...]
>>>>
>>>> no_user applies equally to -device and device_add.
>>>
>>> In the codebase as it stands, it applies only to -device.
>>> I agree that we should be consistent here, which we could do
>>> by applying Christian's patch or some variation to make device_add
>>> honour no_user. (Or by removing no_user altogether :-))
>>
>> Actually, it appears to apply only to help now!
>>
>> git-bisect blames this one:
>
> Let's step back and try to figure out the problem we're trying to solve.
>
> What is -devices help trying to show?  Devices that are valid to for a
> user to pass?  Hint: on a PC, the only thing that's valid to add are
> devices that implement a certain bus type.  In fact, it depends on the
> bus model.
>
> So if you want to make -device help prettier, we should add a filter
> that looks at the busses available and filters anything that isn't an
> instance of the appropriate bus types.

Necessary, but not sufficient; see the two examples I posted upstream.
Both devices would pass a "appropriate bus is available" filter.  Both
devices cannot possibly work.  One of them starts up fine (mayhem at
guest runtime expected), the other makes qemu crash & burn immediately.