Re: [Qemu-devel] [PATCH 1/6] s390x/virtio-ccw: enable has_dynamic_sysbus

[Cornelia Huck]

On Wed, 22 Apr 2015 11:14:40 +0200
Alexander Graf <address@hidden> wrote:

> On 04/22/2015 10:25 AM, Cornelia Huck wrote:
> > On Tue, 21 Apr 2015 21:06:42 +0200
> > Alexander Graf <address@hidden> wrote:
> >
> >> On 04/17/2015 09:52 AM, Cornelia Huck wrote:
> >>> From: Xu Wang <address@hidden>
> >>>
> >>> We have to enable this flag to support dynamically adding devices to the
> >>> sysbus. This change is needed for the the upcoming diag288 watchdog.
> >> s390 doesn't have a "sysbus" per se. Please create a new bus type.
> > So what's wrong with the sysbus? I don't see why we should be different
> > than everyone else.
> 
> The idea behind sysbus is that you have MMIO, PIO and IRQ pins 
> connecting to a PIC. It provides a lot of infrastructure for those 
> interfaces. S390 doesn't use any of them and instead wants registration 
> on "diag" interfaces for example which I'd put on the same layer as PIO 
> or MMIO registration.

I don't think a "diag" bus makes sense. The individual diagnoses are
way too heterogenous beyond the fact that they use the same base
instruction.

So where's the proper place for "misc" devices? My impression was that
they can go on the sysbus.