On Fri, 24 Mar 2017 16:23:18 -0300 Eduardo Habkost <ehabk...@redhat.com> wrote:
> On Fri, Mar 24, 2017 at 05:08:56PM +0000, Peter Maydell wrote: > > On 24 March 2017 at 16:58, Markus Armbruster <arm...@redhat.com> wrote: > > > "Sysbus" isn't a bus. In qdev's original design, every device had to > > > plug into a bus, period. The ones that really didn't were made to plug > > > into "sysbus". > > > > > > Pretty much the only thing "sysbus" devices had in common was that they > > > couldn't be used with device_add and device_del. > > > > This isn't really true. Sysbus devices support having MMIO regions > > and IRQ lines and GPIO lines. If you need those you're a > > sysbus device; otherwise you can probably just be a plain old Device. > > > > > We fixed the design to permit bus-less devices, but we didn't get rid of > > > "sysbus". > > > > Call it what you want, but we should have some common code support > > for "I want to have MMIOs and IRQs and GPIO lines". You could > > argue for moving all that into Device I suppose. > > Even if we don't move all that into Device, this sounds like an > argument for the existence of struct SysBusDevice. But I still > don't understand the reason TYPE_SYSTEM_BUS still exists. ISTR some surprises that reset (or some other) callbacks were not called as expected if there wasn't a sysbus device among the ancestors. Don't know if that's still true.
