Re: [Xen-devel] [RFC] Add support for Xen ARM guest on FreeBSD

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 01/17/2014 09:29 AM, Ian Campbell wrote:
> On Fri, 2014-01-17 at 00:36 +0000, Julien Grall wrote:
> > On 01/16/2014 01:56 AM, Nathan Whitehorn wrote:
> > > On the subject of simple-bus, they usually aren't necessary. For
> > > example, all hypervisor devices on IBM hardware live under /vdevice,
> > > which is attached to the device tree root. They don't use MMIO, so
> > > simple-bus doesn't really make sense. How does Xen communicate with the
> > > OS in these devices?
> > > -Nathan
> > As I understand, only the simple bus code (see simplebus_attach) is
> > translating the interrupts in the device on a resource.
> > So if you have a node directly attached to the root node with interrupts
> > and MMIO, the driver won't be able to retrieve and translate the
> > interrupts via bus_alloc_resources.
> Is the root node not considered to be a "top-level simple-bus" with a
> 1:1 mapping of MMIO and interrupts? (Linux seems to treat it this way,
> but I haven't trawled the docs for a spec reference to back that
> behaviour up). I take it BSD doesn't do this?
There is 2 different paths on FreeBSD to decode interrupt/MMIO 
(depending if you are under the root node or a simple-bus node). Most of 
the code is duplicated but there are some parts which differs (for 
instance interrupt decoding, see my answer to Nathan).
I will look at closer to the code this week-end and see if I can fix it.

--
Julien Grall

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