Re: [Xen-devel] [PATCH v5 p2 16/19] tools/libxl: arm: Use an higher value for the GIC phandle

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Julien Grall writes ("Re: [Xen-devel] [PATCH v5 p2 16/19] tools/libxl: arm: Use 
an higher value for the GIC phandle"):
> On 09/04/15 17:17, Ian Jackson wrote:
> > I have to say I have no idea what a phandle is...
> 
> A phandle is a way to reference another node in the device tree.
> Any node that can referenced defines a phandle property with a unique
> unsigned 32 bit value.

Thanks for the explanation.

> >> Reserve the ID 65000 for the GIC phandle. I think we can safely assume
> >> that the partial device tree will never contain a such ID.
> > 
> > Do we control the DT compiler ?  What if it should change its
> > phandle allocation algorithm ?
> 
> We don't control the DT compiler. But the algorithm of the phandle will
> unlikely change. FWIW, the compiler is very tiny, it's not GCC.

Right.

> I only expect people using the partial device tree in very specific use
> case. Generic use case is not even possible with the current status of
> non-PCI (i.e device tree) passthrough. So people control their environment.
> 
> As I said later in patch, supporting dynamic allocation will require
> some rework in the device tree creation for the guest.
> 
> So I was suggesting this solution as temporary in order to not block the
> DT passthrough.

What would happen if our assumption about the DT compiler were
violated ?

Ian.

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