Re: [Xen-devel] [PATCH v7b 8/8] xen/arm: add dom0-less device assignment info to docs

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 2 Oct 2019, Julien Grall wrote:
> Hi Stefano,
> 
> On 10/1/19 12:30 AM, Stefano Stabellini wrote:
> > +- xen,reg
> > +
> > +  The xen,reg property is an array of:
> > +
> > +    <phys_addr size guest_addr>
> > +
> > +  They specify the physical address and size of the device memory
> > +  ranges together with the corresponding guest address to map them to.
> > +  The size of `phys_addr' and `guest_addr' is determined by
> > +  #address-cells, the size of `size' is determined by #size-cells, of
> > +  the partial device tree.
> > +  The memory will be mapped as device memory in the guest (Device-nGnRE).
> > +
> > +- xen,path
> > +
> > +  A string property representing the path in the host device tree to the
> > +  corresponding device node.
> > +
> > +- xen,force-assign-without-iommu
> > +  If present, xen,path is optional (otherwise it is always required).
> 
> I am ok with the implementation to allow xen,path to be optional. But I think:
> 
>   1) This is a good habit to have xen,path present in the DT because it acts
> as documentation (the user directly know the associated node in the host DT).
> 
>   2) It is easier to relax a binding in the future over tightening again.
> 
>   3) This avoids the multiple behavior depending on the properties present.
> 
> So I would much prefer if the document is more strict than the actual
> implementation.

I am OK with that. I'll remove that sentence "If present, xen,path is
optional (otherwise it is always required)." and adjust the following
sentence:

- xen,force-assign-without-iommu
  If xen,force-assign-without-iommu is present Xen continues booting
  even on IOMMU setup errors for the device (i.e. the device is not
  protected by an IOMMU).


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