Re: [Xen-devel] [PATCH v3 22/24] tools/libxl: arm: Use an higher value for the GIC phandle

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 29/01/15 12:28, Stefano Stabellini wrote:
> On Thu, 29 Jan 2015, Julien Grall wrote:
>> On 29/01/15 11:07, Stefano Stabellini wrote:
>>> On Tue, 13 Jan 2015, Julien Grall wrote:
>>>> The partial device tree may contains phandle. The Device Tree Compiler
>>>> tends to allocate the phandle from 1.
>>>>
>>>> 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.
>>>>
>>>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
>>>> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>>>> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>>>>
>>>
>>> Shouldn't we at least check that the partial device tree doesn't contain
>>> a conflicting phandle?
>>
>> I don't think so. This will unlikely happen, and if it happens the guest
>> will crash with an obvious error.
> 
> It is good that the error is obvious.
> 
> But how expensive is to check for it?

I would have to check the validity of the properties (name + value
size). At least the properties "linux,phandle" and "phandle" should be
checked.

Though I could do in copy_properties but I find it hackish.

> Think about the poor user that ends up in this situation: the fact that
> is unlikely only makes it harder for a user to figure out what to do to
> fix it.

The poor use will have to write his device tree by hand to hit this
error ;).

So using the right phandle is not a huge drawback.

Regards,

-- 
Julien Grall

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