Re: [Xen-devel] [PATCH V1 16/29] xen/arm: Build DOM0 FDT by browsing the device tree structure

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 09/10/2013 11:47 AM, Ian Campbell wrote:
> On Tue, 2013-09-10 at 11:39 +0100, Julien Grall wrote:
>> On 09/10/2013 09:58 AM, Ian Campbell wrote:
>>> On Mon, 2013-09-09 at 22:53 +0100, Julien Grall wrote:
>>>
>>>>>>>
>>>>>>> This comment is saying that the name of the name property used to be
>>>>>>> something else? What was it? Which version of FDT was that -- do we need
>>>>>>> to care?
>>>>>>
>>>>>> Right, on older FDT version (< 0x10) each node has 2 different name:
>>>>>>     - the name just after FDT_BEGIN_NODE in the fdt which correspond to
>>>>>> the "filename".
>>>>>>     - the name in property "name" which is a convenient name.
>>>>>>
>>>>>> So we can't use the name field in device tree to retrieve the name to
>>>>>> create the node.
>>>>>>
>>>>>> For the FDT version, I don't know if we need to care. Linux pays
>>>>>> attention to it in the device tree code.
>>>>>
>>>>> I'm not sure we need to care either, I expect we will never see <0x10 in
>>>>> our uses (they are probbaly burnt into the ROMs of PPC machines) but of
>>>>> it is easy enough to so we might as well I guess?
>>>>
>>>> I forgot that there is another issue, the ePAR describes the name has 
>>>> node-name@unit-address. The name field will contains node-name and not 
>>>> the full node name.
>>>>
>>>> Lets say Xen only uses the field name (ie node-name) to create the FDT 
>>>> node name. We Linux will create the procfs for the device tree 
>>>> (/proc/devicetree), it's possible to have numerous warning because there 
>>>> is 2 nodes with the same name.
>>>
>>> Yes, we need to avoid that. Isn't there a full_name field or something?
>>
>> The full_name field contains the full path to this node, for instance
>> /cpus/cpu@0. So we can retrieve the node-name@unit-address with a
>> basename-like function.
> 
> Bit of a shame to have to jump through such hoop, but OK.
> 
> Do we keep the unit-address in the datastructure?

No because the unit-address is optional and is equal to the first
address of the property "reg".

-- 
Julien Grall

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