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

[Julien Grall <julien.grall@linaro.org>]

On 09/09/2013 01:39 PM, Ian Campbell wrote:
> On Mon, 2013-09-09 at 13:26 +0100, Julien Grall wrote:
>> On 09/09/2013 12:33 PM, Ian Campbell wrote:
>>> On Wed, 2013-08-28 at 15:47 +0100, Julien Grall wrote:
>>>>        if ( early_info.modules.nr_mods >= MOD_KERNEL &&
>>>>             early_info.modules.module[MOD_KERNEL].cmdline[0] )
>>>>            bootargs = &early_info.modules.module[MOD_KERNEL].cmdline[0];
>>>>
>>>> -    for ( prop = fdt_first_property_offset(fdt, node);
>>>> -          prop >= 0;
>>>> -          prop = fdt_next_property_offset(fdt, prop) )
>>>> +    for_each_property_of_node (np, pp)
>>>
>>> Is "of" here as in "the property of the node" or is it a stray Open
>>> Firmware from the Linux naming of these functions?
>>>
>>> Perhaps a dt_ prefix to match all the others?
>>
>> Right. I will send a patch to rename for_each_property_of_node to
>> dt_for_each_property_of_node.
>
> Might dt_for_each_node_property fit better with the other functions?

Sounds good.

>>>
>>> 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.

> The alternative would be an explicit check for versions we know we
> understand.

-- 
Julien Grall