Re: [Xen-devel] [PATCH v3 15/24] xen/dts: Provide an helper to get a DT node from a path provided by a guest

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 23/02/15 16:27, Ian Campbell wrote:
> On Mon, 2015-02-23 at 16:01 +0000, Julien Grall wrote:
>> Hi Ian,
>>
>> On 23/02/15 15:30, Ian Campbell wrote:
>>> On Tue, 2015-01-13 at 14:25 +0000, Julien Grall wrote:
>>>
>>>> +/* This limit is used by the hypercalls to restrict the size of the path 
>>>> */
>>>> +#define DEVICE_TREE_MAX_PATHLEN 1024
>>>
>>> Is this something you've made up or derived from the DT spec/ePAPR etc?
>>
>> I didn't find a such requirements on the spec.
> 
> I vaguely recall a limit on the length of a single node name, and a
> limit on the depth which they may nest, which can be multiplied. It's
> probably an unhelpfully large number though, so...
> 
>> I chose this number based on the linux pathlen because the path is also
>> used in the sysfs (/sys/firmware/devicetree).
> 
> ...that's a good as anything I suppose!

Hmmm... I'm not so sure about the 1024 limit anymore. Linux is defining
PATH_MAX to 4096 but I don't see many usage in the sysfs code.

And this value may change from one OS to another. Although, 1024 sounds
a very long path to write in the configuration file... Maybe we should
support alias too?

Regards,

-- 
Julien Grall

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