linux-kernel - Re: [Question] refcount of DT node

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Date:	Thu, 14 Apr 2016 09:10:44 -0700
From:	Frank Rowand <frowand.list@...il.com>
To:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
CC:	Mark Rutland <mark.rutland@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	devicetree@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Question] refcount of DT node

On 4/14/2016 3:02 AM, Pantelis Antoniou wrote:
> Hi Mark,
> 
>> On Apr 14, 2016, at 12:59 , Mark Rutland <mark.rutland@....com> wrote:
>>
>> On Thu, Apr 14, 2016 at 09:48:49AM +0100, Russell King - ARM Linux wrote:
>>> On Thu, Apr 14, 2016 at 04:47:57PM +0900, Masahiro Yamada wrote:
>>>> Hi experts.
>>>>
>>>> My understanding of refcount of DT node is poor.
>>>
>>> The message from DT people is... don't worry about DT node refcounting.
>>> Do whatever you want with it, they don't care whether you have correct
>>> refcounting or not.
>>>
>>> The background behind that is that I've tried to fix the refcounting,
>>> and even had the coccinelle people generate some stuff to work on this
>>> issue, but DT people's attitude towards it is "don't bother".
>>>
>>> So yes, people may get it wrong, but it seems it's something that DT
>>> people want ignored.
>>
>> I'm not sure that's quite fair; the last discussion I recall about this
>> ended up concluding that we need a better API, rather than papering over
>> problems.
>>
>> That said, there isn't much obvious progress on that front.
>>
>> Frank, Pantelis, Rob, were there any conclusions on this from ELC, or is
>> this something that needs someone to propose something?
>>
> 
> Frank mentioned that he wants a new API. I have some ideas about it too.
> 
> My take is that drivers should never do reference counting, we have to figure
> out a way for DT access using copy semantics or locks.
> 
> References would still be required for core DT code, but that’s a sane subset.

Yes.  Nothing concrete about implementation was decided at ELC, but this issue
is on my todo list.

-Frank

> 
>> Mark.
>>
>> [1] http://permalink.gmane.org/gmane.linux.drivers.devicetree/153777
> 
> Regards
> 
> — Pantelis
> 
> .
>