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

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Message-Id: <06E9E2D3-4627-4970-ABBB-34B5ED620709@konsulko.com>
Date:	Thu, 14 Apr 2016 13:02:56 +0300
From:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	rank Rowand <frowand.list@...il.com>,
	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

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.

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

Regards

— Pantelis