linux-kernel - Re: [Kernel] [PATCH 1/5] input: twl6040-vibra: fix DT node memory management

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Message-Id: <3F1CB46B-87AA-4B65-9D2E-56927F2EB9E8@goldelico.com>
Date:	Sun, 8 May 2016 08:49:27 +0200
From:	"H. Nikolaus Schaller" <hns@...delico.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Fabio Estevam <fabio.estevam@...escale.com>,
	linux-input@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Discussions about the Letux Kernel 
	<letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [Kernel] [PATCH 1/5] input: twl6040-vibra: fix DT node memory management

Hi Dmitry,

> Am 20.04.2016 um 11:03 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
> 
>> Am 19.04.2016 um 19:06 schrieb Dmitry Torokhov <dmitry.torokhov@...il.com>:
>> 
>> On Tue, Apr 19, 2016 at 09:43:08AM +0200, H. Nikolaus Schaller wrote:
>>> 
>>>> Am 18.04.2016 um 23:22 schrieb Dmitry Torokhov <dmitry.torokhov@...il.com>:
>>>> 
>>>> On Mon, Apr 18, 2016 at 09:55:37PM +0200, H. Nikolaus Schaller wrote:
>>>>> commit e7ec014a47e4 ("Input: twl6040-vibra - update for device tree support")
>>>>> 
>>>>> made the separate vibra DT node to a subnode of the twl6040.
>>>>> 
>>>>> It now calls of_find_node_by_name() to locate the "vibra" subnode.
>>>>> This function has a side effect to call of_node_put on() for the twl6040
>>>>> parent node passed in as a parameter. This causes trouble later on.
>>>>> 
>>>>> Solution: we must call of_node_get() before of_find_node_by_name()
>>>> 
>>>> God, what messed up API.
>>> 
>>> Yes, indeed. It is opposite to the usual object ownership rule that the code
>>> fragment that asks for a handle has to release it.
>>> 
>>> Usually it does not become obvious because often CONFIG_OF_DYNAMIC=n.
>>> This disables all of_node refcounting completely so such bugs remain unnoticed.
>>> 
>>>> Any chance we can make it a bit more sane and
>>>> not drop the reference inside it instead?
>>> 
>>> Well, if you want to change ~2000 files, test on all platforms and ask Linus
>>> for agreement?
>> 
>> It's not that bad, let's see what DT maintainers say to the patch I
>> posted...
> 
> Thanks! Would make me more happy a well.

Any progress on this?

BR,
Nikolaus