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SubjectRe: [PATCH 1/5] input: twl6040-vibra: fix DT node memory management
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> Am 18.04.2016 um 23:22 schrieb Dmitry Torokhov <dmitry.torokhov@gmail.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?

>
>>
>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> drivers/input/misc/twl6040-vibra.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/input/misc/twl6040-vibra.c b/drivers/input/misc/twl6040-vibra.c
>> index ea63fad..7221a00 100644
>> --- a/drivers/input/misc/twl6040-vibra.c
>> +++ b/drivers/input/misc/twl6040-vibra.c
>> @@ -262,6 +262,7 @@ static int twl6040_vibra_probe(struct platform_device *pdev)
>> int vddvibr_uV = 0;
>> int error;
>>
>> + of_node_get(twl6040_core_dev->of_node);
>> twl6040_core_node = of_find_node_by_name(twl6040_core_dev->of_node,
>> "vibra");
>> if (!twl6040_core_node) {
>> --
>> 2.7.3
>>
>
> --
> Dmitry

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