Re: [PATCH 2/3] of: irq: make callers of of_irq_parse_one() release the device node

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On 02/03/2023 08:49, Geert Uytterhoeven wrote:
Hi Jean-Jacques,

Thanks for your patch!

On Wed, Mar 1, 2023 at 7:53 PM Jean-Jacques Hiblot
<jjhiblot@xxxxxxxxxxxxxxx> wrote:
of_irq_parse_one() does a get() on the device node returned in out_irq->np.
Callers of of_irq_parse_one() must do a put() when they are done with it.

What does "be done with it" really mean here?

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>

--- a/arch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c
+++ b/arch/arm/mach-shmobile/regulator-quirk-rcar-gen2.c
@@ -184,6 +184,7 @@ static int __init rcar_gen2_regulator_quirk(void)
                         kfree(quirk);
                         continue;
                 }
+               of_node_put(argsa->np);

The quirk object, which is a container of argsa, is still used below,
and stored in a linked list.  I agree argsa->np is not dereferenced,
but the pointer itself is still compared to other pointers.
Hi Geert,

I fail to see when the pointers are compared. It looks to me that only the args are compared. Am I missing something ?
In any case, looking more closely at the code, I guess that indeed the
of_node_put() shouldn't be added here because this code expects that the
nodes never go away. That is probably a good assertion in case of PMICs

JJ
IIUIC, calling of_node_put() might cause the reference count to drop to
zero, and the underlying struct node object to be deallocated.
So when a future reference to the same DT node will be taken, a new
struct node object will be allocated, and the pointer comparison below
will fail?

Or am I missing something?

Gr{oetje,eeting}s,

                         Geert




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