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

[Jean-Jacques Hiblot]

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