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Re: powerpc/mpc5xxx: Use of_get_next_parent to simplify code

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On Sun, 2015-11-10 at 20:27:40 UTC, Christophe Jaillet wrote:
> of_get_next_parent can be used to simplify the while() loop and
> avoid the need of a temp variable.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  arch/powerpc/sysdev/mpc5xxx_clocks.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/mpc5xxx_clocks.c b/arch/powerpc/sysdev/mpc5xxx_clocks.c
> index f4f0301..5732926 100644
> --- a/arch/powerpc/sysdev/mpc5xxx_clocks.c
> +++ b/arch/powerpc/sysdev/mpc5xxx_clocks.c
> @@ -13,7 +13,6 @@
>  
>  unsigned long mpc5xxx_get_bus_frequency(struct device_node *node)
>  {
> -	struct device_node *np;
>  	const unsigned int *p_bus_freq = NULL;
>  
>  	of_node_get(node);
> @@ -22,9 +21,7 @@ unsigned long mpc5xxx_get_bus_frequency(struct device_node *node)
>  		if (p_bus_freq)
>  			break;
>  
> -		np = of_get_parent(node);
> -		of_node_put(node);
> -		node = np;
> +		node = of_get_next_parent(node);
>  	}
>  	of_node_put(node);


This conversion is OK, but the logic in the function is still wrong.

It uses of_get_property() inside the loop, but then drops the reference to the
node before dereferencing the p_bus_freq pointer, which could by then point to
junk if the node has been freed.

Instead it should use of_property_read_u32() to actually read the property
value before dropping the reference.

cheers
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[PATCH] powerpc/mpc5xxx: Use of_get_next_parent to simplify code Christophe JAILLET <christophe.jaillet@wanadoo.fr> - 2015-10-11 22:40 +0200
  Re: [PATCH] powerpc/mpc5xxx: Use of_get_next_parent to simplify  code Julia Lawall <julia.lawall@lip6.fr> - 2015-10-11 22:50 +0200
    Re: [PATCH] powerpc/mpc5xxx: Use of_get_next_parent to simplify code Christophe JAILLET <christophe.jaillet@wanadoo.fr> - 2015-10-12 07:10 +0200
  Re: powerpc/mpc5xxx: Use of_get_next_parent to simplify code Michael Ellerman <mpe@ellerman.id.au> - 2015-10-14 06:10 +0200
    [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially freed memory Christophe JAILLET <christophe.jaillet@wanadoo.fr> - 2015-10-15 08:00 +0200
      Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially  freed memory Michael Ellerman <mpe@ellerman.id.au> - 2015-10-15 08:40 +0200
        Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially freed  memory Christophe JAILLET <christophe.jaillet@wanadoo.fr> - 2015-10-16 08:30 +0200
          Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially  freed memory Gabriel Paubert <paubert@iram.es> - 2015-10-16 09:50 +0200
          Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially  freed memory Michael Ellerman <mpe@ellerman.id.au> - 2015-10-16 11:50 +0200
            Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially freed  memory Christophe JAILLET <christophe.jaillet@wanadoo.fr> - 2015-10-16 22:10 +0200
  Re: powerpc/mpc5xxx: Use of_get_next_parent to simplify code Michael Ellerman <mpe@ellerman.id.au> - 2015-10-15 13:20 +0200

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