Re: [PATCH v3] of/base: Fix PowerPC address parsing hack

[Grant Likely <grant.likely@linaro.org>]

On Fri, 14 Nov 2014 17:55:03 +1100
, Benjamin Herrenschmidt <benh@kernel.crashing.org>
 wrote:
> We have a historical hack that treats missing ranges properties as the
> equivalent of an empty one. This is needed for ancient PowerMac "bad"
> device-trees, and shouldn't be enabled for any other PowerPC platform,
> otherwise we get some nasty layout of devices in sysfs or even
> duplication when a set of otherwise identically named devices is
> created multiple times under a different parent node with no ranges
> property.
> 
> This fix is needed for the PowerNV i2c busses to be exposed properly
> and will fix a number of other embedded cases.
> 
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: <stable@vger.kernel.org>

Acked-by: Grant Likely <grant.likely@linaro.org>

Rob will pick up this patch and send it to Linus in his fixups tree for
v3.18

g.

> ---
> 
> V2: Make it less horrendously ugly
> 
> V3: use IS_ENABLED()
> 
>  drivers/of/address.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index e371825..42e416a 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -403,6 +403,21 @@ static struct of_bus *of_match_bus(struct device_node *np)
>  	return NULL;
>  }
>  
> +static int of_empty_ranges_quirk(void)
> +{
> +	if (IS_ENABLED(CONFIG_PPC)) {
> +		/* To save cycles, we cache the result */
> +		static int quirk_state = -1;
> +
> +		if (quirk_state < 0)
> +			quirk_state =
> +				of_machine_is_compatible("Power Macintosh") ||
> +				of_machine_is_compatible("MacRISC");
> +		return quirk_state;
> +	}
> +	return false;
> +}
> +
>  static int of_translate_one(struct device_node *parent, struct of_bus *bus,
>  			    struct of_bus *pbus, __be32 *addr,
>  			    int na, int ns, int pna, const char *rprop)
> @@ -428,12 +443,10 @@ static int of_translate_one(struct device_node *parent, struct of_bus *bus,
>  	 * This code is only enabled on powerpc. --gcl
>  	 */
>  	ranges = of_get_property(parent, rprop, &rlen);
> -#if !defined(CONFIG_PPC)
> -	if (ranges == NULL) {
> +	if (ranges == NULL && !of_empty_ranges_quirk()) {
>  		pr_err("OF: no ranges; cannot translate\n");
>  		return 1;
>  	}
> -#endif /* !defined(CONFIG_PPC) */
>  	if (ranges == NULL || rlen == 0) {
>  		offset = of_read_number(addr, na);
>  		memset(addr, 0, pna * 4);
> 
> 
>