Re: [PATCH v4 5/6] arch: introduce memremap_cache() and memremap_wt()

[Toshi Kani]

On Thu, 2015-06-11 at 17:19 -0400, Dan Williams wrote:
> Existing users of ioremap_cache() are mapping memory that is known in
> advance to not have i/o side effects.  These users are forced to cast
> away the __iomem annotation, or otherwise neglect to fix the sparse
> errors thrown when dereferencing pointers to this memory.  Provide
> memremap_*() as a non __iomem annotated ioremap_*().
> 
> The ARCH_HAS_MEMREMAP kconfig symbol is introduced for archs to assert
> that it is safe to recast / reuse the return value from ioremap as a
> normal pointer to memory.  In other words, archs that mandate specific
> accessors for __iomem are not memremap() capable and drivers that care,
> like pmem, can add a dependency to disable themselves on these archs.
  : 
> +#ifdef CONFIG_ARCH_HAS_MEMREMAP
> +/*
> + * memremap() is "ioremap" for cases where it is known that the resource
> + * being mapped does not have i/o side effects and the __iomem
> + * annotation is not applicable.
> + */
> +static bool memremap_valid(resource_size_t offset, size_t size)
> +{
> +	if (region_is_ram(offset, size) != 0) {

I noticed that region_is_ram() is buggy and always returns -1.  I will
submit the fix shortly.

Thanks,
-Toshi


> +		WARN_ONCE(1, "memremap attempted on ram %pa size: %zu\n",
> +				&offset, size);
> +		return false;
> +	}
> +	return true;
> +}



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