Re: [PATCH v1] x86/mm, asm-generic: Add IOMMU ioremap_uc() variant default

[Bjorn Helgaas]

On Thu, Jul 9, 2015 at 7:28 PM, Luis R. Rodriguez
<mcgrof@xxxxxxxxxxxxxxxx> wrote:

> +/**
> + * DOC: ioremap() and ioremap_*() variants
> + *
> + * If you have an IOMMU your architecture is expected to have both ioremap()
> + * and iounmap() implemented otherwise the asm-generic helpers will provide a
> + * direct mapping.
> + *
> + * There are ioremap_*() call variants, if you have no IOMMU we naturally will
> + * default to direct mapping for all of them, you can override these defaults.
> + * If you have an IOMMU you are highly encouraged to provide your own
> + * ioremap variant implementation as there currently is no safe architecture
> + * agnostic default. To avoid possible improper behaviour default asm-generic
> + * ioremap_*() variants all return NULL when an IOMMU is available. If you've
> + * defined your own ioremap_*() variant you must then declare your own
> + * ioremap_*() variant as defined to itself to avoid the default NULL return.

Are the references above to "IOMMU" typos?  Should they say "MMU"
instead, so they match the #ifdef below?

> + */
> +
> +#ifdef CONFIG_MMU
> +
> +#ifndef ioremap_uc
> +#define ioremap_uc ioremap_uc
> +static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
> +{
> +       return NULL;
> +}
> +#endif
> +
> +#else /* !CONFIG_MMU */
> +
>  /*
>   * Change "struct page" to physical address.
>   *
> @@ -743,7 +772,6 @@ static inline void *phys_to_virt(unsigned long address)
>   * you'll need to provide your own definitions.
>   */
>
> -#ifndef CONFIG_MMU
>  #ifndef ioremap
>  #define ioremap ioremap
>  static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
> --
> 2.3.2.209.gd67f9d5.dirty
>
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