Simplify ioremap() comments to make it clear that arches with an MMU *must* implement ioremap() and iounmap(), and that the default implementations only apply to non-MMU arches. It's obvious how to override the defaults; no need to educate people here. Remove the ancient "struct page" comment that doesn't seem related to anything here. Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> --- include/asm-generic/io.h | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h index e0a331a22346..3f8a7e589071 100644 --- a/include/asm-generic/io.h +++ b/include/asm-generic/io.h @@ -780,8 +780,7 @@ static inline void pci_iounmap(struct pci_dev *dev, void __iomem *p) #endif /* CONFIG_GENERIC_IOMAP */ /* - * Change virtual addresses to physical addresses and vv. - * These are pretty trivial + * Change virtual addresses to physical addresses and vice versa. */ #ifndef virt_to_phys #define virt_to_phys virt_to_phys @@ -802,18 +801,11 @@ static inline void *phys_to_virt(unsigned long address) /** * DOC: ioremap() and ioremap_*() variants * - * If you have an MMU your architecture is expected to have both ioremap() - * and iounmap() implemented otherwise the asm-generic helpers will provide a - * direct mapping. + * If you have an MMU, your architecture must implement both ioremap() and + * iounmap(). * - * There are ioremap_*() call variants, if you have no MMU we naturally will - * default to direct mapping for all of them, you can override these defaults. - * If you have an MMU 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 MMU 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. + * It must also implement variants such as ioremap_uc(). The default + * implementation here returns failure (NULL) to avoid improper behavior. */ #ifdef CONFIG_MMU @@ -829,10 +821,8 @@ static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size) #else /* !CONFIG_MMU */ /* - * Change "struct page" to physical address. - * - * This implementation is for the no-MMU case only... if you have an MMU - * you'll need to provide your own definitions. + * If you don't have an MMU, the default implementations here provide + * direct identity mapping. You can override these if necessary. */ #ifndef ioremap
