On Tuesday 25 June 2013, Leif Lindholm wrote: > x86 and ia64 have the early_ioremap()/early_iounmap() functions, which are > useful for supporting things like UEFI, ACPI and SMBIOS, where configuration > tables need to be parsed before proper memory management is available, > regardless of highmem status. > > This patchset implements a restricted form of early_ioremap(), available > before paging_init() only. Like the x86 code on which it is based, it > (p)re-uses the fixmap regions for its virtual mapping range. Up to 7 > simultaneous mappings of up to 128KB can be accommodated in the available > fixmap space. +rmk I made a similar suggestion to extending the use of fixmap recently, see "Re: SCU registers mapping for CA9/CA5 cores". Russell pointed out that fixmap is intentionally limited to just kmap_atomic uses at the moment and changing that would potentially have a significant impact when we run out of pages in the fixmap area. The method we use on ARM normally is the iotable_init() function, which requires hardcoding a virtual address at the moment. It might be nicer to change that code than to put early_ioremap into fixmap. Note that early_ioremap in fixmap is a bit of a kludge on x86 as well because it is very much /not/ a fixed mapping like the rest of fixmap, they just use it because it's convenient. Extending the iotable mechanism on ARM would be the convenient solution for us I think. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
