This patch provides documentation of the early_ioremap() and early_memremap() functionality,including its implementation and usage instructions. Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx> Acked-by: Rob Landley <rob@xxxxxxxxxxx> --- Documentation/arm/00-INDEX | 2 ++ Documentation/arm/early_ioremap.txt | 23 +++++++++++++++++++++++ 2 files changed, 25 insertions(+) create mode 100644 Documentation/arm/early_ioremap.txt diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index 36420e1..4978456 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX @@ -24,6 +24,8 @@ SPEAr - ST SPEAr platform Linux Overview VFP/ - Release notes for Linux Kernel Vector Floating Point support code +early_ioremap.txt + - documentation of the early_ioremap() functionality empeg/ - Ltd's Empeg MP3 Car Audio Player mem_alignment diff --git a/Documentation/arm/early_ioremap.txt b/Documentation/arm/early_ioremap.txt new file mode 100644 index 0000000..e1c0b16 --- /dev/null +++ b/Documentation/arm/early_ioremap.txt @@ -0,0 +1,23 @@ +early_ioremap()/early_memremap() and early_iounmap() provide a mechanism for +temporarily mapping in small blocks of memory, identified by their physical +address, into the fixmap virtual address block before paging_init() has run +and more flexible mapping functions are available. + +Due to its direct method, it also gets around potential need for special +handling of regions that end up in highmem. + +It supports up to 7 simultaneously mapped regions of up to 128KB each. +All mappings created by early_ioremap() are non-shareable device memory. +All mappings created by early_memremap() are uncached normal memory. + +Any residual mappings will be overridden by subsequent kmap() calls (but do +use early_iounmap()). + +Specify 'early_ioremap_debug' on the kernel commandline for verbose output. + +SYNOPSIS + #include <asm/io.h> + + void *early_ioremap(resource_size_t phys_addr, unsigned long size); + void *early_memremap(resource_size_t phys_addr, unsigned long size); + void early_iounmap(void *addr, unsigned long size); -- 1.7.10.4 -- 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
