ioremap_nocache

Name

ioremap_nocache --  map bus memory into CPU space

Synopsis

void * ioremap_nocache (unsigned long offset, unsigned long size);

Arguments

offset

bus address of the memory

size

size of the resource to map

Description

ioremap_nocache performs a platform specific sequence of operations to make bus memory CPU accessible via the readb/readw/readl/writeb/ writew/writel functions and the other mmio helpers. The returned address is not guaranteed to be usable directly as a virtual address.

This version of ioremap ensures that the memory is marked uncachable on the CPU as well as honouring existing caching rules from things like the PCI bus. Note that there are other caches and buffers on many busses. In paticular driver authors should read up on PCI writes

It's useful if some control registers are in such an area and