参照元

説明

引数

返り値

参考

実装

/**
 * ioremap_nocache     -   map bus memory into CPU space
 * @phys_addr:    bus address of the memory
 * @size:      size of the resource to map
 *
 * 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 particular driver authors should read up on PCI writes
 *
 * It's useful if some control registers are in such an area and
 * write combining or read caching is not desirable:
 *
 * Must be freed with iounmap.
 */
void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size)
{
        /*
         * Ideally, this should be:
         *      pat_enabled() ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS;
         *
         * Till we fix all X drivers to use ioremap_wc(), we will use
         * UC MINUS. Drivers that are certain they need or can already
         * be converted over to strong UC can use ioremap_uc().
         */
        enum page_cache_mode pcm = _PAGE_CACHE_MODE_UC_MINUS;
        return __ioremap_caller(phys_addr, size, pcm,
                                __builtin_return_address(0));
}
EXPORT_SYMBOL(ioremap_nocache);

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Last-modified: 2016-02-24 (水) 13:02:55