Linux中readl和writel函數(shù)的使用方法

readX/writeX()?are?used?to?access?memory?mapped?devices.?On?some

*?architectures?the?memory?mapped?IO?stuff?needs?to?be?accessed

*?differently.?On?the?simple?architectures,?we?just?read/write?the

*?memory?location?directly.

writel()?往內(nèi)存映射的?I/O?空間上寫(xiě)數(shù)據(jù)，wirtel()??I/O?上寫(xiě)入?32?位數(shù)據(jù)?(4字節(jié))。

原型：

#include??

void?writel?(unsigned?char?data?,?unsigned?short?addr?)

readl()?從內(nèi)存映射的?I/O?空間讀取數(shù)據(jù),readl?從?I/O?讀取?32?位數(shù)據(jù)?(?4?字節(jié)?)。

原型：

#include??

unsigned?char?readl?(unsigned?int?addr?)

變量????addr??是?I/O?地址。

返回值?：?從?I/O?空間讀取的數(shù)值。

定義

#define?readb?__raw_readb

#define?readw(addr)?__le16_to_cpu(__raw_readw(addr))

#define?readl(addr)?__le32_to_cpu(__raw_readl(addr))

#ifndef?__raw_readb

static?inline?u8?__raw_readb(const?volatile?void?__iomem?*addr)

{

return?*(const?volatile?u8?__force?*)?addr;

}

#endif

#ifndef?__raw_readw

static?inline?u16?__raw_readw(const?volatile?void?__iomem?*addr)

{

return?*(const?volatile?u16?__force?*)?addr;

}

#endif

#ifndef?__raw_readl

static?inline?u32?__raw_readl(const?volatile?void?__iomem?*addr)

{

return?*(const?volatile?u32?__force?*)?addr;

}

#endif

#define?writeb?__raw_writeb

#define?writew(b,addr)?__raw_writew(__cpu_to_le16(b),addr)

#define?writel(b,addr)?__raw_writel(__cpu_to_le32(b),addr)

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