對I/O memory region寫值

Q: 假設有一個I/O addr和一個value，請說明將value寫進addr的步驟？

A：用 check_mem_region(mem_addr, mem_size) 函数来检查该内存地址有没有被用到， 可以用的话调用函数 request_mem_region(mem_addr, mem_size, "设备名称") 申请该内存，成功的话， 调用 writeb(values, mem_addr)，或者 writew(values, mem_addr)，writel(values, mem_addr)， 来在 mem_addr 地址 写入 value 值，三个函数分别为写入 8位，16位和32位的值。 最后需要调用 release_mem_region(mem_addr, mem_size) 函数来…

I/O Resource Management

Functions (Detailed Description)

struct resource *	request_region (unsigned long start, unsigned long n, const char *name)
	Allocate I/O port region.
struct resource *	request_mem_region (unsigned long start, unsigned long n, const char *name)
	Allocate I/O memory region.
void	release_region (unsigned long start, unsigned long n)
	Release I/O port region.
void	release_mem_region (unsigned long start, unsigned long n)
	Release I/O memory region.
int	release_resource (struct resource *res)
	Release any resource.
int	check_region (unsigned long start, unsigned long n)
	Check I/O port region availability.
int	check_mem_region (unsigned long start, unsigned long n)
	Check I/O memory region availability.
void *	ioremap (unsigned long phys_addr, unsigned long size)
	Remap I/O memory into kernel address space.
void *	ioremap_nocache (unsigned long phys_addr, unsigned long size)
	Remap I/O memory into kernel address space (no cache).
void	iounmap (void *addr)
	Unmap I/O memory from kernel address space.