9.5. Quick Reference This chapter introduced the following symbols related to hardware management:- #include <linux/kernel.h>
- void barrier(void)
This "software"
memory barrier requests the
compiler to consider all memory volatile across this instruction.
- #include <asm/system.h>
- void rmb(void);
- void read_barrier_depends(void);
- void wmb(void);
- void mb(void);
Hardware memory barriers. They request the CPU (and the compiler) to checkpoint all memory reads, writes, or both across this instruction.
- #include <asm/io.h>
- unsigned inb(unsigned port);
- void outb(unsigned char byte, unsigned port);
- unsigned inw(unsigned port);
- void outw(unsigned short word, unsigned port);
- unsigned inl(unsigned port);
- void outl(unsigned doubleword, unsigned port);
Functions that are used to read and write I/O ports. They can also be called by user-space programs, provided they have the right privileges
to access ports.
- unsigned inb_p(unsigned port);
- ...
If a small delay is needed after an I/O operation, you can use the six pausing counterparts of the functions introduced in the previous entry; these pausing functions have names ending in _p.
- void insb(unsigned port, void *addr, unsigned long count);
- void outsb(unsigned port, void *addr, unsigned long count);
- void insw(unsigned port, void *addr, unsigned long count);
- void outsw(unsigned port, void *addr, unsigned long count);
- void insl(unsigned port, void *addr, unsigned long count);
- void outsl(unsigned port, void *addr, unsigned long count);
The "string functions" are
optimized to transfer data from an input port to a region of memory, or the other way around. Such transfers
are performed by reading or writing the same port count times.
- #include <linux/ioport.h>
- struct resource *request_region(unsigned long start, unsigned long len, char
- *name);
- void release_region(unsigned long start, unsigned long len);
- int check_region(unsigned long start, unsigned long len);
Resource allocators for I/O ports. The (deprecated) check function returns 0 for success and less than 0 in case of error.
- struct resource *request_mem_region(unsigned long start, unsigned long len,
- char *name);
- void release_mem_region(unsigned long start, unsigned long len);
- int check_mem_region(unsigned long start, unsigned long len);
Functions that handle resource allocation for memory regions.
- #include <asm/io.h>
- void *ioremap(unsigned long phys_addr, unsigned long size);
- void *ioremap_nocache(unsigned long phys_addr, unsigned long size);
- void iounmap(void *virt_addr);
ioremap
remaps a physical address range into the processor's virtual address space, making it available to the kernel. iounmap frees the mapping when it is no longer needed.
- #include <asm/io.h>
- unsigned int ioread8(void *addr);
- unsigned int ioread16(void *addr);
- unsigned int ioread32(void *addr);
- void iowrite8(u8 value, void *addr);
- void iowrite16(u16 value, void *addr);
- void iowrite32(u32 value, void *addr);
Accessor functions that are used to work with I/O memory.
- void ioread8_rep(void *addr, void *buf, unsigned long count);
- void ioread16_rep(void *addr, void *buf, unsigned long count);
- void ioread32_rep(void *addr, void *buf, unsigned long count);
- void iowrite8_rep(void *addr, const void *buf, unsigned long count);
- void iowrite16_rep(void *addr, const void *buf, unsigned long count);
- void iowrite32_rep(void *addr, const void *buf, unsigned long count);
"Repeating" versions of the I/O memory primitives.
- unsigned readb(address);
- unsigned readw(address);
- unsigned readl(address);
- void writeb(unsigned value, address);
- void writew(unsigned value, address);
- void writel(unsigned value, address);
- memset_io(address, value, count);
- memcpy_fromio(dest, source, nbytes);
- memcpy_toio(dest, source, nbytes);
Older, type-unsafe functions for accessing I/O memory.
- void *ioport_map(unsigned long port, unsigned int count);
- void ioport_unmap(void *addr);
A driver author that wants to treat I/O ports as if they were I/O memory may pass those ports to ioport_map. The mapping should be done (with ioport_unmap) when no longer needed.
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