%I/O
%Thadeu Cascardo

# I/O Ports versus Memory Mapped Devices

* Separate I/O space in x86 architecture
* Other architectures emulate this I/O space access

# Resource allocation

* Different drivers must not conflict when using device resources, like I/O
  ports or memory space
* They must request these resources and release them

# I/O port allocation

* linux/ioport.h
* request\\_region(port, num, name)
* release\\_region(port, num)
* /proc/ioports

# I/O ports access

* asm/io.h
* inb(port)
* outb(data, port)
* inw(port)
* outw(data, port)
* inl(port)
* outl(port)
* String operations
* Pausing I/O
* Platform Issues

# Memory Region Allocation

* request\\_mem\\_region(start, len, name)
* release\\_mem\\_region(start, len)

# Memory Mapping

* ioremap(phys\\_addr, size)
* iounmap(virt\\_addr)

# Memory Access

* ioread8(addr)
* ioread16(addr)
* ioread32(addr)
* iowrite8(val, addr)
* iowrite16(val, addr)
* iowrite32(val, addr)
* memset\\_io(addr, val, cnt)
* memcpy\\_fromio(dst, src, cnt)
* memcpy\\_toio(dst, src, cnt)

# Mapping I/O Ports to Memory

* ioport\\_map(port, cnt)
* ioport\\_unmap(addr)

# Memory Barries

* linux/kernel.h
* barrier()
* asm/system.h
* rmb()
* wmb()
* mb()
* smp\\_rmb
* smp\\_wmb
* smp\\_mb