Linux IO 管理

物理地址空间资源

内核用 struct resource 来管理系统的物理地址空间资源（RAM、controler register 、device register/memory  etc.)。

按映射方式分为 IO port maping 和IO memory maping

struct resource ioport_resource =

{

.name = "PCI IO",

.start = 0,

.end = IO_SPACE_LIMIT,

.flags = IORESOURCE_IO,

};

struct resource iomem_resource =

{

.name = "PCI mem",

.start = 0,

.end = -1,

.flags = IORESOURCE_MEM,

};

/proc # cat ioports

a8000000-a80fffff : PCI io

/proc # cat iomem

00000000-01ffffff : System RAM

   0003f000-001eaf57 : Kernel code

   001eaf58-00233bab : Kernel data

10000000-107fffff : flash

b0000000-b03fffff : PCI non-prefetchable

b0400000-b07fffff : PCI prefetchable

regioi申请

#define request_region(start,n,name) __request_region(&ioport_resource, (start), (n), (name))
#define request_mem_region(start,n,name) __request_region(&iomem_resource, (start), (n), (name))

I/O物理地址到内核虚地址映射

静态映射:

struct map_desc {

unsigned long virtual;

unsigned long pfn;

unsigned long length;

unsigned int type;

 };

paging_init(struct meminfo *mi, struct machine_desc *mdesc)

    +->devicemaps_init(struct machine_desc *mdesc)

        +->create_mapping(struct map_desc *md)

        +->mdesc->map_io()

           +->iotable_init(struct map_desc *io_desc, int nr)

               +->create_mapping(struct map_desc *md)

动态映射: ioremap()

 

struct machine_desc 每个target board 都要定义一个该结构体实例。

struct machine_desc {
 /*
  * Note! The first four elements are used
  * by assembler code in arch/arm/kernel/heard.S

  */
 unsigned int  nr;  /* architecture number */
 unsigned int  phys_io; /* start of physical io */ debug
 unsigned int  io_pg_offst; /* byte offset for io   

/* Map in IO space for serial debugging.

 * This allows debug messages to be output

* via a serial console before paging_init.

* page tabe entry 

*/

 const char  *name;  /* architecture name */
 unsigned long  boot_params; /* tagged list  */

 unsigned int  video_start; /* start of video RAM */
 unsigned int  video_end; /* end of video RAM */

 unsigned int  reserve_lp0 :1; /* never has lp0 */
 unsigned int  reserve_lp1 :1; /* never has lp1 */
 unsigned int  reserve_lp2 :1; /* never has lp2 */
 unsigned int  soft_reboot :1; /* soft reboot  */
 void   (*fixup)(struct machine_desc *,
      struct tag *, char **,
      struct meminfo *);
 void   (*map_io)(void);/* IO mapping function */
 void   (*init_irq)(void);
 struct sys_timer *timer;  /* system tick timer */
 void   (*init_machine)(void);
};