I/O资源如何映射到内核虚拟空间（转载）

(1) 系统启动初始化时iotable_init()
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MACHINE_START(AT91SAM9261EK, "ATMEL AT91SAM9261")
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        .map_io         = at91sam9261_map_io,
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MACHINE_END
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void __init at91sam9261_map_io(void)
{
iotable_init(at91sam9261_io_desc, ARRAY_SIZE(at91sam9261_io_desc));
}
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/*
* System peripheral registers mapped at virtual address.
*/

static struct map_desc at91sam9261_io_desc[] __initdata = {
{
   .virtual = AT91C_VA_BASE_SYS,
   .pfn = __phys_to_pfn(AT91C_BASE_AIC),
   .length = SZ_4K,
   .type = MT_DEVICE
},
{
   .virtual = AT91C_VA_BASE_EBI,
   .pfn = __phys_to_pfn(AT91C_BASE_EBI),
   .length = SZ_4K,
   .type = MT_DEVICE
},
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};

<./linux/include/asm-arm/map.h>－－－－－－－－－－－－－－－－－－－－－－－
struct map_desc {
unsigned long virtual;
unsigned long pfn;
unsigned long length;
unsigned int type;   //标志位：domain、read、write、cache、buffer
};

#define __phys_to_pfn(paddr)             ((paddr) >> PAGE_SHIFT)
#define __pfn_to_phys(pfn)                 ((pfn) << PAGE_SHIFT)
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   iotable_init()函数<./arch/arm/mm/mm-armv.c>循环调用create_mapping()函数完成IO的虚拟地址到物理地址的映射。

(2) 系统启动后，在驱动中ioremap()
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static struct platform_device *smdk2410_devices[] __initdata = {
&s3c_device_usb,    //片上的各个设备
&s3c_device_lcd,    //下面以s3c_device_lcd为例
&s3c_device_wdt,
&s3c_device_i2c,
&s3c_device_iis,
};
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struct platform_device s3c_device_lcd = {
.name = "s3c2410-lcd", //此处设备的命名应和相应驱动程序命名一致以实现driver bind
.id = -1,                        //-1表示不支持同类多个设备
.num_resources = ARRAY_SIZE(s3c_lcd_resource),
.resource = s3c_lcd_resource,
.dev = {
.dma_mask = &s3c_device_lcd_dmamask,
.coherent_dma_mask = 0xffffffffUL
}
};

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/* LCD Controller */
static struct resource s3c_lcd_resource[] = {   //LCD的两个资源
[0] = {
.start = S3C2410_PA_LCD,
.end = S3C2410_PA_LCD + S3C2410_SZ_LCD,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_LCD,
.end = IRQ_LCD,
.flags = IORESOURCE_IRQ,
}

};
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/* －－－－－－－Resource type －－－－－－－－ */
#define IORESOURCE_IO                0x00000100       
#define IORESOURCE_MEM                0x00000200
#define IORESOURCE_IRQ                0x00000400
#define IORESOURCE_DMA                0x00000800
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－－－－－s3c_device_lcd的resource中硬件地址－－－－－－－－－－－－－－－

#define S3C2410_LCDREG(x) (x)

/* LCD control registers */
#define S3C2410_LCDCON1     S3C2410_LCDREG(0x00)
#define S3C2410_LCDCON2     S3C2410_LCDREG(0x04)
#define S3C2410_LCDCON3     S3C2410_LCDREG(0x08)
#define S3C2410_LCDCON4     S3C2410_LCDREG(0x0C)
#define S3C2410_LCDCON5     S3C2410_LCDREG(0x10)

/* LCD controller */
#define S3C2410_PA_LCD    (0x4D000000)
#define S3C24XX_SZ_LCD    SZ_1M
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/**
* platform_device_register - add a platform-level device
* @pdev: platform device we're adding
*
*/
int platform_device_register(struct platform_device * pdev)
{
device_initialize(&pdev->dev);        //初始化设备结构
return platform_device_add(pdev); //添加一个片上的设备到设备层
}
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/**
* platform_device_add - add a platform device to device hierarchy
* @pdev: platform device we're adding
*
* This is part 2 of platform_device_register(), though may be called
* separately _iff_ pdev was allocated by platform_device_alloc().
*/
int platform_device_add(struct platform_device *pdev)
{
int i, ret = 0;
if (!pdev)
   return -EINVAL;

if (!pdev->dev.parent)
   pdev->dev.parent = &platform_bus;
pdev->dev.bus = &platform_bus_type;

if (pdev->id != -1)
   snprintf(pdev->dev.bus_id, BUS_ID_SIZE, "%s.%u", pdev->name, pdev->id);
                 /* 若支持同类多个设备，则用pdev->name和pdev->id在总线上标识该设备 */
else
   strlcpy(pdev->dev.bus_id, pdev->name, BUS_ID_SIZE);
                /*               否则，用pdev->name(即"s3c2410-lcd")在总线上标识该设备               */

for (i = 0; i < pdev->num_resources; i++) {
                /*           遍历资源数，并为各自在总线地址空间请求分配            */
   struct resource *p, *r = &pdev->resource[i];

   if (r->name == NULL)
    r->name = pdev->dev.bus_id;

   p = r->parent;
   if (!p) {
    if (r->flags & IORESOURCE_MEM)
      p = &iomem_resource;
                                          /*    LCD寄存器地址作为IO内存资源分配   */
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                                                      struct resource iomem_resource = {
                                                              .name   = "PCI mem",
                                                              .start = 0UL,
                                                              .end    = ~0UL,
                                                              .flags = IORESOURCE_MEM,
                                                               };
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    else if (r->flags & IORESOURCE_IO)
      p = &ioport_resource;
   }
                      
   if (p && insert_resource(p, r)) {
                              /*   将LCD寄存器地址插入到IO内存空间 */
    printk(KERN_ERR
          "%s: failed to claim resource %d\n",
          pdev->dev.bus_id, i);
    ret = -EBUSY;
    goto failed;
   }
}

pr_debug("Registering platform device '%s'. Parent at %s\n",
   pdev->dev.bus_id, pdev->dev.parent->bus_id);

ret = device_add(&pdev->dev);
if (ret == 0)
   return ret;

failed:
while (--i >= 0)
   if (pdev->resource[i].flags & (IORESOURCE_MEM|IORESOURCE_IO))
    release_resource(&pdev->resource[i]);
return ret;
}
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static struct platform_driver s3c2410fb_driver = {
.probe   = s3c2410fb_probe,
.remove   = s3c2410fb_remove,
.suspend = s3c2410fb_suspend,
.resume   = s3c2410fb_resume,
.driver   = {
   .name = "s3c2410-lcd",
   .owner = THIS_MODULE,
},
};

platform_driver_register(&s3c2410fb_driver)----->
driver_register(&drv->driver)----->
bus_add_driver(drv)----->
driver_attach(drv)----->
bus_for_each_dev(drv->bus, NULL, drv, __driver_attach)----->
__driver_attach(struct device * dev, void * data)----->
driver_probe_device(drv, dev)----->
really_probe(dev, drv)----->

在really_probe()中：
            为设备指派管理该设备的驱动：dev->driver = drv
            调用s3c2410fb_probe()初始化设备：drv->probe(dev)
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static int __init s3c2410fb_probe(struct platform_device *pdev)
{
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                res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
                /*          取得LCD控制寄存器的物理地址           */

size = (res->end - res->start)+1;
info->mem = request_mem_region(res->start, size, pdev->name);
               /* 个人理解:设备注册时已经分配区域，驱动这里应该不是必须的*/

info->io = ioremap(res->start, size);
               /*      此时驱动便可以用指针info->io 读写LCD控制寄存器了    */
               /*              eg： readl(info->io + S3C2410_LCDCON1)              */
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}

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以下是AT91SAM9261EK的IOMEM：

:~# cat /proc/iomem
00500000-005fffff : usb-ohci.0
00500000-005fffff : ohci_hcd
00600000-00600fff : sidsa-lcdc.0     //支持同类多个设备，在驱动中未分配I/O内存区域
20000000-23ffffff : System RAM
20022000-20225e47 : Kernel text
20226000-2028da23 : Kernel data
30000000-30000003 : dm9000.0   
30000000-30000003 : dm9000   
30000044-300000ff : dm9000.0
30000044-300000ff : dm9000
fffa4000-fffa7fff : at91_udc            //不支持同类多个设备，在驱动中也分配I/O内存区域
fffa4000-fffa7fff : at91_udc
fffb0000-fffb3fff : usart.1
fffb4000-fffb7fff : usart.2
fffc8000-fffcbfff : spi.0
fffff200-fffff3ff : usart.0

http://www.cnitblog.com/vsolo/archive/2008/04/26/42786.aspx