NeusoftInstituteofInformation嵌入式系統(tǒng)工程系--嵌入式Linux設(shè)備驅(qū)動(dòng)開(kāi)發(fā)目錄一ARM體系結(jié)構(gòu)三Linux板級(jí)LED驅(qū)動(dòng)程序二GPIO訪問(wèn)作品簡(jiǎn)介L(zhǎng)inux內(nèi)核訪問(wèn)外設(shè)I/O資源的方式一、動(dòng)態(tài)映射(ioremap)方式對(duì)I/O內(nèi)存的操作需按如下步驟完成:

1.申請(qǐng)structresource*request_mem_region(unsignedlongstart,unsignedlonglen,char*name)

2.映射void*ioremap(unsignedlongphys_addr,unsignedlongsize)

3.訪問(wèn)unsignedioread8(void*addr)voidiowrite8(u8value,void*addr)

4.釋放voidiounmap(void*addr)Linux內(nèi)核訪問(wèn)外設(shè)I/O資源的方式一、動(dòng)態(tài)映射(ioremap)方式定義#defineS3C2410_PA_IIS (0x55000000)映射our_card->regs=ioremap(S3C2410_PA_IIS,0x100);

訪問(wèn)readl(our_card->regs)writel(value,our_card->regs)Linux內(nèi)核訪問(wèn)外設(shè)I/O資源的方式二、靜態(tài)映射(map_desc)方式

通過(guò)map_desc結(jié)構(gòu)體靜態(tài)創(chuàng)建I/O資源映射表

內(nèi)核或驅(qū)動(dòng)中訪問(wèn)該I/O資源時(shí)則無(wú)需再進(jìn)行ioreamp動(dòng)態(tài)映射，可以直接通過(guò)映射后的I/O虛擬地址去訪問(wèn)./*include/asm-arm/mach/map.h*/

structmap_desc{

unsignedlongvirtual;

/*映射后的虛擬地址*/

unsignedlongpfn;

/*I/O資源物理地址所在的頁(yè)幀號(hào)*/

unsignedlonglength;

/*I/O資源長(zhǎng)度*/

unsignedinttype;

/*I/O資源類(lèi)型*/

};二、靜態(tài)映射(map_desc)方式staticstructmap_descs3c2410_iodesc[]__initdata={

{

.virtual

=

(unsignedlong)S3C24XX_VA_LCD),

.pfn

=

__phys_to_pfn(S3C24XX_PA_LCD),

.length

=

S3C24XX_SZ_LCD,

.type

=

MT_DEVICE

},

……

};Map_io成員函數(shù)會(huì)在系統(tǒng)初始化過(guò)程中被調(diào)用,流程如下：Start_kernel->setup_arch()-->paging_init()-->devicemaps_init()中被調(diào)用.

自動(dòng)創(chuàng)建設(shè)備文件

創(chuàng)建設(shè)備文件的方法:

1.mknod手工創(chuàng)建

2.?自動(dòng)創(chuàng)建（2.4內(nèi)核）devfs_register(devfs_handle_tdir,constchar *name,unsignedintflags,unsignedint major,unsignedintminor,umode_tmode,void*ops, void*info)在指定的目錄中創(chuàng)建設(shè)備文件。dir:目錄名，為空表示在/dev/目錄下創(chuàng)建；name:文件名；flags:創(chuàng)建標(biāo)志；major：主設(shè)備號(hào)；minor:次設(shè)備號(hào)；mode:創(chuàng)建模式；ops:操作函數(shù)集;info:通常為空

自動(dòng)創(chuàng)建（2.6內(nèi)核）從Linux2.6.13開(kāi)始，devfs不復(fù)存在，udev成為devfs的替代。相比devfs，udev（mdev）存在于應(yīng)用層。利用udev(mdev)來(lái)實(shí)現(xiàn)設(shè)備文件的自動(dòng)創(chuàng)建很簡(jiǎn)單，在驅(qū)動(dòng)初始化的代碼里調(diào)用class_create為該設(shè)備創(chuàng)建一個(gè)class，再為每個(gè)設(shè)備調(diào)用device_create創(chuàng)建對(duì)應(yīng)的設(shè)備。自動(dòng)創(chuàng)建（2.6內(nèi)核）例：structclass*myclass=class_create(THIS_MODULE, “my_device_driver”);class_device_create(myclass,NULL,MKDEV(major_num,0),NULL, “my_device”);當(dāng)驅(qū)動(dòng)被加載時(shí)，udev(mdev)就會(huì)自動(dòng)在/dev下創(chuàng)建my_device設(shè)備文件。staticstructclass*led_class;if(LED_MAJOR){ dev=MKDEV(LED_MAJOR,LED_MINOR); result=register_chrdev_region(dev,scull_nr_devs,"DEVICE_NAME

"); }else{ result=alloc_chrdev_region(&dev,LED_MINOR,scull_nr_devs,"DEVICE_NAME

"); LED_MAJOR=MAJOR(dev); }//注冊(cè)一個(gè)類(lèi)，使mdev可以在"/dev/"目錄下面建立設(shè)備節(jié)點(diǎn)

led_class=class_create(THIS_MODULE,DEVICE_NAME); if(IS_ERR(led_class)) { printk("Err:failedinNeusoft-ledsclass.\n"); return-1; } //創(chuàng)建一個(gè)設(shè)備節(jié)點(diǎn)，節(jié)點(diǎn)名為DEVICE_NAME

class_device_create(led_class,NULL,MKDEV(LED_MAJOR,