一。linux中访问外设的方法.
1.IO端口(IO port)
linux系统给外设分配不同的端口号，linux利用端口号来访问设备（驱动） (cpu x86)
cpu访问外设通过端号，访问通过地址
gec@ubuntu:/mnt/hgfs/tea/demo2$ cat /proc/ioports
0000-0cf7 : PCI Bus 0000:00
0000-001f : dma1
0020-0021 : pic1
0040-0043 : timer0
0050-0053 : timer1
0060-0060 : keyboard
0064-0064 : keyboard
0070-0071 : rtc0
0080-008f : dma page reg
00a0-00a1 : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : 0000:00:07.1
0170-0177 : ata_piix
2.IO内存 (IO mem) ---> ARM/MPIS
cpu访问外设的方法和访问内存方法都是一样，都是根据地址来方问。
外设(GPIO,ADC,WDT)都内存一样，是统一编址。
二。LINUX中IO内存的使用
思想:申请IO内存区-->动态是映射--->使用虚拟地址--> 解除动态映射击--->释放IO内存区。
1.IO内存的申请
struct resource *request_mem_region(resource_size_t start,resource_size_t n,const char *name)
参数值:
start-->资源的内存区的开始地址(物理地址)
n ----->物理内存区的大小
name --->自定义内存区的名字 cat /proc/iomem
返回值:
struct resource * -->申请到的资源
NULL--->申请失败
2.释放IO内存
void release_mem_region(resource_size_t start,resource_size_t n)
例：
struct resource *ledp=request_mem_region（OxE0200280,8,"gpj2_led"）;
----------------------------------------------------------------------------
3.IO内存的动态映射
void __iomem * ioremap (unsigned long phys_addr, unsigned long size)
参数：
unsigned long phys_addr--》需要映射的物理内存的地址（开始地址）
unsigned long size -->需要映射的物理内存大小
返值:
void __iomem * --->映射后虚拟地址(开始地址)
NULL --->失败
4。IO内存动态映射解除
void iounmap(void *addr)
void *addr--->映射后的虚拟地址
例：
#define OxE0200280 GPJ2CON_PA
unsigned int *GPJ2CON_VA =ioremap(GPJ2CON_PA,8);
unsigned int *GPJ2DAT_VA =GPJ2CON_VA+1；
iounmap(GPJ2CON_VA);
-------------------------------------------------
5.访问虚拟地址的函数(读写)
1.
unsigned int ioread32(void __iomem *addr)
void __iomem *addr--->虚拟地址
unsigned int ---》数据
void iowrite32(u32 b, void __iomem *addr);
例:
unsigned int a=ioread(GPJ2CON_VA);
a &= ;
iowrite32(a,GPJ2CON_VA)
2.
static inline u32 readl(const volatile void __iomem *addr)
static inline void writel(unsigned int b, volatile void __iomem *addr)
3.
static inline u32 __raw_readl(const volatile void __iomem *addr)
static inline void __raw_writel(u32 v, volatile void __iomem *addr)
实例：LED字符设备的驱动模块、
#include <linux/module.h>
#include <linux/kernel.h>
#include<linux/cdev.h>
struct cdev chrdev3;
unsigned int TestMajor=0;
unsigned int TestMinor=0;
#define *** GPJ*CON_PA
#define *** GPJ*DAT_PA
unsigned int *GPJ2CON_VA;
dev_t dev_no;
int testopen(struct inode *inode, struct file *file)
{
//LED输出
printk("led init
");
}
int testclose (struct inode *inode, struct file *file);
{
printk("close");
return 0;
}
ssize_t testwrtie(struct file *, char __user *usr, size_t len, loff_t *off)
{
char buf[12];
copy_from_user(buf,usr,);
buf[12];
//if(buf[]=='1')
// led点明
printk(,buf);
}
ssize_t testread(struct file *, char __user *usr, size_t len, loff_t *);
{
char buf='r';
read_led;
copy_to_user(usr,buf,);
}
struct file_operations fops= --->结构体初始化 .---???????????????
{ .owner=THIS_MODULE,
.open=testopen,
.write=testwrite,
.release=testclose,
}
static int __init test_init(void) //入口函数
{
printk("hello world!
"); //相当于printf()
int ret;
dev_no =MKDEV(TestMajor,TestMinor)
if(dev_no>0)
{
ret=register_chrdev_region(dev_no, 1,"chrdev_test");//静态注册设备号
}
else //动态申请设备号
{
alloc_chrdev_region(&dev_no,TestMinor, 1,"chrdev_test");
}
if(ret<0)
{
return ret;
}
cdev_init(&chrdev3,&fops);
cdev.owner=THIS_MODULE;
cdev_add(&chrdev3,dev_no,1);
request_mem_region（）;
GPJ2CON_VA =ioremap(GPJ2CON_PA,8);
GPJ2DAT_VA =GPJ2CON_VA+1；
return 0;
}
static void __exit test_exit(void) //出口函数
{
unregister_chrdev_region(dev_no, 1);
cdev_del(&chrdev3);
}
module_init(test_init); //驱动的入口 #insmod *.ko
module_exit(test_exit); //驱动的出口 #rmmod *.ko
//#modinfo *.ko 可以查看module的信息
MODULE_AUTHOR("fbx@GEC");
MODULE_DESCRIPTION("the first module of drivers");
MODULE_LICENSE("GPL");
MODULE_VERSION("V1.0");
1 #include<linux/module.h> 2 #include<linux/kernel.h> 3 #include<linux/cdev.h> 4 #include<linux/fs.h> 5 #include<linux/kdev_t.h> 6 #include<linux/types.h> 7 #include<linux/uaccess.h> 8 #include<linux/string.h> 9 #include<linux/ioport.h> 10 #include<asm/io.h> 11 12 #define GPJ2CON_PA 0xe0200280 13 #define GPJ2DAT_PA 0xe0200280 14 unsigned int *GPJ2CON_VA; 15 unsigned int *GPJ2DAT_VA; 16 struct cdev chrdev; 17 struct resource *res; 18 unsigned int TestMajor=0; 19 unsigned int TestMinor=0; 20 dev_t dev_no; 21 int ret; 22 23 int testopen(struct inode *inode,struct file *file) 24 { 25 unsigned int a = ioread32(GPJ2CON_VA); 26 a |= 0x1111; 27 iowrite32(a,GPJ2CON_VA); 28 printk("cdev init "); 29 return 0; 30 31 } 32 ssize_t testwrite(struct file *file, const char __user *usr, size_t len, loff_t *off) 33 { 34 unsigned int a; 35 36 copy_from_user(&a,usr,len); 37 iowrite32(a,GPJ2DAT_VA); 38 39 40 } 41 ssize_t testread(struct file *file, char __user *usr, size_t len, loff_t *off) 42 { 43 unsigned int a = ioread32(GPJ2DAT_VA); 44 copy_to_user(usr,&a,len); 45 46 47 } 48 int testrelease(struct inode *inode, struct file *file) 49 { 50 printk("close "); 51 return 0; 52 53 } 54 55 struct file_operations fops= 56 { 57 .owner=THIS_MODULE, 58 .open = testopen, 59 .write = testwrite, 60 .read = testread, 61 .release = testrelease, 62 }; 63 static int __init test_init(void) 64 { 65 dev_no = MKDEV(TestMajor,TestMinor); 66 if(dev_no>0) 67 { 68 ret = register_chrdev_region(dev_no,1,"chrdev_test"); 69 } 70 else 71 { 72 alloc_chrdev_region(&dev_no,0,1,"chrdev_test"); 73 } 74 if(ret<0) 75 { 76 return ret; 77 } 78 cdev_init(&chrdev,&fops); 79 chrdev.owner=THIS_MODULE; 80 cdev_add(&chrdev,dev_no,1); 81 res = request_mem_region(GPJ2CON_PA,8,"gpj2_led"); 82 GPJ2CON_VA = ioremap(GPJ2CON_PA,8); 83 GPJ2DAT_VA = GPJ2CON_VA + 1; 84 return 0; 85 } 86 87 static int __exit test_exit(void) 88 { 89 unregister_chrdev_region(dev_no,1); 90 cdev_del(&chrdev); 91 iounmap(GPJ2CON_VA); 92 release_mem_region(GPJ2CON_PA,8); 93 return 0; 94 } 95 96 module_init(test_init); 97 module_exit(test_exit); 98 99 100 MODULE_AUTHOR("FENG"); 101 MODULE_DESCRIPTION("the first module of char drivers"); 102 MODULE_LICENSE("GPL"); 103 MODULE_VERSION("V1.0");
test.c 使一盏led循环点灭
1 #include<stdio.h> 2 #include <sys/stat.h> 3 #include <fcntl.h> 4 #include <errno.h> 5 #include <unistd.h> 6 #include <string.h> 7 8 int main() 9 { 10 unsigned int ledconfig; 11 char buf1[20]; 12 int fd = open("/dev/chrdev_test",O_RDWR); 13 if(fd<0) 14 perror("open() error! "); 15 bzero(buf1,20); 16 while(1) 17 { 18 read(fd,&ledconfig,4); 19 ledconfig ^=0x1; 20 write(fd,&ledconfig,4); 21 sleep(1); 22 } 23 }