1.調用關係
應用程序:open read write
應用層 -----------------------------------------
c庫 (swi val)
=================================================
內核: system call interface
(在異常處理函數裏面,根據發生中斷的原因,調用
不同的處理函數)
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sys_open sys_read sys_write
(VFS Virtual File System)
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驅動: led_open led_read led_write
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硬件: led flash ....
2.驅動程序框架:
1)寫出led_on led_read
2)通知內核
1>構造file_operations
.open
.write
...
2>入口函數中:register_chrdev
unregister_chrdev
3>first_drv_init(自定義的入口函數)
first_drv_exit
4>module_init修飾入口函數
module_exit
3.
用戶空間
APP: open("/dev/xxx") read write
屬性:c(設備類型),111(主設備號)
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C庫
==============================================================
內核 system call interface
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VFS major作爲索引
————————————————————————
| 數組 | | |... |file_operations| |
————————————————————————
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led_open led_read led_write
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VFS根據打開的文件的屬性:設備類型、主設備號,這兩個屬性就能找到
register_chrdev函數註冊進內核的file_operations結構體
4.Makefile
KERN_DIR = /work/system/linux-2.6.22.6 all: make -C $(KERN_DIR) M=`pwd` modules clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order obj-m += first_drv.o
5.字符設備驅動程序:
#include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/init.h> #include <linux/delay.h> #include <asm/uaccess.h> #include <asm/irq.h> #include <asm/io.h> #include <asm/arch/regs-gpio.h> #include <asm/hardware.h> static struct class *firstdrv_class; static struct class_device *firstdrv_class_dev; volatile unsigned long *gpfcon = NULL; volatile unsigned long *gpfdat = NULL; static int first_drv_open(struct inode *inode, struct file *file) { //printk("first_drv_open\n"); /* 配置GPF4,5,6爲輸出 */ *gpfcon &= ~((0x3<<(4*2)) | (0x3<<(5*2)) | (0x3<<(6*2))); *gpfcon |= ((0x1<<(4*2)) | (0x1<<(5*2)) | (0x1<<(6*2))); return 0; } static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos) { int val; //printk("first_drv_write\n"); copy_from_user(&val, buf, count); // copy_to_user(); if (val == 1) { // 點燈 *gpfdat &= ~((1<<4) | (1<<5) | (1<<6)); } else { // 滅燈 *gpfdat |= (1<<4) | (1<<5) | (1<<6); } return 0; } static struct file_operations first_drv_fops = { .owner = THIS_MODULE, /* 這是一個宏,推向編譯模塊時自動創建的__this_module變量 */ .open = first_drv_open, .write = first_drv_write, }; //驅動的入口函數 int major; static int first_drv_init(void) { //0系統自動分配主設備號 major = register_chrdev(0, "first_drv", &first_drv_fops); // 註冊, 告訴內核 firstdrv_class = class_create(THIS_MODULE, "firstdrv"); firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, "xyz"); /* /dev/xyz */ //0x56000050爲GPFCON的物理地址 gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16); gpfdat = gpfcon + 1; return 0; } static void first_drv_exit(void) { unregister_chrdev(major, "first_drv"); // 卸載 class_device_unregister(firstdrv_class_dev); class_destroy(firstdrv_class); iounmap(gpfcon); } module_init(first_drv_init); module_exit(first_drv_exit); //不添加,則不能夠識別 MODULE_LICENSE("GPL");
6.測試程序:
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> /* firstdrvtest on * firstdrvtest off */ int main(int argc, char **argv) { int fd; int val = 1; fd = open("/dev/xyz", O_RDWR); if (fd < 0) { printf("can't open!\n"); } if (argc != 2) { printf("Usage :\n"); printf("%s <on|off>\n", argv[0]); return 0; } if (strcmp(argv[1], "on") == 0) { val = 1; } else { val = 0; } write(fd, &val, 4); return 0; }
7.運行
1>cat /proc/devices
//加載驅動
2>insmod first_drv.ko
//創建設備節點
3>mknod /dev/xxx c 111 0
4>運行
5>lsmod
6>rmmod first_drv
7>rm /dev/xxx
8. 自動分配主設備號,自動創建設備
1)驅動:①自動分配主設備號
②手工指定
2)應用:
open("/dev/xxx")
1>mknod /dev/xxx c 主設備號 次設備號
2>自動創建設備 udev mdev(根據系統信息,創建設備節點)
class_create()
class_device_create()
3)查看系統信息
cd /sys/class
cd firstdrv
cd xyz
ls
4)
/etc/init.d/rc.S
echo /sbin/mdev > /proc/sys/kernel/hotplus