1. 对于驱动程序中有两个关键的结构体：struct file *filp：
有一个关键的成员 -> void *private_data，用于存放用于私人的数据
inode：
有一个关键的成员 -> unsigned int i_flags
2. 一个驱动多个设备的程序思路：1个驱动程序，
1个struct file_operations 结构体
2个用户结构体数据(包含 struct cdev 结构体)
在 struct file_operation 结构体的 open 方法中根据 inode 结构体中的 i_cdev 成员找到 包含 cdev 的整个结构体，从而能在read/write中能够操作这个结构体的其他成员，具体如下：
在 open 中 将得到的 cdev 通过 struct file 结构体中的private_data 传递给 read/write 方法：
filp->private_data = dev;
当然设备号和设备节点都是两个，通过访问不同的 /dev 下的设备，访问不同的用户数据
3. 程序：
char_multi_dev.c
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print?<img id="aimg_b5595" class="zoom" width="12" height="12" file="https://code.csdn.net/assets/CODE_ico.png" border="0" alt="" /><img id="aimg_v8f00" class="zoom" width="12" height="12" file="https://code.csdn.net/assets/ico_fork.svg" border="0" alt="" />
#include <linux/module.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/cdev.h> #include <asm/uaccess.h> #include <linux/device.h> MODULE_LICENSE (&quot;GPL&quot;); int hello_major = 250; int hello_minor = 0; int number_of_devices = 2; struct class *my_class; struct hello_device { char data[128]; struct cdev cdev; } hello_device[2]; static int hello_open (struct inode *inode, struct file *filp) { struct hello_device *dev = container_of(inode->i_cdev, struct hello_device, cdev); filp->private_data = dev; printk (KERN_INFO &quot;Hey! device opened\n&quot;); return 0; } static int hello_release (struct inode *inode, struct file *filp) { printk (KERN_INFO &quot;Hmmm... device closed\n&quot;); return 0; } ssize_t hello_read (struct file *filp, char *buff, size_t count, loff_t *offp) { ssize_t result = 0; struct hello_device *dev = filp->private_data; if (count < 0) return -EINVAL; if (count > 127) count = 127; if (copy_to_user (buff, dev->data, count)) { result = -EFAULT; } else { printk (KERN_INFO &quot;wrote %d bytes\n&quot;, (int)count); result = count; } return result; } /* *ssize_t hello_write (struct file *filp, const char *buf, size_t count, * loff_t *f_pos) *{ * ssize_t ret = 0; * * printk (KERN_INFO &quot;Writing %d bytes\n&quot;, count); * if (count > 127) return -ENOMEM; * if (count < 0) return -EINVAL; * if (copy_from_user (data, buf, count)) { * ret = -EFAULT; * } * else { * data[count] = '\0'; * printk (KERN_INFO&quot;Received: %s\n&quot;, data); * ret = count; * } * * return ret; *} */ struct file_operations hello_fops = { .owner = THIS_MODULE, .open = hello_open, .release = hello_release, .read = hello_read, /* .write = hello_write */ }; static void char_reg_setup_cdev (struct cdev *cdev, dev_t devno) { int error; cdev_init (cdev, &hello_fops); cdev->owner = THIS_MODULE; error = cdev_add (cdev, devno , 1); if (error) printk (KERN_NOTICE &quot;Error %d adding char_reg_setup_cdev&quot;, error); } static int __init hello_2_init (void) { int result; dev_t devno; devno = MKDEV (hello_major, hello_minor); result = register_chrdev_region (devno, number_of_devices, &quot;hello_multi&quot;); if (result < 0) { printk (KERN_WARNING &quot;hello: can't get major number %d\n&quot;, hello_major); return result; } my_class = class_create(THIS_MODULE,&quot;multi_dev_class&quot;); if(IS_ERR(my_class)) { printk(&quot;Err: failed in creating class.\n&quot;); return -1; } device_create(my_class,NULL, devno, NULL, &quot;multi_dev0&quot;); device_create(my_class,NULL, devno + 1, NULL, &quot;multi_dev1&quot;); char_reg_setup_cdev (&hello_device[0].cdev, devno); char_reg_setup_cdev (&hello_device[1].cdev, devno+1); printk (KERN_INFO &quot;char device registered\n&quot;); strcpy(hello_device[0].data, &quot;0000000000000000000&quot;); strcpy(hello_device[1].data, &quot;1111111111111111111&quot;); return 0; } static void __exit hello_2_exit (void) { dev_t devno = MKDEV (hello_major, hello_minor); cdev_del (&hello_device[0].cdev); cdev_del (&hello_device[1].cdev); device_destroy(my_class, devno); // delete device node under /dev//必须先删除设备，再删除class类 device_destroy(my_class, devno + 1); // delete device node under /dev//必须先删除设备，再删除class类 class_destroy(my_class); // delete class created by us unregister_chrdev_region (devno, number_of_devices); printk(&quot;char device exited\n&quot;); } module_init (hello_2_init); module_exit (hello_2_exit);
关键点是 96行 和 98行
对 container_of 函数的理解请看：http://blog.csdn.net/boygrass/article/details/9962161?locationNum=1
Makefile
[python] view plain copy
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ifeq ($(KERNELRELEASE),) KERNELDIR ?= /lib/modules/$(shell uname -r)/build #KERNELDIR ?= ~/wor_lip/linux-3.4.112 PWD := $(shell pwd) modules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules modules_install: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install clean: rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions modules* Module* .PHONY: modules modules_install clean else obj-m := char_multi_dev.o endif
test.c
[cpp] view plain copy
print?<img id="aimg_rYfT2" class="zoom" width="12" height="12" file="https://code.csdn.net/assets/CODE_ico.png" border="0" alt="" /><img id="aimg_UPcgc" class="zoom" width="12" height="12" file="https://code.csdn.net/assets/ico_fork.svg" border="0" alt="" />
#include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> int main (void) { int fd1, fd2; char buf[64]; if ((fd1 = open (&quot;/dev/multi_dev0&quot;,O_RDONLY)) < 0) { perror(&quot;fail to open&quot;); return -1; } if ((fd2 = open (&quot;/dev/multi_dev1&quot;,O_RDONLY)) < 0) { perror(&quot;fail to open&quot;); return -1; } read(fd1, buf, 64); printf(&quot;read from device0 : %s\n&quot;, buf); read(fd2, buf, 64); printf(&quot;read from device1 : %s\n&quot;, buf); return 0; }
结果：
>sudo insmod char_multi_dev.ko
>sudo ./a.out
read from device0 : 0000000000000000000
read from device1 : 1111111111111111111
>sudo rmmod char_multi_dev
>dmesg
[11074.012373] char device registered
[11087.349961] Hey! device opened
[11087.349965] Hey! device opened
[11087.349967] wrote 64 bytes
[11087.350021] wrote 64 bytes
[11087.350055] Hmmm... device closed
[11087.350057] Hmmm... device closed
[11115.543117] char device exited |
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