Linux 驱动-5 字符设备号

块设备与字符设备独立编号 proc下面放临时信息

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w@w:~/linux_kernel/dev_t$ cat hello.c

#include <linux/init.h>

#include <linux/module.h>

#include <linux/kdev_t.h>

#include <linux/fs.h>

static int major = 233;      //主设备号

static int minor = 0;          //次设备号

static dev_t devno;             //定义设备号变量

static int hello_init(void)

{

        int result;

        printk("hello_init \n");

        devno = MKDEV(major,minor);       //创建主次设备号

        result = register_chrdev_region(devno, 1, "test");    //注册设备号， 1：代表注册一个设备，名称叫test

        if(result<0)                  //创建成功为0，失败一般为负值

        {

                printk("register_chrdev_region fail \n");

                return result;

        }

        return 0;

}

static void hello_exit(void)               //设备号也是资源，不用必须删除注销

{

        printk("hello_exit \n");

        unregister_chrdev_region(devno,1);

        return;

}

module_init(hello_init);

module_exit(hello_exit);

//proc/devices

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Makefile

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w@w:~/linux_kernel/dev_t$ cat Makefile

ifneq ($(KERNELRELEASE),)

$(info "2nd")

obj-m:=hello.o

else

KDIR :=/lib/modules/$(shell uname -r)/build

PWD  :=$(shell pwd)

all:

        $(info "1st")

        make -C $(KDIR) M=$(PWD) modules

clean:

        rm -f *.ko *.o *.mod.o *.symvers *.cmd  *.mod.c *.order

endif

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w@w:~/linux_kernel/dev_t$ sudo make

"1st"

make -C /lib/modules/5.4.0-104-generic/build M=/home/w/linux_kernel/dev_t modules

make[1]: Entering directory '/usr/src/linux-headers-5.4.0-104-generic'

"2nd"

  CC [M]  /home/w/linux_kernel/dev_t/hello.o

"2nd"

  Building modules, stage 2.

  MODPOST 1 modules

WARNING: modpost: missing MODULE_LICENSE() in /home/w/linux_kernel/dev_t/hello.o

see include/linux/module.h for more information

  CC [M]  /home/w/linux_kernel/dev_t/hello.mod.o

  LD [M]  /home/w/linux_kernel/dev_t/hello.ko

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加载模块，设备节点被创建 卸载模块，节点被注销