linux4.10.8 Kernel porting (quad)---character device driver _led driver

Introduction of character device driver

　　

The app uses open, read, write, and other functions to operate the underlying hardware. The driver also has corresponding functions such as Xxx_open. How to find a driver in a function depends on the driver framework.

II. Building a Driver Framework 2.1 preliminary Framework 2.1.1 Makefile

　　

2.1.2 JZ2440_LED.C

1#include <linux/module.h>2#include <linux/of.h>3#include <linux/of_device.h>4#include <linux/regmap.h>5#include <linux/fs.h>6 7 #defineJz2440_leds_major 111/* Main device number */8 9 Ten Static intJz2440_drv_open (structInode *inode,structFile *file) One { APrintk"Jz2440_drv_open"); -     return 0; - } the  - Static intJz2440_drv_close (structInode *inode,structFile *file) - { -Printk"Jz2440_drv_close"); +     return 0;  - } +  A Staticssize_t Jz2440__drv_read (structFile *file,Char__user * buf, size_t count, loff_t *PPOs) at { -Printk"Jz2440__drv_read"); -     return 0; - } -  - Staticssize_t Jz2440_drv_write (structFile *file,Const Char__user * buf, size_t count, loff_t *PPOs) in { -Printk"Jz2440_drv_write"); to     return 0; + } -  the Static structFile_operations Jz2440_leds_ops = { *. Owner =This_module, $. Read =Jz2440__drv_read,Panax Notoginseng. Open =Jz2440_drv_open, -. Write =Jz2440_drv_write, the. Release =Jz2440_drv_close, + }; A  the Static int__init Jz2440_drv_leds_init (void) + { -Register_chrdev (Jz2440_leds_major,"jz2440_drv_leds", &jz2440_leds_ops);//register the driver, which tells the kernel $     return 0; $ } -  - Static void__exit Jz2440_drv_leds_exit (void) the { -Unregister_chrdev (Jz2440_leds_major,"jz2440_drv_leds");Wuyi } the  - //point to Entry function Jz2440_drv_leds_init Wu Module_init (jz2440_drv_leds_init); - //Export function Unload drive About Module_exit (jz2440_drv_leds_exit); $  -Module_license ("GPL"); -Module_description ("jz2440 LEDs driver");

Compile:

　　

Burn Write Run:

　　

　　

Go to the Development Board U-boot interface:

Set command line startup parameters

Set Bootargs noinitrd root=/dev/nfs Nfsroot=192.168.0.192:/home/ubuntu/work/nfs_root/fs_mini ip= 192.168.0.191:192.168.0.192:192.168.0.1:255.255.255.0::eth0:off INIT=/LINUXRC console=ttySAC0,115200

Boot kernel: Boot

　　

NFS Directory Mount succeeded.

To view the proc directory:

　　

The device number is available.

Load module:

　　

Check to see if loading is in:

　　

Test program

1#include <sys/types.h>2#include <sys/stat.h>3#include <fcntl.h>4#include <stdio.h>5#include <unistd.h>6 7 intMainintargcChar**argv)8 {9     intFD;Ten     intval =1; One      AFD = open ("/dev/xxx", O_RDWR); -     if(FD <0) -     { theprintf"can ' t open!\n"); -     } -      -Write (FD, &val,4); +     return 0; -}

Compile burn write into board, execute

　　

Create a device node;

　　

Executive A.out

　　

　　

　　

　　

linux4.10.8 Kernel porting (quad)---character device driver _led driver