韦东山嵌入式Linux驱动开发基础知识学习笔记
文章中大多内容来自韦东山老师的文档,还有部分个人根据自己需求补充的内容
视频教程地址:https://www.bilibili.com/video/BV14f4y1Q7ti
上一章在驱动中引入面向对象和分层的设计思想
在驱动里简单来说面向对象就是抽象一个结构体作为设备的类,然后将结构体成员作为对象
而分层设计思想简单来说就是将 内核相关的操作和硬件强相关操作分离 达到内核相关操作通用,硬件相关操作个性化目的
本节将介绍分离思想
【嵌入式Linux】嵌入式Linux驱动开发基础知识之LED驱动框架–面向对象、分层设计思想
▲面向对象、分层、分离思想体现
将使能、操作GPIO的流程抽象成统一的接口,LED的init可以去调用这些接口,其中添加struct led_resource
结构体,其中保存了LED需要的资源即GPIO的group & pin
,实现初始化。一系列操作相当于封装了GPIO的寄存器相关操作供设备使用
led_opr.h
:包含led设备结构体类
#ifndef _LED_OPR_H
#define _LED_OPR_H
struct led_operations {
int (*init) (int which); /* 初始化LED, which-哪个LED */
int (*ctl) (int which, char status); /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
int (*exit) (void);
};
struct led_operations *get_board_led_opr(void);
#endif
leddrv.c
:给APP提供接口
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "led_opr.h"
#define LED_NUM 2
/* 1. 确定主设备号 */
static int major = 0;
static struct class *led_class;
struct led_operations *p_led_opr;
#define MIN(a, b) (a < b ? a : b)
/* 3. 实现对应的open/read/write等函数,填入file_operations结构体 */
static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return 0;
}
/* write(fd, &val, 1); */
static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
int err;
char status;
struct inode *inode = file_inode(file);
int minor = iminor(inode);
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
err = copy_from_user(&status, buf, 1);
/* 根据次设备号和status控制LED */
p_led_opr->ctl(minor, status);
return 1;
}
static int led_drv_open (struct inode *node, struct file *file)
{
int minor = iminor(node);
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
/* 根据次设备号初始化LED */
p_led_opr->init(minor);
return 0;
}
static int led_drv_close (struct inode *node, struct file *file)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return 0;
}
/* 2. 定义自己的file_operations结构体 */
static struct file_operations led_drv = {
.owner = THIS_MODULE,
.open = led_drv_open,
.read = led_drv_read,
.write = led_drv_write,
.release = led_drv_close,
};
/* 4. 把file_operations结构体告诉内核:注册驱动程序 */
/* 5. 谁来注册驱动程序啊?得有一个入口函数:安装驱动程序时,就会去调用这个入口函数 */
static int __init led_init(void)
{
int err;
int i;
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
major = register_chrdev(0, "100ask_led", &led_drv); /* /dev/led */
led_class = class_create(THIS_MODULE, "100ask_led_class");
err = PTR_ERR(led_class);
if (IS_ERR(led_class)) {
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
unregister_chrdev(major, "led");
return -1;
}
for (i = 0; i < LED_NUM; i++)
device_create(led_class, NULL, MKDEV(major, i), NULL, "100ask_led%d", i); /* /dev/100ask_led0,1,... */
p_led_opr = get_board_led_opr();
return 0;
}
/* 6. 有入口函数就应该有出口函数:卸载驱动程序时,就会去调用这个出口函数 */
static void __exit led_exit(void)
{
int i;
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
p_led_opr->exit();
for (i = 0; i < LED_NUM; i++)
device_destroy(led_class, MKDEV(major, i)); /* /dev/100ask_led0,1,... */
device_destroy(led_class, MKDEV(major, 0));
class_destroy(led_class);
unregister_chrdev(major, "100ask_led");
}
/* 7. 其他完善:提供设备信息,自动创建设备节点 */
module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
board_A_led
:包含LED所需要的资源信息
#include "led_resource.h"
static struct led_resource led_resources = {
.num = 2,
/* PA10 green */
.pin[0] = GROUP_PIN(0,10),
/* PG8 yellow */
.pin[1] = GROUP_PIN(6,8),
};
struct led_resource *get_led_resouce(void)
{
return &led_resources;
}
chip_demo_gpio.c
:包含GPIO相关操作、使能函数,LED设备对象从这里获得接口
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "led_opr.h"
#include "led_resource.h"
/* registers */
// RCC_PLL4CR地址:0x50000000 + 0x894
static volatile unsigned int *RCC_PLL4CR;
// RCC_MP_AHB4ENSETR 地址:0x50000000 + 0xA28
static volatile unsigned int *RCC_MP_AHB4ENSETR;
// GPIOA_MODER 地址:0x50002000 + 0x00
static volatile unsigned int *GPIOA_MODER;
// GPIOA_BSRR 地址: 0x50002000 + 0x18
static volatile unsigned int *GPIOA_BSRR;
// GPIOG_MODER 地址:0x50008000 + 0x00
static volatile unsigned int *GPIOG_MODER;
// GPIOG_BSRR 地址: 0x50008000 + 0x18
static volatile unsigned int *GPIOG_BSRR;
/* registers end */
struct led_resource *led_rsc;
static int board_demo_led_init (int which) /* 初始化LED, which-哪个LED */
{
if (!led_rsc)
{
led_rsc = get_led_resouce();
}
/* 寄存器映射到变量 */
if (!RCC_PLL4CR)
{
// RCC_PLL4CR地址:0x50000000 + 0x894
RCC_PLL4CR = ioremap(0x50000000 + 0x894, 4);
// RCC_MP_AHB4ENSETR 地址:0x50000000 + 0xA28
RCC_MP_AHB4ENSETR = ioremap(0x50000000 + 0xA28, 4);
// GPIOA_MODER 地址:0x50002000 + 0x00
GPIOA_MODER = ioremap(0x50002000 + 0x00, 4);
// GPIOA_BSRR 地址: 0x50002000 + 0x18
GPIOA_BSRR = ioremap(0x50002000 + 0x18, 4);
// GPIOG_MODER 地址:0x50008000 + 0x00
GPIOG_MODER = ioremap(0x50008000 + 0x00, 4);
// GPIOG_BSRR 地址: 0x50008000 + 0x18
GPIOG_BSRR = ioremap(0x50008000 + 0x18, 4);
}
switch(GROUP(led_rsc->pin[which]))
{
case 0:
{
printk("init pin of group A ...\n");
/* enalbe PLL4, it is clock source for all gpio */
*RCC_PLL4CR |= (1<<0);
while ((*RCC_PLL4CR & (1<<1)) == 0);
/* enable gpio */
*RCC_MP_AHB4ENSETR |= (1<<GROUP(led_rsc->pin[which]));
/*
* configure gpio as output
*/
*GPIOA_MODER &= ~(3 << (PIN(led_rsc->pin[which])*2) );
*GPIOA_MODER |= (1<< (PIN(led_rsc->pin[which])*2) );
/* ... */
break;
}
case 6:
{
printk("init pin of group G ...\n");
/* enalbe PLL4, it is clock source for all gpio */
*RCC_PLL4CR |= (1<<0);
while ((*RCC_PLL4CR & (1<<1)) == 0);
/* enable gpio */
*RCC_MP_AHB4ENSETR |= (1<<GROUP(led_rsc->pin[which]));
/*
* configure gpg8 as gpio
* configure gpio as output
*/
*GPIOG_MODER &= ~((PIN(led_rsc->pin[which])*2));
*GPIOG_MODER |= ((PIN(led_rsc->pin[which])*2));
break;
}
default:
printk("not support %d\n", led_rsc->pin[which]);
}
return 0;
}
static int board_demo_led_ctl (int which, char status) /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
{
//printk("%s %s line %d, led %d, %s\n", __FILE__, __FUNCTION__, __LINE__, which, status ? "on" : "off");
printk("set led %s: group %d, pin %d\n", status ? "on" : "off", GROUP(led_rsc->pin[which]), PIN(led_rsc->pin[which]));
switch(GROUP(led_rsc->pin[which]))
{
case 0:
{
printk("set pin of group A ...\n");
*GPIOA_BSRR = ( 1<< (16*status + PIN(led_rsc->pin[which])));
break;
}
case 6:
{
printk("set pin of group G ...\n");
*GPIOG_BSRR = ( 1<< (16*status + PIN(led_rsc->pin[which])));
break;
}
default:
printk("not support %d\n", led_rsc->pin[which]);
}
return 0;
}
static int board_demo_led_exit (void)
{
if(RCC_PLL4CR)
{
iounmap(RCC_PLL4CR);
iounmap(RCC_MP_AHB4ENSETR);
iounmap(GPIOA_MODER);
iounmap(GPIOA_BSRR);
iounmap(GPIOG_MODER);
iounmap(GPIOG_BSRR);
}
return 0;
}
static struct led_operations board_demo_led_opr = {
.init = board_demo_led_init,
.ctl = board_demo_led_ctl,
.exit = board_demo_led_exit,
};
struct led_operations *get_board_led_opr(void)
{
return &board_demo_led_opr;
}
ledtest.c
#include
#include
#include
#include
#include
#include
/*
* ./ledtest /dev/100ask_led0 on
* ./ledtest /dev/100ask_led0 off
*/
int main(int argc, char **argv)
{
int fd;
char status;
/* 1. 判断参数 */
if (argc != 3)
{
printf("Usage: %s \n" , argv[0]);
return -1;
}
/* 2. 打开文件 */
fd = open(argv[1], O_RDWR);
if (fd == -1)
{
printf("can not open file %s\n", argv[1]);
return -1;
}
/* 3. 写文件 */
if (0 == strcmp(argv[2], "on"))
{
status = 1;
write(fd, &status, 1);
}
else
{
status = 0;
write(fd, &status, 1);
}
close(fd);
return 0;
}