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韦东山嵌入式linux系列-具体单板的按键驱动程序(查询方式)

news 2025/9/14 5:29:10

1 GPIO 操作回顾

（1）使能模块；

（2）设置引脚的模式（工作于GPIO模式）；

（3）设置GPIO本身（输入/输出）；

（4）GPIO作为输入引脚时，读某个data寄存器获得引脚的电平。

2 百问网 STM32MP157 的按键驱动程序(查询方式)

在 STM32MP157 开发板上，我们为它设计了 2 个按键。

2.1 先看原理图确定引脚及操作方法

平时按键电平为低，按下按键后电平为高。

按键引脚为 GPIOG_IO03、 GPIOG_IO02。

2.2 再看芯片手册确定寄存器及操作方法

步骤1：使能GPIOG

下图为针对 APU 的 GPIOA 至 K 的时钟使能寄存器，低11位有效。为了使用GPIOG，我们需要将对应的 b[6]位设置为 1

英文明明写的是MPU

MPU/MCU -- Microprocessor/Micro controller Unit，微处理器/微控制器，一般用于低计算应用的RISC计算机体系架构产品，如ARM-M系列处理器。

APU、BPU、CPU、DPU、FPU、GPU、HPU、IPU、MPU、NPU、RPU、TPU、VPU、WPU、XPU、ZPU 都是什么？ - 一杯清酒邀明月 - 博客园 (cnblogs.com)

地址偏移量:0xA28
复位值:0x0000 0000

该寄存器用于将相应外设的外设时钟使能位设置为“1”。它将用于为MPU分配外设。写“0”没有作用，读有作用，返回相应位的有效值。写入'1'将相应的位设置为'1'

Bits 31:11保留，必须保持在复位值。
bit10 GPIOKEN: GPIOK外设时钟使能软件设置。
0:写“0”无效，读“0”表示禁用外设时钟
1:写“1”使能外设时钟，读“1”使能外设时钟

其他位一样

步骤2：设置GPIOG_IO03、 GPIOG_IO02为GPIO输入模式

GPIOx_MODER用于配置GPIO的模式，包括输入、通用输出、多功能和模拟共四种模式。该寄存器共32位，涉及16个GPIO，每个GPIO对应 2 位。GPIOx_MODER 的各位定义如下，在这里分别选择00和01两种，各自对应输入和输出模式。（上电默认为输入悬空模式）。其中 00 对应输入功能， 01 对应输出功能

设置 b[7:6]为00就可以配置GPIOG_IO03为输入模式，

配置 b[5:4]为00就可以配置GPIOG_IO02为输入模式。

步骤 3：读取GPIOG_IO02、GPIOG_IO03引脚电平

寄存器地址为：

在参考手册搜关键字gpio

读取 IDR 寄存器获取引脚状态寄存器，得到引脚电平

Bits 31:16保留，必须保持复位值。
bit 15:0 IDR[15:0]:端口x输入数据I/O引脚y (y = 15 ~ 0)，这些位是只读的。它们包含相应I/O端口的输入值。

3 代码

board_drv.c

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/signal.h>
#include <linux/mutex.h>
#include <linux/mm.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/poll.h>
#include <linux/capi.h>
#include <linux/kernelcapi.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/moduleparam.h>#include "button_drv.h"// 1主设备号
static int major = 0;
static struct class* button_class;
static struct button_operations *p_button_operations;void register_button_operations(struct button_operations *opr)
{int i;p_button_operations = opr;for (i = 0; i < opr->count; i++){device_create(button_class, NULL, MKDEV(major, i), NULL, "winter_button@%d", i);}
}void unregister_button_operations(void)
{int i;for (i = 0; i < p_button_operations->count; i++){device_destroy(button_class, MKDEV(major, i));}
}EXPORT_SYMBOL(register_button_operations);
EXPORT_SYMBOL(unregister_button_operations);// 3实现open/read函数
static int button_open (struct inode *inode, struct file *file)
{int minor = iminor(inode);// 利用此设备号初始化p_button_operations->init(minor);return 0;
}static ssize_t button_read (struct file *file, char __user *buf, size_t size, loff_t *off)
{unsigned int minor = iminor(file_inode(file));char level;int err;level = p_button_operations->read(minor);// 将内核数据拷贝到用户空间，也就是读数据err = copy_to_user(buf, &level, 1);return 1;
}// 2file_operations结构体
static struct file_operations button_operations = {.open = button_open,.read = button_read,
};// 4在入口函数中注册file_operations结构体
int button_init(void)
{// 注册file_operations结构体major = register_chrdev(0, "winter_button", &button_operations);// 注册结点button_class = class_create(THIS_MODULE, "winter_button");if (IS_ERR(button_class))return -1;return 0;}// 出口函数
void button_exit(void)
{class_destroy(button_class);unregister_chrdev(major, "winter_button");
}module_init(button_init);
module_exit(button_exit);
MODULE_LICENSE("GPL");

board_drv.h

#ifndef BUTTON_DRV_H
#define BUTTON_DRV_Hstruct button_operations {int count;void (*init) (int which);int (*read) (int which);
};void register_button_operations(struct button_operations *opr);
void unregister_button_operations(void);#endif

board_xxx.c

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/signal.h>
#include <linux/mutex.h>
#include <linux/mm.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/poll.h>
#include <linux/capi.h>
#include <linux/kernelcapi.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/moduleparam.h>#include "button_drv.h"static void board_xxx_button_init_gpio (int which)
{printk("%s %s %d, init gpio for button %d\n", __FILE__, __FUNCTION__, __LINE__, which);
}static int board_xxx_button_read_gpio (int which)
{printk("%s %s %d, read gpio for button %d\n", __FILE__, __FUNCTION__, __LINE__, which);return 1;
}static struct button_operations my_buttons_ops ={.count = 2,.init  = board_xxx_button_init_gpio,.read  = board_xxx_button_read_gpio,
};int board_xxx_button_init(void)
{register_button_operations(&my_buttons_ops);return 0;
}void board_xxx_button_exit(void)
{unregister_button_operations();
}module_init(board_xxx_button_init);
module_exit(board_xxx_button_exit);
MODULE_LICENSE("GPL");

board_test.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>/** ./button_test /dev/100ask_button0**/
int main(int argc, char **argv)
{int fd;char val;/* 1. 判断参数 */if (argc != 2) {printf("Usage: %s <dev>\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 */read(fd, &val, 1);printf("get button : %d\n", val);close(fd);return 0;
}

上面4个和之前的都一样，主要不同在board_100ask_stm32mp157.c

主要看 board_100ask_stm32mp157-pro.c。涉及的寄存器挺多，一个一个去执行 ioremap 效率太低。先定义结构体，然后对结构体指针进行 ioremap。对于 GPIO，可以如下定义：

struct stm32mp157_gpio {volatile unsigned int MODER;    /*!< GPIO port mode register,               Address offset: 0x00      */volatile unsigned int OTYPER;   /*!< GPIO port output type register,        Address offset: 0x04      */volatile unsigned int OSPEEDR;  /*!< GPIO port output speed register,       Address offset: 0x08      */volatile unsigned int PUPDR;    /*!< GPIO port pull-up/pull-down register,  Address offset: 0x0C      */volatile unsigned int IDR;      /*!< GPIO port input data register,         Address offset: 0x10      */volatile unsigned int ODR;      /*!< GPIO port output data register,        Address offset: 0x14      */volatile unsigned int BSRR;     /*!< GPIO port bit set/reset,               Address offset: 0x18      */volatile unsigned int LCKR;     /*!< GPIO port configuration lock register, Address offset: 0x1C      */volatile unsigned int AFR[2];   /*!< GPIO alternate function registers,     Address offset: 0x20-0x24 */
} ;

这个顺序是按照偏移量列出的

看一个驱动程序，先看它的入口函数，下列代码向上层驱动注册一个button_operations 结构体,代码如下。

static struct button_operations my_buttons_ops = {.count = 2,.init = board_stm32mp157_button_init,.read = board_stm32mp157_button_read,
};
// 入口函数
int board_stm32mp157_button_drv_init(void)
{register_button_operations(&my_buttons_ops);return 0;
}void board_stm32mp157_button_drv_exit(void)
{unregister_button_operations();
}

button_operations 结构体中有 init 函数指针，它指向board_stm32mp157_button_init 函数，在里面将会初始化 LED 引脚：使能、设置为 GPIO 模式、设置为输出引脚。代码如下。
值得关注的下列代码中对 ioremap 函数的使用，它们是得到寄存器的虚拟地址，以后使用虚拟地址访问寄存器。

/* RCC_PLL4CR */
static volatile unsigned int *RCC_PLL4CR; /* RCC_MP_AHB4ENSETR */
static volatile unsigned int *RCC_MP_AHB4ENSETR;/* KEY1: PG3, KEY2: PG2 */
static struct stm32mp157_gpio *gpiog;/* 初始化button, which-哪个button */
static void board_stm32mp157_button_init (int which)
{// 没有使能if (!RCC_PLL4CR){RCC_PLL4CR = ioremap(0x50000000 + 0x894, 4);RCC_MP_AHB4ENSETR = ioremap(0x50000000 + 0xA28, 4);gpiog = ioremap(0x50008000, sizeof(struct stm32mp157_gpio));}if (which == 0){/* 1. enable PLL4 * CG15, b[31:30] = 0b11*/*RCC_PLL4CR |= (1<<0);while((*RCC_PLL4CR & (1<<1)) == 0);/* 2. enable GPIOG */*RCC_MP_AHB4ENSETR |= (1<<6);/* 3. 设置PG3为GPIO模式, 输入模式 */gpiog->MODER &= ~(3<<6);}else if(which == 1){/* 1. enable PLL4 * CG15, b[31:30] = 0b11*/*RCC_PLL4CR |= (1<<0);while((*RCC_PLL4CR & (1<<1)) == 0);/* 2. enable GPIOG */*RCC_MP_AHB4ENSETR |= (1<<6);/* 3. 设置PG2为GPIO模式, 输入模式 */gpiog->MODER &= ~(3<<4);}}

button_operations 结构体中还有有 read 函数指针，它指向board_stm32mp157_button_read 函数，在里面将会读取并返回按键引脚的电平。代码如下

static int board_stm32mp157_button_read (int which) /* 读button, which-哪个 */
{//printk("%s %s line %d, button %d, 0x%x\n", __FILE__, __FUNCTION__, __LINE__, which, *GPIO1_DATAIN);if (which == 0)return (gpiog->IDR & (1<<3)) ? 1 : 0;elsereturn (gpiog->IDR & (1<<2)) ? 1 : 0;
}

参考：韦东山嵌入式linux系列-LED驱动程序-CSDN博客

board_100ask_stm32mp157.c

#include <linux/module.h>#include <linux/fs.h>
#include <linux/io.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <asm/io.h>#include "button_drv.h"/* RCC_PLL4CR */
static volatile unsigned int* RCC_PLL4CR; /* RCC_MP_AHB4ENSETR */
static volatile unsigned int* RCC_MP_AHB4ENSETR; /* KEY1: PG3, KEY2: PG2 */
static struct stm32mp157_gpio* gpiog;struct stm32mp157_gpio {volatile unsigned int MODER;    /*!< GPIO port mode register,               Address offset: 0x00      */volatile unsigned int OTYPER;   /*!< GPIO port output type register,        Address offset: 0x04      */volatile unsigned int OSPEEDR;  /*!< GPIO port output speed register,       Address offset: 0x08      */volatile unsigned int PUPDR;    /*!< GPIO port pull-up/pull-down register,  Address offset: 0x0C      */volatile unsigned int IDR;      /*!< GPIO port input data register,         Address offset: 0x10      */volatile unsigned int ODR;      /*!< GPIO port output data register,        Address offset: 0x14      */volatile unsigned int BSRR;     /*!< GPIO port bit set/reset,               Address offset: 0x18      */volatile unsigned int LCKR;     /*!< GPIO port configuration lock register, Address offset: 0x1C      */volatile unsigned int AFR[2];   /*!< GPIO alternate function registers,     Address offset: 0x20-0x24 */
};/* 初始化button, which-哪个button */      
static void board_stm32mp157_button_init (int which) 
{if (!RCC_PLL4CR){RCC_PLL4CR = ioremap(0x50000000 + 0x894, 4);RCC_MP_AHB4ENSETR = ioremap(0x50000000 + 0xA28, 4);gpiog = ioremap(0x50008000, sizeof(struct stm32mp157_gpio));}if (which == 0){/* 1. enable PLL4 * CG15, b[31:30] = 0b11*/*RCC_PLL4CR |= (1<<0);while((*RCC_PLL4CR & (1<<1)) == 0);/* 2. enable GPIOG */*RCC_MP_AHB4ENSETR |= (1<<6);/* 3. 设置PG3为GPIO模式, 输入模式 */gpiog->MODER &= ~(3<<6);}else if(which == 1){/* 1. enable PLL4 * CG15, b[31:30] = 0b11*/*RCC_PLL4CR |= (1<<0);while((*RCC_PLL4CR & (1<<1)) == 0);/* 2. enable GPIOG */*RCC_MP_AHB4ENSETR |= (1<<6);/* 3. 设置PG2为GPIO模式, 输入模式 */gpiog->MODER &= ~(3<<4);}
}/* 读button, which-哪个 */
static int board_stm32mp157_button_read (int which)
{//printk("%s %s line %d, button %d, 0x%x\n", __FILE__, __FUNCTION__, __LINE__, which, *GPIO1_DATAIN);if (which == 0){return (gpiog->IDR & (1<<3)) ? 1 : 0;}else{return (gpiog->IDR & (1<<2)) ? 1 : 0;}
}static struct button_operations my_buttons_ops = {.count = 2,.init = board_stm32mp157_button_init,.read = board_stm32mp157_button_read,
};int board_stm32mp157_button_drv_init(void)
{register_button_operations(&my_buttons_ops);return 0;
}void board_stm32mp157_button_drv_exit(void)
{unregister_button_operations();
}module_init(board_stm32mp157_button_drv_init);
module_exit(board_stm32mp157_button_drv_exit);MODULE_LICENSE("GPL");

编译

4 测试

在开发板挂载 Ubuntu 的NFS目录

mount -t nfs -o nolock,vers=3 192.168.5.11:/home/book/nfs_rootfs/ /mnt

将ko文件和测试代码拷贝到挂载目录，安装驱动

insmod button_drv.ko
insmod board_100ask_stm32mp157.ko

执行测试程序观察它的返回值(执行测试程序的同时操作按键)：

./button_test /dev/winter_button@0
./button_test /dev/winter_button@1

执行程序的同时，按下按键，输出是0