韦东山嵌入式学习---具体单板的按键驱动程序

一.普适的 GPIO 引脚操作方法

GPIO操作基本步骤

1. 芯片手册一般有相关章节，用来介绍：power/clock
   可以设置对应寄存器使能某个 GPIO 模块(Module)
   有些芯片的 GPIO 是没有使能开关的，即它总是使能的
2. 一个引脚可以用于 GPIO、串口、USB 或其他功能，
   有对应的寄存器来选择引脚的功能
3. 对于已经设置为 GPIO 功能的引脚，有方向寄存器用来设置它的方向：输出、输入
4. 对于已经设置为 GPIO 功能的引脚，有数据寄存器用来写、读引脚电平状态
   5
   二.具体代码
   主要是根据单板修改board_xxx.c为board_ky.c（imx6ull）
   board_ky.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"


struct iomux {    //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
    volatile unsigned int unnames[23];
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO00; /* offset 0x5c */
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO01;//递增4
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO02;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO03;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO04;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO05;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO06;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO07;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO08;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO09;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_UART1_TX_DATA;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_UART1_RX_DATA;
    volatile unsigned int IOMUXC_SW_MUX_CTL_PAD_UART1_CTS_B;
};


struct imx6ull_gpio {//对于gpio4 gpio5他们内部排列是一样的
    volatile unsigned int dr;
    volatile unsigned int gdir;
    volatile unsigned int psr;
    volatile unsigned int icr1;
    volatile unsigned int icr2;
    volatile unsigned int imr;
    volatile unsigned int isr;
    volatile unsigned int edge_sel;
};

/* enable GPIO4 */
static volatile unsigned int *CCM_CCGR3; 

/* enable GPIO5 */
static volatile unsigned int *CCM_CCGR1; 

/* set GPIO5_IO03 as GPIO */
static volatile unsigned int *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER1;

/* set GPIO4_IO14 as GPIO */
static volatile unsigned int *IOMUXC_SW_MUX_CTL_PAD_NAND_CE1_B;

static struct iomux *iomux;

static struct imx6ull_gpio *gpio4;
static struct imx6ull_gpio *gpio5;



static void board_imx6ull_button_init (int which) /* 初始化button, which-哪个button */      
{
    if (!CCM_CCGR1)
    {
        CCM_CCGR1 = ioremap(0x20C406C, 4);
        CCM_CCGR3 = ioremap(0x20C4074, 4);//在芯片手册中搜索这些寄存器，将物理地址映射为虚拟地址
        IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER1 = ioremap(0x229000C, 4);
		IOMUXC_SW_MUX_CTL_PAD_NAND_CE1_B        = ioremap(0x20E01B0, 4);

        iomux = ioremap(0x20e0000, sizeof(struct iomux));//0x20C406C为IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO00的第一个地址   iomux的第一个
        gpio4 = ioremap(0x020A8000, sizeof(struct imx6ull_gpio));//0x020A8000为gpio4的基地址    *gpio4指向gpio4的基地址
        gpio5 = ioremap(0x20AC000, sizeof(struct imx6ull_gpio));
    }

    if (which == 0)
    {
        /* 1. enable GPIO5 
         * CG15, b[31:30] = 0b11
         */
        *CCM_CCGR1 |= (3<<30);//按位或后赋值
        
        /* 2. set GPIO5_IO01 as GPIO 
         * MUX_MODE, b[3:0] = 0b101
         */
        *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER1 = 5;

        /* 3. set GPIO5_IO01 as input 
         * GPIO5 GDIR, b[1] = 0b0
         */
        gpio5->gdir &= ~(1<<1);//&= 意思为：按位与后赋值  ~取反
    }
    else if(which == 1)
    {
        /* 1. enable GPIO4 
         * CG6, b[13:12] = 0b11
         */
        *CCM_CCGR3 |= (3<<12);
        
        /* 2. set GPIO4_IO14 as GPIO 
         * MUX_MODE, b[3:0] = 0b101
         */
        IOMUXC_SW_MUX_CTL_PAD_NAND_CE1_B = 5;

        /* 3. set GPIO4_IO14 as input 
         * GPIO4 GDIR, b[14] = 0b0
         */
        gpio4->gdir &= ~(1<<14);
    }
    
}

static int board_imx6ull_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 (gpio5->psr & (1<<1)) ? 1 : 0;
    else
        return (gpio4->psr & (1<<14)) ? 1 : 0;
}

static struct button_operations my_buttons_ops ={ //实现了一个 button_operations 结构体
    .count = 2,
    .init  = board_imx6ull_button_init,//初始化引脚的函数
    .read  = board_imx6ull_button_read,//读引脚的函数
};

int board_imx6ull_button_drv_init(void)
{
    register_button_operations(&my_buttons_ops);//注册上面的结构体,底层代码调用 register_button_operations 函数，向上提供这个结构体指针。
    return 0;
}

void board_imx6ull_button_drv_exit(void)
{
    unregister_button_operations();//销毁上面的结构体
}

module_init(board_imx6ull_button_drv_init);
module_exit(board_imx6ull_button_drv_exit);
MODULE_LICENSE("GPL");

makelife

# 1. 使用不同的开发板内核时, 一定要修改KERN_DIR
# 2. KERN_DIR中的内核要事先配置、编译, 为了能编译内核, 要先设置下列环境变量:
# 2.1 ARCH,          比如: export ARCH=arm64
# 2.2 CROSS_COMPILE, 比如: export CROSS_COMPILE=aarch64-linux-gnu-
# 2.3 PATH,          比如: export PATH=$PATH:/home/book/100ask_roc-rk3399-pc/ToolChain-6.3.1/gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu/bin 
# 注意: 不同的开发板不同的编译器上述3个环境变量不一定相同,
#       请参考各开发板的高级用户使用手册

KERN_DIR = /home/ky/100ask_imx6ull-sdk/Linux-4.9.88

all:
# -C选项的作用是指将当前的工作目录转移到制定的 目录，即（KERN_DIR）目录，程序到（shell pwd）当前目录查找模块源码，将其编译，生成.ko文件。
	make -C $(KERN_DIR) M=`pwd` modules  
	$(CROSS_COMPILE)gcc -o button_test button_test.c 

clean:
	make -C $(KERN_DIR) M=`pwd` modules clean
	rm -rf modules.order
	rm -f ledtest

# 参考内核源码drivers/char/ipmi/Makefile
# 要想把a.c, b.c编译成ab.ko, 可以这样指定:
# ab-y := a.o b.o
# obj-m += ab.o

#将这两个文件编译成.ko 
obj-m	+= button_drv.o 
obj-m	+= board_ky.o

其他的文件跟上一篇一样呀，就改了一个文件。框架已经有了，代码注释的很详细

本文地址：https://blog.csdn.net/agentky/article/details/107914339