linux 内核驱动编写流程

1. 查询内核是否安装

 dpkg-query -s linux-headers-$(uname -r)

2. 内核头文件目录

/usr/src

3. 增加头文件include

export ARMGCC_DIR="/opt/gcc-arm-none-eabi-10.3-2021.10/"
export IMX6_SDK="/home/jeams/SDK_2.2_MCIM6ULL/devices/MCIMX6Y2/":"/home/jeams/SDK_2.2_MCIM6ULL/devices/MCIMX6Y2/drivers/":"/home/jeams/SDK_2.2_MCIM6ULL/devices/MCIMX6Y2/utilities/":"/home/jeams/SDK_2.2_MCIM6ULL/CORTEXA/Include":"/home/jeams/SDK_2.2_MCIM6ULL/CMSIS/Include"
export LINUX_KERNEL_INCLUDE="/usr/src/linux-headers-6.5.0-45-generic/include/"

export C_INCLUDE_PATH=$C_INCLUDE_PATH:$IMX6_SDK:$LINUX_KERNEL_INCLUDE
## export cds_root="/home/jeams/cadence/installs/SPB172/"

export PATH=$PATH:$ARMGCC_DIR/bin/
export XDG_RUNTIME_DIR=/usr/lib/
export RUNLEVEL=3

4. 驱动代码

#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/tty.h>

/* 1. 确定主设备号 */
static int major = 0;
static struct class *gpioctr_class;
static struct gpio_desc *gpioctr_gpio;
/* 2. 实现对应的 open/read/write 等函数，填入 file_operations 结构体*/
static ssize_t gpio_drv_read(struct file *file, char __user *buf, size_t size, loff_t *offs et)
{
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}
static ssize_t gpio_drv_write(struct file *file, const char __user *buf, size_t size, loff_ t *offset)
{
    int err;
    char status;
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    err = copy_from_user(&status, buf, 1);
    gpiod_set_value(gpioctr_gpio, status);
    return 1;
}
static int gpio_drv_open(struct inode *node, struct file *file)
{
    gpiod_direction_output(gpioctr_gpio, 0);
    return 0;
}
static int gpio_drv_close(struct inode *node, struct file *file)
{
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    return 0;
}

/* 定义自己的 file_operations 结构体*/
static struct file_operations gpioctr_drv = {
    .owner = THIS_MODULE,
    .open = gpio_drv_open,
    .read = gpio_drv_read,
    .write = gpio_drv_write,
    .release = gpio_drv_close,
};
/* 从 platform_device 获得 GPIO
 * 把 file_operations 结构体告诉内核：注册驱动程序
 */
static int chip_demo_gpio_probe(struct platform_device *pdev)
{
    /* 设备树中定义有: gpioctr-gpios=<...>; */
    gpioctr_gpio = gpiod_get(&pdev->dev, "gpioctr", 0);
    if (IS_ERR(gpioctr_gpio))
    {
        dev_err(&pdev->dev, "Failed to get GPIO for led\n");
        return PTR_ERR(gpioctr_gpio);
    }
    /* 注册 file_operations */
    major = register_chrdev(0, "myir_gpioctr", &gpioctr_drv); /* /dev/gpioctr */
    gpioctr_class = class_create(THIS_MODULE, "myir_gpioctr_class");
    if (IS_ERR(gpioctr_class))
    {
        printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
        unregister_chrdev(major, "gpioctr");
        gpiod_put(gpioctr_gpio);
        return PTR_ERR(gpioctr_class);
    }
    device_create(gpioctr_class, NULL, MKDEV(major, 0), NULL, "myir_gpioctr%d", 0);
    return 0;
}
static int chip_demo_gpio_remove(struct platform_device *pdev)
{
    device_destroy(gpioctr_class, MKDEV(major, 0));
    class_destroy(gpioctr_class);
    unregister_chrdev(major, "myir_gpioctr");
    gpiod_put(gpioctr_gpio);
    return 0;
}
static const struct of_device_id myir_gpioctr[] = {
    {.compatible = "myir,gpioctr"},
    {},
};
/* 定义 platform_driver */
static struct platform_driver chip_demo_gpio_driver = {
    .probe = chip_demo_gpio_probe,
    .remove = chip_demo_gpio_remove,
    .driver =
        {
            .name = "myir_gpioctr",
            .of_match_table = myir_gpioctr,
        },
};
/* 在入口函数注册 platform_driver */
static int __init gpio_init(void)
{
    int err;
    err = platform_driver_register(&chip_demo_gpio_driver);
    return err;
}
/* 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
 * 卸载 platform_driver
 */
static void __exit gpio_exit(void)
{
    platform_driver_unregister(&chip_demo_gpio_driver);
}
/* 其他完善：提供设备信息，自动创建设备节点 */
module_init(gpio_init);
module_exit(gpio_exit);
MODULE_LICENSE("GPL");