字符设备应用之私有ioctl的使用

ops/2024/9/20 1:32:00/ 标签: wifi, linux, ioctl

ioctl和netlink是用于用户态程序和内核态模块交互的两种方法，这里主要讲解ioctl的使用方法；
-----再牛逼的梦想，也抵不住傻逼般的坚持！ ----20240722 08:26

留一个思考问题，ioctl和netlink的优缺点分别是什么？

使用ioctl，ioctl的入参有个cmd，cmd的格式如下, 共两个字节，分别包含了type, number

/* -------------------- DEV PRIVATE IOCTL LIST -------------------- */
/* --------|-type-|-number-|-direction-|-size--|--------------------*/
/* --------|-8bit-|--8bit--|----2bit---|-14bit-|--------------------*/#define SIOCGCHIPID 0x9160 /*get wifi chip id*/
#define SIOCGCHIPTEMP 0x9161

cmd[31:30]—数据（args）的传输方向（读写） cmd[29:16]—数据（args）的大小
cmd[15:8]—>命令的类型，可以理解成命令的密钥，一般为ASCII码（0-255的一个字符，有部分字符已经被占用，每个字符的序号段可能部分被占用）
cmd[7:0] —>命令的序号，是一个8bits的数字（序号，0-255之间）

其实cmd本质是一个命令码，不按照上述的规则定义可以嘛？当然可以，只要上下都是你自己做的，发什么cmd做什么事情你自己清楚就好

接下来是干货，直接上Demo （需要自己根据自己的业务，做下微调）
用户态：

#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <string.h>
#include <unistd.h>#define DEVICE_PATH "/dev/test_s_cdev"/*get wifi module chip id or other info*/
int get_dev_info(int cmd, char *buf) 
{int fd = -1;char info[32] = "";printf("open [%s]\n", DEVICE_PATH);fd = open(DEVICE_PATH, O_RDWR);if (fd < 0) {perror("Failed to open device--");return 1;}int ret = ioctl(fd, cmd, info);if (ret < 0) {printf("IOCTL failed\n");}else{printf("Got string: %s\n", info);memcpy(buf, info, strlen(info));}close(fd);return 0;
}

内核态：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/uaccess.h>#include "ipc_msg.h"#define DEVICE_NAME "test_s_cdev"
static char wifi_chip_id[32] = "";static struct cdev test_s_cdev;
static struct class *test_s_class;
static struct device *test_s_dev;extern struct ssv_hw *g_ssv_hw;
extern struct ssv_rftool_cfg rftool_cfg;extern int ssv_send_priv_msg_rf_cmd_wait_resp(struct ssv_rftool_softc *srfc, struct ssv_rf_tool_param *param);static int device_open(struct inode *inode, struct file *file)
{return 0;
}
static int device_write(struct inode *inode, struct file *file)
{return 0;
}
static int device_read(struct inode *inode, struct file *file)
{return 0;
}
static int device_release(struct inode *inode, struct file *file)
{return 0;
}
long test_s_set_chip_id(char *chip_id)
{if (copy_to_user(wifi_chip_id, chip_id, strlen(chip_id))){printk("[test_s] set chip id fail[%s]\n", chip_id);return -EFAULT;}printk("[test_s]set chip id success[%s]\n", wifi_chip_id);return strlen(wifi_chip_id);
}static void test_s_get_temp()
{struct ssv_rf_tool_param rf_tool_param = {0};rf_tool_param.rf_cmd = (u32)SSV6XXX_RFPHY_CMD_RF_TOOL_TEMPERATURE;rf_tool_param.wait_resp = 1;ssv_send_priv_msg_rf_cmd_wait_resp(g_ssv_hw->srfc, &rf_tool_param);printk("temperature = %d\n", rftool_cfg.temperature);
}static long test_s_private_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{// char *buffer = NULL;printk("[test_s]ssv recv ioctl[%04x]\n", cmd);if (cmd == SIOCGCHIPID) {#if 0buffer = kmalloc(strlen(wifi_chip_id) + 1, GFP_KERNEL);if (!buffer){return -ENOMEM;}strcpy(buffer, wifi_chip_id);#endifif (copy_to_user((void __user *)arg, wifi_chip_id, strlen(wifi_chip_id))) {// kfree(buffer);return -EFAULT;}// kfree(buffer);return 0;}else if (SIOCGCHIPTEMP == cmd){test_s_get_temp();if (copy_to_user((void __user *)arg, &rftool_cfg.temperature, sizeof(s8))) {return -EFAULT;}return 0;}return -EINVAL;
}static struct file_operations test_s_fops = {.owner = THIS_MODULE,.open = device_open,.read = device_read,.write = device_write,.release = device_release,.unlocked_ioctl = test_s_private_ioctl,
};int test_s_char_module_init(void)
{int ret = -1;/*设备节点初始化*/cdev_init(&test_s_cdev, &test_s_fops);/*动态申请主设备号*/ret = alloc_chrdev_region(&test_s_cdev.dev, 0, 1, DEVICE_NAME);if (0 != ret) {printk("[test_s]alloc_chrdev_region fail\n");return ret;}test_s_cdev.owner = THIS_MODULE;ret = cdev_add(&test_s_cdev, test_s_cdev.dev, 1);if (0 != ret) {printk("[test_s]cdev_add fail\n");return ret;}test_s_class = class_create(THIS_MODULE, DEVICE_NAME);if (IS_ERR(test_s_class)) {printk("[test_s]class_create fail\n");return PTR_ERR(test_s_class);}test_s_dev = device_create(test_s_class, NULL, test_s_cdev.dev, NULL, DEVICE_NAME);if (IS_ERR(test_s_dev)) {printk("[test_s]device_create fail\n");return PTR_ERR(test_s_dev);}printk("[test_s]device_create success\n");return 0;
}void test_s_char_module_exit(void)
{device_destroy(test_s_class, test_s_cdev.dev);class_destroy(test_s_class);unregister_chrdev_region(test_s_cdev.dev, 1);
}