原文出處:https://www.cnblogs.com/cyyljw/p/8477594.html
補充:補充了小白知識,原文中沒有說明要做字符設備的文件創建,,,這個小白一般不知道。未提供ko文件的編譯腳本,,這個小白不一定會,,原文未適配3.xx之後的linux內核,,原文代碼未加打印
【一】driver的代碼
memdev.h
#ifndef _MEMDEV_H_
#define _MEMDEV_H_
#include <linux/ioctl.h>
#ifndef MEMDEV_MAJOR
#define MEMDEV_MAJOR 0 /*預設的mem的主設備號*/
#endif
#ifndef MEMDEV_NR_DEVS
#define MEMDEV_NR_DEVS 2 /*設備數*/
#endif
#ifndef MEMDEV_SIZE
#define MEMDEV_SIZE 4096
#endif
/*mem設備描述結構體*/
struct mem_dev
{
char *data;
unsigned long size;
};
/* 定義幻數 */
#define MEMDEV_IOC_MAGIC 'k'
/* 定義命令 */
#define MEMDEV_IOCPRINT _IO(MEMDEV_IOC_MAGIC, 1)
#define MEMDEV_IOCGETDATA _IOR(MEMDEV_IOC_MAGIC, 2, int)
#define MEMDEV_IOCSETDATA _IOW(MEMDEV_IOC_MAGIC, 3, int)
#define MEMDEV_IOC_MAXNR 3
#endif /* _MEMDEV_H_ */
memdev.c
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/version.h>
#if LINUX_VERSION_CODE > KERNEL_VERSION(3, 3, 0)
#include <asm/switch_to.h>
#else
#include <asm/system.h>
#endif
#include <asm/io.h>
#include <asm/uaccess.h>
#include "memdev.h"
static int mem_major = MEMDEV_MAJOR;
module_param(mem_major, int, S_IRUGO);
struct mem_dev *mem_devp; /*設備結構體指針*/
struct cdev cdev;
/*文件打開函數*/
int mem_open(struct inode *inode, struct file *filp)
{
struct mem_dev *dev;
/*獲取次設備號*/
int num = MINOR(inode->i_rdev);
printk("mem_open");
if (num >= MEMDEV_NR_DEVS)
return -ENODEV;
dev = &mem_devp[num];
/*將設備描述結構指針賦值給文件私有數據指針*/
filp->private_data = dev;
return 0;
}
/*文件釋放函數*/
int mem_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*IO操作*/
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
static int memdev_ioctl(
struct inode *indoe,
struct file *filp,
unsigned int cmd,
unsigned long arg)
{
#else
static long memdev_unlocked_ioctl(
struct file *filp,
unsigned int cmd,
unsigned long arg)
{
struct inode *inode = inode = file_inode(filp);
#endif
int err = 0;
int ret = 0;
int ioarg = 0;
/* 檢測命令的有效性 */
if (_IOC_TYPE(cmd) != MEMDEV_IOC_MAGIC)
return -EINVAL;
if (_IOC_NR(cmd) > MEMDEV_IOC_MAXNR)
return -EINVAL;
/* 根據命令類型,檢測參數空間是否可以訪問 */
if (_IOC_DIR(cmd) & _IOC_READ)
err = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));
else if (_IOC_DIR(cmd) & _IOC_WRITE)
err = !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));
if (err)
return -EFAULT;
/* 根據命令,執行相應的操作 */
switch(cmd) {
/* 打印當前設備信息 */
case MEMDEV_IOCPRINT:
printk("<--- CMD MEMDEV_IOCPRINT Done--->\n\n");
break;
/* 獲取參數 */
case MEMDEV_IOCGETDATA:
ioarg = 1101;
ret = __put_user(ioarg, (int *)arg);
break;
/* 設置參數 */
case MEMDEV_IOCSETDATA:
ret = __get_user(ioarg, (int *)arg);
printk("<--- In Kernel MEMDEV_IOCSETDATA ioarg = %d --->\n\n",ioarg);
break;
default:
return -EINVAL;
}
return ret;
}
/*文件操作結構體*/
static const struct file_operations mem_fops =
{
.owner = THIS_MODULE,
.open = mem_open,
.release = mem_release,
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
.ioctl = memdev_ioctl,
#else
.unlocked_ioctl = memdev_unlocked_ioctl,
#endif
};
/*設備驅動模塊加載函數*/
static int memdev_init(void)
{
int result;
int i;
dev_t devno = MKDEV(mem_major, 0);
printk("memdev_init\n");
/* 靜態申請設備號*/
if (mem_major){
printk("begin register_chrdev_region\n");
result = register_chrdev_region(devno, 2, "memdev");
}
else /* 動態分配設備號 */
{
printk("begin alloc_chrdev_region\n");
result = alloc_chrdev_region(&devno, 0, 2, "memdev");
printk("alloc_chrdev_region result=%i\n",result);
mem_major = MAJOR(devno);
}
printk("alloc result=%i\n",result);
if (result < 0)
return result;
/*初始化cdev結構*/
cdev_init(&cdev, &mem_fops);
cdev.owner = THIS_MODULE;
cdev.ops = &mem_fops;
/* 註冊字符設備 */
cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);
printk("cdev_add finished\n");
/* 爲設備描述結構分配內存*/
mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
if (!mem_devp) /*申請失敗*/
{
printk("kmalloc for mem_devp failed\n");
result = - ENOMEM;
goto fail_malloc;
}
printk("kmalloc for mem_devp sucess\n");
memset(mem_devp, 0, sizeof(struct mem_dev));
/*爲設備分配內存*/
printk("kmalloc for devices\n");
for (i=0; i < MEMDEV_NR_DEVS; i++)
{
mem_devp[i].size = MEMDEV_SIZE;
mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
memset(mem_devp[i].data, 0, MEMDEV_SIZE);
}
//ret = device_register(dev);
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}
/*模塊卸載函數*/
static void memdev_exit(void)
{
printk("memdev_exit\n");
cdev_del(&cdev); /*註銷設備*/
kfree(mem_devp); /*釋放設備結構體內存*/
unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*釋放設備號*/
}
MODULE_AUTHOR("David Xie");
MODULE_LICENSE("GPL");
module_init(memdev_init);
module_exit(memdev_exit);
【ap端】
app-ioctl.c
#include <stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdlib.h>
#include "../driver/memdev.h" /* 包含命令定義 */
int main()
{
int fd = 0;
int cmd;
int arg = 0;
char Buf[4096];
/*打開設備文件*/
fd = open("/dev/memdev0",O_RDWR);
if (fd < 0)
{
printf("Open Dev Mem0 Error!,%i\n",fd);
return -1;
}
/* 調用命令MEMDEV_IOCPRINT */
printf("<--- Call MEMDEV_IOCPRINT --->\n");
cmd = MEMDEV_IOCPRINT;
if (ioctl(fd, cmd, &arg) < 0)
{
printf("Call cmd MEMDEV_IOCPRINT fail\n");
return -1;
}
/* 調用命令MEMDEV_IOCSETDATA */
printf("<--- Call MEMDEV_IOCSETDATA --->\n");
cmd = MEMDEV_IOCSETDATA;
arg = 2007;
if (ioctl(fd, cmd, &arg) < 0)
{
printf("Call cmd MEMDEV_IOCSETDATA fail\n");
return -1;
}
/* 調用命令MEMDEV_IOCGETDATA */
printf("<--- Call MEMDEV_IOCGETDATA --->\n");
cmd = MEMDEV_IOCGETDATA;
if (ioctl(fd, cmd, &arg) < 0)
{
printf("Call cmd dme fail\n");
return -1;
}
printf("<--- In User Space MEMDEV_IOCGETDATA Get Data is %d --->\n\n",arg);
close(fd);
return 0;
}
【驅動編譯腳本】
和memdev.c同目錄放置
Makefile
ifneq ($(KERNELRELEASE),)
obj-m := memdev.o
else
KERN_DIR ?= /usr/src/linux-headers-$(shell uname -r)/
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERN_DIR) M=$(PWD) modules
endif
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
【app側編譯可執行文件】
在app-ioctl.c目錄下執行 $gcc *.c
執行:./a.out
【創建字符設備】
1.ko文件加載 insmod memdev.ko
2.查看設備的major ID: $cat /proc/devices
假定有一行 245 memdev
3.創建字符設備 $sudo mknod /dev/memdev0 c 245 0
創建成功後查看/dev/目錄
附:這裏選的是手動創建字符設備,但其實是還可以在init代碼裏調用create-device()來創建創建的。這塊後續測試通過後補充進來
【流程順序】
1.完成代碼編譯
2.編譯構建驅動ko文件,app的可執行文件
3.創建字符設備
4.執行app的可執行文件查看效果。如果執行報錯,有可能是權限不夠導致,試下sudo xx
5.執行dmesg查看驅動打印。若驅動日誌過多 執行dmesg -c
【驅動開發相關資料鏈接彙總】
https://blog.csdn.net/zqixiao_09/article/details/50888795 Linux 設備驅動開發 —— platform設備驅動應用實例解析
http://v4l.videotechnology.com/dwg/v4l2.pdf v4l2開發api
https://blog.csdn.net/simonforfuture/article/details/78743800
http://www.yellowmax2001.com/2018/07/02/V4L2%E6%A1%86%E6%9E%B6-media-device/ V4L2框架-media-device media_device
,media_entity
,media_link
,media_pad