linux字符驱动遇到问题
第一次写博客，不知道写什么，写我遇到的问题吧 --程序员多年，还是那么水的我
背景：参考 https://www.cnblogs.com/acm-icpcer/p/8029656.html 编译内核安装OK后，(我安装的是https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/linux-4.13.16.tar.gz，注意VMware安装的ubuntu 16.04开始时1G内存，安装新内核后，启动失败，需要将内存改为2G，why?）
然后从网上找了个globalmem的字符模块代码，以及makefile, 经过注释掉一些错误，后编译加载成功，但是printk内容无效，makefile增加 warning info error 都不打印内容，shell命令echo正常打印。
将代码贴在下面。有大神看到，请指教一二，遇到问题找不到路
Makefile
# Makefile
$(error, "here add the debug info")
ifneq ($(KERNELRELEASE),)
# kbuild syntax. dependency relationship of files and target modules are listed here.
$(warning, $(KERNELRELEASE))
$(warning, "here add the debug info")
obj-m := globalmem.o
else
PWD := $(shell pwd)
KERNEL_VER ?= $(shell uname -r)
KERNEL_DIR := /lib/modules/$(KERNEL_VER)/build
$(error, "here add the debug info")
$(info, $(PWD))
$(info, $(KERNEL_VER))
$(info, $(KERNEL_DIR))
all:
@echo "start the compilexxxxxxxxxxxxxxxxxxxxxxx"
@echo $(KERNEL_DIR)
$(MAKE) -C $(KERNEL_DIR) M=$(PWD) modules
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c
endif
globalmem.c
/*********************************************************************************
* Copyright: (C) 2014 liuchengdeng <[email protected]>
* All rights reserved.
*
* Filename: globalmem.c
* Description: This file
*
* Version: 0.0.0(08/28/2014~)
* Author: liuchengdeng <[email protected]>
* ChangeLog: 1, Release initial version on "08/28/2014 09:42:22 AM"
*
********************************************************************************/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
//#ifndef KERNEL_VERSION
//#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
//#endif
//#ifndef LINUX_VERSION_CODE
//#define LINUX_VERSION_CODE KERNEL_VERSION(4,13,16)
//#endif
#if LINUX_VERSION_CODE > KERNEL_VERSION(3,3,0)
#include
#else
#include
#endif
#include
#define GLOBALMEM_SIZE 0x1000
#define MEM_CLEAR 0x1
#define GLOBALMEM_MAJOR 150
static int globalmem_major = GLOBALMEM_MAJOR;
struct globalmem_dev {
struct cdev cdev;
unsigned char mem[GLOBALMEM_SIZE];
};
struct globalmem_dev *globalmem_devp;
int globalmem_open(struct inode *inode, struct file *filp)
{
struct globalmem_dev *dev;
dev = container_of(inode->i_cdev, struct globalmem_dev, cdev);
filp->private_data = dev;
return 0;
}
int globalmem_release(struct inode *inode, struct file *filp)
{
return 0;
}
static long globalmem_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct globalmem_dev *dev = filp->private_data;
switch (cmd) {
case MEM_CLEAR:
memset(dev->mem, 0, GLOBALMEM_SIZE);
printk(KERN_INFO "globalmem is set to zero\n");
break;
default:
return -EINVAL;
}
return 0;
}
static ssize_t globalmem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
printk(" globalmem_read\n ");
#if 1
struct globalmem_dev *dev = filp->private_data;
if (p >= GLOBALMEM_SIZE)
return 0;
if (count>GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if (copy_to_user(buf, (void *)(dev->mem + p), count)) {
ret = -EFAULT;
}
else {
*ppos += count;
ret = count;
printk(KERN_INFO "read %u bytes from %lu\n", count, p);
}
#endif
return ret;
}
static ssize_t globalmem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
printk(" globalmem_write\n ");
#if 1
struct globalmem_dev *dev = filp->private_data;
if (p >= GLOBALMEM_SIZE)
return 0;
if (count>GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if (copy_from_user(dev->mem + p, buf, count))
ret = -EFAULT;
else {
*ppos += count;
ret = count;
printk(KERN_INFO "written %u bytes from %lu\n", count, p);
}
#endif
return ret;
}
static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig)
{
loff_t ret = 0;
switch (orig)
{
case 0:
if (offset<0)
{
ret = -EINVAL;
break;
}
if ((unsigned int)offset > GLOBALMEM_SIZE)
{
ret = -EINVAL;
break;
}
filp->f_pos = (unsigned int)offset;
ret = filp->f_pos;
break;
case 1:
if ((filp->f_pos + offset)>GLOBALMEM_SIZE)
{
ret = -EINVAL;
break;
}
if ((filp->f_pos + offset)<0)
{
ret = -EINVAL;
break;
}
filp->f_pos += offset;
ret = filp->f_pos;
break;
default:
ret = -EINVAL;
break;
}
return ret;
}
static const struct file_operations globalmem_fops = {
.owner = THIS_MODULE,
.llseek = globalmem_llseek,
.read = globalmem_read,
.write = globalmem_write,
.unlocked_ioctl=globalmem_ioctl,
.open = globalmem_open,
.release = globalmem_release,
};
static void globalmem_setup_cdev(struct globalmem_dev *dev, int index)
{
int err, devno = MKDEV(globalmem_major, index);
cdev_init(&dev->cdev, &globalmem_fops);
dev->cdev.owner = THIS_MODULE;
err = cdev_add(&dev->cdev, devno, 1);
if (err)
printk(KERN_NOTICE "error %d adding globalmem %d", err, index);
}
int globalmem_init(void)
{
int result;
dev_t devno = MKDEV(globalmem_major, 0);
printk(" globalmem say hello !\n");
if (globalmem_major)
result = register_chrdev_region(devno, 2, "globalmem");
else
{
result = alloc_chrdev_region(&devno, 0, 2, "globalmem");
globalmem_major = MAJOR(devno);
}
if (result<0)
return result;
globalmem_devp = kmalloc(2 * sizeof(struct globalmem_dev), GFP_KERNEL);
if (!globalmem_devp)
{
result = -ENOMEM;
goto fail_malloc;
}
memset(globalmem_devp, 0, 2 * sizeof(struct globalmem_dev));
globalmem_setup_cdev(&globalmem_devp[0], 0);
globalmem_setup_cdev(&globalmem_devp[1], 1);
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}
void globalmem_exit(void)
{
printk(" globalmem say byebye !\n");
cdev_del(&globalmem_devp[0].cdev);
cdev_del(&globalmem_devp[1].cdev);
kfree(globalmem_devp);
unregister_chrdev_region(MKDEV(globalmem_major, 0), 2);
}
module_init(globalmem_init);
module_exit(globalmem_exit);
module_param(globalmem_major, int, S_IRUGO);
MODULE_AUTHOR("liu chengdeng <[email protected]>");
MODULE_LICENSE("Dual BSD/GPL");