[SOLVED] Misunderstandings with the function printk

lbontron · 11-21-2016, 03:21 PM

Hello everybody,
I continue my driver development and I have a small problem (not important)

My program :

Quote:

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/fs.h>
#include <asm/uaccess.h> // for put_user //

#define DEVICE_NAME "GPIO_RaspberryPi2"
#define LICENSE "GPL"
#define AUTHOR "Ludovic BONTRON"
#define GPIO_BASE ((unsigned long)0x3f200000)
#define GPIO_SIZE ((unsigned long)0x00004096)

MODULE_LICENSE(LICENSE);
MODULE_AUTHOR(AUTHOR);

static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t * offset);
static ssize_t device_write(struct file *filp, const char *buff, size_t len, loff_t * off);
static int device_open(struct inode *inode, struct file *file);
static int device_release(struct inode *inode, struct file *file);

static int Major = 0;
struct resource *s_res = NULL;

static struct file_operations fops =
{

.owner = THIS_MODULE,
.open = device_open,
.release = device_release,
.read = device_read,
.write = device_write

};

int init_module(void)
{

int iRet = 0;
Major = register_chrdev(0, DEVICE_NAME, &fops);

if (0 > Major)
{

printk(KERN_ALERT "Registering char device failed with %d\n", Major);
iRet = Major;
}
else
{

printk(KERN_INFO "My major number is %d\n", Major);
s_res = request_mem_region(GPIO_BASE, GPIO_SIZE, DEVICE_NAME);
printk(KERN_INFO "test");
if (NULL == s_res)
{

printk(KERN_INFO "Module can access at the memory between %lu and %lu", GPIO_BASE, GPIO_BASE + GPIO_SIZE);
}
else
{

printk(KERN_INFO "Access confirmed");
}
}
return iRet;

}

void cleanup_module(void)
{

if (NULL != s_res)
{

release_mem_region(GPIO_BASE, GPIO_SIZE);
}
printk(KERN_INFO "Module deleted");
unregister_chrdev(Major, DEVICE_NAME);

}

static int device_open(struct inode *inode, struct file *file)
{

printk(KERN_INFO "device_open() \n");
return -EINVAL;

}

static int device_release(struct inode *inode, struct file *file)
{

printk(KERN_INFO "device_release() \n");
return -EINVAL;

}

static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t * offset)
{

printk(KERN_INFO "device_read() \n");
return -EINVAL;

}

static ssize_t device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
{

printk(KERN_INFO "device_write() \n");
return -EINVAL;

}

My Makefile :

Quote:

ifndef KERNELDIR

KERNELDIR := /lib/modules/$(shell uname -r)/build

endif

obj-m += myfirstdriver.o

all:

# make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

clean:

# make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
$(MAKE) -C $(KERNELDIR) M=$(PWD) clean

After compilation I insert my module with :
$ insmod mydriver.ko
And I execute the command dmesg for analyse the behavior
$ dmesg -c
The result is :
[1130280.724078] My major number is 243
[1130280.737180] test
[1130280.739104] Module can access at the memory between 1059061760 and 1059078294

It's normal...
But when I remove my module I have an problem
$ rmmod mydriver
$ dmesg -c
The buffer is empty.
When I insert my module, so I have the information that the module was deleted
$ insmod mydriver.ko
$ dmesg -c
Resultat :
[1130559.978404] Module deleted
[1130571.107927] My major number is 243
[1130571.121103] test
[1130571.123037] Module can access at the memory between 1059061760 and 1059078294

My question is why I don't have this message before ???

smallpond · 11-22-2016, 02:28 PM

Add a newline to "Module deleted"

lbontron · 11-22-2016, 03:27 PM

Quote:

Originally Posted by smallpond

Add a newline to "Module deleted"

Thank you.