I have written a simple block device driver in which i
m just displaying messages
in read & write part e.g " Device Reading .... " & "
Device Writing .....".
I have succesfully loaded that module in memory using
"insmod" .
& then use " mknod " command ...as :
mknod block_dev b 100 0
where , block_dev : name of device
b : as i m using block device driver
100 : major number
0 : minor number
Even this is also working without error, now after
this command device "block_dev" is created (i have
checked it wit ls command ).
But , now while using "cat" & "echo" i am getting
error as :
[root@localhost root]# cat char_devc
cat: char_devc: No such device or
address
[root@localhost root]# echo "hello"
> char_devc
bash: char_devc: No such device or
address
Is it ok to use 'b' in mknod command while working
with block device driver,
as i hav used (shown above).
Im attaching C-code also,so plz help me....if you have
another simple code for block device driver please
send me : [email protected]
Please tell me what is going wrong in this code.....
__________________________________________________________
Yahoo! India Matrimony: Find your partner online. Go to http://yahoo.shaadi.com#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/kdev_t.h>
#define DEVICE_NAME "block_dev"
#define MAJOR_NUM 100
MODULE_LICENSE("GPL");
atomic_t Device_Open = ATOMIC_INIT(0);
struct block_dev
{
struct request_queue *queue ;
spinlock_t lock;
};
struct block_dev *dev;
static void bdd_request(request_queue_t *q)
{
struct request *req;
int write ;
while ((req = elv_next_request(q)) != NULL)
{
if (! blk_fs_request(req))
{
printk (KERN_ALERT "Skip non-fs request\n");
end_request(req, 0);
continue;
}
write=rq_data_dir(req);
if(write==0)
printk(KERN_ALERT "Reading Device .....");
else
printk(KERN_ALERT "Writing Device .....");
end_request(req, 1);
}
}
static int device_open(struct inode *inode, struct file *file)
{
printk(KERN_ALERT "OPENING DEVICE.....\n");
atomic_inc(&Device_Open);
try_module_get(THIS_MODULE);
return 0;
}
static int device_release(struct inode *inode, struct file *file)
{
printk(KERN_ALERT "RELEASING DEVICE....\n");
atomic_dec(&Device_Open);
module_put(THIS_MODULE);
return 0;
}
static struct block_device_operations bdd_ops =
{
.open = device_open,
.release = device_release,
};
static int init_function(void)
{
int ret_val;
dev = (struct block_dev*)kmalloc(sizeof(struct block_dev),GFP_KERNEL);
ret_val=register_blkdev(MAJOR_NUM,DEVICE_NAME);
if(ret_val<0)
{
printk(KERN_ALERT "Sorry, registering the block device");
return ret_val;
}
printk(KERN_ALERT "Initialization\n");
dev->queue=blk_init_queue(bdd_request,&dev->lock);
return 0;
}
static void exit_function(void)
{
int ret_val;
ret_val=unregister_blkdev(MAJOR_NUM,DEVICE_NAME);
printk(KERN_ALERT "Exit\n");
if(ret_val<0)
{
printk(KERN_ALERT "Sorry, Error in Unregistering the block device");
}
}
module_init(init_function);
module_exit(exit_function);
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