send message from kernel to user application

[yhus]

Hi,

Sorry, my question was not clear. Is it possbile to call msgsnd() from kernel space to user space?

Thank you.

Kind Regards.

[pinkie]

copy_from_user/copy_to_user may meet your need.

But I myself am confusing about these functions. I hope someone give me some explanation.

Here is prototype of the function:

unsigned long copy_to_user (void __user * to, const void * from, unsigned long n);

I see that function appears in kernel driver's file operations like the following:

char data; /*kernel driver global variabe*/
ssize_t device_read (struct file *filp, char *buffer, size_t length, loff_t *ppos)
{
    copy_to_user(buffer,&data, 1);
    return 1;
}

In this case the to pointer transfered into the function copy_to_user is buffer. At this point I know that when calling

read(some_file_hande, user_space_buffer)

from userspace, user_space_buffer will be buffer in the file operation read of kernel driver. I don't know how this user_space_buffer in userspace is transfered to the file operation read in kernel driver. Just think it's some kernel implementation. But my wonder is, if I want to get a pointer of userspace address from within kernel module in general case (not in file operations of a driver), how can I do it?