On Tue, Jan 12, 2010 at 4:55 AM, Sam Carter <sam.w.carter@xxxxxxxxx> wrote:
I've just installed strace and run as you advised although there is no extra information on top of the 'No such device or address'. Does my driver and loader code look right?
Thanks for the continued support, Sam
Where is your read/write function defined? there may be some error in these functions.
~cnanda
~cnanda
2010/1/8 Durga Prasad <writexdp@xxxxxxxxx>
On quick glance, do you know what is throwing up the error?Can you do 'strace -vv cat .. '
From: Sam Carter <sam.w.carter@xxxxxxxxx>
To: Daniel Baluta <daniel.baluta@xxxxxxxxx>
Cc: kernelnewbies <kernelnewbies@xxxxxxxxxxxx>
Sent: Fri, January 8, 2010 6:02:54 PM
Subject: Re: 'No such device or address' when writing to device driver
Hi all,
Thanks for the responses. Here is the load/unload part of my driver.
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/version.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/dirent.h>
#include <asm/uaccess.h>
#include <linux/cdev.h>
#include "memo.h"
static int __init memo(void);
static void __exit cleanup(void);
static int ioctlManager(int i);
static int read(void);
static int write(char *s);
static int testDirent(int is64bit, int length, void *p);
static int modulePrint(char *s);
int dev, result;
struct cdev *memoc;
static struct file_operations fops = {
.owner = THIS_MODULE,
.llseek = NULL,
.read = read,
.write = write,
.ioctl = ioctlManager,
.open = NULL,
.release = NULL,
};
extern void (*interceptor)(int, int, void *);
static int __init memo(void){
if(MAJOR){
dev = MKDEV(MAJOR, MINOR);
result = register_chrdev_region(dev, number_of_devices, "memo");
}else{
result = alloc_chrdev_region(&dev, MINOR, number_of_devices, "memo");
}
memoc = cdev_alloc();
cdev_init(memoc, &fops);
memoc->owner = THIS_MODULE;
if(cdev_add(memoc, 249, 1) < 0){
printk("cdev device registration failed\n");
}else{
printk("cdev device registration success\n");
}
printk(KERN_INFO "- Module interceptor loaded -\n");
interceptor = testDirent;
if(result < 0){
printk(KERN_WARNING "memo: can't get major/minor numbers");
return result;
}else{
return 0;
}
}
static void __exit cleanup(void){
int i = 0;
unregister_chrdev_region(dev, number_of_devices);
cdev_del(memoc);
interceptor = NULL;
printk(KERN_INFO "- Module interceptor cleanup -%d\n",i);
}
And here is the load script I'm using to load the module.
module="memo"
device="memo"
mode="664"
#if grep -q '^staff:' /etc/group; then
# group="staff"
#else
# group="wheel"
#fi
group="root"
/sbin/insmod ./$module.ko $* || exit 1
rm -f /dev/${device}
major=$(awk "\$2==\"$module\" {print \$1}" /proc/devices)
mknod /dev/${device} c $major 0
chgrp $group /dev/${device}
chmod $mode /dev/${device}
As far as I'm aware the Major/Minor numbers match up fine. With ls -l /dev, the major is 249, which is the same as in /proc/devices once I've loaded the module. Hope this helps someone find the problem.
Sam2010/1/8 Daniel Baluta <daniel.baluta@xxxxxxxxx>Is the major/minor number of /dev/myDevice the same with major/minorOn Thu, Jan 7, 2010 at 3:31 AM, Sam Carter <sam.w.carter@xxxxxxxxx> wrote:
> Hi all,
>
> I'm trying to write a simple char driver following the 'Linux Device
> Drivers' book from O' Reilly. My driver appears in /proc/devices and under
> lsmod. I've been trying to register the device fops table so I can
> read/write to it, however when I try to cat some data to it in /dev/myDevice
> I get the error 'No such device or address'. The device does appear on the
> list with ls /dev/.
>
> Can anyone help me find the source of this problem? Thanks in advance.
allocated in your driver ?
Can you post a pointer to your code?
thanks,
Daniel.
