Hi guys
Who have read and gone through examples successfully of the book ”Linux Device Drivers, Third Edition”

First scull module does not work properly. The functions scull_read and scull_write are note invoked

At least I cannot notice it using debugging techniques offered in this book: gdb kdb printk
Results of work of this module are fine
data is always 0;
scull_devices[0].data = 0x0

cat > /dev/scull
Hello World

I pressed Ctrl-D

cat /dev/scull
Hello World

Please help