(Forget the last e-mail, please, stupid Gmail) Hi, I'm looking for some information about : struct kobj_attribute { struct attribute attr; ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr, char *buf); ssize_t (*store)(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count); }; My function to handle the operation: static ssize_t my_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { char *buffer; buffer = (char*) kcalloc(count, sizeof(char), GFP_KERNEL); copy_from_user(buffer, buf, count); ..... ..... etc.... } So, this *const char *buf, *where ti come from ? Kernel space? My copy_from_user it's not working. Should return zero. There any Macro or function to test if the pointer *buf *is a kernel pointer ? Thanks Lucas Tanure