Write System Call for virtual keyboard

writesyscall.c

static ssize_t virtKeyboard_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos){
    u32 keycode = 0u;
    u8 *kernel_buf = (u8*)kzalloc(len,GFP_KERNEL);
    int ret = 0;
    pr_info(LOG("Length : %d"),len);
    if(kernel_buf == NULL){
        pr_err(LOG("Not enough memory"));
        return -ENOMEM;
    }
    
    ret = copy_from_user(kernel_buf,buf,len);
    if (ret == 0u){
        ret = sscanf(kernel_buf,"%x",&keycode);
        if(ret != 1u){
            pr_err(LOG("Failed to read keycode"));
            kfree(kernel_buf);
            return -ENOMEM;
        }
        
        
        pr_info(LOG("Keycode input : %x"),keycode);
        kfree(kernel_buf);        
        
        keyPressed = (~keyPressed);
        input_report_key(virtKeyabord_dev, KEY_A,keyPressed);
        
        input_sync(virtKeyabord_dev);
        
        
        return len;
    }else{
        pr_err(LOG("copy_from_user error : %d"),ret);
        kfree(kernel_buf);
        return -1;
    }
    

}