Hi, I'm currently writing my first kernel module, but i got stuck with address translations. I want my pcie device to access a buffer which was allocated in userspace (page aligned, currently smaller than one page to ignore scattering). I tried to translate the userspace address to a bus address in my ioctrl handler like this: void __user *data = arg; down_read(¤t->mm->mmap_sem); get_user_pages(current, current->mm, (unsigned long)data, len/*1*/, 1, 0, &pages, NULL); up_read(¤t->mm->mmap_sem); void* kvaddr = kmap(pages[0]); unsigned long baddr = virt_to_bus(kaddr); kunmap(pages[0]); page_cache_release(pages[0]); //... data is page-aligned and was locked in userspace with mlock. There is some address in baddr, but the device does not write to the correct location and sometimes causes kernel freezes. Can someone tell me, what is wrong with this code?TheI device works with a address, that was received in different way (closed source driver). I use 32 bit Ubuntu with an 2.6.32 kernel.