[[!meta copyright="Copyright © 2009, 2011 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] [[!tag open_issue_gnumach open_issue_hurd]] This is a collection of resources concerning *user-space device drivers*. Also see [[device drivers and IO systems]]. [[community/gsoc/project ideas/driver glue code]]. [[!toc levels=2]] # Issues ## IRQs * Can be modeled using [[RPC]]s. * Security considerations: IRQ sharing. * *Omega0* paper defines an interface. * As is can be read in the *Mach 3 Kernel Principles*, there is an *event object* facility in Mach that can be used for having user-space tasks react to IRQs. However, at least in GNU Mach, that code (`kern/eventcount.c`) doesn't seem functional at all and isn't integrated properly in the kernel. * IRC, freenode, #hurd, 2011-07-29 < antrik> regarding performance of userspace drivers, there is one thing that really adds considerable overhead: interrupt handling. whether this is relevant very much depends on the hardware in question. when sending many small packets over gigabit ethernet, it might be noticable; in most other cases it's irrelevant < youpi> some cards support interrupt coalescin < youpi> could be supported by DDE too ## DMA * Security considerations. * I/O MMU. ## I/O Ports * Security considerations. ## PCI and other buses * Security considerations: sharing. ## Latency of doing RPCs * [[GNU Mach|microkernel/mach/gnumach]] is said to have a high overhead when doing RPC calls. ## System Boot IRC, freenode, #hurd, 2011-07-27 < braunr> btw, was there any formulation of the modifications required to have disk drivers in userspace ? < braunr> (which would obviously need something like initrd/initramfs/whatever and may also need the root file system not to be the first task started) < braunr> hm actually, we may not need initrd < braunr> the boot loader could just load more modules < antrik> braunr: I have described all that in my thesis report... in German :-( < braunr> and the boot scripts could be adjusted to pass around the right ports < Tekk_> braunr: yeah, we could probably load a module that kciks us into userspace and starts the disk driver < braunr> modules are actualy userspace executables < Tekk_> ah < Tekk_> so what's the issue? < Tekk_> oh! I'm thinking the ext2fs server, which is already in userspce < braunr> change the file systems to tell them which underlying disk driver to use < Tekk_> mhm < braunr> s/disk/storage/ # Plan * Examine what other systems are doing. * L4 * Hurd on L4: deva, fabrica * [[/DDE]] * Minix 3 * Start with a simple driver and implement the needed infrastructure (see *Issues* above) as needed. * Some (unfinished?) code written by Robert Millan in 2003: PC keyboard and parallel port drivers, using `libtrivfs`. # Documentation * [An Architecture for Device Drivers Executing as User-Level Tasks](http://portal.acm.org/citation.cfm?id=665603), 1993, David B. Golub, Guy G. Sotomayor, Freeman L. Rawson, III * [Performance Measurements of the Multimedia Testbed on Mach 3.0: Experience Writing Real-Time Device Drivers, Servers, and Applications](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.40.8685), 1993, Roger B. Dannenberg, David B. Anderson, Tom Neuendorffer, Dean Rubine, Jim Zelenka * [User Level IPC and Device Management in the Raven Kernel](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.57.3733), 1993, D. Stuart Ritchie, Gerald W. Neufeld * [Creating User-Mode Device Drivers with a Proxy](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.26.3055), 1997, Galen C. Hunt * [The APIC Approach to High Performance Network Interface Design: Protected DMA and Other Techniques](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.56.1198), 1997, Zubin D. Dittia, Guru M. Parulkar, Jerome R. Cox, Jr. * [The Fluke Device Driver Framework](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.4.7927), 1999, Kevin Thomas Van Maren * [Omega0: A portable interface to interrupt hardware for L4 system](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.21.5958), 2000, Jork Löser, Michael Hohmuth * [Userdev: A Framework For User Level Device Drivers In Linux](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.3.4461), 2000, Hari Krishna Vemuri * [User Mode Drivers](http://www.linuxjournal.com/article/5442), 2002, Bryce Nakatani * [Towards Untrusted Device Drivers](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.13.1725), 2003, Ben Leslie, Gernot Heiser * [Encapsulated User-Level Device Drivers in the Mungi Operating System](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.6.1531), 2004, Ben Leslie Nicholas, Nicholas FitzRoy-Dale, Gernot Heiser * [Linux Kernel Infrastructure for User-Level Device Drivers](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.10.1408), 2004, Peter Chubb * [Get More Device Drivers out of the Kernel!](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.59.6333), 2004, Peter Chubb * * [Initial Evaluation of a User-Level Device Driver](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.59.4531), 2004, Kevin Elphinstone, Stefan Götz * [User-level Device Drivers: Achieved Performance](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.59.6766), 2005, Ben Leslie, Peter Chubb, Nicholas FitzRoy-Dale, Stefan Götz, Charles Gray, Luke Macpherson, Daniel Potts, Yueting Shen, Kevin Elphinstone, Gernot Heiser * [Virtualising PCI](http://www.ice.gelato.org/about/oct06_presentations.php#pres14), 2006, Myrto Zehnder, Peter Chubb * [Microdrivers: A New Architecture for Device Drivers](http://www.cs.rutgers.edu/~vinodg/papers/hotos2007/), 2007, Vinod Ganapathy, Arini Balakrishnan, Michael M. Swift, Somesh Jha * [[!tag open_issue_documentation]] * [[!tag open_issue_documentation]] # External Projects * [[/DDE]] * *