Slashdot Mirror
Linux Kernel To Have Stable Userspace Drive
liquidat writes "Linus Torvalds has included patches into the mainline tree which implement a stable userspace driver API into the Linux kernel. The stable driver API was already announced a year ago by Greg Kroah-Hartman. The last patch to Linus' tree included the new API elements. The idea is to make life easier for driver developers: 'This interface allows the ability to write the majority of a driver in userspace with only a very small shell of a driver in the kernel itself. It uses a char device and sysfs to interact with a userspace process to process interrupts and control memory accesses.'"
A stable kernel api for drivers is what linux needs as proprietary driver writers make poor quality and buggy implementations. While this is not a kernel one its a good compromise as proprietary drivers are here to stay as much as it would be great if we had free gnu ones inside the kernel.
I wonder if it would be easy to port it to windows and macosx? IT would be cool for hardware makers to have a driver that works with all operating systems with minimal effort in porting. Costs are one of the issues besides the difficulty in porting windows drivers to linux which many makers do not bother doing.
http://saveie6.com/
Perhaps in ten years time Linux will be a microkernel
http://michaelsmith.id.au
So I immediately thought of a spaceship running Linux... I mean, could it really be otherwise?
The most common use, I would imagine, would be as a testbed platform. Writing things directly into the kernel has many unquantifiable variables - I'm highly respectful of all who develop kernel code on a regular basis, that is no small achievement. Developing the same code in userspace with an API to link over eliminates many of the possible ways you can screw up a machine, although the code would still need to be written with an eye to being used in kernel space. For much of the writing and testing, though, you'd be in a more predictable environment.
The second-most common use would be for proprietary closed-source drivers to be written for userspace. Writing them for the kernel is problematic as the kernel internals change too much, and many such companies spend so little on maintenance that the drivers rapidly become obsolete - requiring users to either use inferior kernels or different technology, with the latter often not being possible or practical. I don't imagine older Linux drivers to be ported this way, any more than they've been maintained by the pathetic commercial vendors who pull such stunts, but newer such drivers should now be less pathetic and marginally more portable, which will be good.
Oh, wrt comments by others, Linux should absolutely never become a microkernel. Message-passing as a methodology is barely adequate for networks - RPC and CORBA are hardly famed for their elegance or performance, and when was the last time you saw Globus or MPI being used to link machines in a LAN gaming session? For that matter, STREAMS has been available for Linux since about Linux 1.2, if I recall correctly. I can't think of a single driver - even outside any of the standard or experimental trees - that uses it. I like the idea of such a patch, as I like the idea of maximum flexibility, but if it were truly useful, it would be used. It isn't.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
FWIW, not trying to troll, but thought I would point out that this feature is one of Vista's improvements over XP, and simultaneously the primary reason why Vista's compatibility isn't that great right now, and thus the primary reason why many people don't switch to Vista yet. Most of the hardware vendors have to make big changes to their drivers in order to accommodate this, especially nvidia who has to make about 4 different user space drivers (one for d3d, one for opengl, and an SLI version of both of those.) This is a good thing to have for both security and stability reasons, and I was waiting for when somebody would add this to the Linux kernel.
Linux has the advantage in that with Linux you can use both the old "kernel only" drivers, and the user space drivers at the same time. Vista could have done this as well, however Microsoft felt that if they allowed this to happen, then most hardware vendors would be lazy and continue to use their old kernel mode drivers, thus defeating the purpose. And to be honest, I agree with them. Linux doesn't need this on the other hand, as eventually somebody who is interested will make these kinds of changes to all of the open source drivers anyways as needed, which can't really happen because most windows drivers are binary only, so Linux can more or less take the "phased change" approach.
Disclaimer: I use both Vista and Linux (gentoo is my preferred distribution,) and am not afraid to say that I don't hate either of them, and rather like both of them.
Careful with names containing L slashdot.org/~AiphaWolf_HK slashdot.org/~AlphaWoif_HK slashdot.org/~AiphaWoif_HK
What is impossible is fast thread switching, kernel synchronization primitives, access to the network stack (wireless!), ring-0 CPU instructions, real-time timing access, and the huge reduction in context switches / cache flushes that comes from running within the kernel (moving code to user-mode increases latency by a factor of 3, roughly). Kiss the lag-free desktop goodbye as hard drive latency skyrockets, watch your 3D framerate drop by 70%, see your webcam stutter into unusability.
Nice rant there. Let me summarize it:
"What is impossible in user space driver is kernel space features".
No shit. That's the point of a user-space driver. If you give a user-space app access to ring-0, it's no longer user-space. Or did you imagine there's some sort of unwet water that the stupid developers of the kernel keep missing.
The user-space driver is not set to replace all kernel mode drivers. Just like Vista, it's set to replace *some* of them, for example USB devices with low traffic. It's not a solution from heaven, it's just a reduction of fail-prone pieces that lurk in your system.
If you RTFA you probably had to read the summary as well where it's said user-space drivers aren't suitable for high-performance gear such as graphics cards.