The sound driver has to be in kernel space because it makes heavy use of
DMA and interrupts. We are actually trying to move stuff into user space
(you'll note that theres a definitely shift with ALSA and the newer drivers
away from having all the advanced sequencing in kernel space. Things like
Esound do mixing in user space and keep the kernel side clean. Right now
sound is a good example of kernel side bloat.
Video as it happens is going IRQ and DMA based more and more so its unlikely
the PC Xservers will remain entirely user space. The NVidia already screws
people horribly because of the IRQ problem. So in the longer term a kernel/user
split is going to have to occur. Thats a foregone conclusion. Getting the split
right is very important. Bizarrely enough the problem is slightly intelligent
cards. Both dumb frame buffers and the most recent accelerated cards with
graphic command queues work well with a user/kernel split. Stuff like the
earlier S3 cards are where the fun is.
> Then there's the OS/2 model: minimal drivers to map memory in ring 0, the
> rest of the privileged part of the drivers live in ring 2 (not 3). (This
> would also work for the sound drivers, come to think of it.)
That is close to the KGIcon model. I'd hope nobody is advocating "insmod X11".
Let me make that clear - I _really_ hope nobody is advocating insmod X11.
Alan
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