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SubjectVramfs: filesystem driver to utilize extra RAM on VGA devices
Hey guys.
About a month ago while covered in the Seattle snowstorm I hacked
together this pseudofilesystem that might be of interest.

I thought that this driver could solve two issues that I have:

one, that today's graphics cards have relatively obscene amounts of RAM
on them even if you're not using it. If you're running it as a server
and not using it for 3D graphics, why not mount the VRAM on the graphics
card as a filesystem and store things there to get some extra space?

two, if 3D hardware acceleration and access to GPU or texture memory
could be provided to user-space, one way to do it would be to provide
sections of VRAM as a filesystem that most languages (yes---even Perl!)
could use to work with todays graphics cards. They could treat the
texture memory the way they treat files in /dev/shm: read/write it for
general access or mmap it for direct manipulation. At least, it makes
far more sense to me from a programming point of view than to abstract
it using specialized ioctls through the DRI. It might make writing an
OpenGL driver for this kind of arrangement cleaner, too.

http://www.nerdgrounds.com/vramfs-20090126-1458.tar.gz

So far I've tested it against 2.6.25.17 and 2.6.28 on both x86 and
x86_64 with reads, writes, directory creation, symlink creation, and
mmap() and it seems to work fine.
Just give it a range of memory on the bus, or the
domain:bus:device:function numbers of a VGA PCI device, and it will
mount the VGA video RAM and allow files to exist there.
As a special hack: you can also specify the size of the active
framebuffer console so that fbcon doesn't collide with this driver
(unless you want to see what your files look like splattered across your
screen, ha). The active VRAM area becomes a "sentinel" file named
"framebuffer".

What do you guys think?

Jonathan Campbell
Impact Studio Pro



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