Vramfs: filesystem driver to utilize extra RAM on VGA devices
Peter W. Morreale
pmorreale at novell.com
Thu Jan 29 17:04:09 UTC 2009
On Mon, 2009-01-26 at 15:50 -0800, Jonathan Campbell wrote:
> vramfs is designed to take the memory range and directly turn it into a
> usable filesystem.
> The structures are not actually in VRAM, but the file contents are.
> Vramfs has a builtin mechanism as described to avoid conflicting with
> the region in use by the framebuffer console.
> I don't really know about the mtd device, but I thought it would be good
> kernel coding practice to write a filesystem driver to pull off a stunt
> like that.
> I also wrote this in consideration of the GPU which probably wouldn't
> know how to handle the fragmentation that would inevitably happen if
> ext3 needed to write blocks in a non-contiguous manner, this fs enforces
> the rule that files are always unbroken with only a start and length.
How do you accomplish that?
(I haven't yet looked at your code...)
> Also, doesn't mtd come in as a block device?
> So you'd have to format the memory region using a filesystem like ext3,
> And as a block device you can't use mmap() to map that region directly
> into your process space, right?
> > Jonathan Campbell wrote:
> >> So far I've tested it against 126.96.36.199 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?
> > How is this different from the MTD driver we already have?
> > -hpa
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