Vramfs: filesystem driver to utilize extra RAM on VGA devices
Jonathan Campbell
jon at nerdgrounds.com
Mon Jan 26 23:50:54 UTC 2009
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.
Also, doesn't mtd come in as a block device?
So you'd have to format the memory region using a filesystem like ext3,
right?
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 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?
>>
>
> How is this different from the MTD driver we already have?
>
> -hpa
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