> Well I tried to mbuff in kernel, than use this for mbuff_alloc_at in
> user space but to no avail, returned 0 as I recall. Can I expect a
> better chance by append mem=xxM to the boot parameters than using
> __va(ptr) in kernel and mmap("/dev/mem") in user instead?
I don't think you will what you want by using ram above linux. The
significant advantage with that memory is that you can be certain it is
physically contiguous which means you can perform DMA to/from without
messing with, or worrying about, scatter/gather complexity and overhead.
When you access such memory with the CPU, the memory management unit is
still in use.
I'm assuming you are looking for a method whereby the same pointer
value can be used by different programs. Have a look at the mmap page.
You can request mmap use a specific pointer value for the base of your
requested space. You just supply the base pointer you would like to use
and you should include the MAP_FIXED flag. The man page also says "Use
of this option is discouraged."
If this doesn't do what you want, you could perhaps make a copy of the
mmap code and modify it to do what you want and then recompile the kernel
and include your new function.
-Wayne
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