lkml.org 
[lkml]   [1999]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: mm questions
On Sun, 12 Dec 1999, Terence Ripperda wrote:
> I'm working on a loadable and had some questions about memory management.
>
> One of the things I'd like to be able to do is allocate DMA buffers in the
> kernel and remap those to user space. remap_page_range looks like it
> provides the functionality I need, but of course only works on non-RAM
> memory addresses and "reserved" pages.

Check out Alan Cox's 2.3.18ac patch series. It includes a dmaram driver
which does exactly what you describe here, if I'm not mistaken.


> Some code I've seen gets around this by twiddling with the "reserved" bit
> in the pages, but this is of course a bad hack. I noticed that the bttv
> driver calls mem_map_reserve() on the desired pages, and then has no
> problem remapping the buffers into user space.
>
> Is this the "Right" and "acceptable" way to go about doing this, or just
> less of a hack?
>
> I was also looking for a way to mark pages uncacheable. It didn't look
> like there was any way to do this (nor other cache-related functionality,
> such as flushing caches) on x86 architectures, but that there seemed to be
> such things on other architectures (such as arm and m68k).
>
> I realize MTRR functionality exists for marking cache behavior for ranges
> of physical memory, but recent Intel processors provide Page Allocation
> Table bits to allow fine-grained control at a page level. Would such code
> likely be accepted into the kernel, or are there reasons for avoiding such
> functionality?

There is ioremap_nocache and io_remap_page_range, but I don't think
those are applicable to your situation.

Regards,

Jeff






-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:55    [W:0.033 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site