NT and Windows makes it “Are sure you REALLY REALLY want to do this for a
reason.” It is a very good way to crash the system. A bad range given to
memcpy and you will be looking at a BSOD.
Gary G. Little
Staff Engineer
Broadband Storage, Inc.
xxxxx@broadstor.com
-----Original Message-----
From: Stephen Williams [mailto:xxxxx@icarus.com]
Sent: Thursday, October 25, 2001 12:47 PM
To: NT Developers Interest List
Subject: [ntdev] RE: No right way to share PCI device memory with user mod
e?
xxxxx@diebold.com said:
There is no good way of sharing memory between a driver and a user
mode application. Thats why you haven’t found any direct answers. NT
was designed to isolate the hardware from user tasks, so sharing
memory is contrary to NT’s design.
Sharing memory between device and application is sorta contrary to
NT’s design, but Gary Little has already presented good way to do it.
Use MmMapLockedPages. I can vouch for the technique, as I use it as well.
It is a perfectly reasonable thing to want to do, it’s irritating
that Windows 2000/Windows NT make it so difficult. The real trick
is figuring out how to build an MDL.
MmMapLockedPages is probably also a reasonable way to direct map
hardware memory. This is how AGP drivers (or at least the M$ example
AGP driver) works.
Steve Williams “The woods are lovely, dark and deep.
steve at icarus.com But I have promises to keep,
steve at picturel.com and lines to code before I sleep,
http://www.picturel.com And lines to code before I sleep.”
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