AW: Re: AW: RE: Mapping scattered pages into process addr- ess spac e

Stephen,

your constraints are the 4GB limit that most PCI HW have at the moment.
Win2000 doesn’t allocate any memory above 4GB (physical) to your application
when not using the AWE extension which makes use of Pentiums PAE feature.

Simply malloc()'ing in your app should give you buffers inside the 32bit
address limit. I think LINUX does it the other way around, i.e. when using
the BIGMEM feature applications will get anything while kernel clients will
only get physical memory above 4GB when specifying the GFP_HIGHMEM bit in
kmalloc() calls.

Does that solve your questions?

Dipl.Ing. (FH) Klaus P. Gerlicher
Software design engineer
ATi Research GmbH
Tel. +49-(0)8151-266-420
xxxxx@ATi.com

-----Urspr?ngliche Nachricht-----
Von: Stephen Williams [SMTP:xxxxx@icarus.com]
Gesendet am: Sonntag, 5. August 2001 01:55
An: NT Developers Interest List
Betreff: [ntdev] Re: AW: RE: Mapping scattered pages into
process address spac e

xxxxx@ati.com said:
> 2) If your device can do scatter/gather, why even worry about
common
> buffers? You’re trying to share your memory with an application,
so
> simply malloc() it in your app and pass it to the driver via an
IOCTL.

I can live with this, I even suggested it as a possibility myself,
but the reason for common buffers is to make buffers that the PCI
device can access as well as the processor. Will memory that is
pinned
to RAM by MmProbeAndLockPagesSpecifyCache for certain be accessible
to my PCI device? Even with map registers?


Steve Williams “The woods are lovely, dark and deep.
xxxxx@icarus.com But I have promises to keep,
xxxxx@picturel.com and lines to code before I sleep,
http://www.picturel.com And lines to code before I sleep.”


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