GetUncachedExtension

NTDEV
1

Hi,
I am working on a storport miniport, which needs physically contiguous buffer to be allocated for DMA operations.
WDK says GetUncachedExtension to be used for getting physically contiguous memory that can be used for a DMA operation.

  • What is the maximum number of bytes that can be allocated through this call?
  • What I have noticed is, if I make multple calles to StorPortGetUncachedExtension(), i am getting the same address all the time!!
  • What exactly is the uncached memory? Is it part of the Non-paged pool in the kerenl address space?
  • Is there any documenation on usage of the uncached extension available?

thanks in advance
Praveen

2

“The HwScsiFindAdapter routine can call ScsiPortGetUncachedExtension only
once for each bus-master HBA the miniport driver supports.”

That seems pretty clear to me. Add up all of your requirements, adjust for
boundary conditions, and make one call to StorPortGetUncachedExtension.
Also, always consult the Scsiport docs if the storport docs seem a little on
the brief side. Note especially that you call this once in
HwStorFindAdapter.

From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of prvn ns
Sent: Friday, November 17, 2006 5:54 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] GetUncachedExtension

Hi,

I am working on a storport miniport, which needs physically contiguous
buffer to be allocated for DMA operations.

WDK says GetUncachedExtension to be used for getting physically contiguous
memory that can be used for a DMA operation.

  • What is the maximum number of bytes that can be allocated through this
    call?

  • What I have noticed is, if I make multple calles to
    StorPortGetUncachedExtension(), i am getting the same address all the time!!

  • What exactly is the uncached memory? Is it part of the Non-paged pool in
    the kerenl address space?

  • Is there any documenation on usage of the uncached extension available?

thanks in advance

Praveen

Questions? First check the Kernel Driver FAQ at
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