DIRECT_IO doubt ?

NTDEV
1

HI all

I have a doubt on DIRECT_IO . Let us say we have three drivers stacked
together like Driver 1/ Driver 2 /Driver 3. If Driver 2 and Driver 3 are
set to DIRECT_IO flag in their device objects , Would Driver 1 still send
the requests in Direct IO mode ? If Driver 1 sets its flag to Buffered IO ,
Will it send the requests in Buffered IO mode or Direct IO mode ? And Is
this configuaration is possible ?

Thanks in advance
srinivasa

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2

The stack you describe would be unusual. In general, stacked device
objects replicate the flags set by the device object they are stacked
above. I say in general as there are obvious exceptions, such as file
system drivers, which may very well specify NEITHER_IO, while the
storage stack below them is expecting (and must receive) DIRECT_IO. In
such cases, and in the example you describe, it is the responsibility of
the upper driver to respect the IO mode expectations of the lower
driver.

=====================
Mark Roddy
Windows XP/2000/NT Consulting
Hollis Technology Solutions 603-321-1032
www.hollistech.com
xxxxx@hollistech.com
For Windows Device Driver Training: see www.azius.com

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Srinivasa Rao
Deevi
Sent: Thursday, February 21, 2002 6:57 PM
To: NT Developers Interest List
Subject: [ntdev] DIRECT_IO doubt ?

HI all

I have a doubt on DIRECT_IO . Let us say we have three drivers stacked
together like Driver 1/ Driver 2 /Driver 3. If Driver 2 and Driver 3
are set to DIRECT_IO flag in their device objects , Would Driver 1
still send the requests in Direct IO mode ? If Driver 1 sets its flag to
Buffered IO , Will it send the requests in Buffered IO mode or Direct
IO mode ? And Is this configuaration is possible ?

Thanks in advance
srinivasa

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