From: Gary G. Little [glittle@broadstor.com]
Sent: Wednesday, May 15, 2002 12:31 PM
To: NT Developers Interest List
Subject: [ntdev] Re: METHOD_DIRECT - Please help!

Jamey Hanrahan in a seminar I took describes it best ---

METHOD_*_DIRECT redefines the use of the input/output buffers. Input becomes a pointer to a control buffer, where as output becomes the data buffer. On entry to your drivers Dispatch control method IRP->Associated buffer points to the "control" buffer where as IRP->MdlAddress points the MDL that has been created for the data buffer.

As to why "control" might be NULL, I would hazard a guess that the Input pointer was null and or the size was 0.

-- 
Gary G. Little
glittle@broadstor.com
glittle@inland.net
  "Johnny D" <niceguy303@hotmail.com> wrote in message news:28233@ntdev...
  In an IOCTL if I am copying more than 1 page worth of data from user->kernel space and also the other way around.. am I safe with using METHOD_OUT_DIRECT?

  I once saw that the Irp->AssociatedIrp.SystemBuffer was NULL when inside my IOCTL handler.. this is with > 1 page worth of data being transferred in... Would someone know why that I am getting that?


  Thanks 
  -Johnny 


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