Instead of formal way of binding to the beneath NIC adapter.
Can I bind to the Miniport driver instead using the miniport driver’s name?
If yes please show me how.
Thank you
From: “Roddy, Mark”
>Reply-To: “NT Developers Interest List”
>To: “NT Developers Interest List”
>Subject: [ntdev] Re: doubt about calling thread context
>Date: Fri, 20 Apr 2001 14:08:35 -0400
>
>The MmGetMdlVirtualAddress value is really being used as an index into the
>start of a physical page,and should be named something like
>MmGetMdlUserBufferOffsetIndexIntoFirstPhysicalPageAndDontEverUseThisAsAPoint
>erOrYouWillDieAHorribleAndJustlyDeservedDeath
>
>Lower level drivers may indeed access the user’s data, but if they do they
>will do so by calling MmGetSystemAddressForMdl or they will suffer the
>consequences.
>
>IoBuildPartialMdl uses the existing MDL plus your input values for
>‘VirtualAddress’ (our ambiguous friend MmGetMdlVirtualAddress plus some
>offset) and Length to create a new MDL. However it does not AND CANNOT
>access the user buffer through the value of VirtualAddress.
>
>The existing MDL already contains a complete description of the physical
>pages that contain the user data. the MDLs created by IoBuildPartialMdl use
>this existing description plus your input values to create subset
>descriptions of the same physical pages.
>
>In the ideal MDL path no driver ever accesses the user data buffer
>directly.
>Instead only the MDL is accessed.
>
>Mark Roddy
>xxxxx@hollistech.com
>www.hollistech.com
>603 321 1032
>WindowsNT Windows 2000 Consulting Services
>
>
>
>-----Original Message-----
>From: Srinivasa Rao Deevi [mailto:xxxxx@Transilica.com]
>Sent: Friday, April 20, 2001 1:59 PM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
>As you said I don’t need to view the contents of what MDL is pointing to it
>. But I was confused by the statement in the DDK documentation :
>
>“MmGetMdlVirtualAddress returns a virtual address that is not necessarily
>valid in the current thread context. Lower-level drivers should not attempt
>to use the returned virtual address to access memory, particularly
>user-space memory.”
>
>I am trying to create a new MDL and using the Virtual Addresss returned by
>MmGetMDlVirtualAddress and then call IoBuildPartialMdl to map from the old
>MDL to new MDl created at driver level . Then later it is passed to lower
>level driver ( Which I suppose Bus driver ) . When I send an MDL with user
>buffer virtual address in it , the lower level driver will not touch the
>contents of user buffer while transmitting on the bus . I may be wrong ,
>please correct me .
>
>Or when I call IoBuildPartialMdl while it is mapping does it map any
>differently so that lower level drivers can use it ?
>
>
>srinivasa
>
>
>-----Original Message-----
>From: Roddy, Mark [mailto:xxxxx@stratus.com]
>Sent: Friday, April 20, 2001 10:27 AM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
>If you actually need to access the contents of the user data directly from
>your driver using a pointer, that is what MmGetSystemAddressForMdl gives
>you: a kernel virtual address for the physical pages that contain the user
>data. But if you are simply setting up MDLs to describe portions of the
>user
>data, then you do not need anything other than the CurrentVA ‘index’
>constructed by the opaque (non-pointer) use of the value returned by
>MmGetMdlVirtualAddress. I think that you probably do not have to actually
>access the buffer contents. Aren’t you just building a set of MDLs to pass
>on down to the controller? Unless there is some content within the buffer
>that you need to be aware of, you should never have to actually access the
>user data. If that is all you are doing then you do not need
>MmGetSystemAddressForMdl.
>
>You should be aware that the first driver to call MmGetSystemAddressForMdl
>on an MDL incurs a substantial overhead, as the system mapping for the user
>buffer is not performed until some kernel component asks for it.
>MmGetMdlVirtualAddress has no such overhead associated with it.
>
>
>Mark Roddy
>xxxxx@hollistech.com
>www.hollistech.com
>603 321 1032
>WindowsNT Windows 2000 Consulting Services
>
>
>
>-----Original Message-----
>From: Srinivasa Rao Deevi [mailto:xxxxx@Transilica.com]
>Sent: Friday, April 20, 2001 1:20 PM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
>Thanks Mark .
>
>then what would be the best way to get the contents of user buffer pointed
>by the MDL in the IRP that is received by the driver ?
>
>Obviously we wanted to tranmit the data from the user buffer ( which is
>from
>application ) So through MDL we would be passing the Virtual address to the
>driver ( Though after calling IoAllocateMdl and IoBuildPartialMdl calls).
>But as per documentation we may have some problem if used that way .
>
>I understand the point what you are trying to mention. Why microsoft don’t
>mention that the use of that particular command is according to the context
>of other commands that are used .
>
>As you mentioned I had a problem when I tried to use
>MmGetSystemAddressForMdl instead of MmGetMdlVirtualAddress .
>
>Thanks and regards
>Srinivas
>
>-----Original Message-----
>From: Roddy, Mark [mailto:xxxxx@stratus.com]
>Sent: Friday, April 20, 2001 6:54 AM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
>The value returned by MmGetMdlVirtualAddress (or a subsequent result
>derived
>from this value,) is REQUIRED as input to some of the MDL-specific
>functions. While it would be wrong to use the returned value as a pointer
>to
>memory, it would be equally wrong to use the value returned by
>MmGetSystemAddressForMdl where the return value for MmGetMdlVirtualAddress
>is required.
>
>Thus you will see DDK references such as:
>
>“A driver can get the initial CurrentVa for the start of a packet-based DMA
>transfer by calling MmGetMdlVirtualAddress. However, the value returned is
>an index into the Mdl, rather than a valid virtual address. If the driver
>must split a large transfer request into more than one DMA operation, it
>must update CurrentVa and Length for each DMA operation.”
>
>(MapTransfer)
>
>The DDK refuses to speak plainly here. CurrentVA is used as an index into
>the set of physical pages that describe the user data buffer. The user data
>buffer may very well not be PAGE_ALIGNED. The initial value of CurrentVA -
>which is to say the value returned by MmGetMdlVirtualAddress is used by
>various functions to determine the offset into the physical pages where a
>DMA transfer operation should start.
>
>The value returned by MmGetSystemAddressForMdl may not share the same
>alignment characteristics. Huge problem then if you substitute this value
>instead of the required MmGetMdlVirtualAddress value.
>
>
>Mark Roddy
>xxxxx@hollistech.com
>www.hollistech.com
>603 321 1032
>WindowsNT Windows 2000 Consulting Services
>
>
>
>-----Original Message-----
>From: Srinivasa Rao Deevi [mailto:xxxxx@Transilica.com]
>Sent: Thursday, April 19, 2001 10:05 PM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
>Thanks alot MAX .
>
>One more doubt , Even though the use of MmGetVirtualAddress has certain
>limitations , the example programs for bulk transfers in USB still use this
>and the virtual address returned by it is made available to the lower level
>driver. I am not sure that how those drivers work in actual environments .
>Because DDk docs says those virtual address which belongs to user space
>should not be refered by any lower level drivers. I may be wrong but I am
>having some problem when I am trying to implement in the same way (as in
>bulk usb sample ).
>
>Thanks and regards
>srinivas
>
>-----Original Message-----
>From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
>Sent: Thursday, April 19, 2001 6:33 PM
>To: NT Developers Interest List
>Subject: [ntdev] Re: doubt about calling thread context
>
>
> > What is the meaning of necessarily valid in current current thread
>context
> > when the virtual addresses that are described by the MDL when those
>pages
> > are locked by OS ?
>
>This VA can be the user VA which is process-dependent.
>If you want to have a kernel VA for the MDL - the VA which is guaranteed to
>be the kernel one - use MmGetSystemAddressForMdlSafe, it will allocate
>system PTEs pointing to it.
>Single-page MDLs are usually “mapped” bu stupidly adding 0x80000000 to the
>page’s physical address.
>
> Max
>
>
>—
>You are currently subscribed to ntdev as: xxxxx@transilica.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@stratus.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@transilica.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@stratus.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@transilica.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@stratus.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
>
>—
>You are currently subscribed to ntdev as: xxxxx@hotmail.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com
—
You are currently subscribed to ntdev as: $subst(‘Recip.EmailAddr’)
To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
