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How do I cancel an IRP that another thread may be completing at the same time?

Let's say that you allocated a PIRP and sent it down your device stack. You free the PIRP in the completion routine and then return STATUS_MORE_PROCESSING_REQUIRED. To make life more fun, you decide that you want to be able to cancel the sent IRP after Read More...
Posted Sunday, June 29, 2008 11:16 PM by doronh | 1 Comments
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How to share HW resources with another driver not in the same PnP hierarchy

First, I have to say that I don't agree with this design pattern at all . I think it leads to too many problems and complications that are not worth the pain. The only reason I am writing this entry is that I have seen so many people get this wrong or Read More...
Posted Wednesday, October 24, 2007 3:56 PM by doronh | 1 Comments
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Setting a security descriptor on a legacy device object

Setting the security descriptor allows you to control who can open a handle to the device object. Typically you can call IoCreateDeviceSecure to create the device object and have the correct DACL from the start. One issue with IoCreateDeviceSecure is Read More...
Posted Tuesday, October 16, 2007 4:45 PM by doronh | 1 Comments
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Problems with not having a current IRP stack location, part 2

This problem falls into the category being hidden by a macro that does not indicate in its name what it touches. If you call IoMarkIrpPending on an IRP that you allocated in your driver, chances are that you are corrupting memory. First, let's look at Read More...
Posted Monday, April 09, 2007 9:04 AM by doronh | 2 Comments
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Filtering HID collections and setting I/O flags

Over the past 3 years or so, I have been casually referring to KMDF as the ultimate driver compat layer. Just like Windows has an application compatibility layer which shields applications from OS changes, KMDF provides the same type of compatibility Read More...
Posted Monday, March 26, 2007 5:19 PM by doronh | 0 Comments
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Power relationships in a bus driver

A small but important rule in WDM is that while a PDO is in D0, the parent must be in D0 as well. A very simple statement that can cause a lot of trouble ;). What I have seen is that very few WDM drivers enforce this rule (while KMDF does implement this Read More...
Posted Friday, March 02, 2007 5:28 PM by doronh | 0 Comments
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Problems associated with arming yourself for wake

Hindsite in this case is 20/20, but arming your device for wake can open yourself up to multitude of race conditions and hard problems. Some of them you can solve in your driver, some of them you must accept that they are there and leave them be. Arming Read More...
Posted Tuesday, February 27, 2007 2:59 PM by doronh | 0 Comments
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Which PnP and power IRPs are synchronized against each other?

In my previous post , I talked about how state changing PnP IRPs (refered to from now own as just PnP IRPs) are serialized against each other and briefly mentioned which power IRPs they were synchronized against. This merits its own entry. In short, PnP Read More...
Posted Tuesday, February 06, 2007 10:26 PM by doronh | 1 Comments
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How does WdfDeviceSetFailed work? (AKA the case of the missing WDK documentation for REENUMERATE_SELF_INTERFACE_STANDARD)

KMDF is built on top of public interfaces. This means that it uses only APIs found in the WDK (or what was the DDK). This creates a dilemma. On the one hand we want to add features to the framework that are compelling and add value, but on the other we Read More...
Posted Tuesday, January 23, 2007 2:30 PM by doronh | 1 Comments
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How to return the number of bytes required for a subsequent operation

A very common pattern is to allow a caller to ask for the number bytes (or elements) required and then ask for the data, many user mode Win32 APIs (like RegQueryValueEx ) and kernel mode (like IoGetDeviceProperty ) implement it. You first ask for the Read More...
Posted Tuesday, December 12, 2006 5:18 PM by doronh | 7 Comments
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WDM to KMDF porting guide now available on WHDC

We have been working on this one for the last couple of weeks. There is now a WDM to KMDF porting guide on WHDC. There are 2 documents in the download. The first is a very in depth document which goes into great detail about each function, IRP major code, Read More...
Posted Tuesday, September 12, 2006 12:14 PM by doronh | 5 Comments
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How do I know which device interface is being opened?

Let's say your device supports two interfaces and you want to expose both of them on the same device object. Furthermore, let's say that the I/O interface to each device interface is different. For instance, let's say that one interface allows only one Read More...
Posted Friday, August 18, 2006 4:08 PM by doronh | 2 Comments
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The duality of IoRegisterPlugPlayNotification and when you should call it

IoRegisterPlugPlayNotification() is a pretty scary looking function at first glance. The documentation is not that simple either. So what does this function do and why do you want to use it? IoRegisterPlugPlayNotification() does 2 things (OK 3, but the Read More...
Posted Thursday, July 20, 2006 8:05 AM by doronh | 0 Comments
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When is a reported PDO recognized as PDO by PnP?

Sometimes as a bus driver you need to access the PDO's Device Parameters key of its device node (to set a value for a class installer for instance) or register a device interface for a raw PDO. These are actually instances of a bigger problem, when is Read More...
Posted Monday, June 12, 2006 10:22 PM by doronh | 2 Comments
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How to create an exclusive device or debug why your device is exclusive

Certain devices are exclusive access, or in simpler terms, only one handle can be opened for a particular device. A serial port is an example of an exclusive device; it would make no sense for 2 applications to have the port open because each would expect Read More...
Posted Thursday, May 25, 2006 9:07 PM by doronh | 8 Comments
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