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October 2007 - Posts

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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WdfDeviceRetrieveDeviceInterfaceString and PDOs

When you initially create a PDO, it takes a few steps for PnP to recognize it. I wrote this problem of determining when a PDO becomes a PDO last year . At the end of the post I mentioned that KMDF handles all of this state management for you underneath Read More...
Posted Monday, October 22, 2007 4:56 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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Fast Resume and how if affects your driver

Fast resume, which was introduced in Windows XP, is often mentioned when implementing power support in your WDM driver. But what does "fast resume" mean and when implementing fast resume, what side effects occur in your driver? I'll to answer both of Read More...
Posted Monday, October 15, 2007 10:33 AM by doronh | 1 Comments
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Vista IO manager changes in handling FILE_DEVICE_SECURE_OPEN

After having the IO manager developer review my last 2 posts, he pointed out to me that the IO manager handling of FILE_DEVICE_SECURE_OPEN (FDSO) has changed slightly in Vista. News to me and probably news to all of you as well. The change involves the Read More...
Posted Friday, October 05, 2007 8:00 AM by doronh | 1 Comments
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Making sure the IO manager evaluates the security of your device

Last time I wrote about how the IO manager handles the creation of file handles and pointed out a potential security hole. If there is a namespace (or path) after your device's name in the path passed to CreateFile, the IO managed does not evaluate the Read More...
Posted Thursday, October 04, 2007 9:00 AM by doronh | 1 Comments
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Devices and namespaces (or how the IO manager handles file creation)

Ever wonder how the creation of a handle works? It doesn't matter type of resource the handle you are opening is backed by (a COM port, a file, a network share, a custom piece of hardware, etc), it all goes through CreateFile (which should be a little Read More...
Posted Wednesday, October 03, 2007 11:55 AM by doronh | 4 Comments
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I am back

First off, man have I been lame. I fell off the blogging horse and it has taken me nearly 3 months to get back on. Posts should be more regular going forward. Typically I use the gaps during the work day to write an entry, but these past few months (going Read More...
Posted Tuesday, October 02, 2007 4:11 PM by doronh | 1 Comments
 
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