Iterate over open driver file objects

NTDEV
1

Hi,
how can I find and iterate over all open (user mode) file objects to my KMDF device (from inside my KMDF driver providing a device object)?

Thanks, for any hint or recommendation!
Cheers,
Hagen.

2

How about making a list… At CreateFile put the WDFFILEOBJECT in a WDFCOLLECTION. Just be sure to provide a Cleanup even processing callback so you know when to remove/delete it.

Does that not work?

Peter
OSR
@OSRDrivers

3

Thanks, Peter,
OK. That would work.

But I thought the OS keeps track of the relation of device and file objects and I could ask for it (instead of inventing something which I would be responsible for keeping in sync with what the OS does anyways).

Thanks,
Hagen.

4

The os doesn?t have a list of file objects that are based on a device object. It is a ob reference count based system. After you have your list, what are you going to use it for?

Sent from Outlook Mailhttp: for Windows 10

From: xxxxx@dynax.at
Sent: Saturday, August 1, 2015 8:24 AM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Iterate over open driver file objects

Thanks, Peter,
OK. That would work.

But I thought the OS keeps track of the relation of device and file objects and I could ask for it (instead of inventing something which I would be responsible for keeping in sync with what the OS does anyways).

Thanks,
Hagen.

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5

Thanks, Doron,
for the clarification!

The reason behind that question:
I need to notify the user clients of asynchronous data arrival/space available events. Which could be done with threads and shared events as well, but I thought it would be a bit of an overkill.

The user clients itself do have shared user/kernel memory (ring buffers) which contain the updated data which the device is going to inform about.

Cheers and thanks,
Hagen.

6

Just put each type of event request in its own wdfqueue. Drain the queue when the event occurs. No need to track handles

Sent from Outlook Mailhttp: for Windows 10

From: xxxxx@dynax.at
Sent: Saturday, August 1, 2015 9:22 AM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Iterate over open driver file objects

Thanks, Doron,
for the clarification!

The reason behind that question:
I need to notify the user clients of asynchronous data arrival/space available events. Which could be done with threads and shared events as well, but I thought it would be a bit of an overkill.

The user clients itself do have shared user/kernel memory (ring buffers) which contain the updated data which the device is going to inform about.

Cheers and thanks,
Hagen.

—
NTDEV is sponsored by OSR

Visit the list at: http://www.osronline.com/showlists.cfm?list=ntdev

OSR is HIRING!! See http://www.osr.com/careers

For our schedule of WDF, WDM, debugging and other seminars visit:
http://www.osr.com/seminars

To unsubscribe, visit the List Server section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer</http:>

7

Thanks, Doron,

I will consider WDFQUEUEs for the signalling.

Cheers,
Hagen.