Keyboard filter driver

NTDEV
1

Hello All,
I am writing a device upper filter driver to the keyboard
and i used the inf file provided in ddk (version 3615) to install the
driver.
My driver get loaded i get IRP_MJ_PNP and IRP_MJ_POWER calls but i don’t get
IRP_MJ_READ calls so i am not able to intercept press and release of the
keys.
But if i add a registry entry
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\
Class{4D36E96B-E325-11CE-BFC1-08002BE10318}] and edit “UpperFilters” entry
than
i get IRP_MJ_READ calls.Can anybody tell me why

Thanks in advance
Ashish

2

You only get the reads if you are *above* kbdclass. If you are below
kbdclass (either via the reg value or if you added yourself as a device
upper filter) the you must hook yourself into the service callback
chain. Kbdclass abstracts the read irp logic/queueing away from the
port driver. Look at the kbdfiltr example in the DDK on how to hook
into the chain.

If you want to stop scan codes from reaching the OS, just don’t call the
service callback above you.

D

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-----Original Message-----
From: xxxxx@Itronix.com [mailto:xxxxx@Itronix.com]
Sent: Tuesday, April 23, 2002 4:25 PM
To: NT Developers Interest List
Subject: [ntdev] Keyboard filter driver

Hello All,
I am writing a device upper filter driver to the keyboard
and i used the inf file provided in ddk (version 3615) to install the
driver. My driver get loaded i get IRP_MJ_PNP and IRP_MJ_POWER calls but
i don’t get IRP_MJ_READ calls so i am not able to intercept press and
release of the keys. But if i add a registry entry
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\
Class{4D36E96B-E325-11CE-BFC1-08002BE10318}] and edit “UpperFilters”
entry than i get IRP_MJ_READ calls.Can anybody tell me why

Thanks in advance
Ashish

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